Merci Jeffrey

Merci À Véronique

Margot, Élisabeth, Elodie Delphine Charlotte

Merci Aux

Ifrémériens Thomas

Flo

Pierre Shray

Maud Aux Doctorants De Lgo Maxence

Virgil Charles

Alden Ruth

Clarisse Léna

Maëlle Merci

Marie Thoby

Nicolo Grazie Ai Triestini Simon

Alessandra Giulia

Marchetto, Fadl Elisabetta Gigi

Oliviero Grazie

À Tyfenn

Nathalie Max

Cécile Brest

Maïween, Romain, Manu, Jody, Édouard, Clem, Roza, Yann, Renaud, Océane, Maël Cécile Ploug

Léa Acknowledgment

Gere

Feb, Fede, Fede, Silvia, Tonio, Gamma, Elodie, Alio, Isa Nico Jean

Sarà Düra

Massimo Bellucci

Jeffrey Poort

Francis Lucazeau

Christian Gorini

Frédérique Rolandone

Damien Do Couto

Daniel Aslanian

Maryline Moulin

Marina Rabineau

Estelle Leroux

Romain Pellen

Anna Del Ben

Angelo Camerlenghi

ANNEXE-2 HEAT FLOW MEASUREMENTS, MODELS AND RHEOLOGY EXPERIMENT "OGNUNO DI NOI DEVE DARE QUALCOSA IN MODO CHE ALCUNI DI NOI NON SIANO

Keywords: Heat Flow, Western Mediterranean Sea, Passive margin, Fluid circulation

This thesis has been an adventure, made up of extremes, ups and downs, filled with people, places and ideas.

I would like to thank a number of people who, to a greater or lesser extent, have been part of these three and a half years and have helped me to get to the end. Without them I would still be sailing in lagoon waters, looking for salt pillows in the Penfeld.

First of all, I would like to thank Jean Paul Callot and David Iacopini for agreeing to be examiners for this thesis. You will probably find it long and a bit redundant, but I hope you appreciate the message it carries (and there are lots of figures and annexes!). Thanks also to Bruno Vendeville, Andrea Moscariello and Adriano Viana for accepting to be part of the Jury.

At the top of the list of people to thank is the fuego team who have supported me for more than three years.

Merci Marina, qui a cru en moi dès le début et a continué à croire en moi même dans mes moments de paresse. La facilité avec laquelle tu quittes la paperasse à la vue d'un profil sismique, ton expérience, ton humanité et ta douceur ont fait que je ne me suis jamais senti complètement seul dans ce voyage. Je garderai avec moi le souvenir des longues discussions sur les profils, où tu apportais un regard expert et courageux qui m'a étonné à plusieurs reprises.

Merci de m'avoir soutenu, conseillé et amené jusqu'ici. Merci à Daniel, coeur et tête de cette thèse, pour les discussions interminables, pour m'avoir guidé, réprimandé et défendu. Tu m'as beaucoup appris, sur la vie, la science et la vertu. Je t'en suis reconnaissant. Merci à Mary, pour ton soutien, humanité, rigueur et le naturel avec lequel tu crois en ce que tu fais. Merci à Estelle, pour avoir toujours été là, surtout dans la phase initiale. Ta présence constante, ta joie de vivre et ta rigueur scientifique m'ont été d'un grand secours. Merci beaucoup à Romain pour ton aide et ton soutien précieux dès le premier jour où j'ai atterri en Bretagne. Merci pour les milliers de moments que nous avons partagés ensemble. Je te souhaite le futur que tu mérites.

INTRODUCTION

Salt played a fundamental position in ancient societies for its role in diet, food preservation, manufacture, sealed agreements and mystical and religious myths. Although its value today is negligible, salt was used as a bargaining chip and source of power by many ancient population, most notably the Romans. Just as it can change the fate of a culinary recipe, abreast its presence has a strong impact on the evolution of sedimentary basins. Formed from sodium chloride generally after seawater evaporation, nowadays we can find it buried under kilometres of sediment. Its unique rheological characteristics cause salt to deform at the scale of geological time, giving rise to widely varying shapes and structures. The interest in salt tectonics brought by the scientific community is primarily due to its role in oil exploration: salt participated in the structural traps sealing, it influences reservoir distribution and can act as hydrocarbon migration seal. Most of the world's great hydrocarbons provinces are located in salt-bearing basins.

This thesis leads on the study of salt structures mainly in the Western Mediterranean, where salt was deposited following the Messinian Salinity Crisis. The Western Mediterranean, due to its geodynamic history and the particular salt deposition not involved in passive margin formation, proves to be a privileged area for the study of salt tectonics.

The main objective is to establish whether there is a relationship between the provinces of salt morphologies and the deep crustal segmentation and to establish the causes of this possible coincidence. The observations between the geometric relationships were also sought elsewhere, in the world's most iconic passive margins, with the aim of understanding whether the observations made in the Mediterranean could be extended to other contexts.

In addition, the aim is to analyse most of the elements inducing salt deformation in the Western Mediterranean, in order to understand the role they play in the evolution of structures from their deposition to the present day.

The structure of this thesis has been constructed in such a way as to lead the reader to follow a logical thread of unresolved issues regarding the formation of passive margins, the processes of salt tectonics, and our observations at various salt-bearing margins.

The first chapter, entitled "Passive continental margins", aims to summarise the history and scientific issues in the study of passive continental margins. The thermal regime and its importance in the evolution of a margin will be introduced as well as a structural and geodynamic introduction to the Western Mediterranean and its major unresolved problems.

INTRODUCTION

Le sel a joué un rôle fondamental dans les sociétés anciennes pour son rôle dans l'alimentation, la conservation des aliments, la fabrication, les accords et les mythes mystiques et religieux. Bien que sa valeur soit aujourd'hui négligeable, le sel était utilisé comme monnaie d'échange et source de pouvoir par de nombreuses populations antiques, notamment les Romains. Tout comme il peut changer le destin d'une recette culinaire, sa présence a un fort impact sur l'évolution des bassins sédimentaires. Formé à partir du chlorure de sodium généralement après l'évaporation de l'eau de mer, on le trouve aujourd'hui enfoui sous des kilomètres de sédiments. Ses caractéristiques rhéologiques uniques font que le sel se déforme à l'échelle des temps géologiques, donnant lieu à des formes et des structures très variées. L'intérêt que porte la communauté scientifique à la tectonique salifère est principalement dû à son rôle dans l'exploration pétrolière: le sel participe au scellement des pièges structurels, influence la distribution des réservoirs et peut servir de joint de migration aux hydrocarbures. La plupart des grandes provinces d'hydrocarbures du monde sont en effet situées dans des bassins salifères.

Cette thèse porte sur l'étude des structures salifères principalement en Méditerranée occidentale, où le sel s'est déposé suite à la Crise de Salinité Messinienne. La Méditerranée occidentale, en raison de son histoire géodynamique et du dépôt particulier de sel qui n'est pas impliqué dans la formation de marges passives, s'avère être une zone privilégiée pour l'étude de la tectonique salifère.

L'objectif principal est de vérifier s'il existe une relation entre les provinces des morphologies salifères et la segmentation crustale profonde et d'identifier les causes de cette possible correspondance. Les observations entre les relations géométriques ont également été recherchées ailleurs, parmi les marges passives les plus emblématiques du monde, dans le but de comprendre si les observations faites en Méditerranée pouvaient être étendues à d'autres contextes.

En outre, cette thèse vise à analyser la plupart des éléments induisant les déformations salifères en Méditerranée occidentale, afin de comprendre le rôle qu'ils jouent dans l'évolution des structures depuis leur dépôt jusqu'à nos jours.

La structure de cette thèse a été établie de manière à amener le lecteur à suivre un fil conducteur de questions non résolues concernant la formation des marges passives, les processus de la tectonique salifère, et nos observations sur diverses marges passives.

Le premier chapitre, intitulé " Passive continental margins " vise à résumer l'histoire et les questionnements scientifiques relatifs à l'étude des marges continentales passives. Le régime thermique et son importance dans l'évolution d'une marge seront présentés, ainsi qu'une introduction structurelle et géodynamique à la Méditerranée occidentale et ses principales problèmatiques non résolues.

Le deuxième chapitre, intitulé " Deposition processes and deformation of salt ", vise à résumer les processus de dépôt de sel ainsi que les processus à petite et moyenne échelle impliqués dans sa tectonique. Une grande partie du chapitre se concentre sur le rôle de la température dans la rhéologie et les implications encore inconnues qu'elle peut avoir sur la tectonique régionale salifère. Je conclus par un état des connaissances de la tectonique du sel en Méditerranée occidentale, manquant jusqu'à ce jour d'un apercu regional complet.

Le troisième chapitre, intitulé "Dataset and method", se concentre sur la description des données et des méthodes utilisées tout au long de cette thèse. La première partie traite de la description du jeu de données de sismique réflexion utilisé, des campagnes de réfraction grand-angle utilisées pour la définition de la segmentation crustale et des mesures de flux de chaleur, un outil pour étudier le régime thermique et ses variations locales et régionales. La deuxième partie traite des méthodes, y compris de l'utilisation d'un modèle thermo-cinématique pour tenter d'étudier l'évolution thermique des marges.

Le chapitre 4, intitulé "Salt structures in the Western Mediterranean Sea ", traite de la tectonique salifère en Méditerranée occidentale, de sa relation avec la segmentation crustale, de ses causes et de sa chronologie.

Le chapitre 5, intitulé "Thermal context in the Western Mediterranean Sea ", traite de l'analyse du flux de chaleur et de la tentative de déterminer et de contraindre le régime thermique.

Le chapitre 6, intitulé "Crustal segmentation and salt morphologies in other salt-bearing passive margins", traite de l'analyse de la correspondance entre les morphologies salifères et la segmentation crustale dans certaines des marges passives les plus connues au monde.

Ce manuscrit se termine par les principales conclusions et les perspectives futures liées aux objectifs de ce travail.

Dans le chapitre Annexe-1, le lecteur peut trouver la production scientifique résultant de ce travail de thèse. Dans le chapitre Annexe-2, les mesures HF et leur correction ainsi que des tests supplémentaires utilisant le modèle thermo-cinématique et des tests rhéologiques sont représentés.

CHAPTER 1. PASSIVE CONTINENTAL MARGINS

Distribution and general classification

In this chapter I will review some fundamental aspects of passive margin distribution and their formation, focusing mainly on salt-bearing passive margins. Passive continental margins are the result of the separation between two lithospheric plates and represent the transition between continental and oceanic lithosphere: the lithospheric thinning led to the tear and the formation of the first oceanic crust. They are situated at the borders of the oceanic areas in expansion and are the seat of abundant sedimentation. They are characterised by reduced seismic activity (hence the name passive margin), which suggests tectonic stability during and after the break-up. During the formation of a passive margin, the lithospheric divergence may be linked with rise of volcanic material to the surface. The subdivision of passive margins into groups with same features is an exercise that the scientific community has been engaged since the first models proposed in the late 1970s (e.g. [START_REF] Mckenzie | Some remarks on the development of sedimentary basins[END_REF][START_REF] Wernicke | Uniform-sense normal simple shear of the continental lithosphere[END_REF][START_REF] Geoffroy | Volcanic passive margins[END_REF][START_REF] Péron-Pinvidic | The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view[END_REF][START_REF] Huismans | Depth-dependent extension, two-stage breakup and cratonic underplating at rifted margins[END_REF][START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF]. The various classifications try to group the major characteristics in terms of morphology, sedimentation, volcanism and geodynamic environment.

One of the main characteristics for the subdivision of margins is the presence of volcanic deposits linked to lithospheric break-up. Some margins, called magma-rich passive margins with seaward dipping volcanic reflectors (SDRs) (red segments in fig. 1.1), have recorded an abundant magmatic Not exhaustive and simplification of magma-rich (red segments) and magma-poor (green segments) passive margins (after Geoffroy, 2005;Aslanian, personal communication;[START_REF] Reston | The structure, evolution and symmetry of the magma-poor rifted margins of the North and Central Atlantic: A synthesis[END_REF][START_REF] Haupert | Upper-plate magma-poor rifted margins: Stratigraphic architecture and structural evolution[END_REF]. Yellow stars and hexagons indicate Type I and Type II margin example, respectively (from [START_REF] Huismans | Depth-dependent extension, two-stage breakup and cratonic underplating at rifted margins[END_REF].To note that in some magma-poor passive margins may be present evidences of volcanic deposits.

activity while others, called magma-poor passive margins (green segments in fig. 1.1), have had a magmatic activity considered secondary to the other characteristics. In many cases, these so-called magma-poor passive margins present a great quantity of magmatism (for instance: the Santos [START_REF] Gomes | The outer high of the Santos Basin, southern Sao Paulo Plateau, Brazil: tectonic setting, relation to volcanic events and some comments on hydrocarbon potential[END_REF] and the Sergipe-Alagoas Margins [START_REF] Campos | Geology of the Brazilian continental margin[END_REF]. The difference often lies in the timing of the volcanic implementation: in the so-called magma-poor passive margins, the magmatism occurring generally after a more or less long sequence of sedimentary deposits in the transitional domain. Among the magma-poor margins, some are characterized by the presence of thick evaporites sequence, which deposition is involved into the margin opening. It is worth to note that a classification is often only valid in a first order insight because, for example, among the so-called poor margins the differences are considerable and grouping them in the same generational category can pose problems (e.g. [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Manatschal | Inter-relationship between the tectonic and magmatic evolution of hyper-extended margins and break-up[END_REF]Péron-Pinvidic et al., 2013). In the following paragraph, we will use an alternative classification based on the presence of salt deposits.

To avoid confusion between the different interpretation on the quantity and timing of volcanic material emplacement in these margins, these will be called salt-bearing passive margins.

Magma -SDR type -rich margins

The magma-rich margins (with clearly presence of SDR's) will be briefly dealt with in this thesis given their general incompatibility to the salt basins. In the typical volcanic passive margins formation, with large SDRs emplacement, no evaporitic deposition is involved (e.g. east-Greenland and Pelotas margins). They are associated with large magmatic activity formed by a mantle fusion and accretion of thick magmatic crust during the extension process (e.g. [START_REF] Planke | Crustal structure off Norway, 62 to 70 north[END_REF][START_REF] Geoffroy | Southeast Baffin volcanic margin and the North American-Greenland plate separation[END_REF][START_REF] Geoffroy | Volcanic passive margins[END_REF][START_REF] Quirk | A mechanism for construction of volcanic rifted margins during continental breakup[END_REF][START_REF] Gernigon | Conjugate volcanic rifted margins, seafloor spreading, and microcontinent: Insights from new high-resolution aeromagnetic surveys in the Norway Basin[END_REF][START_REF] Paton | Evolution of seawarddipping reflectors at the onset of oceanic crust formation at volcanic passive margins: Insights from the South Atlantic[END_REF]. The volcanic deposits are seismically imaged as Seaward Dipping Reflectors (SDR's), formed by floodbasalts and tuffs, which are placed in the transitional domain, between the continental and a thick oceanic crust (Fig. 1.2). The continental crust thinning is rather abrupt and coincident to the emplacement of the SDRs. However, the nature of the underlying deeper basement is still a matter of debate. Some examples of well-studied magma rich margins (with presence of SDR's) are the Namibian margin [START_REF] Gladczenko | Namibia volcanic margin[END_REF][START_REF] Bauer | Deep structure of the Namibia continental margin as derived from integrated geophysical studies[END_REF][START_REF] Fernandez | The deep lithospheric structure of the Namibian volcanic margin[END_REF], the Pelotas margin [START_REF] Abreu | Geologic evolution of conjugate volcanic passive margins: Pelotas Basin (Brazil) and offshore Namibia (Africa). Implication for global sea level changes[END_REF][START_REF] Stica | The evolution of rifting on the volcanic margin of the Pelotas Basin and the contextualization of the Paraná-Etendeka LIP in the separation of Gondwana in the South Atlantic[END_REF][START_REF] Blaich | Crustal breakup and continent-ocean transition at South Atlantic conjugate margins[END_REF][START_REF] Chauvet | Conjugate volcanic passive margins in the austral segment of the South Atlantic-Architecture and development[END_REF], the Hatton Bank margin [START_REF] Morgan | A geophysical study of the Hatton Bank volcanic margin: a summary of the results from a combined seismic, gravity and magnetic experiment[END_REF]Elliot and Parson, 2008;Eldholm and Gruen 1994;[START_REF] White | Crustal structure of the Hatton and the conjugate east Greenland rifted volcanic continental margins, NE Atlantic[END_REF] and the conjugated East-Greenland margins [START_REF] Korenaga | Crustal structure of the southeast Greenland margin from joint refraction and reflection seismic tomography[END_REF][START_REF] Geoffroy | Southeast Baffin volcanic margin and the North American-Greenland plate separation[END_REF][START_REF] Callot | Magma flow directions of shallow dykes from the East Greenland volcanic margin inferred from magnetic fabric studies[END_REF][START_REF] Callot | Magma flow in the East Greenland dyke swarm inferred from study of anisotropy of magnetic susceptibility: magmatic growth of a volcanic margin[END_REF]Brooks, 2011) (Fig. 1.1). The thickness and extension of SDR's reflectors is very different among the volcanic margins, suggesting difference in magma generation processes among them (e.g. [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF].

Salt-bearing passive margins (magma-poor passive margins)

The term magma-poor passive margin was defined following the studies in the Alps and Pyrenees [START_REF] Lemoine | The continental margin of the Mesozoic Tethys in the Western Alps[END_REF][START_REF] Manatschal | New models for evolution of magma-poor rifted margins based on a review of data and concepts from West Iberia and the Alps[END_REF][START_REF] Mohn | Unravelling the interaction between tectonic and sedimentary processes during lithospheric thinning in the Alpine Tethys margins[END_REF] and the results of deep sea drilling projects in the conjugate margins of Iberia and Newfoundland (e.g. [START_REF] Boillot | Mesozoic evolution of Ortegal Spur, North Galicia Margin: Comparison with adjacent margins[END_REF][START_REF] Van Avendonk | Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada[END_REF][START_REF] Manatschal | New models for evolution of magma-poor rifted margins based on a review of data and concepts from West Iberia and the Alps[END_REF][START_REF] Péron-Pinvidic | The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view[END_REF]2010). Following these authors, the magma-poor passive margins are dominated by crustal stretching and thinning without the influence of thermal weakening due to intrusions or volcanism. Again, it is worth to note that all the Atlantic margins are affected by local magmatic events, except for the Iberia-Newfoundland system (Aslanian, personal communication). Huismans andBeaumont, (2011, 2014) using numerical approach, proposed to sub-divide the so-called magma-poor margins in two endmember, called Type I and Type II margin styles (Figs. 1.3,1.4).

Figure 1.2. Schematic section of a volcanic passive margin. To note the presence of SDR's all along the relatively narrow transitional domain. Sketch from the Austral segment of the South Atlantic conjugate (From Chauvet et al., 2021).

Following the authors, the Type I margins present some particular features, as indicated in figure 3 (listing numbers following the tag numbers on the figure):

(1) major listric faults which penetrate into the crust;

(2) a narrow areas of crustal thinning;

(3) asymmetric geometry with possible uplift in the rift flanks; (4) break-up of The numbers represent the features described in the text (modified from [START_REF] Huismans | Depth-dependent extension, two-stage breakup and cratonic underplating at rifted margins[END_REF].

Figure 1.3. Sketch of Type I rifted margin and associated profile, below. To note, among other features, the absence of well-developed sag basins and the asymmetric geometry. The natural example of Type I margin is the Iberia-Newfoundland conjugated margin, represented here in its northern sector (Galicia bank-Flemish Cap conjugated margins). The numbers represent the features described in the text (modified from [START_REF] Huismans | Depth-dependent extension, two-stage breakup and cratonic underplating at rifted margins[END_REF].

the crust before the break-up of the mantle; (5) exhumation and exposure of serpentinized continental mantle lithosphere at transitional zone (OCT); (6) little or absent magmatism during rifting; (7) delayed establishment of an oceanic spreading centre and normal oceanic crust production.

A natural example of Type I margins is the Iberia -Newfoundland conjugated margin and an example is given in figure 1.3 (northern sector of the margin, Galicia Bank-Flemish Cap conjugated margin). The discovery of exhumed mantle rocks, together with the discovery of exhumed lower continental rocks, along the Galicia margin (ODP Leg 103 in 1987; [START_REF] Boillot | Ocean-continent boundary off the Iberian margin: a serpentinite diapir west of the Galicia Bank[END_REF][START_REF] Boillot | Mesozoic evolution of Ortegal Spur, North Galicia Margin: Comparison with adjacent margins[END_REF] and the refraction and reflection studies carried out along the Iberian margin have allowed the creation of some rifting models based on this natural example (e.g. [START_REF] Manatschal | New models for evolution of magma-poor rifted margins based on a review of data and concepts from West Iberia and the Alps[END_REF][START_REF] Péron-Pinvidic | The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view[END_REF], which are often used for the description of other margins formation (e.g. [START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF]Zalan, 2015). However, due to their great diversity with features affecting the local setting, no single margin should be taken alone to design a general model. The main issue, and the most difficult one, is to decipher between local and general features on each passive margin and the need for a comparison between many different of them [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF].

The Type II margins (Fig. 1.4) are characterized by some features that make them undoubtedly different from the often referenced example of the Iberia margin (Type 1). These characteristics are:

(A) an ultrawide region of thin continental crust; (B) faulted early syn-rift sedimentary basins; (C) undeformed late syn-rift sediments, also called sag basin; (D) above the sag basin, a sedimentary/evaporitic sequences deposited in shallow water; (E) limited syn-rift subsidence because of replacement of underlying continental mantle by hot asthenosphere which keeps the system in high position until, at least, the break-up; (F) no syn-rift uplifts ; (G) no exhumed mantle, but some possible syn-rift magmatism; (H) lower-crustal regions with seismic velocities consistent with magmatic underplating and (I) a normal magmatic mid-oceanic ridge/crust system established soon after crustal breakup.

These characteristics all fit in the natural examples of margins in the Central segment of South Atlantic, described by different authors [START_REF] Fairhead | Differential opening of the Central and South Atlantic Oceans and the opening of the West African rift system[END_REF][START_REF] Rabinowitz | The Mesozoic South Atlantic Ocean and evolution of its continental margins[END_REF]Nurnberg and Muller, 1991;[START_REF] Eagles | New angles on South Atlantic opening[END_REF]Darros de Matos, 2000;Contrucci et al., 2004a;[START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Torsvik | A new scheme for the opening of the South Atlantic Ocean and the dissection of an Aptian salt basin[END_REF], Evain et al., 2015;Loureiro et al., 2018, Aslanian et al., submitted). Although these margins present some different features, they above all share the presence of a wide sag basin, a large post-rift subsidence and small to no syn-rift flank uplifts. As highlighted in the Angolan margin [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF], the shallow marine conditions which led to the deposition of the salt, deposited above the sag sequences, are late syn-rift/early post-rift, thus confirming that the thinning process seems to maintain the system in an elevated position (at sealevel) until, at least, the break-up [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF][START_REF] Péron-Pinvidic | The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF]. Following Huismans andBeaumont, (2011, 2014) the weak syn-ryft subsidence would require a syn-rift isostatic balance, keep in equilibrium by hot depleted lower cratonic lithosphere. Moreover, the Type I and II models mentioned above are characterized by depthdependent extension, as also suggested by other authors (e.g. [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF]. Although the discussion on the formation of passive margins is still widely open, there seems to be agreement on discarding the uniform lithospheric extension models (see chapter below).

Rifting mechanisms

Since the works of [START_REF] Mckenzie | Some remarks on the development of sedimentary basins[END_REF] and [START_REF] Wernicke | Uniform-sense normal simple shear of the continental lithosphere[END_REF] the authors have investigated the deep structure and the evolution of a passive continental margin as well as the formation of associated sedimentary basins.

Thanks to new seismic techniques and the increasing number of high quality seismic surveys, together with magnetic and gravimetric investigations, the evolution of the proposed rifting models, as well the knowledge of the deep structures, have developed over the years. The improvement of seismic data acquisition allowed the introduction of new concepts in passive margin study. Perhaps the industrial company that most of all has led to a new era in the quality of seismic data is the ION Geophysical (https://www.iongeo.com/). First with the acquisition of the GulfSPAN (2002) surveys all around the world passive margins and then introducing the GX Technology (2004) for the data processing, this company have introduced a deep imaging of a quality that had never before been achieved, especially for the sedimentary layers. An example is given in figure 1.5, where is shown an ultra-deep depth seismic section in the Santos basin (after Zalan, 2013) with special seismic visualisation that highlights the reflectors with greater amplitudes (tecVA_RFASE; Petrobras patented in-house technique). The profile, in depth, highlights very deep crustal reflectors as well as shallower reflectors and is located in the Santos basin, characterized by thick salt from the slope to the deep basin. The base of salt seems to be well-imaged in some points but is hampered when the salt is thicker, in the distal part (Fig. 1.5). The amplitude of the reflectors at the base of salt seem to be accentuated, even if they are probably only artefacts given by salt reflectivity scattering. Several works used these typologies of profiles to study the passive margins, as in the Angola margin [START_REF] Unternehr | Hyper-extended crust in the South Atlantic: in search of a model[END_REF], Santos margin (Zalan et al., 2011, Zalan, 2013), Pelotas margin [START_REF] Stica | The evolution of rifting on the volcanic margin of the Pelotas Basin and the contextualization of the Paraná-Etendeka LIP in the separation of Gondwana in the South Atlantic[END_REF] and East Indian margin (Nemcok et al., 2013). However, the same set of data can produce opposite interpretation for the deep crustal structure, in particular concerning the presence of exhumed mantle or not. This is clearly shown in the Santos Basin between the interpretation of Zalan This is probably due to the fact that even these very good MCS seismic data have a depth limitation: following the well-known rule of thumb (e.g. [START_REF] Yilmaz | Seismic data analysis: Processing, inversion, and interpretation of seismic data[END_REF], the length cable should be equal to z, the depth of the surveying. Below this boundary depth, either artefacts or rough approximation can be created, as it is clearly shown when wide-angle data are available (Evain et al., 2015, figure 21) or in Jequitinhonha Basin (Loureiro et al., 2018 -Figures 13 and 19). 2011) and the absence following [START_REF] Kumar | From oceanic crust to exhumed mantle: A 40 year (1970-2010) perspective on the nature of crust under the Santos Basin, SE Brazil[END_REF].

Some of the main questions raised by scientific community dwell in understanding the continental crust thinning, the lithospheric mantle rising and the role of lower crust, until recently overlooked. Now-days, a meaningful discussion in the models proposed in literature is between the so-called conservative models, where the crustal thinning is not influenced by the interaction of the mantle, and the non-conservative models, where the mantle plays an active role in the rifting and drifting processes.

Conservative models

The first conservative rifting model was developed by [START_REF] Mckenzie | Some remarks on the development of sedimentary basins[END_REF]. The author considered an instantaneous and uniform extension of the lithosphere and crust with passive upwelling of hot asthenosphere. This "pure shear" model assumes a perfectly symmetric rifting where the basin subsidence and the lithosphere heating are solely caused by the stretching (Fig. [START_REF] Mckenzie | Some remarks on the development of sedimentary basins[END_REF] and B) simple shear [START_REF] Wernicke | Uniform-sense normal simple shear of the continental lithosphere[END_REF] models. (1985), which suggested a lithosphere extension accomplished by a gently dipping shear zone (Fig.

1.7B). The shear zone would separates an upper plate consisting of a weakly upper continental crust from a lower plate dominated by a highly deformed lower crust. The innovative aspect was the prediction of spatial variations of crust to mantle thinning which thus imply an asymmetry in the subsidence and history either side of a continental rift zone.

Subsequently, some hybrid models (Lister and Davis, 1983;[START_REF] Davis | Mechanics of fold-and-thrust belts and accretionary wedges[END_REF][START_REF] Davis | Structural evolution of the Whipple and South Mountains shear zones, southwestern United States[END_REF]) have better explained some features observed in passive margins, such as some distinct uplift-subsidence histories (southwest USA). These authors favoured a geometry of evolving shear zones rooted in the crust, at structural levels beneath the brittle-ductile transition. The crust is subjected to asymmetrical deformation while the lithospheric mantle is subjected to symmetrical deformation.

Regarding the shear zone models, the main question was to determinate on which side the upper and lower plate are on. An example are the two diametrically opposed interpretations from the same dataset (Usami et al., 1986 and[START_REF] Castro | The northeastern Brazil and Gabon basins: a double rifting system associated with multiple crustal detachment surfaces[END_REF] shown in [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF]. This example shows that the study of passive margins cannot be separated from the study of the complete conjugate system, where kinematics plays a major role.

Although nowadays the inconsistencies with respect to real cases are high, these models must be acknowledged to have been the precursors of current studies on the evolution and formation of passive margins. Some of the elements and inconsistencies found in the passive margins and discussed in this work derive from a constant relationship with the above mentioned models, which are the starting point for discussion. In the next subchapter I will discuss some fundamental points of modern approaches on the study of passive margins, focusing more on the ongoing discussion about the nonconservative models and the kinematic constraints to keep in mind.

Non-conservative models: new approaches from South Atlantic margins

The models described above, as mentioned, have laid the foundations for the study of passive margins. Nevertheless, some recent observations have changed the vision and the basic concepts of margin formation. The conservative models do not fully explain some features observed in several passive margins, such as: i) the relatively elevated position of the margin until, at least, the break-up, as observed for instance in Gulf of Lion [START_REF] Bache | Evolution Oligo Miocène des marges du micro océan Liguro-Provençal[END_REF][START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF], in the Moroccan margin [START_REF] Labails | Crustal structure of the SW Moroccan margin from wide-angle and reflection seismic data (the Dakhla experiment). Part B-The tectonic heritage[END_REF]; in the Iberian margin (Péron-Pinvidic and [START_REF] Péron-Pinvidic | The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view[END_REF]) and in the central segment of South Atlantic margins [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF], witnessed by sub-aerial evaporites deposition or sub-aerial erosional surfaces.

These observations contrast to the syn-rift subsidence claimed by McKenzie, (1987) and play a major role on the discussion on mantle role;

ii) the absence of numerous widely extensive faults in the margins [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]Karner and Gamboa, 2007;[START_REF] Unternehr | Hyper-extended crust in the South Atlantic: in search of a model[END_REF][START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF], Moulin et al., 2015, Loureiro et al., 2018), key feature in the "pure" shear model. Although some listric faults and some tilted blocks are observed, they are structures of secondary importance that do not characterize the margins. This observation implies a reduced extension of the system compared to what was thought until now;

iii) the anomalous heat flow in the transitional domain [START_REF] Dupré | Integrated tectonic study of the South Gabon Margin. Insights on the rifting style from seismic, well and gravity data analysis and numerical modelling[END_REF][START_REF] Dupré | Seafloor geological studies above active gas chimneys off Egypt (Central Nile Deep Sea Fan)[END_REF][START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF][START_REF] Lucazeau | Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden[END_REF], which suggests a different deep mantle segmentation between the different crustal domains. The anomalies can be persistent in time, well after the break-up, as highlighted by some authors [START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF], Goutorbe et al., 2008a, 2011).

iv) the presence of a strong reflector in the lower crust and the interpretation of exhumed lower crust and/or serpentinized mantle (e.g. Hoffman and Reston;1992;[START_REF] Boillot | Ocean-continent boundary off the Iberian margin: a serpentinite diapir west of the Galicia Bank[END_REF][START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Péron-Pinvidic | The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view[END_REF][START_REF] Jolivet | Continental breakup and the dynamics of rifting in back-arc basins: The Gulf of Lion margin[END_REF][START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF][START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF]Louriero et al., 2018;[START_REF] Gillard | The role of serpentinization and magmatism in the formation of decoupling interfaces at magma-poor rifted margins[END_REF]Lagabrielle et al., 2019;[START_REF] Aslanian | Deep structure of the Pará-Maranhão/Barreirinhas passive margin in the Equatorial Atlantic (NE Brazil)[END_REF]. All these features seem to rule out a volume conservation during rifting processes and indicate a physical interaction between mantle and crust.

Another fundamental issue was raised by [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF] and [START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF], concerning the horizontal movement and the kinematic reconstruction in a passive margins system, implying the need to study together both sides of the system. Following the authors, the problem in conservative models is purely geometrical as if no lower crust/mantle interactions is involved, the thinning process of continental crust can be directly converted in horizontal movement because the final volume of continental crust would be the same of the initial volume, before the stretching. Figure 1.8 shows the conceptual (conservative) and kinematic approaches, as shown in [START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF]. Using the conjugated Angola and Espirito Santo continental passive margins as cases study (Contrucci et al., 2004a;[START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Unternehr | Hyper-extended crust in the South Atlantic: in search of a model[END_REF], the authors defined the part 1 as upper continental crust and part 2 as allochthonous domain, which can be composed by exhumed lower crust, serpentinized upper mantle, atypical oceanic crust or intruded continental crust. Following the conservative models constraints and the initial crust thickness in South Atlantic, the horizontal movement expected would be as great as 240 km [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF]. If some parts of intermediate domain would be composed by serpentinized mantle (as claimed, for instance, by [START_REF] Unternehr | Hyper-extended crust in the South Atlantic: in search of a model[END_REF], this amount would be even greater. The kinematic constraints situation (figure 1.8b) shows the tightest situation given by reconstruction by [START_REF] Moulin | A new starting point for the South and Equatorial Atlantic Ocean[END_REF], which implies only 100 km of horizontal movement.

To comply with kinematic constraints, [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF] proposed two options (Fig. 1.8b), whether the part is of continental or of non-continental nature. In both cases, a large amount of lower crust is missing and the thinning process seems to be depth-dependent and mainly concerns to the lower part of the continental crust. As described also by [START_REF] Huismans | Symmetric and asymmetric lithospheric extension: Relative effects of frictional-plastic and viscous strain softening[END_REF], 2008, 2011, 2014) and others [START_REF] Zuber | Lithospheric necking: a dynamic model for rift morphology[END_REF][START_REF] Nagel | Control of rheological stratification on rifting geometry: a symmetric model resolving the upper plate paradox[END_REF][START_REF] Weinberg | Mantle detachment faults and the breakup of cold continental lithosphere[END_REF][START_REF] Kusznir | Continental lithospheric thinning and breakup in response to upwelling divergent mantle flow: application to the Woodlark, Newfoundland and Iberia margins[END_REF] the mechanisms involved in the rifting are depth-dependent, which thus involved a buoyant lower continental lithosphere laterally and underplated the rift axis ahead of the upwelling asthenosphere (for mechanisms details see Huismans and[START_REF] Huismans | Depth-dependent extension, two-stage breakup and cratonic underplating at rifted margins[END_REF]Beaumont and[START_REF] Beaumont | Effect of depleted continental lithosphere counterflow and inherited crustal weakness on rifting of the continental lithosphere: General results[END_REF].

Figure 1.8. Conservative model versus kinematic approaches describing the continental crust thinning process. A) In the conceptual approach (conservative) model the area of continental crust is equal to the initial area, therefore the continental crust thinning can be converted in the horizontal movement. B) In the kinematic approach the horizontal movement is given by kinematic reconstruction. A wide thinned basin remains in that case. The quantity of missing lower continental crust depends on the nature of the allochthonous domain (see text). The sketch comes from Angola and Espirito Santos conjugated margins case study (after [START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF].

Following the kinematic reconstructions of [START_REF] Moulin | A new starting point for the South and Equatorial Atlantic Ocean[END_REF] and analysing seismic and gravity profiles in the South Atlantic margins, [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF] proposed three main phases of thinning process (Fig. 1.9). The first phase is characterized by extension with some possible tilted block. The second phase is characterized by the major extension process, concomitant with the exhumation. Evaporites deposition and continental to lacustrine sedimentation witness the shallow environment and the relatively high position of the system. The break-up and spreading occur during the last phase. Another important feature depicted in passive margins and highlighted by the authors is the purely vertical subsidence of the sag basin, leaving the basin closed to sea-level (continental sedimentation), and which drastically increased after the break-up. This vertical collapse, also observed in the Gulf of Lion [START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF][START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF], probably means that in the allochthonous part the exchange between lower crust and/or mantle is rapid [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF].

The allochthonous domain can be defined as the part created by horizontal movement (exhumed mantle and/or lower crust, intruded continental crust..) (Type III in figure 1.9) while the Figure 1.9. The three phases of thinning processes described in [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF] considering seismic, gravity and kinematic reconstructions data (from [START_REF] Moulin | Etude géologique et géophysique des marges continentales passives: exemple du Zaïre et de l'Angola[END_REF]. To note the vertical subsidence of the sag basin and the relatively shallow position of the system before the break-up.

autochthonous domain (Type I and Type II in figure 1.9) is made by upper continental crust. The autochthonous domain can be defined as the original part of continental thinned crust while the allochthonous as the part resulting from the exhumation phase.

Hypothesis on heat mantle segmentation

I have so far briefly described some of the most important issues related to the formation of passive margins and their evolution. As explained above, there are still many obscure points in their understanding, such as the comprehension of the continental crust thinning process, the syn-rift significance and how, where and when the oceanic crust breaks-up.

The key role of mantle [START_REF] Péron-Pinvidic | The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view[END_REF][START_REF] Huismans | Depth-dependent extension, two-stage breakup and cratonic underplating at rifted margins[END_REF] and lower continental crust [START_REF] Bott | Evolution of young continental margins and formation of shelf basins[END_REF][START_REF] Huismans | Depth-dependent extension, two-stage breakup and cratonic underplating at rifted margins[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF] in passive margin seems to be confirmed by several authors. Moreover, the structural morphology diversity, the high position of the system and the high heat flow in the transitional domain questioned the role of the heat mantle segmentation in the passive margin. A thermal segmentation, both on oceanic (e.g. [START_REF] Sahabi | Morphological reorganization within the Pacific-Antarctic discordance[END_REF][START_REF] Vlastélic | Chemical systematics of an intermediate spreading ridge: The Pacific-Antarctic Ridge between 56 S and 66 S[END_REF][START_REF] Ondréas | Variations in axial morphology, segmentation, and seafloor roughness along the Pacific-Antarctic Ridge between 56 S and 66 S[END_REF] and transitional domain (e.g. [START_REF] Dupré | Seafloor geological studies above active gas chimneys off Egypt (Central Nile Deep Sea Fan)[END_REF][START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Goutorbe | Global heat flow trends resolved from multiple geological and geophysical proxies[END_REF], seems henceforth to be realistic and could have an influence on the sedimentary column above the basement, through fluid circulations or thermal convection. Below, I will introduce some of the main issues about the heat flow in passive margins, focusing on the heat flow differences between the crustal natures. The heat flow in the transitional domain is still doubtful, as well as the crustal nature of this domain.

Understanding the thermal regime in this area can therefore give information on the nature of the crust, to which the thermal regime is closely linked.

Evaporitic deposits, as we will see later in this manuscript, are a peculiarity in some passive margins. In these cases, their deposits cover most of the deep margin domains, playing a significant role in their evolution. One of the main objectives of this thesis is to understand the relationship between crustal segmentation and the deformation of evaporitic systems. If, as mentioned, the crustal segmentation is linked to the heat segmentation, these would exert an influence on the salt deposits.

Salt deformation could then be related to the deep crustal nature and could provide valuable information about its structure. The connection between deep and surface processes in the passive margins is a fundamental task as it could indirectly give us information about the deep structures.

Salt, due to its deformation characteristics, could be the key element in this relationship.

1.3 Thermal regime in passive continental margins

Thermal regime of the oceanic crust

The seafloor heat flow is highest at mid-ocean ridges and decreases with distance (e.g. Von [START_REF] Von Herzen | Heat flow through the eastern Pacific Ocean floor[END_REF][START_REF] Langseth | Crustal structure of the mid-ocean ridges: 5. Heat flow through the Atlantic Ocean floor and convection currents[END_REF]. It has been shown that a plate cooling model can well describe the first order heat flow and subsidence evolutions in the oceans [START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF]Parson and Sclater, 1977).

Considering that the PSM (Parsons-Sclater-Model, 1977) overestimated depth and underestimates the heat flow for old seafloor, [START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF] derived and alternative model (GDH1) using as a case study data from North Pacific and northwest Atlantic and finding a better fit to depth and heat flow values (Fig. 1.10). Historically, two types of lithospheric cooling models yield reasonable fits to bathymetry data and assume either a constant basal temperature (plate model: [START_REF] Mckenzie | Some remarks on heat flow and gravity anomalies[END_REF][START_REF] Parsons | An analysis of the variation of ocean floor bathymetry and heat flow with age[END_REF][START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF][START_REF] Carlson | On modeling the thermal evolution of the oceanic upper mantle: An assessment of the cooling plate model[END_REF][START_REF] Mckenzie | Thermal structure of oceanic and continental lithosphere[END_REF] or constant lithospheric heat flow (Chablis model [START_REF] Crough | Thermal model of oceanic lithosphere[END_REF][START_REF] Doin | Thermal evolution of the oceanic lithosphere: an alternative view[END_REF][START_REF] Goutorbe | Combining seismically derived temperature with heat flow and bathymetry to constrain the thermal structure of oceanic lithosphere[END_REF]. They use several types of data, mainly including subsidence and heat flow. However, in all models, the heat flow values observed in young oceanic crust are lower than those observed in young oceanic crust predicted from lithospheric cooling models. The lower values are often attributed to ventilated hydrothermal circulation recharge and discharge at crustal outcrops or where the sedimentary thickness is thin (e.g. [START_REF] Lister | On the thermal balance of a mid-ocean ridge[END_REF][START_REF] Langseth | The hydrogeological regime of isolated sediment ponds in mid-oceanic ridges[END_REF][START_REF] Hasterok | Oceanic heat flow: Implications for global heat loss[END_REF][START_REF] Hasterok | A heat flow based cooling model for tectonic plates[END_REF]. [START_REF] Hasterok | Oceanic heat flow: Implications for global heat loss[END_REF] therefore considered only measures with >400 m of sedimentary cover and located >60 km from the nearest seamount and they tried to minimize the hydrothermal effect finding a better fit with the HF measured data (Fig. 1.11). At oceanic ridges, [START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF] and Parson and Sclater, (1977). Points are measured heat flow and lines are modelled ones. The plot on the left represents the heat flow variations compared to the age whilst the plot on the right the ocean depth against the age (modified after [START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF].

fluid circulations have proven to be efficient mechanisms of heat redistribution (e.g. [START_REF] Fisher | Models of hydrothermal circulation within 106 Ma seafloor: Constraints on the vigor of fluid circulation and crustal properties, below the Madeira Abyssal Plain[END_REF][START_REF] Gal | Heat flow, morphology, pore fluids and hydrothermal circulation in a typical Mid-Atlantic Ridge flank near Oceanographer Fracture Zone[END_REF], especially in old oceanic domain (> 65 Ma). Nevertheless, even in the latter model improved by filtering and new heat flow data, an uncertainty persists at young ages (<25 Ma), which could be due to a not complete thermal stabilisation of hydrothermal processes, uncertainties in sediment thickness or a deep thermal disequilibrium, probably mantle-like, not yet well understood.

The plate cooling models proposed so far show a good match between model-measured data for relatively old oceanic crust (>50 Ma). For young oceanic crust, as may be the case in the Western Mediterranean Sea, the models do not perfectly fit the measurements, leaving still some doubt about their truthfulness and possibility of use. Young oceanic crust is assumed to be far from thermal equilibrium and therefore more prone to deep mantle influences related to its formation or hydrothermal circulation. Furthermore, as we shall see later, the oceanic crust in deep Western Mediterranean basins does not appear to have the thicknesses and seismic velocities (see references below) of typical Atlantic oceanic crust (e.g. [START_REF] White | Oceanic crustal thickness from seismic measurements and rare earth element inversions[END_REF].

Thermal regime of the rifted continental domain (thinned continental and transitional crust)

Continental margins are the transition between ocean and continent. The thermal regime of the margin shows both influence resulting from thin lithosphere and radioactive elements. The thermal [START_REF] Hasterok | Oceanic heat flow: Implications for global heat loss[END_REF] after filtering results with >400 m sediment cover and more than 60 km far away to the nearest seamount. a) Heat flow versus age. Open circles contain <10 sites, full circles >10 sites. Squares are from [START_REF] Hasterok | Oceanic heat flow: Implications for global heat loss[END_REF] data. In grey the standard deviation. b) Number of available data before (grey) and after (black) filtering.

regime of this area is classically modelled according to rifting and crustal thinning described in [START_REF] Mckenzie | Some remarks on the development of sedimentary basins[END_REF]. This model assumes an instantaneous heating associated to the initial tectonic subsidence and a second phase of cooling that goes with the thermal subsidence. The model assumes only vertical heat transfer (1D), without taking into consideration the possible lateral physical exchanges and flows. Moreover, the model assumes that the lithosphere, and its thermal state, is passively tending towards its initial state (pre-rift), while crust remains thinned. After approximately 60 Ma, the thermal regime in this model returns close to its initial state [START_REF] Mckenzie | Some remarks on the development of sedimentary basins[END_REF][START_REF] Hellinger | Some comments on two-layer extensional models for the evolution of sedimentary basins[END_REF][START_REF] Cochran | Effects of finite rifting times on the development of sedimentary basins[END_REF][START_REF] Buck | Thermal consequences of lithospheric extension: pure and simple[END_REF]. Different ameliorations of this model has been worked to include 2D effects (lateral heat), heat production, different mantle and crustal thinning, etc.

(example in fig. 1.12). Similarly to the oceanic plate cooling models, heat flow decrease with age (Fig. 1.12) showing a strong decrease in the first 50 Ma and a stabilisation thereafter. Nevertheless, several compilation (black squares in fig. 1.12) highlights higher measured heat flow with respect the model: the heat flow is hence perturbed at the surface.

For example, [START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF], in the young passive margin in Gulf of Aden, showed clearly contrasted thermal regime in the crustal domains. The oceanic and OCT domain has a similar elevated heat flow which drops, abruptly, in the continental domain near the proximal margin (Fig. , (1978) to account heat production for different stretching factors (1.25, 2.00, 3.50). The red line shows the plate cooling oceanic model (from [START_REF] Jaupart | Treatise on Geophysics. Temperatures, Heat and Energy in the Mantle of the Earth[END_REF].

1.13). The authors explained this drastically change as the result of a thermal anomaly, which persisted after the break-up, made by ocean-continent edge-driven convection at mantle level.

The heat flow in OCT domains is generally higher than expected, even in more mature margins, such as: Labrador margin (Canada) [START_REF] Goutorbe | Heat flow of the eastern Canadian rifted continental margin revisited[END_REF]Mareschal et al., 2000a); Gulf of Guinea [START_REF] Lucazeau | High-resolution heat flow density in the lower Congo basin[END_REF]; Senegal (Latil-Brun and Lucazeau, 1988); South Africa (Goutorbe et al., 2008a); Gulf of Mexico [START_REF] Husson | Thermal regime of the NW shelf of the Gulf of Mexico. Part A: Thermal and pressure fields[END_REF][START_REF] Nagihara | Geothermal heat flow in the northeast margin of the Gulf of Mexico[END_REF]; South West India and Makran (Calves et al., 2010;[START_REF] Rao | Estimates of geothermal gradients and heat flow from BSRs along the Western Continental Margin of India[END_REF]; Mozambique [START_REF] Nyblade | Heat flow across the East African plateau[END_REF]; Australian margins [START_REF] Goutorbe | Surface heat flow and the mantle contribution on the margins of Australia[END_REF] and Iberia margin [START_REF] Louden | Variations in heat flow across the oceancontinent transition in the Iberia abyssal plain[END_REF]. Several causes to explain an higher heat flow in OCT domain are argued by the authors, such as high heat production in the sediments [START_REF] Mckenna | Radiogenic Heat Production in Sendimentary Rocks of the Gulf of Mexico Basin, South Texas[END_REF] or in the crust [START_REF] Louden | Variations in heat flow across the oceancontinent transition in the Iberia abyssal plain[END_REF][START_REF] Nagihara | Geothermal heat flow in the northeast margin of the Gulf of Mexico[END_REF], volcanism [START_REF] Rao | Estimates of geothermal gradients and heat flow from BSRs along the Western Continental Margin of India[END_REF], fluid circulation [START_REF] Deming | Catastrophic release of heat and fluid flow in the continental crust[END_REF][START_REF] Reiter | Estimates of terrestrial heat flow in offshore eastern Canada[END_REF] or mantle convective circulation [START_REF] Armitage | The instability of continental passive margins and its effect on continental topography and heat flow[END_REF]Grigne et al., 2007;[START_REF] Guillou-Frottier | Heat flow variations in the Grenville Province, Canada[END_REF][START_REF] King | Edge-driven convection[END_REF]. Goutorbe et al., (2008a) calculated the mantle contributions of surface heat flow in the Australian margins and conclude that an increase in mantle contribution is needed to explain the high oceanic domain heat flow values.

Figure 1.13. Seismic profile and heat flow measurements in the Gulf of Aden, after [START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF]. The grey area corresponds to the range of values expected for the age of the oceanic floor according to [START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF]. Yellow colour represents sediment thickness. To note the high heat flow in the OCT domain, similar to those measured in the oceanic domain.

At local scale, several mechanisms can be the source of surface HF variations. The hydrothermal circulation of fluids can be a strong source of perturbation, in every crustal domains of a passive margin (e.g. Poort and Polyanski, 2002;[START_REF] Poort | Absence of a regional surface thermal high in the Baikal rift; new insights from detailed contouring of heat flow anomalies[END_REF][START_REF] Grevemeyer | Fluid flow through active mud dome Mound Culebra offshore Nicoya Peninsula, Costa Rica: evidence from heat flow surveying[END_REF][START_REF] Lucazeau | Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden[END_REF]. Fluids can be sourced from deeper overpressured layers, be part of regional fluid circulation systems or as a consequence of magmatic intrusions. To detect the fluids perturbation the HF are often associated with distinct geochemical signature [START_REF] Berndt | Focused fluid flow in passive continental margins[END_REF][START_REF] Campbell | Hydrocarbon seep and hydrothermal vent paleoenvironments and paleontology: Past developments and future research directions[END_REF]. Fluid circulation can also be depicted by morphological manifestations in bathymetry or shallow seismic, often associated with thermal anomalies. Some of these phenomena are pockmarks (e.g. [START_REF] Loncke | Mud volcanoes, gas chimneys, pockmarks and mounds in the Nile deep-sea fan (Eastern Mediterranean): geophysical evidences[END_REF], mud volcanoes [START_REF] Camerlenghi | Geological evidence for mud diapirism on the Mediterranean Ridge accretionary complex[END_REF][START_REF] Mascle | Distribution and geological control of mud volcanoes and other fluid/free gas seepage features in the Mediterranean Sea and nearby Gulf of Cadiz[END_REF], gas bubbles in the water column [START_REF] Dupré | Seafloor geological studies above active gas chimneys off Egypt (Central Nile Deep Sea Fan)[END_REF] and fluids/gas vents in the sedimentary column. The heat refraction as a result of lateral thermal conductivity variation can be another major source of perturbation. Basement highs and salt structures are an example of heat refraction; salt structures strongly alter the local distribution of heat flow, due to the high thermal conductivity of salt (e.g. [START_REF] Nagihara | High heat flow anomalies over salt structures on the Texas continental slope, Gulf of Mexico[END_REF].

Following the discovery of exhumed mantle in the Iberian margin [START_REF] Boillot | Mesozoic evolution of Ortegal Spur, North Galicia Margin: Comparison with adjacent margins[END_REF] and the passive margin formation models that followed (e.g. [START_REF] Boillot | The formation of passive margins: constraints from the crustal structure and segmentation of the deep Galicia margin, Spain[END_REF][START_REF] Manatschal | New models for evolution of magma-poor rifted margins based on a review of data and concepts from West Iberia and the Alps[END_REF][START_REF] Péron-Pinvidic | The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view[END_REF], the transitional crust has been interpreted as formed by exhumed, possibly serpentinized mantle [START_REF] Boillot | Undercrusting by serpentinite beneath rifted margins[END_REF]. This is the case, for example, for the margins of the Norwegian Sea (Rupke et al., 2013); Pyrenees (e.g. [START_REF] Lagabrielle | Mantle exhumation, crustal denudation, and gravity tectonics during Cretaceous rifting in the Pyrenean realm (SW Europe): Insights from the geological setting of the lherzolite bodies[END_REF]; Vietnam [START_REF] Savva | Seismic evidence of hyper-stretched crust and mantle exhumation offshore Vietnam[END_REF]; Tyrrhenian [START_REF] Prada | Mantle exhumation and sequence of magmatic events in the Magnaghi-Vavilov Basin (Central Tyrrhenian, Italy): New constraints from geological and geophysical observations[END_REF]; Gulf of Lion [START_REF] Jolivet | Continental breakup and the dynamics of rifting in back-arc basins: The Gulf of Lion margin[END_REF]; Ligurian (Dannoswki et al., 2020) and Gulf of Aden [START_REF] Autin | Continental break-up history of a deep magma-poor margin based on seismic reflection data (northeastern Gulf of Aden margin, offshore Oman)[END_REF]. Associated to the mantle exhumation, serpentinized continental mantle has been observed along detachment faults in the OCT [START_REF] Manatschal | New models for evolution of magma-poor rifted margins based on a review of data and concepts from West Iberia and the Alps[END_REF]. The meteoric fluids probably penetrated the basement and participated in the exhumation phase during rifting [START_REF] Cannat | Oceanic corrugated surfaces and the strength of the axial lithosphere at slow spreading ridges[END_REF]. During the exhumation phase, the mantle peridotites at the outcrop are hydrated and form serpentine. Hydrothermal processes have been identified on the margins of Norway and California [START_REF] Berndt | Rifting under steam-How rift magmatism triggers methane venting from sedimentary basins[END_REF] or inthe Gulf of Aden [START_REF] Lucazeau | Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden[END_REF] by the particular structures of the seabed, the chaotic facies observed in seismic and the seismic velocities. The serpentinization is an exothermic geochemical process. Delescluse and Chamot-Rooke, (2008) explained a higher heat flow of about 25-30 mW/m2 (reached after 2 to 6 Ma) as the consequence of a serpentinization pulse in the Central Indian Basin. Serpentinization may therefore have produced heat on the one hand and promoted hydrothermal circulation on the other, thus inducing heat loss from the basement. These processes, however, appear to be related to the early phases of mantle exhumation and oceanic break-up and would no longer be visible in the more mature margins [START_REF] Louden | Variations in heat flow across the oceancontinent transition in the Iberia abyssal plain[END_REF], which are buried by thick sedimentation [START_REF] Lucazeau | Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden[END_REF].

Western Mediterranean Sea

The Western Mediterranean Sea represents a unique natural laboratory to study the interaction between deep and surficial processes and for addressing some fundamental questions about margin formation [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF][START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF][START_REF] Leroux | Post-rift evolution of the Gulf of Lion margin tested by stratigraphic modelling[END_REF].

In this work, I will analysed the relationship between crustal nature and salt deformation in

Western Mediterranean Sea because it is characterised by a set of features that make it a privileged area of study, such as: i) an area in which the plate kinematic reconstructions are relatively wellconstrain (Liguro-Provençal basin) and another in which models are contradictory (Algerian basin),

ii) an important amount of tectonic and stratigraphic data and studies available, iii) a young salt deposition, which preclude an evolved salt tectonics characterized by several deformation phases, overlying a thick sedimentary layers iv) a relatively stable tectonic activity.

The Cenozoic opening of the Western Mediterranean in an overall convergence context between Africa and Eurasia is closely linked to the creation of the Alpine chains, which surround it (e.g. [START_REF] Doglioni | The western Mediterranean extensional basins and the Alpine orogen[END_REF][START_REF] Gelabert | A new proposal for the late Cenozoic geodynamic evolution of the western Mediterranean[END_REF][START_REF] Carminati | Geodynamic evolution of the central and western Mediterranean: Tectonics vs. igneous petrology constraints[END_REF]. Since Late Oligocene, the slab [START_REF] Jolivet | Lithospheric-scale geodynamic context of the Messinian salinity crisis[END_REF], 2009[START_REF] Roure | Alpine inversion of the North African margin and delamination of its continental lithosphere[END_REF]and Leroux et al., 2019).

retreat is predominant in the formation of back-arc basins, such as the Alboran, the Liguro-Provençal, the Tyrrhenian and the Aegean basins [START_REF] Jolivet | Mediterranean extension and the Africa-Eurasia collision[END_REF]. The Western Mediterranean basins are essentially different from the eastern Mediterranean, where the remnants of Mesozoic oceanic crust (Neothethys) are probably preserved below the sediments (Fig. 1.14) (de [START_REF] Voogd | Twoship deep seismic soundings in the basins of the Eastern Mediterranean Sea (Pasiphae cruise)[END_REF][START_REF] Ben-Avraham | Crustal structure of the Levant Basin, eastern Mediterranean[END_REF]. Small part of Tyrrhenian, the central part of the Provençal basin and some parts of the Algerian basin are probably floored by oceanic crust while the remaining submarines part are composed by continental crust. The continental crust is formed by Palaeozoic and pre-Palaeozoic rocks deformed by Caledonian and Variscan orogenic cycles [START_REF] Carminati | Geodynamic evolution of the central and western Mediterranean: Tectonics vs. igneous petrology constraints[END_REF] or by Mesozoic to Cenozoic Alpine orogenic cycle [START_REF] Guennoc | Histoire géologique du Golfe du Lion et cartographie du rift oligo-aquitanien et de la surface messinienne[END_REF]. The Liguro-Provençal basin is at present day composed by the Ligurian Sea, the Gulf of Lion and the Western Sardinian margins and the deep Provençal basin (Fig. 1.14). The Algerian basin can be sub-divided in three structural domains, called the East, the Central and the West Algerian basins [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF].

Geodynamical context and ongoing controversies

The opening of the Alpine Tethys resulted from the break-up of Pangea in the late Palaeozoic [START_REF] Frizon De Lamotte | The southernmost margin of the Tethys realm during the Mesozoic and Cenozoic: Initial geometry and timing of the inversion processes[END_REF]. The expansion of Central Atlantic, starting in the Sinemurian [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF], caused a lateral sinistral movement between Iberia and Africa, leading the opening of the western branch of the Tethyan Ocean. The convergence between Africa and Europe, started after the change of African plate trajectory (Upper Cretaceous; ~80 Ma after [START_REF] Dewey | Plate tectonics and the evolution of the Alpine system[END_REF], led to the closure of the Tethys Alpine and the consequent subduction and collision between the two plates [START_REF] Olivet | Cinematique des plaques et paleogeographie; une revue[END_REF][START_REF] Olivet | La cinématique de la plaque ibérique[END_REF]Dewey et al., 1989;[START_REF] Ricou | Tethys reconstructed: plates, continental fragments and their Boundaries since 260 Ma from Central America to South-eastern Asia[END_REF]Rosenbaum et al., 2002a;[START_REF] Cavazza | The Mediterranean area and the surrounding regions: active processes, remnants of former Tethyan oceans and related thrust belts[END_REF][START_REF] Schettino | Tectonic history of the western Tethys since the Late Triassic[END_REF]. The initiation of the Africa-Europe convergence have determined the whole Cenozoic evolution history of the Western Mediterranean. During the Oligocene, both extension and compression simultaneously affected the Mediterranean area, leading to: i) a significant continental extension in the Alboran and northern Tyrrhenian basins, with oceanisation in the Liguro-Provençal, Algerian, and southern Tyrrhenian basins, and ii) the formation of mountain ranges in the Mediterranean region, such as the Alps, the Maghrebides, the Apennines, and the Betico-Rif Cordillera (Fig. 1.14). The rifting process in Liguro-Provençal basin is the result of the counter clockwise rotation of the Corso-Sardinia block with respect to the Ibero-European plate since the Late Eocene (Priabonian,33.7 Ma). This range period, dated thanks to the sediments drilled in the Gulf of Lion [START_REF] Gorini | Géodynamique d'une marge passive: le Golfe du Lion (Méditerranée occidentale[END_REF], is followed by a drifting period dated from 19 to 15-16 Ma, according to paleomagnetic data and kinematic reconstructions [START_REF] Vigliotti | When did Sardinia stop rotating? New palaeomagnetic results[END_REF][START_REF] Olivet | La cinématique de la plaque ibérique[END_REF][START_REF] Speranza | Age of the Corsica-Sardinia rotation and Liguro-Provençal Basin spreading: new paleomagnetic and Ar/Ar evidence[END_REF][START_REF] Gattacceca | Miocene rotation of Sardinia: New paleomagnetic and geochronological constraints and geodynamic implications[END_REF][START_REF] Advokaat | Eocene rotation of Sardinia, and the paleogeography of the western Mediterranean region[END_REF]. Although the general mechanisms of margin formation are widely accepted in literature, there is still a debated on amplitude and timing of the rotation and in the extent of oceanic crust [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF].

The kinematic reconstructions of the Western Mediterranean differ with regard to the age of the onset of convergence and subduction between Africa (and its northern promontory Adria) and Iberia.

These differences are the result of different reconstructions interpretations of marine magnetic anomalies and Iberia plate reconstruction with respect to the Atlantic Ocean. The choice to include or omit the paleo-magnetic data from Iberia and the different geological and geophysical interpretations of the Pyrenees formation led to different reconstruction of the Western Mediterranean Sea evolution (see for instance Dewey et al., 1989;[START_REF] Olivet | La cinématique de la plaque ibérique[END_REF]Rosenbaum et al., 2002a;Sibuet et al., 2004). The first issue still unsolved concerns the lateral extent of the subduction zone at the onset of rollback, with two main options regarding the opening direction of the Algerian basin: a dominant N-S or a dominant E-W opening (Figs. 1.15 and 1.16).

The models proposed dealt with stretching and fragmentation of the original relics which are now distributed over four regions: the Alboran region (Betics, Spain, Rif), the Kabylides (Algeria), the Peloritani mountains (Sicily) and the Calabria, binned in the conceptual AlKaPeCa terranes (Bouillin et al., 1986) (Fig. 1.16).

The first school of thought (Scenario 1; fig. 1.15A) assumes a presently inactive slab under the North African margin and a minor rollback in the Gibraltar region accommodated in the Alboran domain (~200 km) [START_REF] Gueguen | On the post-25 Ma geodynamic evolution of the western Mediterranean[END_REF][START_REF] Carminati | The role of slab detachment processes in the opening of the western-central Mediterranean basins: some geological and geophysical evidence[END_REF]Frizon de Lamotte et al., 2000;[START_REF] Wortel | Subduction and slab detachment in the Mediterranean-Carpathian region[END_REF][START_REF] Gelabert | A new proposal for the late Cenozoic geodynamic evolution of the western Mediterranean[END_REF][START_REF] Faccenna | Lateral slab deformation and the origin of the western Mediterranean arcs[END_REF]Rosenbaum and Lister, 2004b;[START_REF] Schettino | Plate kinematics of the Western Mediterranean region during the Oligocene and Early Miocene[END_REF][START_REF] Jolivet | From mantle to crust: Stretching the Mediterranean[END_REF]. In this scenario, the slab started to roll back from Gibraltar to Corsica and the subduction started along an E-W trending collisional zone. Figure 1.16A illustrates the N-S scenario and it shows the position of the AlKaPeCa blocks at 20 Ma, just (after Van Hinsbergen et al., 2014).

before the oceanisation in the Liguro-Provençal basin, and at 16 Ma, time in which the Corso-Sardinian block stopped and the Kabylides reached the North Algerian margin. The reconstruction of the N-S scenario requires a position of the Alboran block, at 20 Ma, further to the south-west, which will then move westward of about 200 km to occupy the current position.

The second hypothesis follows a E-W opening direction generate from the Hannibal High area, considered as a ridge centre [START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF](Mauffret et al., , 2007a;;[START_REF] Camerlenghi | Morphogenesis of the SW Balearic continental slope and adjacent abyssal plain, Western Mediterranean Sea[END_REF], between 16 and 8 Ma. The opening would be associated with slab rupture along and removal of slab under the North African margin (Scenario 2; fig. 1.15B) [START_REF] Gutscher | Evidence for active subduction beneath Gibraltar[END_REF][START_REF] Spakman | A tomographic view on western Mediterranean geodynamics[END_REF][START_REF] Duggen | Magmatic evolution of the Alboran region: The role of subduction in forming the western Mediterranean and causing the Messinian Salinity Crisis[END_REF][START_REF] Duggen | Post-collisional transition from subduction-to intraplate-type magmatism in the westernmost Mediterranean: evidence for continental-edge delamination of subcontinental lithosphere[END_REF]. In this case the roll back slab was confined to the Balearic-Corso-Sardinian segment and the Alboran domain would migrated towards the west (600-700 km; Van Hinsbergen et al., 2014) , generating a left-lateral deformation along the Western and Central Algerian margins and right-lateral deformation along the Balearic Promontory [START_REF] Camerlenghi | Morphogenesis of the SW Balearic continental slope and adjacent abyssal plain, Western Mediterranean Sea[END_REF]. The subduction initiation in the Pliocene would be along a fossil transform (subduction transform edge propagator (STEP)) fault.

Recent reconstruction [START_REF] Etheve | Extensional vs contractional Cenozoic deformation in Ibiza (Balearic Promontory, Spain): Integration in the West Mediterranean back-arc setting[END_REF] south at 20 Ma, this would imply a different opening which might not have led to the formation of oceanic crust, but to the formation of thinner crust of transitional nature. This scenario would pose further questions about the nature of the crust north of the above mentioned blocks, whose traces would be difficult to recognise today.

The rollback process is the most generally accepted way to explain the concomitance of compression and expansion in this region [START_REF] Malinverno | Extension in the Tyrrhenian Sea and shortening in the Apennines as result of arc migration driven by sinking of the lithosphere[END_REF][START_REF] Royden | Evolution of retreating subduction boundaries formed during continental collision[END_REF][START_REF] Lonergan | Origin of the Betic-Rif mountain belt[END_REF], although other mechanisms such as a crustal collapse of continental crust previously thickened during the alpine phase [START_REF] Dewey | Extensional collapse of orogens[END_REF][START_REF] Platt | Extensional collapse of thickened continental lithosphere: A working hypothesis for the Alboran Sea and Gibraltar arc[END_REF] or a lithospheric delamination [START_REF] Seber | Geophysical evidence for lithospheric delamination beneath the Alboran Sea and Rif-Betic mountains[END_REF][START_REF] Platt | Thermal evolution, rate of exhumation, and tectonic significance of metamorphic rocks from the floor of the Alboran extensional basin, western Mediterranean[END_REF] are proposed by some authors, particularly in the case of the Alboran domain. The lithospheric delamination has been proposed by [START_REF] Roure | Alpine inversion of the North African margin and delamination of its continental lithosphere[END_REF] as an opening mechanism, which therefore questions the rollback theories.

As mentioned, the kinematic and amount of displacement between the different segments of the AlKaPeCa terranes is a key data to determine origin and role of the observed limit between each onshore and offshore domain developed during the opening of the Western Mediterranean, as shown by some options in figure 1.16. The different models proposed by the authors can impose geodynamic constraints which leave many questions open, such as the nature of the crust, the role of the Hannibal High in the central Algerian basin, the magnetic anomalies pattern in the East Algerian basin, the initial position of the AlKaPeCa and therefore the complete geodynamic evolution of the Western Mediterranean Sea.

Crustal nature and segmentation

One of the objectives of this work is the comparison between crustal segmentation and salt morphologies in the major salt-bearing margins in the world. Our work is focused mainly on the Western Mediterranean Sea, which can be divided into two large distinct basins: the Liguro-Provençal and Algerian basins. The segmentation and the nature of the crust are intimately linked to the movements of the plates as there is a forced relationship between lithosphere and geodynamics. Figure 1.17 represents the crustal segmentation in the Western Mediterranean Sea after interpretation of wide-angle refraction data, reflection, gravity and magnetic data (references in the legend). The refraction studies considered in this work are the SARDINIA (DOI: 10.17600/6010150), the SPIRAL (DOI: 10.17600/9010050) and the WESTMED (ISSN 0935-9974) surveys while the gravity and magnetic data come from, respectively, Sandwell and Smith, (1997) and [START_REF] Galdeano | Assemblage à altitude constante des cartes d'anomalies magnétiques couvrant l'ensemble du bassin occidental de la Méditerranée[END_REF].

In the Liguro-Provençal basin, during the SARDINIA survey in 2006, six coincident MCS reflection and wide-angle seismic profiles were collected in the Gulf of Lion (Fig. 1.18A) and in the western Sardinian (Fig. 1.18B) conjugated margin. The interpretation of velocity models, with the support of gravity and magnetic data and numerical stratigraphic modelling, allowed the authors to divide the basin in 5 domains [START_REF] Gailler | Crustal structure of a young margin pair: new results across the Liguro-Provencal Basin from wide-angle seismic tomography[END_REF][START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF]Moulin et al., 2015;Afhilado et al., 2015;[START_REF] Leroux | Post-rift evolution of the Gulf of Lion margin tested by stratigraphic modelling[END_REF]2019) (9-10-11 in fig. 1.17). These domains are similar between the conjugate margins, showing a symmetrical distribution [START_REF] Gailler | Crustal structure of a young margin pair: new results across the Liguro-Provencal Basin from wide-angle seismic tomography[END_REF], except for the dimensions of the transitional domain, which is wider in the Gulf of Lion.

The first domain, which follows the onshore unthinned continental crust domain, is the "continental slope crust" domain (11; fig. 1.17), characterized by the main crustal thinning zone, mainly focused on the lower crust where, in the Gulf of Lion, thickness decreases from 15 to 7 km. Basinward, the transitional domain (10; fig. 1.17) is characterized by a relatively high crustal velocity, varying between 6.0 and 6.4 km/s for the upper layer and 6.6 and 7.5 km/s for the lower layer in the Gulf of Lion and 6.8-7.25 km/s in the Western Sardinian (Fig. 1.18)

and is interpreted as exhumed lower continental crust [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF], whilst, based on the study of single MCS profile , [START_REF] Jolivet | Continental breakup and the dynamics of rifting in back-arc basins: The Gulf of Lion margin[END_REF] proposed an exhumed lower crust and upper mantle. [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF][START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. With red lines are indicated the SARDINIA wide-angle and coincidents reflection seismic lines. In the Algerian basin the dashed lines indicate the segmentation from gravity and magnetic data from [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. In the North Algerian basin, the black dashed lines indicate the interpretation of crustal domains from SPIRAL wide-angle survey (from [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF][START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF][START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF][START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF]Aidi et al., 2018). SPIRAL lines are indicated with red solid lines. WESTMED refraction survey in South Balearic margin is shown with red lines (from Vina Gaza, 2016;Gomez de la Pena et al., 2018) but is not considered in segmentation interpretation. The segmentation in the Valencia and Menorca segments is from [START_REF] Pellen | The Minorca Basin: a buffer zone between the Valencia and Liguro-Provençal Basins (NW Mediterranean Sea)[END_REF] and [START_REF] Etheve | Extensional vs contractional Cenozoic deformation in Ibiza (Balearic Promontory, Spain): Integration in the West Mediterranean back-arc setting[END_REF]. The South Minorca block position and interpretation is from Driussi et al., (2015a). NBFZ: North Balearic Fracture Zone. CFZ: Central Fracture Zone. Gravity map from [START_REF] Smith | Global sea floor topography from satellite altimetry and ship depth soundings[END_REF]; magnetic map from [START_REF] Galdeano | Assemblage à altitude constante des cartes d'anomalies magnétiques couvrant l'ensemble du bassin occidental de la Méditerranée[END_REF]. [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. The first profile on the top is the SARDINIA01 crossing NW-SE the Gulf of Lion whilst the other two cross it with a NE-SW direction. B) West Sardinian margin profiles with a WNW-ESE direction, from [START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF]. The profiles are at the same scale.

The central domain is characterized by a decrease in velocity and velocity gradient in the lower crust [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF] and presents an "atypical" relatively thin (5 km) oceanic crust (9; fig. 1.17) (e.g. Le [START_REF] Le Douaran | Deep structure of the north-western Mediterranean Basin: Results of a two-ship seismic survey[END_REF][START_REF] Gailler | Crustal structure of a young margin pair: new results across the Liguro-Provencal Basin from wide-angle seismic tomography[END_REF][START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. The oceanic crust is thinner than the Atlantic type but the velocity and gradients confirm the oceanic nature (Fig. 1.18) [START_REF] Gailler | Crustal structure of a young margin pair: new results across the Liguro-Provencal Basin from wide-angle seismic tomography[END_REF] and its close relationship with the transitional domain [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF]. The segmentation is confirmed by gravimetric (Sandwell and [START_REF] Smith | Global sea floor topography from satellite altimetry and ship depth soundings[END_REF] and aeromagnetic [START_REF] Galdeano | Assemblage à altitude constante des cartes d'anomalies magnétiques couvrant l'ensemble du bassin occidental de la Méditerranée[END_REF] data [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF].

The Valencia basin is characterized by the Menorca basin and the Valencia basin sensu stricto (VBss) (8 and 7 respectively, in fig. 1.17) [START_REF] Etheve | Extensional vs contractional Cenozoic deformation in Ibiza (Balearic Promontory, Spain): Integration in the West Mediterranean back-arc setting[END_REF][START_REF] Pellen | The Minorca Basin: a buffer zone between the Valencia and Liguro-Provençal Basins (NW Mediterranean Sea)[END_REF]. These two domains are bordered by the Central and the North Balearic Fracture Zones (e.g. [START_REF] Olivet | La cinématique de la plaque ibérique[END_REF]. The two transfer zones represent the witness of the Corso-Sardinian movement, which in turn have induced the movement of the Menorca block towards SE while no movement are depicted on the Ibiza and Majorca Islands [START_REF] Pellen | Géodynamique et impact de la crise d'érosion et de salinité Messinienne sur les transferts sédimentaires (bassins de Valence et Adriatique)[END_REF][START_REF] Pellen | The Minorca Basin: a buffer zone between the Valencia and Liguro-Provençal Basins (NW Mediterranean Sea)[END_REF].

The North Algerian margin was surveyed during the SPIRAL survey [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF][START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF][START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF][START_REF] Badji | Structure Profonde de la croûte et potentiel pétrolier des bassins sédimentaires à l'ouest de l'Algérie[END_REF][START_REF] Medaouri | The transition from Alboran to Algerian basins (Western Mediterranean Sea): chronostratigraphy, deep crustal structure and tectonic evolution at the rear of a narrow slab rollback system[END_REF][START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF][START_REF] Hamai | Flexural behaviour of the north Algerian margin and tectonic implications[END_REF], Arab et al., 2016a,b and Aidi et al., 2018) where five wide-angle profiles were acquired with a more or less N-S direction, from the east to the west ends of the Algerian basin (Fig. 1.19A-B-C-D-E). The results show a narrow thinning continental crust domain (from 20 to 60 km wide) along the entire Algerian margin with possible heterogeneous thinning between upper and lower crust in some transects (Lepretre et al., 2013;[START_REF] Arab | Coupling stratigraphic and petroleum system modeling tools in complex tectonic domains: case study in the North Algerian Offshore[END_REF]Aidi et al., 2018). Likewise, the transitional domain is narrow (Fig. 1.19), often associated with graben structures at the surface and interpreted by some authors as the surface expression of the subduction-transform edge propagator (STEP) fault [START_REF] Govers | Lithosphere tearing at STEP faults: Response to edges of subduction zones[END_REF] with several accretion axes [START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF]Aidi et al., 2018).

The as oceanic the nature of the crust in the deep basin, despite differences in thickness and velocity compared to the typical Atlantic oceanic crust compiled by [START_REF] White | Oceanic crustal thickness from seismic measurements and rare earth element inversions[END_REF]. [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF][START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF][START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF][START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF], Mihoubi et al., 2015, Aidi et al., 2018). The profiles are at the same scale. [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF], according to magnetic and gravity data, divided the Algerian basin into five main segments, from east to west (Fig. 1.17):

The East Algerian basin (EAB) is situated between the NBFZ, the South Menorca Block and the Hannibal High. According to Driussi et al., (2015a), the South Menorca Block corresponds to a continental block south of Menorca microplate. The triangle-shaped NNW-SSE aligned magnetic anomalies presents in the EAB seem to indicate the presence of oceanic crust in this area. It is worth to note that this area in the Western Mediterranean basin is the only one in which can be observed alignments of magnetic anomalies typical of the presence of oceanic crust.

To the west, the Hannibal High area, interpreted by some authors as a ridge (e.g. [START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF], is characterized by strong positive magnetic anomalies and shallow basement (Aidi et al., 2018), suggesting the presence of magmatic structures.

The Western Algerian basin (WAB) can be subdivided into two deep domains (III and IV, fig. 1.17) and two proximal domains (V and VI, fig. 1.17) and is characterized by some isolated NW-SE magnetic alignments and steep borders in the South Balearic and North Algerian margins. The Mazarron and Emile Baudot escarpments (e.g. [START_REF] Acosta | The morphotectonic setting of the Southeast margin of Iberia and the adjacent oceanic Algero-Balearic Basin[END_REF], situated in the South Balearic margin, are often interpreted as right-lateral deformation caused by the westward movement of the Alboran domain during the WAB opening (e.g. [START_REF] Camerlenghi | Morphogenesis of the SW Balearic continental slope and adjacent abyssal plain, Western Mediterranean Sea[END_REF].

The geodynamic of the Algerian basin is still matter of debate. The different possible options coexist as the nature of the crust of the various segments is still questionable. While the presence of oceanic crust in the EAB (aligned magnetic anomalies) seems to be confirmed, the nature of the Hannibal High and the WAB (segment III and IV, fig. 1.17) are still uncertain.

Some authors seem to agree on the oceanic nature of the deep basin of the WAB (e.g. [START_REF] Grevemeyer | Seismic constraints on the nature of crust in the AlgerianBalearic basin implications for lithospheric construction at backarc spreading centers[END_REF][START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF][START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF]Aidi et al., 2018), but its formation must be adequately demonstrated from a geodynamic point of view. The crustal nature and segmentation are therefore primordial in understanding the opening mechanisms of Algerian basin, as well as in understanding the movements of AlKaPeCa terranes.

The Messinian salt, as we will see in the next chapters, plays a key role in sedimentary Western Mediterranean filling. Its deposits are mainly located in deep basins, above a sedimentary blanket covering the basement. This deposition occurred far after the last plate movement in the Liguro-Provençal and Algerian Basins: the salt sequence covered at the time of its deposition the entire deep basins. The salt deformation geometries, which have a strong impact on sedimentary overburden, are variable in all the Western Mediterranean Sea.

Understand the reasons of the spatial salt structures variations is a goal of this thesis.

Moreover, some observations made in Gulf of Lion [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF] and Angola margin [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF] suggest a geometrical relationship between the salt geometries and the different crust forming the margins. We will go further in the analysis of this coincidence to figure out if it is systematic and whether it is influenced by other factors. As mentioned above, we will test the heat mantle segmentation hypothesis and how this could affect the passive margin formation and potentially also the salt deformation. The Messinian salt and its regional deformation could give information not only on tectonic heritage but also about the nature and the thermicity of the crust.

Summary chapter 1

The chapter provides a non-exhaustive summary of the distribution, While the eastern basin shows fan-shaped magnetic anomalies typical of oceanic crust, the crustal nature of the western basin is still uncertain as well as the models that led to its opening. In this thesis, I

will not delve into the geodynamic and crustal nature of this area but I will show how crustal segmentation may be related to salt morphologies.

Résumé chapitre 1

Le chapitre fournit un résumé non exhaustif de la distribution, des

CHAPTER 2. SALT DEPOSITION PROCESSES AND DEFORMATION

One of the main objectives of this thesis is the description of salt structures and their correlation with the segmentation and crustal nature. In this chapter I will try to summarise the crucial aspects of salt tectonics as described by different authors. The salt rock (halite) deforms due to its particular properties that make it viscous. I will therefore focus first of all on the intrinsic characteristics of halite and the global distribution of its deposits. I will then analyse the key aspects of salt deformation along passive margin and in the West Mediterranean Sea. I try to highlight the inconsistencies we have found in the authors' descriptions, thus introducing some issues that will be discussed in the next chapters.

Salt deposition

The evaporite is a salt rock that was originally precipitated from a saturated surface or nearsurface brine by hydrology driven solar evaporation (e.g. [START_REF] Warren | Evaporites: sediments, resources and hydrocarbons[END_REF]. The mineral crystallization occurs when the concentration of the solution exceeds the solubility of the material, i.e. when the solution is supersaturated for a given mineral species. The five main families of minerals considered as strictly evaporitic are chlorides, sulphates, certain carbonates, silicates and borates (e.g. [START_REF] Rouchy | Les évaporites: matériaux singuliers, milieux extrèmes[END_REF]. The crystallisation sequence changes in relation to the composition of the solution. In seawater the sequence starts with carbonates, followed by the precipitation of calcium sulphate in the form of gypsum (CaSO4•2H2O) before and anhydrite (CaSO4) afterwards (Fig. 2.1) [START_REF] Usiglio | Études sur la composition de l'eau de la Méditerranée et sur l'exploitation des sels qu'elle contient[END_REF]. Only after, when the water concentration is twelve times higher than seawater, the halite deposits. The sequence ends later with the deposition of potash and magnesium salts (e.g. [START_REF] Harvie | The prediction of mineral solubilities in natural waters: The Na-K-Mg-Ca-H-Cl-SO4-OH-HCO3-CO3-CO2-H2O system to high ionic strengths at 25 C[END_REF]. [START_REF] Warren | Evaporites: sediments, resources and hydrocarbons[END_REF] Pure sequences of halite are rare in nature, so, when we will speak about salt, we do not exclude the presence of other evaporites in the rock salt aggregates. Salt inclusions may be of igneous nature or clastic sediments. Moreover, salt bodies may include and contain varying amounts of other evaporites, especially anhydrite and gypsum:

-Gypsum is the most common sulphate mineral and occurs in nature as flattened and often twinned crystals, and transparent, cleavable masses, called selenite. It may also be granular, or very fine-grained white and in this case is called alabaster.

-The anhydrite rarely develops crystals, the mineral usually is presenting the form of cleavage masses. It may appear with three main structures: nodular, mosaic or enterolithic. The capillary evaporation which takes place on the surface allows the formation of anhydrite which requires therefore a water table sufficiently close to the surface to be affected by surface thermal phenomena [START_REF] Warren | Evaporites: sediments, resources and hydrocarbons[END_REF]. Another possibility is the evaporites precipitation directly in the sediments (Sabkha, [START_REF] Warren | Evaporites: sediments, resources and hydrocarbons[END_REF]. It is worth to note that anhydrite, when exposed to water, readily transforms into gypsum. Likewise, the gypsum, at specific temperature conditions, can lose the water content and transforms into anhydrite.

The evaporites can be differentiated into primary or secondary, respectively depending if they have been retaining crystallographic evidence of the depositional process or if they have undergone a diagenetically alteration or recrystallization. A subsequent sub-division of evaporites is into alkaline evaporites (carbonates, dolomite, aragonite and Mg-calcite) and evaporite salts (gypsum, anhydrite, halite, trona, carnallite etc.). The first category tends to be deposited in first stages of brine concentration, whereas the evaporite salts are deposited when the solution concentration is higher. In this study we mainly deal with the evaporite salts, focusing on the halite and, especially in the Western Mediterranean, gypsum and anhydrite.

The development of evaporitic conditions in a sedimentary basin is mainly closely linked to its isolation and climatic aridity (e.g. [START_REF] Warren | Evaporites: sediments, resources and hydrocarbons[END_REF][START_REF] Rouchy | Les évaporites: matériaux singuliers, milieux extrèmes[END_REF]. The isolation of a basin is determined by the ratio between the oceanic and fluvial inflow and the loss of water due to evaporation. The isolation of a basin is often ensured by a barrier that may be of tectonic, sedimentary or other origin, which limits the dilution of saumures in the basin.

If the constraints of basin isolation and aridity are respected, evaporites can precipitate in all types of basins, from oceanic to isolated basins in mountain domains. Many of the larger halitedominated ancient marine deposits accumulated in tectonically-induced sub-sea level depressions that were associated with past times of world-scale continent-continent proximity, especially in times marked by the accretion and disaggregation stages of supercontinents [START_REF] Warren | Evaporites: sediments, resources and hydrocarbons[END_REF].

Non-marine evaporite basins

Because in this work I will mainly focus on marine evaporitic deposits, we do not discuss the fact that the understanding of evaporitic deposition environments, as well as salt tectonics mechanisms, can pass through the analysis of outcrops on land. The non-marine evaporites [START_REF] Warren | Evaporites through time: Tectonic, climatic and eustatic controls in marine and nonmarine deposits[END_REF] are defined as evaporitic basins accumulated in inter-montane depressions, well above the sea level (Fig. 2.2). Most of these basins are of Tertiary period. Others are of Quaternary period, which differentiates them by age from the salt giants analysed in this work. Another well-known endorheic basin (supra-sea level hydrographically-isolated basin, e.g. [START_REF] Warren | Evaporites: sediments, resources and hydrocarbons[END_REF] is the Dead Sea depression, where the halite accumulated since 1979. In addition to the "classic" continental evaporitic basins, there are other more singular ways to lead the evaporites deposition. In the Naica Silver mine (Mexico), several caves contain giant crystal of selenite which can reach 10 metres in length [START_REF] Badino | The exploration of the caves of the giant crystals (Naica, Mexico)[END_REF][START_REF] Forti | The Naica Project-A multidisciplinary study of the largest gypsum crystals of the world[END_REF].

The evaporites grew from cooling hydrothermal solutions created by dissolution of anhydrite, [START_REF] Oliver | Encyclopedia of world climatology[END_REF], characterized by light winds and fine, clear weather.

previously precipitated during late hydrothermal mineralization of the volcanogenic matrix [START_REF] Warren | Evaporites through time: Tectonic, climatic and eustatic controls in marine and nonmarine deposits[END_REF]. Another type of evaporites are those found in inclusions in small volumes of snow or ice in Antarctica. These evaporites derived from relict seawater, the reworking of marine aerosols and the deep circulating seawater [START_REF] Takamatsu | The origin of salts in water bodies of the McMurdo Dry Valleys[END_REF]. Nevertheless, the evaporitic deposits deriving from phenomena not attributable to solar evaporation are secondary, in terms of volume and apparition. Moreover, although the halite volume and the economic impact of the continental salt basins are important, they are insignificant when we compared their volume to the ancient salt giant volumes, as in the South Atlantic or the Mediterranean region.

Marine evaporite basins

The marine evaporites salt basins (or salt giants) are mainly composed of halite, anhydrite and less evaporitic carbonates and potash salts. The borates and sodium sulphates are minor. "Salt giants", often described as basin-wide evaporites basin or basin-central evaporite [START_REF] Kendall | Evaporites. In: Facies Models: Response to sea level change[END_REF] They can be of any age, from Neoproterozoic to Neogene, and are all originated from a reliable seawater seepage source. As in the case of nonmarine evaporites, the salt giants have formed on the past latitudinal equivalents of "horse latitude" (between 30-35 ° both north and south, [START_REF] Oliver | Encyclopedia of world climatology[END_REF], where the evaporation rates of ocean waters were at their maximum. At present day, the evaporites deposits are mainly situated in the areas of adiabatic aridity and in the equatorial belts (Fig. 2.4). et al., 2003).

Figure 2.5. Phanerozoic volume of deposited evaporites against time (Phanerozoic) (after [START_REF] Hay | Evaporites and the salinity of the ocean during the Phanerozoic: Implications for climate, ocean circulation and life[END_REF].

Following [START_REF] Hay | Evaporites and the salinity of the ocean during the Phanerozoic: Implications for climate, ocean circulation and life[END_REF]

Precambrian evaporites

There are several witnesses of very ancient evaporite basins, such as the basins in Australia (Fig. 2.6, marked in black in the legend as Amadeus, Officer, Adavale, Adelaide, Bonaparte, Canning and Carnarvon basins). At the time of the deposition of these evaporites, dated around the Tonian period (~850 Ma), these basins were joined together but then separated at the end of the Neoproterozoic (see for instance [START_REF] Walter | Neoproterozoic stratigraphy of the centralian superbasin, Australia[END_REF]. The evaporites deposition occurred during the evolving margins related to the break-up of the Rodinia, in graben structures bounded by basement-penetrating normal faults [START_REF] Preiss | The Adelaide Geosyncline of South Australia and its significance in Neoproterozoic continental reconstruction[END_REF]. These are the oldest known evaporitic deposits in the world and have undergone, after their deposition, a complex history with several rifting episodes alternating with periods of basin subsidence [START_REF] Preiss | The Adelaide Geosyncline of South Australia and its significance in Neoproterozoic continental reconstruction[END_REF][START_REF] Sandiford | Neotectonics of southeastern Australia: linking the Quaternary faulting record with seismicity and in situ stress[END_REF]. Although very ancient evaporites deposits (Archean and Proterozoic) are Berrechid;23. Bohai Basin;24. Bonaparte (Petrel);25. Brazilian Aptian Basin (Camamu); 26. Brazilian Aptian Basin (Campos-Santos); 27. Brazilian Aptian Basin (Ceara); 28. Brazilian Aptian Basin (Cumuruxatiba); 29. Brazilian Aptian Basin (Sergipe-Alagoas); 30. 31. Canning Basin;33. Carnarvon Basin (Yaringa);34. Carpathian foredeep;35. Carson Basin (Grand Banks);39. Cuban;40. Danakil;41. Dead Sea;44. Eastern Alps;45. Ebro Basin;46. Flemish Pass Basin (Grand Banks);47. Georges Bank;48. Green River Basin;49. Gulf of Mexico (Northern;Gulf coast);50. Gulf of Mexico (Southern;51. Haltenbanken;53. Holbrook Basin;54. Horseshoe Basin (Grand Banks);55. Hudson Bay;56. Ionian;57. Jeanne d'Arc Basin (Grand Banks);58. Jianghan Basin;59. Jura/Rhodanian;60. Katangan;61. Khorat Basin;62. Kuqa Foreland (Tarim Basin);63. La Popa (Monterrey) Basin;64. Lusitanian;65. Mackenzie Basin;66. Maestrat;67. Majunga Basin;68. Mandawa Basin;70. Maritimes Basin;80. Michigan Basin;81. Moesian;82. Moose River Basin;83. Neuquen Basin;84. Nordkapp Basin;85. Officer Basin;86. Olduvai depression;87. Oman (Fahud Salt Basin);88. Oman (Ghaba Salt Basin). 89. Oman (Ghudun Salt Basin); 90. Oman (South Oman Salt Basin); 91. Oriente-Ucayali (Pucara) Basin;92. Orpheus Graben;93. Palmyra;94. Paradox Basin;95. Parry Islands Fold Belt;96. Pricaspian Basin;97. Pripyat Basin;98. Qaidam Basin;100. Red Sea (North);101. Red Sea (South);102. Rot Salt Basin;103. Ruvuma Basin;104. Sabinas Basin;105. Sachun Basin;106. Salar Basin 118 (Grand Banks); 107. Salt Range (Hormuz-Punjab region); 108. Salt Range (Kohat Plateau); 109. Saltville 119 (Appalachian);110. Scotian Basin;111. Siberia,East;112. Sirjan Trough;113. Solimoes;114. SomaliaKenya;115. South Whale Basin (Grand Banks);117. Sverdrup Basin (Melville Is);118. Tabriz Salt Basin;119. Tadjik Basin;120. Takutu Salt Basin;121. Transylvanian;122. Tromso Basin;123. USA Midcontinent; testimonies of past rifting phases, the plate reconstructions are poorly constrained to allow a direct relationship between their formation and the exact past tectonic setting.

Palaeozoic evaporites

Several evaporites basins formed near the Equator, at the limit between Neoproterozoic and Early Cambrian during the Rodinia diachronous break-up (e.g. [START_REF] Li | Assembly, configuration, and break-up history of Rodinia: a synthesis[END_REF]Fig. 2.7), such as the salt basin in in Iran and Persian Gulf (Fig. 2.6, marked in red in the legend as Ma'Rib-Al Jawf/Shabwah, Oman and Zagros salt basins)

The Early Cambrian accounts for 39 percent by volume of all Palaeozoic halite deposition [START_REF] Jackson | Salt tectonics: Principles and practice[END_REF]. Some reconstructions attempted to place these basins at the edge of Rodinia bordering the Panthalassic Ocean (Fig. Cambrian periods (~600-540 Ma) (e.g. [START_REF] Gorin | Late Precambrian-Cambrian sediments of Huqf Group, Sultanate of Oman[END_REF]. Still in the Cambrian period, the Siberian evaporites accumulated in the Siberian craton, forming thus one of the largest salt basin in the world (Zharkov and Yanshin,198). In the middle of Palaeozoic era, several famous salt basins formed, such as American intra-cratonical sag basins (fig 2.6; references in blue).

Again, the Dniepr-Donetz salt basin (fig 2.6, references in yellow) formed during an intracratonic rifting at ~376 Ma ago and it is the only one that shows a complex salt tectonics during its entire history [START_REF] Stovba | Style and timing of salt tectonics in the Dniepr-Donets Basin (Ukraine): implications for triggering and driving mechanisms of salt movement in sedimentary basins[END_REF] whilst the other basins, due to the small amount extensive volcanic activity [START_REF] Scheck | Evolution of the Northeast German Basin-inferences from a 3D structural model and subsidence analysis[END_REF][START_REF] Van Wees | On the origin of the southern Permian Basin, Central Europe[END_REF]. The subsidence related to the Greenland-Norvegian rift formed an intracontinental topographic depression which is catastrophically inundated leading to the evaporites deposition (e.g. [START_REF] Glennie | The Permian Weissliegend of NW Europe: the partial deformation of aeolian dune sands caused by the Zechstein transgression[END_REF]. The salt was deposited as the result of repeated marine transgression in the Upper Permian [START_REF] Strohmenger | Sequence stratigraphy and cyclic development of Basal Zechstein carbonate-evaporite deposits with emphasis on Zechstein 2 off-platform carbonates (Upper Permian, Northeast Germany)[END_REF] and can reach up to 2 km of thickness in the centre of the basin. The Mesozoic sedimentary evolution, which could have controlled the salt tectonics in this area [START_REF] Coward | Salt-influenced structures in the Mesozoic-Tertiary cover of the southern North Sea, UK[END_REF], was mainly controlled by transgression and regression water coming from the southern Tethys Ocean evolution. The scientific community's interests for these huge deposits can be witnessed by the many salt tectonic works carried out, as for instance the halokinetic model of basinal salt described by Thusheim (1960), which was the first to ascribe the movement of the salt to the buoyancy effect. More recently, other authors claimed a major tectonic influences, provoking a thick-skinned tectonics that would trigger the deformation (e.g. [START_REF] Kossow | Style and evolution of salt pillows and related structures in the northern part of the Northeast German Basin[END_REF][START_REF] Scheck | Salt movements in the Northeast German Basin and its relation to major post-Permian tectonic phases-results from 3D structural modelling, backstripping and reflection seismic data[END_REF].

Mesozoic evaporites

The -200 Ma;[START_REF] Maclean | Petroleum geology of the continental margin south of the islands of St. Pierre and Miquelon, offshore Eastern Canada[END_REF]. The structural segmentation proposed by [START_REF] Labails | La marge sud-marocaine et les premières phases d'ouverture de l'océan Atlantique Central[END_REF], after the geodynamic reconstruction of Sahabi et al., (2004) at 195 Ma, shows the salt distribution just before the oceanic break-up [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF] (Fig. 2.10).

Figure 2.10 also highlights some differences in evaporites distribution all along the Central Atlantic, showing a northern province (segment 1) with the highest amount of salt deposits, which decreases towards the south.

It is worth to note the smaller province of Casamance (segment 6) in the southern limit, which shows a conjugated but very narrow salt province in the Caroline Basin, in the American margin [START_REF] Dillon | The Blake plateau basin and Carolina trough[END_REF]. The deposition age in this basin still remains doubtful, ranging from the Late Triassic and Callovian (Middle Jurassic), which is concomitant with the first phase of the Gulf of Mexico opening [START_REF] Labails | La marge sud-marocaine et les premières phases d'ouverture de l'océan Atlantique Central[END_REF].

In the Central Atlantic the salt deposited in a so-called syn-rift context (e.g. [START_REF] Warren | Evaporites through time: Tectonic, climatic and eustatic controls in marine and nonmarine deposits[END_REF][START_REF] Tari | Examples of salt tectonics from West Africa: a comparative approach[END_REF] and the distribution of initial salt was uneven, due to basement highs separating rift half-grabens (Coffin and Rabinowitz, 1988). This depositional context had an impact on salt tectonics and triggered specific salt features, as explained by [START_REF] Tari | Examples of salt tectonics from West Africa: a comparative approach[END_REF]. The subsequent detachment level was irregular and salt individual structures, as sheets and tongues, have originated from autochthons salt in isolated half-grabens. Moreover, the salt deformation [START_REF] Labails | La marge sud-marocaine et les premières phases d'ouverture de l'océan Atlantique Central[END_REF] showing the salt deposits distribution all along both margins before the oceanic break-up (reconstruction at 195 Ma after [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF].

could be non-synchronous between individual sub-basins according to their history and in particular the sediment evolution and distribution through time.

The Jurassic period witnessed the opening of the Gulf of Mexico and the concomitant deposition of a large amount of evaporitic deposits. The initial opening of the Gulf of Mexico began about 210 Ma, in the Late Triassic and continued through the Early Jurassic. The basin formed via a first Late Triassic phase of separation of South America with North America, caused by NE-SW rift of Pangea [START_REF] Pindell | Permo-Triassic reconstruction of western Pangea and the evolution of the Gulf of Mexico/Caribbean region[END_REF] and a second Late Jurassic phase of counter-clockwise rotation of the Yucatan block and subsequently oceanic break-up [START_REF] Marton | Jurassic reconstruction of the Gulf of Mexico Basin[END_REF][START_REF] Pindell | Tectonic evolution of the Gulf of Mexico, Caribbean and northern South America in the mantle reference frame: an update[END_REF]. Some authors (e.g. [START_REF] Salvador | Triassic-Jurassic. The Gulf of Mexico Basin: Boulder, Colorado[END_REF] date the salt deposition at the Early Callovian (165-161 Ma) but with large uncertainties: this age should thus be treated with caution [START_REF] Curry | Extensional models for the development of passive-margin salt basins, with application to the Gulf of Mexico[END_REF]. Regardless, as in many salt passive margins, salt in Gulf of Mexico currently lies in two pieces on the opposite sides of an oceanic basin: the northern part is called Louann salt basin while the southern part the Campeche and the Yucatan salt basins (Fig. 2.11). Some authors invoke a salt deposition near sea-level (Hudec et al., 2013b;[START_REF] Pindell | Rapid outer marginal collapse at the rift to drift transition of passive margin evolution, with a Gulf of Mexico case study[END_REF], followed by significant subsidence related to post-oceanic spreading or a vertical collapse caused by an extension of the transitional domain (Hudec et al., 2013). [START_REF] Rowan | The South Atlantic and Gulf of Mexico salt basins: crustal thinning, subsidence and accommodation for salt and presalt strata[END_REF] infers that evaporites were deposited at the end of rifting, in a relatively shallow-environment at the basin margins up to 2-3 km in the basin centers. The original salt distribution and thickness would be therefore different from the proximal to the distal deep water. The salt was deposited above a thick sedimentary sequence, unfaulted and not brittle deformed, defined as sag basin [START_REF] Miranda | Play hipotetico pre-sal en augas profundas del Golfo de Mexico[END_REF][START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF].

The Cretaceous period marks the last significant salt deposition phase in the Mesozoic.

The salt in the Central segment of the South Atlantic Ocean can be considered as one of the main studied and debated, mainly thanks to industrial interests related to hydrocarbon exploration. While oceanic spreading in the Austral Segment started between 139.5 and 130

Ma (e.g. [START_REF] Rabinowitz | The Mesozoic South Atlantic Ocean and evolution of its continental margins[END_REF][START_REF] Curie | Ouverture de l'Atlantique Sud et discontinuités intra-plaques: une nouvelle analyse[END_REF][START_REF] Moulin | A new starting point for the South and Equatorial Atlantic Ocean[END_REF], the Central Segment oceanic spreading started more than 18 Ma later, [START_REF] Rabinowitz | The Mesozoic South Atlantic Ocean and evolution of its continental margins[END_REF][START_REF] Curie | Ouverture de l'Atlantique Sud et discontinuités intra-plaques: une nouvelle analyse[END_REF][START_REF] Torsvik | A new scheme for the opening of the South Atlantic Ocean and the dissection of an Aptian salt basin[END_REF][START_REF] Moulin | A new starting point for the South and Equatorial Atlantic Ocean[END_REF], at the end of evaporite deposition ( 112Ma, [START_REF] Pautot | Morphology, limits, origin, and age of salt layer along South Atlantic African margin[END_REF]. Concerning the timing of deposition, some authors [START_REF] Jackson | Role of subaerial volcanic rocks and mantle plumes in creation of South Atlantic margins: implications for salt tectonics and source rocks[END_REF][START_REF] Marton | Evolution of the Angolan passive margin, West Africa, with emphasis on post-salt structural styles[END_REF] consider the evaporites as the earliest post-rift strata, deposited above the breakup unconformity and thus after plate separation. Others interpret the sag basin and the evaporites deposition as syn-rift, thus before the oceanic breakup (Karner et al., 2003;[START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]Karner and Gamboa, 2007;[START_REF] Mohriak | Salt tectonics, volcanic centers, fracture zones and their relationship with the origin and evolution of the South Atlantic Ocean: geophysical evidence in the Brazilian and West African margins[END_REF]. [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF] showed that the Aptian salt was deposited in shallow depositional environments on the platform and all (Hudec et al., 2013a).

over the transitional domain, above a pre-salt sediment layer with a homogeneous thickness of about 3-4 km, called, as in Gulf of Mexico, sag basin. The sag basin is characterized by flat layers, regionally horizontal and parallel to the salt base. The salt gave rise to significant salt tectonics, which can be observed in West Africa (Benguela, Kwanza, Lower Congo, Gabon basins) and in Brazilian margin (Santos, Campos, Espirito Santo and Sergipe Alagoas basins).

Cenozoic evaporites

The Cenozoic period is characterized by a strong evaporites deposition, mainly focused in the Neogene period, as seen in Figure 2.5. In the Miocene, salt deposited in broad areas of the Mediterranean, Red Sea and Persian Gulf. The Red Sea rift basin developed in Late Tertiary as a response to plate movements between Africa and Arabia which led to the formation of patches of oceanic crust in the central segment [START_REF] Bosence | Stratigraphic and sedimentological models of rift basins. Sedimentation and Tectonics in Rift Basins Red Sea:-Gulf of Aden[END_REF][START_REF] Bosworth | The Red Sea and Gulf of Aden basins[END_REF]. The salt deposited above a thick sequence of rift sediments [START_REF] Mohriak | Architecture of rifted continental margins and break-up evolution: insights from the South Atlantic, North Atlantic and Red Sea-Gulf of Aden conjugate margins[END_REF] and it starts to deform early, triggered by clastic progradation and extensional tectonics (e.g. [START_REF] Davison | Deformation and sedimentation around active Miocene salt diapirs on the Tihama Plain, northwest Yemen[END_REF]. Salt deposition is Tortonian or Serravalian in age (Hughes et al., 1999). In the Late Miocene, another salt giant took place in the Mediterranean, during the so-called Messinian

Salinity Crisis (MSC).

The Messinian salinity crisis (MSC) is a huge succession of events that has deeply modified the Mediterranean region within a relatively limited time span (Hsu et al., 1973). This short event at the geological scale event (~0.64 Ma, [START_REF] Hilgen | Astronomical tuning as the basis for high resolution chronostratigraphy: the intricate history of the Messinian Salinity Crisis[END_REF] started at ~5.97 Ma and ended 5.33 Ma ago (Krijgsman et al., 1999a;[START_REF] Manzi | Age refinement of the Messinian salinity crisis onset in the Mediterranean[END_REF]. Nowadays, the cause widely accepted by the scientific community lies in the breaking of the connection between the Mediterranean Sea and the Atlantic Ocean. The Tortonian uplift of the present Gibraltar region led to a significant reduction in seawater exchange isolating the Mediterranean (e.g. Krijgsman et al., 1999b;[START_REF] Duggen | Deep roots of the Messinian salinity crisis[END_REF][START_REF] Duggen | Magmatic evolution of the Alboran region: The role of subduction in forming the western Mediterranean and causing the Messinian Salinity Crisis[END_REF]. This uplift is supposed to be one consequence of a global kinematic revolution [START_REF] Leroux | The late Messinian event: A worldwide tectonic revolution[END_REF]. The rapid isolation of the Mediterranean has led to an increase in the salinity of the waters and an estimated sea level drop of 1500 m (e.g. [START_REF] Ryan | The nature and distribution of Messinian erosional surfaces-Indicators of a several-kilometer-deep Mediterranean in the Miocene[END_REF]. Considering that the Mediterranean is composed by bathymetric high and sub-basins, the desiccation took place in discrete stages, not yet completely clear in literature. The massive evaporation of water caused the emergence and erosion of the continental margins surrounding the deep basins [START_REF] Clauzon | Le canyon messinien du Rhone; une preuve decive du" desiccated deep-basin model[END_REF][START_REF] Guennoc | Histoire géologique du Golfe du Lion et cartographie du rift oligo-aquitanien et de la surface messinienne[END_REF], generating a considerable amount of sediments that have poured at the lower slope (e.g. [START_REF] Barber | Messinian subaerial erosion of the proto-Nile Delta[END_REF][START_REF] Lofi | Erosional processes and paleo-environmental changes in the Western Gulf of Lions (SW France) during the Messinian Salinity Crisis[END_REF][START_REF] Sage | Seismic evidence for Messinian detrital deposits at the western Sardinia margin, northwestern Mediterranean[END_REF][START_REF] Bache | Messinian erosional and salinity crises: view from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF][START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF][START_REF] Madof | Discovery of vast fluvial deposits provides evidence for drawdown during the late Miocene Messinian salinity crisis[END_REF][START_REF] Pellen | The Messinian Ebro River incision[END_REF].

Parallel to the margins erosion, the marine water evaporation caused the deposition of evaporites (Fig. 2.12) distributed according to the arrangement of the structural highs and lows, mainly in two areas (Fig. 2.13): a) the marginal (or peripheral) basins, which now-days provide onshore outcrops helping the reconstruction of the Messinian stratigraphy model (for instance Sicily, Piedmont and Sorbas sub-basins) (e.g. [START_REF] Decima | Late Miocene evaporites of the Central Sicilian basin, Italy[END_REF][START_REF] Butler | Tectonics and sequence stratigraphy in Messinian basins, Sicily: constraints on the initiation and termination of the Mediterranean salinity crisis[END_REF][START_REF] Roveri | The Messinian Sicilian stratigraphy revisited: new insights for the Messinian salinity crisis[END_REF][START_REF] Clauzon | New insights on the Sorbas Basin (SE Spain): the onshore reference of the Messinian Salinity Crisis[END_REF], b) the deep basins, which largely correspond to the present-day Mediterranean slopes and bathyal plains (e.g. [START_REF] Ryan | The nature and distribution of Messinian erosional surfaces-Indicators of a several-kilometer-deep Mediterranean in the Miocene[END_REF][START_REF] Bache | Messinian erosional and salinity crises: view from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF][START_REF] Roveri | High-resolution strontium isotope stratigraphy of the Messinian deep Mediterranean basins: Implications for marginal to central basins correlation[END_REF]. One of the main trivial problem in the interpretation of MSC is the stratigraphic correlation between onshore outcrops with offshore records, mainly highlighted by seismic studies.

At the end of the crisis the setting up of the drowning is still matter of debate, especially with regard to the causes and velocity of the event. Authors seem to look for the causes in the local tectonic of the Gibraltar area, which would have opened the connection between the [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF].

Mediterranean and the Atlantic in a relatively short time. For instance, [START_REF] Govers | Choking the Mediterranean to dehydration: the Messinian salinity crisis[END_REF] attributes the end of the crisis to a subsidence induced by the deepening of the Gibraltar slab, which would have led to a Pliocene drowning. According to other interpretations, the rise of the sea level took place in two phases (the first one slow and the second rapid) [START_REF] Bache | A two-step process for the reflooding of the Mediterranean after the Messinian Salinity Crisis[END_REF] or in a single catastrophic phase that would have drowned the Mediterranean from west to east, gradually filling the present sub-basins [START_REF] Garcia-Castellanos | Catastrophic flood of the Mediterranean after the Messinian salinity crisis[END_REF][START_REF] Micallef | Geomorphic evolution of the Malta Escarpment and implications for the Messinian evaporative drawdown in the eastern Mediterranean Sea[END_REF] in the Zanclean age. The modalities and causes are still debated (e.g. [START_REF] Loget | How did the Messinian salinity crisis end?[END_REF][START_REF] Weijermars | Neogene tectonics in the Western Mediterranean may have caused the Messinian Salinity Crisis and an associated glacial event[END_REF]Bourrillot et al., 2010).

As mentioned, the MSC deposition has led to differences in thickness and nature of evaporites sedimentation between deep and currently emerged sub-basins. In the offshore area, corresponding to the present-day deep basins, differences are observed between the western and eastern Mediterranean Sea (Fig. 2.14). In the Western Mediterranean Sea a "trilogy" is present [START_REF] Montadert | De l'âge tertiaire de la série salifère responsable des structures diapiriques en méditerranée occidentales (nord-est des baléares)[END_REF], composed by a Lower Unit, a Mobile Unit and an Upper Unit (following the terminology from Lofi et al., 2011a). The Mobile Unit corresponds to the salt, so called because of its ductile behaviour. In the eastern part of the Mediterranean, a single unit (Mobile Unit) is interpreted, eroded at its top. The Messinian salinity crisis in the Mediterranean Sea is an event of global importance that is part of the Messinian Revolution, as described in [START_REF] Leroux | The late Messinian event: A worldwide tectonic revolution[END_REF]. The Messinian revolution is interpreted as a worldwide kinematic reorganisation at 6 Ma, which led to a global onset of increased sedimentary yields and to the regional Messinian Salinity Crisis. This geodynamic event finds global witnesses that seem to make it part of the latest cyclic global event series [START_REF] Moulin | A new starting point for the South and Equatorial Atlantic Ocean[END_REF][START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. A huge debate about MSC still remains, especially on the correlation between the onshore and offshore stratigraphic records (e.g. [START_REF] Clauzon | Alternate interpretation of the Messinian salinity crisis: controversy resolved?[END_REF][START_REF] Cornée | Onshore to offshore reconstruction of the Messinian erosion surface in Western Sardinia, Italy: Implications for the Messinian salinity crisis[END_REF][START_REF] Roveri | The Messinian salinity crisis: open problems and possible implications for Mediterranean petroleum systems[END_REF][START_REF] Roveri | The synthetic seismic expression of the Messinian salinity crisis from onshore records: Implications for shallow-to deep-water correlations[END_REF], the offshore extension and nature of units (e.g. [START_REF] Bertoni | 3D seismic analysis of circular evaporite dissolution structures, Eastern Mediterranean[END_REF][START_REF] Bache | Messinian erosional and salinity crises: view from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF][START_REF] Bache | A two-step process for the reflooding of the Mediterranean after the Messinian Salinity Crisis[END_REF]Lofi et al., 2011a[START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF][START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF], the causes and processes related to the post-MSC refilling (e.g. [START_REF] Loget | How did the Messinian salinity crisis end?[END_REF][START_REF] Roveri | The Messinian Sicilian stratigraphy revisited: new insights for the Messinian salinity crisis[END_REF][START_REF] Garcia-Castellanos | Catastrophic flood of the Mediterranean after the Messinian salinity crisis[END_REF][START_REF] Estrada | Impact of pulsed Atlantic water inflow into the Alboran Basin at the time of the Zanclean flooding[END_REF][START_REF] Bache | A two-step process for the reflooding of the Mediterranean after the Messinian Salinity Crisis[END_REF][START_REF] Micallef | Geomorphic evolution of the Malta Escarpment and implications for the Messinian evaporative drawdown in the eastern Mediterranean Sea[END_REF] and the timing of major sea-level change during the crisis [START_REF] Ciesm | The messinian salinity crisis from mega-deposits to microbiology -a consensus report[END_REF]Lofi et al., 2011a;[START_REF] Ryan | The nature and distribution of Messinian erosional surfaces-Indicators of a several-kilometer-deep Mediterranean in the Miocene[END_REF].

This general descriptive part on the causes of the deposition aims to underline that

Messinian salt in the West Mediterranean Sea has been deposited in a context not linked to the formation of margins, as the cases previously described during, for instance, the Mesozoic. Messinian salt in the West Mediterranean Sea deposited in an already formed [START_REF] Lofi | Erosional processes and paleo-environmental changes in the Western Gulf of Lions (SW France) during the Messinian Salinity Crisis[END_REF] showing the trilogy depicted in the deep basin. Salt, in yellow, is called Mobile Unit (MU). D) sketch from the Levant basin (Bertoni and Cartwright, 2005a) showing the Mobile Unit, which can be in turn subdivided in 6 sub-units (after Roveri et al., 2014a).

basin and did not undergo major tectonic deformation caused by kinematic plate motion, excepted at local scale (see chapter 1). This significant difference compared to the passive margins makes the Western Mediterranean a special case-study among most of the Salt Giants and will entail another point of view in the discussion of the triggering mechanisms of salt tectonics.

Salt tectonics

Salt tectonics is a term that encompasses the lateral and vertical rock salt flow, intra-strata, salt pillowing and diapirism and all the tectonics deformation involving halite or other evaporites (e.g. [START_REF] Warren | Evaporites: sediments, resources and hydrocarbons[END_REF]. In order to understand salt tectonics, it is first of all necessary to understand the specificity and characteristics of rock salt, considered to be formed mostly by pure halite. Whereas other evaporites could be present, I will mainly focus on features of halite deformation. Salt tectonics is concerned by the geometries and processes associated with a significant thickness of halite on a regional scale and can involve extensional and shortening deformation. In this work, salt tectonics includes the terms coined [START_REF] Trusheim | Mechanism of salt migration in northern Germany[END_REF] "halokinesis", to collectively name all the processes connected with ductile flow of salt and "halotectonics", which refers to the salt structures formed as a result of compressive tectonic forces.

Rock salt characteristics

The particular characteristics of salt makes it different from the other deposits with which it often comes into contact. Its unique deformational style and massive deformational overprint on some divergent margins make it an important component of the sedimentary basins evolution. The first singular characteristic of salt is its nearly constant density during burial history (Fig. 2.15).

Density

The density of salt does not vary during its geological history because it is a relatively incompressible material. This means that salt, unlike other rocks, is not subject to compaction.

Salt buried beneath denser overburden is therefore buoyant and unstable and is liable to rise unless restrained (e.g. [START_REF] Lachmann | Die Natur des Everdingschen deszendenten Hauptsalzkonglomerats[END_REF][START_REF] Barton | Mechanics of formation of salt domes with special reference to Gulf Coast salt domes of Texas and Louisiana[END_REF]. In more shallow formations the salt will have a higher density than other sediments while a depth of at least 1600 m (and more typically 1000 m; fig. 2.15) is required before the average density of the overburden exceeds that of salt [START_REF] Jackson | Salt tectonics: Principles and practice[END_REF] (Fig. 2.15).

Viscosity

Another characteristic that makes salt a special case among the other rocks is its viscosity (Fig. 2.16). Its lower viscosity makes the salt a viscous fluid which flows, under geological strain rates, at the surface and in the subsurface. shows little changes in density with the depth while the other rocks, subjected to the compaction, increase their density (after [START_REF] Jackson | External shapes, strain rates, and dynamics of salt structures[END_REF].

classic viscosity law (Fig. 2.16, [START_REF] Weijermars | Rheological and tectonic modeling of salt provinces[END_REF]. The viscosity is influenced by different parameters, such as the temperature, the grain size, the water content and the force applied (e.g. [START_REF] Carter | Rheology of rocksalt[END_REF][START_REF] Van Keken | The effective viscosity of rocksalt: implementation of steady-state creep laws in numerical models of salt diapirism[END_REF].

Thermal conductivity

Salt is also a formidable heat conductor, because of its thermal conductivity significantly higher than other rocks. Its thermal conductivity changes with temperature (it increases with low temperature), with a mean value around 5.5-6 W/mK (Watts per meter-kelvin). A salt layer in a sedimentary basin would therefore influences the temperature of the deposits, increasing it above the salt and decreasing it below (e.g. [START_REF] Nagihara | High heat flow anomalies over salt structures on the Texas continental slope, Gulf of Mexico[END_REF][START_REF] Mello | Role of salt in restraining the maturation of subsalt source rocks[END_REF]. This property has strong implications on the oil system of a basin since the layer will allow to preserve the oil potential of the underlying rocks at greater depth and improving the maturation of the overlying rocks [START_REF] Warren | Evaporites: sediments, resources and hydrocarbons[END_REF]. Figure 2.17 gives a general view of salt thermal conductivity correlated to other typical rocks, emphasizing its importance on surface heat flow.

Thermal conductivity (λ) varies significantly with temperature (T) and can be represented as:

where T is in degrees Kelvin. Figure 2.18 shows the dependence between temperature and thermal conductivity observed by several authors [START_REF] Birch | The thermal conductivity of rocks and its dependence upon temperature and composition[END_REF][START_REF] Fujisawa | Thermal diffusivity of Mg2SiO4, Fe2SiO4, and NaCl at high pressures and temperatures[END_REF] for different temperatures. The thermal conductivity seems to decrease drastically in the range between 0 and 200 °C. The thermal expansion is another important characteristic of salt rocks, linked to its particular thermal properties. It is considered as the change in shape and volume of a system due to a change in temperature. If a salt body is not free to expand, thermal loading can increase the stress. [START_REF] Jackson | Salt tectonics: Principles and practice[END_REF] explained that thermal convection could expand the salt and, thus, decrease its density and increase its buoyancy.

As mentioned, the evaporites basin present in nature are often composed by alternating layers of different evaporites rocks, mostly made up of halite, gypsum and anhydrite, but not only. Although in general all evaporites have a lower viscosity than other rocks, halite remains a special case, with a lower viscosity that has no equal. The alternation of evaporitic layers of different composition can generate different internal flow velocities and therefore influence deformation on a regional scale. It should not be forgotten, when salt tectonics is dealt with seismic profiles, that each evaporite deposit can behave differently due to its percentage of halite, which is difficult to know without more detailed information from direct samples.

Micro-scale salt deformation processes

Rock salt rheology

In this chapter, I will illustrate the rheology of salt tectonics without going into the mathematical detail of the different models presented in the bibliography. Instead, I will highlight the main factors that can influence the viscous behaviour of salt, focusing more on temperature. A first introduction on rheological behaviour will be followed by a chapter describing the deformation mechanisms present in nature. Finally, I will conclude with some considerations on the current state of the art concerning the influence of temperature on rock salt viscosity.

The term rheology derives from the Greek (rheos-logia, the study of the flow) and it is a branch of physics that deals with the deformation and flow of materials, both solids and liquids.

Rheology of rock salt is fundamental to understand salt tectonics. The deformation and flow mechanisms are relevant to mining operations and drilling engineering in rock salt and also in natural environment where salt responds to over-pressured pore fluids. The rock salt is considered as the most suitable material for underground storage of hydrocarbons as well as the disposal sites for hazardous waste in view of its unique physical and mechanical behaviour.

Experimental deformation provides vital insights into rheology and brittle mechanics of evaporites. The economic importance of the rock salt and, generally, the evaporites, led to have a vast specialized literature of the micro-mechanisms processes involved in the deformation.

Geologists attempt to extrapolate short-term experiments to understand deformation lasting millions of years. The main problems come from the difficulty to reproduce the natural behaviour of evaporites, characterised by lithological and structural inhomogeneity influences, and the deformation mechanisms in the laboratory.

Rock salt is usually formed by halite (NaCl) with a mean grain size of 2-30 mm, though extrusive salts may show much finer mean values (0.5 mm) while secondary salt can be much coarser (10-30 mm). Polycrystalline salt may contain impurities in solution, secondary mineral phases and fluids trapped in inclusions, grain boundaries or in pores.

The rock salt with an adequate and certain confining pressure starts moving with a certain velocity. The movement of dislocations results in a time-dependent ductile deformation in the rock sample (e.g. [START_REF] Khaledi | Recent and active deformation pattern off the easternmost Algerian margin, Western Mediterranean Sea: New evidence for contractional tectonic reactivation[END_REF]. This time-dependent relationship draws the deformation in progress and is called "creep". Several models have tried to reproduce the constitutive law to understand the salt creep, covering all the range of conditions encountered in nature (e.g. [START_REF] Munson | Constitutive model of creep in rock salt applied to underground room closure[END_REF][START_REF] Fossum | Salt mechanics primer for near-salt and sub-salt deepwater Gulf of Mexico field developments[END_REF][START_REF] Weatherby | Three-dimensional finite element simulation of creep deformation in rock salt[END_REF]. These models try to reproduce the rock salt deformation, which can have elastic, plastic and viscous behaviour. The elastic properties of different evaporites are very similar, while their viscous properties are different because of the emplacements and the patterns of heterogeneities and dislocation can influence the flowing of salt (e.g. [START_REF] Renard | Enhanced pressure solution creep rates induced by clay particles: Experimental evidence in salt aggregates[END_REF]. The plastic behaviour is strongly dependent on confining pressure (e.g. [START_REF] Cristescu | A general constitutive equation for transient and stationary creep of rock salt[END_REF]. These three behaviours can be found in the graph (Fig. 2.19), which describes the three salt creep typologies.

The schema describes, under constant differential stress, the behaviour of strain against time after the yield strength. The yield strength or yield stress is the material property defined as the stress at which a material begins to deform plastically. The salt displays a very low yield strength which is, in effect, almost zero. Following Fossum and Frederich, (2002), even at stress differences as low as 0.25 MPa, halite deforms by creep. The salt creep deformation shows an instant elastic response followed by permanent plastic deformation in three stages (Fig. 2.19). Primary creep phase shows a decreasing strain rate, the steady-state creep a constant strain rate while the tertiary creep an increasing strain rate. In the last phase, the creep strain rate increasing is due to the crack growth and, when the damage reaches a certain limit, long-term failure can takes place. If temperature and confining pressure are high and the deformation is relatively slow, rock salt can have considerable difficulty to break [START_REF] Senseny | Mechanical behaviour of rock salt: phenomenology and micromechanisms[END_REF]. The most important stage during the geological time scale is the steadystate viscous creep, which depends only on stress and temperature (Fig. 2.20), while the primary elastic creep is negligible [START_REF] Jackson | Salt tectonics: Principles and practice[END_REF].

Depending

Dislocation creep

The dislocation creep occurs in the crystal lattice and lead to a dislocation effect. The fluid behaviour is non-Newtonian (the viscosity is independent of stress) and the process takes place inside the crystal lattice, without modifications of the grain orientation and boundaries.

Applying a load, the stress inside the lattice generates a dislocation that leads progressively a movement within the whole grid. This movement can be stopped if the grains encounter an obstacle in the lattice structure, as impurities. When all the dislocation affects the sub-grains network, the system goes into "transient" phase (first phase of the Fig. 2.19) because of a contrary and resistant force called "strain hardening". The second phase is reached only later, when the rearrangement of sub-grains structures leads to the recovery of dislocations. This phase of increasing strain energy is called "climb" and, if the loading conditions are kept constant, the number of dislocations which are recovered increases and an equilibrium is [START_REF] Jackson | Salt tectonics: Principles and practice[END_REF].

reached between the dislocation and the recovery sub-grains. If the "strain hardening" and the recovery are not in equilibrium, then the creep relation still stays in the "transient creep" phase. This is the case when a load changes and the system is not yet in equilibrium. The equilibrium phase, once reached, implies a constant rate of deformation (steady-state creep, second phase in Fig. 2.19). This step is mainly dependent on applied force (stress) and temperature (Cristrecu and Hunsche, 1998).

Solution precipitation creep

Pressure solution, or solution precipitation creep, is the mechanism occurring when salt dissolves at grain contacts and then the solution moves and precipitate on low stressed surfaces (Figs. 2.20 and 2.21) [START_REF] Peach | Effect of confining pressure on dilatation, recrystallization, and flow of rock salt at 150 C[END_REF][START_REF] Urai | Flow and transport properties of salt rocks. Dynamics of complex intracontinental basins: The central European basin system[END_REF]. Due to its mechanism, pressure solution is common at low stress and temperature conditions and in wet salts (Fig. 2.20). The pressure-solution mechanism have been widely documented in literature, mostly in synthetic samples, in different conditions of temperature, pressure and water content [START_REF] Urai | Weakening of rock salt by water during long-term creep[END_REF][START_REF] Spiers | 11848[END_REF][START_REF] Renard | Synchrotron 3D microtomography of halite aggregates during experimental pressure solution creep and evolution of the permeability[END_REF][START_REF] Ter Heege | Dynamic recrystallization of wet synthetic polycrystalline halite: dependence of grain size distribution on flow stress, temperature and strain[END_REF]. [START_REF] Khaledi | Recent and active deformation pattern off the easternmost Algerian margin, Western Mediterranean Sea: New evidence for contractional tectonic reactivation[END_REF] who modified the original plot from [START_REF] Munson | Preliminary deformation-mechanism map for salt (with application to WIPP)[END_REF] and [START_REF] Urai | Weakening of rock salt by water during long-term creep[END_REF]. The plot shows in which temperature/pressure fields act the dislocation creep (glide and climb) and the solution precipitation creep.

Microscopically, pressure solution shows grain boundary sliding, dissolutions and precipitation in the pore space (Fig. 2.21). Following some authors (e.g. [START_REF] Urai | The effect of grain boundary water on deformation mechanisms and rheology of rocksalt during long-term deformation[END_REF][START_REF] Urai | Flow and transport properties of salt rocks. Dynamics of complex intracontinental basins: The central European basin system[END_REF], the pressure solution mechanism could be important in wet salt under geological process, when the strain rates and differential stress are relatively low. Such environmental conditions are actually typical in salt extrusions, as for instance salt glacier, and this mechanism can be relevant in these particular context [START_REF] Jackson | Salt tectonics: Principles and practice[END_REF].

Another microstructural processes are the micro-cracking and cataclastic flow. Cataclastic flow is a brittle process that can fracture, slide and rotate the grain under low temperatures, low effective confining pressures and high differential stress conditions. Cataclasis tends to increase the volume as fractures dilate. Above the dilatancy boundary, creep is accompanied by microcracking and increases the permeability; when the differential stress or the confining pressure rise, micro-cracking and dilation are suppressed, and crystal plasticity dominates (Cristescu and Hunsche, 1988). This process is rarely seen in naturally deformed salt.

Temperature role

The temperature influence on creep behaviour has been and continues to be of particular interest for the storage of waste material in salt formation. The radiation processes of nuclear waste deposited in salt formations can indeed increase the temperature of the system and affect the creep behaviour [START_REF] Khaledi | Recent and active deformation pattern off the easternmost Algerian margin, Western Mediterranean Sea: New evidence for contractional tectonic reactivation[END_REF]. The importance of temperature in creep processes occurring in salt tectonics is well documented in bibliography (e.g. [START_REF] Urai | Weakening of rock salt by water during long-term creep[END_REF][START_REF] Urai | Flow and transport properties of salt rocks. Dynamics of complex intracontinental basins: The central European basin system[END_REF][START_REF] Peach | Effect of confining pressure on dilatation, recrystallization, and flow of rock salt at 150 C[END_REF][START_REF] Jackson | Salt tectonics: Principles and practice[END_REF][START_REF] Phatthaisong | Effects of loading rate and temperature on strength and deformability of MahaSarakham salt[END_REF]Ter Heege et al., Figure 2.21. Optical micrograph showing truncation (t) and overgrowth (o) structures typical of pressure solution in a wet synthetic salt aggregate. After [START_REF] Cornet | Long term creep closure of salt cavities[END_REF] 2005a) and is well accepted that the rock salt ductility increases with increasing temperature (e.g. [START_REF] Spiers | 11848[END_REF][START_REF] Hunsche | Rock salt-the mechanical properties of the host rock material for a radioactive waste repository[END_REF][START_REF] Khaledi | Recent and active deformation pattern off the easternmost Algerian margin, Western Mediterranean Sea: New evidence for contractional tectonic reactivation[END_REF].

Figure 2.22 shows low temperature (20-50 °C) laboratory tests for a wide range of salt specimens [START_REF] Urai | Flow and transport properties of salt rocks. Dynamics of complex intracontinental basins: The central European basin system[END_REF]Schleder and Urai, 2005). As explained above, the two mechanisms (dislocation and pressure-solution creep) can act together:for instance for a grain size of 3 mm the two mechanisms contribute equally to the deformation at a strain rate of 10 -10 to 10 -11 s -1 . Following the interpretation of [START_REF] Jackson | Salt tectonics: Principles and practice[END_REF] for this plot, they argued that an extrusive halite, as a salt glacier, deforming at low stress at medium strain rate (0.2 to 2 Mpa and 10 -12 to 10 -8 s -1 ) and having a grain size between 3 and 0.6 mm, would be mainly affected by the pressure-solution mechanism. Instead, a diapir (typical differential stress between 2 and 5 MPa, strain rate tra 10 -14 to 10 -12 s -1 and 10 mm grain size) would be in the crossing point, so where the two mechanisms are equally effective.

The solution precipitation creep dominates in extrusive salt sheets because the salt is damp and has fine grains, and because the low differential stress controls the salt sheets deformation. . Time to reach 10% strain at different strain rates is shown on the right side of the graph (after [START_REF] Schléder | Microstructural evolution of deformation-modified primary halite from the Middle Triassic Röt Formation at Hengelo, The Netherlands[END_REF].

Figure 2.23 shows the relation between the strain rate and the differential stress in a temperature range between 30 to 200 °C [START_REF] Li | Rheology of rock salt for salt tectonics modeling[END_REF]. The salt rheology is strongly dependent on temperature: higher temperature leads to higher strain rate, so higher deformation.

For a certain stress, every 50 °C increase in temperature, the strain rate increases by around 1.5-2 order of magnitude. Likewise, figure 2.24 shows the effects of temperature on the strain (in percentage) in dry rock salt deformed over a long period at strain rate at low as 10 -9 s -1 (after [START_REF] Carter | Rheology of rocksalt[END_REF]. This relation highlights the importance of temperature, even at low stress and dry salt. To a certain applied stress, the strain will be higher at higher temperature. This means that increasing the temperature during creep leads a weakening of rock salt.

The ratio of stress to steady-state strain rate is constant for fixed temperaturepressure conditions and corresponds to the dynamic viscosity, also called viscosity.

Dislocation creep and solution-precipitation creep act together in salt deformation rocks, leading to changes of the viscosity. The total strain rate therefore is the sum of these two mechanisms single strain rates (dislocation and pressure-solution creep). Stress strain curves for dry Avery Island rock salt at constant strain rates over 3.5 years, after [START_REF] Carter | Rheology of rocksalt[END_REF].

structure viscosity, we must think that in the case of a salt glacier the grain is extremely fined and the viscosity can be locally as low as 10 15 Pa s [START_REF] Talbot | Extrusions of Hormuz salt in Iran[END_REF].

In the plot above (Fig. 2.26, Ter [START_REF] Heege | Relationship between dynamic recrystallization, grain size distribution and rheology[END_REF][START_REF] Watanabe | Electrical impedance measurement of plastically deforming halite rocks at 125 C and 50 MPa[END_REF], some results from synthetic rock salt samples for wet and dry salts are represented. The plot shows a first initial phase of work hardening (see above for explanations), followed by a phase of near showing the effect of temperature on the behaviour of wet polycrystalline halite at strain rate of 5-7 10 -7 s -1 . For comparison, two stress-strain curves for dry polycrystalline halite (grey curves) are included [START_REF] Watanabe | Electrical impedance measurement of plastically deforming halite rocks at 125 C and 50 MPa[END_REF]Ter Heege, 2002). To note the temperature influence on strain. (after Van Keken et al., 1993).

steady-state flow stress increasing the stress. It shows that the rock salt is weakening with temperature increasing but also with the addition of water. At a temperature of 125 °C, wet salt has a peak flow stress of about 11 Mpa while in a dry sample of about 20 MPa, with a similar grain size. The traces of water in these samples are in the range of 5 to 45 ppm (Ter Heege et al., 2005a). [START_REF] Mukherjee | Viscosity estimates of salt in the Hormuz and Namakdan salt diapirs, Persian Gulf[END_REF].

In general, the authors use consistent viscosities of about 10 17 -10 18 Pa s for the numerical approaches [START_REF] Turcotte | Geodynamics[END_REF][START_REF] Poliakov | Salt diapirism with simultaneous brittle faulting and viscous flow[END_REF]. The salt viscosity used during the analogue modelling, that supposed to reproduce salt structures, are limited to silicone viscosity (up to 10 18 Pa s; [START_REF] Costa | Experimental insights on the geometry and kinematics of foldand-thrust belts above weak, viscous evaporitic décollement[END_REF], relatively high in nature [START_REF] Mouthereau | The Zagros folded belt (Fars, Iran): constraints from topography and critical wedge modelling[END_REF]). To give an example, in the Hormuz salt (Zagros, Iran), the evaporites are at depth below 5 km [START_REF] Jackson | Salt diapirs of the Great Kavir, central Iran[END_REF] proposed viscosity of the order of 10 15 , very low.

The plot from [START_REF] Carter | Rheology of rocksalt[END_REF] To conclude, the creep equations controlled by microstructure deformation mechanisms are the base of the rheology of salt tectonic deformation under long-term conditions. In bibliography, a wide range of data in different conditions is available, in order to correlate the c) grain size, the smaller it is, the easier the movement will be d) temperature, which if it is higher, the dislocation will be easier.

Although each salt-bearing basin has its own salt characteristics as water content, grain size and impurities, the temperature plays a fundamental role in decreasing the viscosity of the salt.

The decrease of the salt strength given by temperature increase suggests that the thermal energy makes the salt weaker and more plastic, failing at lower stress and higher strain [START_REF] Sriapai | True-triaxial compressive strength of Maha Sarakham salt[END_REF]. Salt strength and stiffness increase with the loading rate and decrease with the temperature, as also recently demonstrated by [START_REF] Phatthaisong | Effects of loading rate and temperature on strength and deformability of MahaSarakham salt[END_REF] and [START_REF] Taheri | Investigation of rock salt layer creep and its effects on casing collapse[END_REF]. Moreover, the temperature effect is larger when salt is under higher mean stress, which is typically the case of a salt buried under kilometres of sediment, as in the different passive margins of the world. This brief review of the relationship between temperature and viscosity shows that this relationship should not overlooked. Despite the temperature influence on rock deformation is undeniable, the authors do not agree on its importance in regional salt tectonics, as it does not seem to be enough to trigger the movement (e.g. [START_REF] Hudec | Terra infirma: Understanding salt tectonics[END_REF][START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF].

Gypsum and Anhydrite rheology

Gypsum (CaSO4*2H20) is one of the weakest and most ductile common rocks [START_REF] Baumann | Rheologische Untersuchungen an Gips[END_REF]De Meer andSpiers 1995, 1997). When the strain increases, the pressure-solution and dynamic recrystallization reduce the grain size, making the gypsum weak. [START_REF] Griggs | Experimental flow of rocks under conditions favouring recrystallization[END_REF] stated that the gypsum is weakened by water and by confining pressure. Nevertheless, for a given differential stress, dry halite deforms about 10 5 times faster than dry gypsum. The dry gypsum, in turn, deforms about 10 7 times faster than dry anhydrite (Figure 2.29;[START_REF] Williams-Stroud | Initiation and growth of gypsum piercement structures in the Zechstein Basin[END_REF]. In general, in the salt tectonics, the deformation of gypsum and anhydrite is not taken into account, as it is too weak. Moreover, it is difficult to well compare the behaviour of halite and gypsum/anhydrite because the flow laws for solution-precipitation creep are not yet known.

Basin-scale salt deformation processes

Salt deformation base models

The mechanisms at micro-scale explained in the previous chapter lead, at a geological time scale, to what is called salt tectonics. Salt tectonics is defined as the deformation of salt bodies, subject to different forces, which can give rise to staggering structures. The forces that come into play in salt tectonics are of 4 types, two actives and two passives, of resistance (Ramberg, 1981a).

• The first active force is the gravitational force (Fg) and depends on the density of the body, its size and the force of gravity. The second active force is the pressure force (Fp), which is influenced by the differential stress applied and the dimension of the body.

• The first resistance force is the viscous force, influenced by the viscosity and the dimension of the body. The lower the viscosity, the lower the resistance and the higher the displacement.

The second resistance force is the frictional force, derived by the friction between particles sliding one past another. The sum of these four forces, given by interaction between salt and its overburden, result in salt movement. If the active forces prevail, salt moves, otherwise salt remains static, even for geological time. As stated, salt moves because of gravitation force and/or by differential stress. This two forces are summarized in the "loading", which is differentiated in "gravitational", "displacement" and "thermal" loading (e.g. [START_REF] Suppe | Principles of structural geology[END_REF][START_REF] Jackson | External shapes, strain rates, and dynamics of salt structures[END_REF]Jackson et al., 1987;[START_REF] Vendeville | Physical models of extensional tectonics at various scales[END_REF]Vendeville and Jackson, 1992).

In the gravitation loading the salt responds to head gradient, which controls the direction and the magnitude of the salt flow. The head gradient is given by the elevation head (the elevation between two points) and the pressure exerted by the overburden. Therefore, salt flows in response to head gradients from points of high head to points with lower head. The gravitational loading can be divided into two end-members, called the gravity spreading and the gravity gliding (Fig. 2.30) (e.g. [START_REF] Ramberg | Gravity, deformation and the Earth's crust in theory, experiments and geological application[END_REF]. During the first the salt collapses under its own weight while in the second the salt, considered as rigid block, flows above a detachment surface, created at the interface with the sediments.

The key factor for the gravity gliding is the dip of the detachment, i.e. the dip of the base of salt, while in the gravity spreading the key factors is the differential internal loading which can led to a vertical collapse and/or lateral spreading (e.g. [START_REF] Davis | Mechanics of fold-and-thrust belts and accretionary wedges[END_REF]Rowan et al., 2004) (Fig. 2.30). [START_REF] Rowan | Gravity-driven fold belts on passive margins[END_REF].

Salt, with its ductile nature, is always deposited as flat horizontal layers. Nevertheless, the base of salt dip may change through time as a result of different processes, such as a) a differential thermal subsidence, which may tilt the passive margin towards the deep basin, b) the presence of prograding sedimentation load, which influence the subsidence and could increase the tilting, c) the tectonics events, at regional scale (e.g. uplift of the craton, [START_REF] Duval | Raft tectonics in the Kwanza basin, Angola[END_REF], or the basement rise due to compression or volcanic activity [START_REF] Rowan | Gravity-driven fold belts on passive margins[END_REF].

Following some authors (e.g. [START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF][START_REF] Brun | Salt tectonics at passive margins: geology versus models-Reply[END_REF] gravity gliding is the main salt flow mechanism that play a role in a passive margin. The trigger of the salt movement would be the tilting of the entire margin, more important at an early stage, where the thinned continental and the oceanic crust cool rapidly, become denser, and sink. To activate the dominant gliding mechanism, the minimum margin tilt angle depends on basin width and on overburden thickness (Fig. 2.31; [START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF]. Following these authors, a salt base with a slope of at least 1 degrees can trigger the salt movement.

Under natural conditions, however, it is difficult to distinguish the two end-members (gliding and spreading), which continuously interact with each other. The significance of the two mechanisms is still debated (see for instance [START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF]2012;[START_REF] Rowan | Salt tectonics at passive margins: Geology versus models-Discussion[END_REF][START_REF] Peel | How do salt withdrawal minibasins form? Insights from forward modelling, and implications for hydrocarbon migration[END_REF] mainly due to differences in interpretation and natural cases (Fig. 2.30c). [START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF]. [START_REF] Peel | How do salt withdrawal minibasins form? Insights from forward modelling, and implications for hydrocarbon migration[END_REF] gave some geometrical instruments to recognize the contributions of the two mechanisms but he also confirmed that the pure spreading or gliding systems are only achieved under exceptional circumstances. For this reason, [START_REF] Schultz-Ela | Excursus on gravity gliding and gravity spreading[END_REF] argued not to use these outdated terms but to find other classifications to the movement given by gravity, such as the approach based on faults patterns defined by [START_REF] Rowan | Salt-related fault families and fault welds in the northern Gulf of Mexico[END_REF]. In this work, for the description of salt tectonics, I will use the two terms (gliding-spreading) to relate them relatively to each other. Although the two terms have limitations, they are still widely used by the scientific community to divide the salt deformation mostly influenced by the dip of the base of salt or by the progradational loading sedimentation.

It is worth to note that these two "displacement" mechanisms (gliding-spreading) for the salt movement, describe a translation from areas where loading is the highest toward areas where it is the lowest. In passive margins, this movement translates into a slipping/translation of the salt towards the deep basin, where it will occupy an allochthonous position (see following chapters for more explanation of allochthonous salt) with respect to its primary deposition. The presence of space in the deep basin where the salt can "settle" after the translation is therefore a sine qua non condition for the gravitational and displacement loading mechanisms.

The other main mechanisms in salt tectonic is the displacement loading, caused by regional shortening or extensional forces (Fig. 2.32). An example of typical extensional structures are the reactive diapirs described by Vendeville and Jackson, (1992). The formation of these structures is closely linked to the extension of the sedimentary overburden, which therefore generate a differential loading above the salt layer. In an extensional domain two main mechanisms can be defined, which are the thin-skinned extension and the thick-skinned extension. The first one (thin-skinned) (Fig. 2.33) is typical of margins where the salt gliding generates faults fully detached from basement. This mechanism is driven by gravity and, the steeper is the dip on the detachment, the greater is the extension of the system.

The second one (thick-skinned) is driven by extension which involves the base of salt and the underlying basement (Fig. 2.34). This mechanism is typical of areas where the salt is deposited just above the basement or separated by a thin sedimentary layer. In this case, when the basement is involved in extension and faulted, the displacement can involve also the salt layer influencing its deformation. [START_REF] Reis | Radial gravitacional gliding indicated by subsalt relief and salt-related structures: the example of the gulf of Lions, western Mediterranean[END_REF] showing an example of thinskinned tectonics. To note the listric faults that not dislocate the base of salt and the Miocene sequence.

The reactive diapirism described by Vendeville and Jackson, (1992) is attributable to a displacement loading, because an extensional tectonic is necessary. However, the main force that allows the movement of the salt remains the gravitational loading, induced by a load gradient formed in the overburden by small grabens.

As in the extensional salt tectonics, the compression leads to a thin and thick shortening, involving the basement and the salt base detachment surfaces. The first one is found in orogen fold belts [START_REF] Letouzey | Evolution of salt-related structures in compressional settings[END_REF][START_REF] Rowan | Gravity-driven fold belts on passive margins[END_REF][START_REF] Morley | Deepwater fold and thrust belt classification, tectonics, structure and hydrocarbon prospectivity: A review[END_REF] while a basementinvolved shortening is typical of tectonic inversion settings, as the Zechstein salt basin (e.g. Ten [START_REF] Ten Veen | Thin-and thick-skinned salt tectonics in the Netherlands; a quantitative approach[END_REF].

The thermal loading is given by the volume change caused by temperature variations in rock salt. Thermal expansion of salt, as explained in chapter 2.2.1, is higher compared to other rocks (e.g. seventy times that of quartz, [START_REF] Jackson | Salt tectonics: Principles and practice[END_REF] and may induce higher stress when the confining pressure is higher enough to avoid expansion. Moreover, a heat source may produces thermal convection, inducing a decrease in kinematic viscosity or thermal expansion. Following some authors [START_REF] Van Keken | The effective viscosity of rocksalt: implementation of steady-state creep laws in numerical models of salt diapirism[END_REF], for a viscosity lower than 10 16 Pa s, a thermal convection seems to be possible in nature, as seen and described by [START_REF] Talbot | Hydrothermal salt-but how much?[END_REF] and [START_REF] Jackson | Salt diapirs of the Great Kavir, central Iran[END_REF]. Thermal convection affects a fluid when their Rayleigh number exceeds the critical Rayleigh number. Without going into mathematical equations, Rayleigh number is mainly influenced by thermal expansivity, salt layer thickness, temperature gradient between base and top and viscosity [START_REF] Turcotte | Geodynamics[END_REF]. Salt, due its special properties, has a low Rayleigh number (e.g. Rc = 656, Chandrasekhar, 1961). [START_REF] Talbot | Halokinesis and thermal convection[END_REF] [START_REF] Warsitzka | The timing of salt structure growth in the Southern Permian Basin (Central Europe) and implications for basin dynamics[END_REF] showing a salt diapir overlying a large-offset normal faults (thick-skinned tectonics). Zechstein salt deposits, south Permian basin. The basement tectonic has a major control on salt deformation.

that the heat gradient could add an extra component on gravitational instability previously considered solely responsible of salt flowing.

To summarize, the salt moves thanks to the action of forces induced by tectonic movements or mainly by gravity, which in turn leads to a differential load. Furthermore, if we also take up the considerations on rheology and thermal loading, it seems that temperature can play a role in deformation, decreasing the viscosity of the salt and therefore helping its movement.

Salt structures

Salt has a significant impact on the evolution of a sedimentary basin as it implies, through its deformation, vertical and horizontal movements on a regional scale. Because of its particular properties (chapter 2.2.1) and through the mechanisms explained in chapter 2.2.2, salt forms, on geological timescales, a staggering variety of structures (Fig. 2.35). [START_REF] Jackson | A glossary of salt tectonics[END_REF].

Diapirs are the more common salt structures present in the world. They are ductile masses of rock or sediments that have pierced their overburden. This term is now-days used to describe several structures sharing piercing behaviour and discordant contacts against their overburden. Diapirs are made of salt but also shale, mud and magmatic material. Others terms are used to describe salt diapirism such as salt stocks and salt walls. The first one is a plug-like body, whereas the second one is more elongated (Fig. 2.35). These two typology of structures are, respectively, the direct maturity evolution of the salt pillows and salt anticlines. In the salt anticlines, the salt is concordant with the overburden, i.e. the salt is overlain by parallel overburden strata, and therefore it does not pierce it.

Several authors (e.g. [START_REF] Jackson | Seismic recognition of salt welds in salt tectonics regimes. In Gulf of Mexico salt tectonics, associated processes and exploration potential[END_REF][START_REF] Vendeville | Champs de failles et tectonique en extension: modélisation expérimentale[END_REF]Worrall and Snelsol, 1989;Vendeville and Jackson, 1992a,b;[START_REF] Weijermars | Rheological and tectonic modeling of salt provinces[END_REF] described three main types of salt diapirs (Fig. 2.36).

The reactive diapir, as mentioned above, is formed during extensional faulting caused by regional tectonics. The salt reacts to the regional stretching and occupies the space created in et al., (1994); (B) after Jackson and Vendeville, (1991a).

the grabens. An active diapir pierces the overburden pushing aside the sedimentary roof. The active diapir has not yet reached the surface and grows and evolves with sedimentation. To allow the growing, the roof must be less than 20 percent of the sediments thickness flanking the diapir [START_REF] Jackson | Structural dynamics of salt systems[END_REF]. When the structures emerge on the surface it becomes passive and continues to grow up while sediment accumulates around it in a process also called "downbuilding" (Barton, 1933) (Fig. 2.37). When the salt starts to flow, the evaporites reliefs force the sedimentary system to be located in the low areas separating them. This sedimentary lows help to maintain the differential loading and, through the process evolution, the overburden will sink into the evaporites layer. This phenomenon maintains the growth of the diapir [START_REF] Rowan | Near-salt deformation in La Popa basin, Mexico, and the northern Gulf of Mexico: A general model for passive diapirism[END_REF], until the complete expulsion of the evaporites and the formation of the so-called weld (Fig. 2.37).

The top of the passive diapir is covered only by a thin cap rock, formed by alteration and dissolution of the halite. The cap rock is mainly characterized by an anhydrite and a calcite zones and in seismic imaging is represented by strong amplitude reflectors (e.g. [START_REF] Posey | Fluid-rock interactions in the salt dome environment: an introduction and review[END_REF].

These three main mechanisms are not mutually exclusive; their modality can change during their evolution, they also may grow in only one of these modes within the entire basin history.

As previously mentioned, the salt structures are mostly influenced by different agents, which are implemented together and play a fundamental role in the evolution of the structures at basin scale.

At geological time scales, one of the main agent controlling the diapir evolution is the adjacent sedimentation (e.g. [START_REF] Cobbold | Some experiments on interacting sedimentation and deformation above salt horizons[END_REF]Vendeville and Jackson, 1992a;[START_REF] Vendeville | Salt tectonics driven by sediment progradation: Part I-Mechanics and kinematics[END_REF][START_REF] Gaullier | Salt tectonics driven by sediment progradation: Part II-Radial spreading of sedimentary lobes prograding above salt[END_REF][START_REF] Loncke | The Nile deep-sea fan: an example of interacting sedimentation, salt tectonics, and inherited subsalt paleotopographic features[END_REF]. [START_REF] Giles | Halokinetic sequence stratigraphy adjacent to the El Papalote diapir, northeastern Mexico[END_REF] proposed the term "Halokinetic sequences" to describe the sedimentary sequence adjacent to a diapir, which provides a good methodology for mapping growth strata packages [START_REF] Ribes | Interaction entre la tectonique salifère et la sédimentation dans des mini-bassins: Exemple de l'Oligo-Miocène du bassin de Sivas[END_REF][START_REF] Barton | Mechanics of formation of salt domes with special reference to Gulf Coast salt domes of Texas and Louisiana[END_REF].

and therefore predict the growth evolution and the interaction with the sedimentation of salt structures.

Figure 2.38 shows the two end-members in halokinetic sequences types: the hook and wedge halokinetic sequences. They are subdivided according to geometries of the unconformities on the diapirs flanks, controlled by the ratio between diapir growth and sedimentary accumulation [START_REF] Giles | Concepts in halokinetic-sequence deformation and stratigraphy[END_REF]. The hook sequence (Fig. 2.38A) is characterized by narrow and steep drape-fold and highly angular unconformities at the top of the sequences. The vertical stacking of these singular sequences forms the tabular composite sequence (Fig. 2.38C) where the strata thinning and the drape-fold take place within 200 m of the diapir. This sequence represents a natural case when the sedimentary accumulation rate is lower than the diapir growth, resulting in the formation of a diapiric relief and a weak sedimentary cover over time. The wedge sequences (Fig. 2.38B) have broad and gentle drapefold geometries over a greater distance compared to the Hook sequences. The vertical stacking forms the tapered composite sequences (Fig. 2.38D), creating a large scale package with a broadly folded tapered form. This sequence represents a case where the sedimentary accumulation rate is greater than the diapir growth, resulting in a thick sedimentary cover on the diapirs flanks. [START_REF] Giles | Concepts in halokinetic-sequence deformation and stratigraphy[END_REF].

These two examples of structures are based on the offshore seismic data and onshore observations and allow to establish and correlate sedimentary accumulation with diapir growth.

In the chapter 4, the sedimentary input and the diapirism growth in the deep basin of the Gulf of Lion will be related, partly taking up the concepts set out in this paragraph.

The salt supply is another main agent which influences the diapirism evolution. Salt supply is related to the salt flow and its velocity. If the salt flows slowly, the rise would be slower and vice versa. The flow of salt is influenced by several structural parameters and its rheology, which in turn is mainly influenced by the forces that come into play and the temperature.

Likewise, the increase of salt supply may be the consequence of sediment aggradation which enlivens salt bodies and/or by the base salt tilting, which help salt to move downdip. Finally, as mentioned above, the regional extension and shortening control the trigger and evolution of a diapir. They shift the balance in the overburden and in the salt supply. The overburden can thin during extensional tectonic and lead to reactive diapir formation or can thicken because of shortening and increase the pressure on salt layer. All these agents can obviously act together and establish some of the main causes and modalities of diapirs formation and evolution.

Insights from passive margins salt tectonics

I have so far discussed the main mechanisms of salt tectonics, highlighting what may be their major influences, both at the level of micro-structures and intrinsic characteristics of salt, as well as at a regional scale with their external causes. In this chapter, I focus on the salt deformation in passive margin context, discussing the main causes defended by different authors.

The evolution of salt tectonics in a passive margin depends primarily on the timing of its deposition. The definition of the rifting phases and their meaning is still debated (e.g. [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Péron-Pinvidic | The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view[END_REF]Rowan, 2014 etc.) and therefore defining salt deposition timing with respect to the formation of margins is tricky. Some authors (e.g. [START_REF] Jackson | Structural dynamics of salt systems[END_REF][START_REF] Tari | Examples of salt tectonics from West Africa: a comparative approach[END_REF][START_REF] Jackson | Salt tectonics: Principles and practice[END_REF] divided salt-bearing passive margins in "Pre-rift", "Syn-rift" and "Post-rift" salt basins (Fig. 2.39). [START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF][START_REF] Rowan | The South Atlantic and Gulf of Mexico salt basins: crustal thinning, subsidence and accommodation for salt and presalt strata[END_REF] edited this first classification and he divided the salt-bearing margins in "Prerift", "Stretching", "Syn-thinning" and "Syn-exhumation", according to rifting model from Péron-Pinvidic and [START_REF] Péron-Pinvidic | The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view[END_REF]. The main problem of these definitions concerns the general applicability of the models to all margins with salt deposits and the validity of the rifting model taken into account, which may find inconsistencies with the interpretation of other authors (e.g. [START_REF] Huismans | Depth-dependent extension, two-stage breakup and cratonic underplating at rifted margins[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF].

Nevertheless, these simplistic classification, which I will discuss in part in the next chapters of this work, provides good starting points for a differentiation of salt deposition in passive margins.

Figure 2.39. Sketch representing the three end-member used to describe the timing of salt deposition with respect the rifting stages. A) Pre-rift salt basins; note the present-day uneven salt distribution along the margin and the absence of a thick pre-salt sedimentary sequence. B) Syn-rift salt basin: uneven initial salt thickness which deposited in structural highs and lows. C) Post-rift salt basins; the salt is highly continuous and is deposited above a thick sag pre-salt sedimentary sequence (from [START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF][START_REF] Jackson | Salt tectonics: Principles and practice[END_REF].

The salt distribution in pre-rift salt basins (Fig. 2.39a; e.g. [START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF][START_REF] Tari | Examples of salt tectonics from West Africa: a comparative approach[END_REF] described by these authors question the way in which salt is deposited: how can it be deposited if rifting has not yet begun and therefore if there is no subsidence or water supply? An example of syn-rift salt basin (Fig. 2.39b) is the Morocco-Nova Scotia conjugated margin, called by Rowan, (2014) syn-stretching and syn-thinning salt basins. In these margins, the salt deposited in lateral transition with continental to coastal sediments in syn-rift half-grabens and the salt structures distribution is influenced by the rift geometry and modified during ongoing extension [START_REF] Hafid | Triassic-early Liassic extensional systems and their Tertiary inversion, Essaouira Basin (Morocco)[END_REF][START_REF] Tari | Salt tectonics along the Atlantic margin of Morocco[END_REF]. Here, the salt tectonics is summarized as the result of thick-skinned tectonics caused by tilting of the margin and differential uplift of the Atlas Mountains, located adjacent to the margin [START_REF] Rowan | Gravity-driven fold belts on passive margins[END_REF][START_REF] Tari | Salt tectonics along the Atlantic margin of Morocco[END_REF].

The last typology are the post-rift salt basins (Fig. 2.39c), described in Rowan, (2014) as synexhumation salt basins, characterized by salt deposited above a thick "sag" sequence which predates the oceanic crust break-up. In this case, salt deformation is triggered and driven by basinward gravity gliding caused by margin tilting and gravity spreading, caused by progradational loading of sediments in the proximal part of the deep basin (e.g. [START_REF] Rowan | Gravity-driven fold belts on passive margins[END_REF][START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF][START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF]2012;[START_REF] Rowan | Salt tectonics at passive margins: Geology versus models-Discussion[END_REF]. Best examples are given as the South Atlantic passive margins and the Gulf of Mexico, characterized by a wide transitional domain between oceanic and continental domain.

Following a general consensus, driving forces of salt tectonics in passive margins are attributable to gravity spreading and gravity gliding end-member models (Fig. 2.40). Although these two terms are difficult to distinguish one from the other (e.g. [START_REF] Schultz-Ela | Excursus on gravity gliding and gravity spreading[END_REF][START_REF] Peel | How do salt withdrawal minibasins form? Insights from forward modelling, and implications for hydrocarbon migration[END_REF], they are still used today to understand the dynamics of salt deformation, from its deposition to nowadays.

Using mainly numerical and analogical modelling and seismic observations, Brun andFort, (2011, 2012) and [START_REF] Rowan | Salt tectonics at passive margins: Geology versus models-Discussion[END_REF] discussed on which mechanism is dominant in the passive margins salt tectonics. The fundamental debates stands on understanding if the sedimentary supply or the base salt tilting is the main dominant force. In this study I will partly discuss their importance in the Western Mediterranean Sea. Both mechanisms are substantially moved by the same force, the loading, which can act and induce the movement of salt through gravity (gliding) or the weight of sediments (spreading) (Fig. 2.40).

As highlighted so far, an important factor described by the authors as a trigger and cause of salt deformation is the gliding of salt and its overburden along an inclined surface, induced by the post-rift subsidence margin tilting. The understanding of the deformation evolution of salt structures from their deposition to the present day goes therefore through the understanding of post-rift subsidence.

Some authors [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF] observed a strong purely vertical subsidence in the Angolan deep basin from the rifting stage to present-day (Fig. 2.41), questioning the tilting of the entire margin. The salt deposited above the sag basin thus subsided without a tilting of the base during all its deformation history. This key observation, depicted also in the Gulf of Lion (see sub-chapter below), calls into question the role of gravity salt gliding in passive margin and will be a significant clue for discussion in the next chapters. [START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF].

Salt tectonics in the Western Mediterranean Sea: previous studies

In this chapter, I discuss the literature works dealing with the salt deformation in Western Mediterranean Sea. As mentioned above (chapter 2.1.4), the Mediterranean salt is deposited during the Messinian Salinity Crisis, a huge paleo-environmental crisis that occurred around 6 Ma ago.

The salt tectonics in Western Mediterranean Sea was discussed since the works of Le Cann (1987), [START_REF] Gorini | Géodynamique d'une marge passive: le Golfe du Lion (Méditerranée occidentale[END_REF] and [START_REF] Gaullier | Diapirisme salifère et dynamique sédimentaire dans le bassin Liguro-Provençal. Données sismiques et modèles analogiques[END_REF], especially in the Liguro-Provençal basin. The authors described for the first time the salt structures already recognized and localised by [START_REF] Alinat | Accidents de terrain en Mer de Ligurie[END_REF] and [START_REF] Pautot | Morphology and extension of the evaporitic structures of the Liguro-Provençal Basin: New Sea-Beam data[END_REF]. The latter firstly quantify the diapirs size in the deep Liguro-Provençal basin, estimating that their crest can rise to 250 m above the sea-bottom.

In the Gulf of Lion some authors noticed the coincidence between the oceanic-continent boundary and the upslope limit of diapir province [START_REF] Le Cann | Le diapirisme dans le bassin Liguro-Provençal (Méditerranée occidentale)[END_REF][START_REF] Mauffret | Étude géodynamique de la marge des îles Baléares[END_REF]Olivet, 1987;[START_REF] Pautot | Morphology and extension of the evaporitic structures of the Liguro-Provençal Basin: New Sea-Beam data[END_REF]Réhault et al., 1984). To explain this surprising coincidence, Le Cann (1987) proposed that the diapirs province allows to locate a structural limit, between the oceanic and the continental crust. This structural limit testifies two distinct structural domains, characterized by different directions of predominant deformation. The first family is characterized by NE-SW direction and is present in the Alps, in the Gulf of Valencia and in the Gulf of Lion. It corresponds to the system which has controlled the opening of the Liguro- (112,2 Ma). The purely vertical subsidence in the deep basin (transitional domain, crust 1 and 2) and the tilting in the continental slope domain are shown. The salt is deposited above a thick, not brittle, sag basin at nearzero water depths. During salt deposition the subsidence is approximately equal to sedimentation rate and strongly increase afterwards (after [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF].

Provençal, and Menorca basins and is widely present in all the basin [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF].

The second family is characterized by N-S and E-W direction and is absent in the oceanic domain. Le Cann therefore proposed, after the rejection of sedimentary and density inversion causes, that the salt diapirs are influenced by a reactivation of this second family of faults that may have had a differential impact on salt structures according to their location within/above a continental or an oceanic domains. More recently, [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF] discarded this hypothesis inferring that the timing of the basement reactivation does not match with the timing of the initiation of salt deformation in this area. They proposed and used analogue modelling to suggest that the basement steps associated with these faults zone could act as dormant basement relief (Fig. 2.42). They explained the coincidence between sub-salt and supra-salt structures in the Gulf of Lion as the influence of the differential compaction of subsalt sediments which transmit upward the basement topography and thereby influence the salt structures.

Figure 2.42. The differential compaction above a basement step during gravitational gliding is shown. The regional slope is of 3°. To note, in figure c, the differential compaction effect above the basement step and the graben formed above the updip part (after [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF]. Note the scale in the experimental set-up, which involved a basement step 2-3 times greater than the silicone (salt) thickness.

The authors summarized that the salt structures and their distribution in Western Mediterranean Sea are the results of several main mechanisms, below described.

The differential loading through the gravity gliding and spreading. In all basins of the Western Mediterranean Sea, as well as in other passive margins, the authors described three domains from the lower slope to the deep basin, characterized by different salt structures (e.g. [START_REF] Vendeville | Champs de failles et tectonique en extension: modélisation expérimentale[END_REF][START_REF] Gaullier | Diapirisme salifère et dynamique sédimentaire dans le bassin Liguro-Provençal. Données sismiques et modèles analogiques[END_REF][START_REF] Gorini | Géodynamique d'une marge passive: le Golfe du Lion (Méditerranée occidentale[END_REF][START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF]Dos Reis et al., 2005;[START_REF] Granado | Geodynamical framework and hydrocarbon plays of a salt giant: the NW Mediterranean Basin[END_REF]. [START_REF] Gaullier | Diapirisme salifère et dynamique sédimentaire dans le bassin Liguro-Provençal. Données sismiques et modèles analogiques[END_REF] carried out analogue experiments simulating the physical properties of salt (using silicone) and structural parameters of the Gulf of Lion. She inferred that these domains are the results of the gravity gliding mechanism, typical of those described in other passive margins (Fig. 2.43) (Vendeville and Jackson, 1992a;[START_REF] Peel | Genetic structural provinces and salt tectonics of the Cenozoic offshore US Gulf of Mexico: A preliminary analysis[END_REF][START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF][START_REF] Cobbold | Seismic and experimental evidence for thin-skinned horizontal shortening by convergent radial gliding on evaporites, deepwater Santos Basin[END_REF].

Following the more recent classification made by Dos [START_REF] Reis Dos | Implications of salt-sediment interactions on the architecture of the Gulf of Lions deep-water sedimentary systems-western Mediterranean Sea[END_REF], the three domains are (Fig. 2.44): i) a proximal Listric Normal Faults Province, ii) an intermediate Rigid Translation Province (Tabular Salt Province) and iii) a distal Salt Domes Province. The upslope first domain is characterized by regional listric faults and associated hanging-wall rollovers and footwall salt rollers; the translation domain is characterized by tabular salt and the deep basin domain is characterized by passive diapirism mainly triggered by sedimentary loading (e.g. [START_REF] Granado | Geodynamical framework and hydrocarbon plays of a salt giant: the NW Mediterranean Basin[END_REF].

These three provinces are the result of thin-skinned tectonics, active everywhere in Mediterranean Sea at the limit between lower slope and deep basin. The salt base acts as a level of décollement and is not involved in regional faults. Moreover, following for instance [START_REF] Vendeville | Salt tectonics driven by sediment progradation: Part I-Mechanics and kinematics[END_REF], [START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF] and [START_REF] Gaullier | Salt tectonics in the deep Mediterranean: indirect clues for understanding the Messinian Salinity Crisis. The Messinian salinity crisis from mega-deposits to microbiology-A consensus report[END_REF] the location and the orientation of the salt structures and associated depocenters are mainly controlled by differential sedimentary loading. The salt diapirs network suggests a multi-directional thin-skinned contraction [START_REF] Gaullier | Salt tectonics driven by sediment progradation: Part II-Radial spreading of sedimentary lobes prograding above salt[END_REF][START_REF] Gaullier | Salt tectonics in the deep Mediterranean: indirect clues for understanding the Messinian Salinity Crisis. The Messinian salinity crisis from mega-deposits to microbiology-A consensus report[END_REF][START_REF] O Obone-Zue-Obame | The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the "MAURESC" cruise[END_REF]. [START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF]Dos Reis et al., 2005, 2008;[START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF][START_REF] Gaullier | Salt tectonics in the deep Mediterranean: indirect clues for understanding the Messinian Salinity Crisis. The Messinian salinity crisis from mega-deposits to microbiology-A consensus report[END_REF] where the setting of the sub-salt influences the salt deformation. In the North Balearic basin, between the Valencia basin and the Gulf of Lion, the North-Balearic Transfer Zone (NBTZ, e.g. [START_REF] Olivet | La cinématique de la plaque ibérique[END_REF] is characterized by an area with extinct or still active volcanism [START_REF] Maillard | Transfer zones and associated volcanic province in the eastern Valencia Basin: Evidence for a hot rifted margin?[END_REF], formed by basement steps, which may have influenced or still influence the salt deformation [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF][START_REF] Gaullier | Salt tectonics in the deep Mediterranean: indirect clues for understanding the Messinian Salinity Crisis. The Messinian salinity crisis from mega-deposits to microbiology-A consensus report[END_REF]. In the north Algerian margin, characterized by a tectonic reactivation caused by the Europe-Africa convergent plate boundary, the salt is involved in the play of active ramps and flats (e.g. [START_REF] Déverchère | Active thrust faulting offshore Boumerdes, Algeria, and its relations to the 2003 Mw 6.9 earthquake[END_REF][START_REF] Domzig | Searching for the Africa-Eurasia Miocene boundary offshore western Algeria (MARADJA'03 cruise)[END_REF]), delineating a typical example of thick-skinned tectonics in which the salt base is dislocated and is influenced by the movements of the sub-salt (Fig. 2.45). Processes as the gravity gliding are depicted offshore Algiers, caused by the rise of a basement plateau as a [START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF]. In each of these salt-structural domains, overburden extension evolved under variable influence of progradational sediments and residual relief in the base salt.

consequence of crustal convergence [START_REF] Domzig | Searching for the Africa-Eurasia Miocene boundary offshore western Algeria (MARADJA'03 cruise)[END_REF]. Dos [START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF], analysing in detail the relationship between sedimentation and salt deformation in the Gulf of Lion, indicated that the thin-skinned tectonics could be influenced also by the relief of the sub-salt basement. In the Gulf of Lion, the salt movement and downslope overburden translation have evolved under the influence of a radial gravitational gliding, caused by the variable morphology of the base salt surface.

The mechanisms just described occur together on a regional scale. The impact of a single element derives from its magnitude, such as the sedimentation or the sudden rise of the basement. Subsequent salt structures, in turn, may influence the bathymetric relief and the overburden can thus influence the facies, thickness and even the distribution pattern of the syntectonic sediments. There is an intricate mutual influence between sedimentation and structure, as explained for instance by Dos [START_REF] Reis Dos | Implications of salt-sediment interactions on the architecture of the Gulf of Lions deep-water sedimentary systems-western Mediterranean Sea[END_REF].

As mentioned in the chapter 1, salt deposition in Western Mediterranean was not involved in passive margin formation, as is the case of South Atlantic for instance. The Messinian salt was deposited about 6 Ma years ago, above a thick Oligo-Miocene and Miocene marine sequences. All the Western Mediterranean sub-basins were already formed at the time of salt deposition. This main difference with some of world passive margins represents a fundamental point for the understanding of salt tectonics. Moreover, as lastly mentioned for the Angolan margin, some authors described a similar purely vertical subsidence in the Gulf of Lion deep basin. Describing the sedimentary markers and their paleo-bathymetric significance, [START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF] observed a purely vertical subsidence in the Gulf of Lion deep basin and a tilting in the continental domain (Fig. 2.46), subsequently confirmed by an extensive 3D regional analysis and a numerical stratigraphic modelling by [START_REF] Leroux | Post-rift evolution of the Gulf of Lion margin tested by stratigraphic modelling[END_REF]. The subsidence domains coincide with deep crustal domain described on deep seismic profile [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF]: the limit between the tilt domain and the purely vertical subsidence domain is located between the thinning continental and the transitional domains (Domain II and III;fig. 2.46). These observations mean that the salt deposited goes through a vertical subsidence during its deformation history, at least in the deep basin, where it is mostly laid.

The almost stationary horizontal tectonic movements, the purely vertical subsidence, the infill of the entire basins during Messinian, after any horizontal movement, make the Western Mediterranean Sea a key area for the discussion of salt tectonic mechanisms. [START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF].

Summary chapter 2

Chapter 2 aims to give an overview of the processes of salt deposition and deformation. The evaporite is a rock that was originally precipitated from a saturated surface or near-surface brine by hydrology-driven solar evaporation. Salt-bearing basins can be found all over the world and are of different ages, from the Precambrian to the Quaternary. Some of the major are the Permian Zechstein salt basin in the Central Europe, the Triassic Central Atlantic margins, the Jurassic Gulf of Mexico salt basins, the Cretaceous South Atlantic margins and the Miocene Mediterranean Salt Giant. The Messinian Salinity Crisis in the Mediterranean led to the deposition of a thick blanket of evaporites, including salt, making it one of the world's largest and youngest salt basins. Salt tectonics is a consequence of the intrinsic properties of salt, which make it viscous and rapidly mobile. Some of these characteristics are its density, which is almost unchanged with depth, its incompressibility and its low viscosity.

Furthermore, the viscosity is indirectly proportional to temperature: at high temperatures, salt moves faster and easier. Moreover, because of its high thermal conductivity, the heat exchange is promoted around it. At the regional level, salt tectonics is mainly described by two models, gravity gliding and sedimentary spreading, given respectively by the head gradient and the differential sedimentary load. These two end-members are supplemented by external tectonic forces that may come into play, such as shortening and extension. The resulting structures have a wide variability due to the coexistence of all these mechanisms. In the Western Mediterranean, a regional study of the mechanisms involved in the salt tectonics is lacking. Several studies, mainly located in the Gulf of Lion, have shown that the role of the base salt slope and sedimentary fans are predominant in the formation of salt morphologies. Nevertheless, some observations on the specificity of the Western Mediterranean cast doubt on the relevance of these models.

Résumé chapitre 2

Le chapitre 2 vise à donner un aperçu des processus de dépôt et de This chapter is dedicated to the presentation of the data and the methodology used in this thesis work. This includes reflection and wide-angle seismic as well as heat flow measurements.

Data

Reflection seismic data

Since the 1960s the West Mediterranean has been investigated by reflection seismic surveys, both with academic and industrial objectives. Although some surveys are relatively old, new processing techniques have allowed a good improvement of quality. The results gave a great variability of available data, with strong differences in resolution and quality. In the Gulf of Lion, a first industrial reflection seismic compilation was made by [START_REF] Gorini | Géodynamique d'une marge passive: le Golfe du Lion (Méditerranée occidentale[END_REF] and Maillard (1993), complemented by [START_REF] Bache | Evolution Oligo Miocène des marges du micro océan Liguro-Provençal[END_REF], [START_REF] Garcia | The Catalan margin during the Messinian Salinity Crisis: Physiography, morphology and sedimentary record[END_REF], [START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF][START_REF] Driussi | Evolution de la région Baléares (Méditerranée ocidentale) du Néogène à l'actuel: aspects géodynamiques et paléoenvironnementaux[END_REF] and [START_REF] Pellen | Géodynamique et impact de la crise d'érosion et de salinité Messinienne sur les transferts sédimentaires (bassins de Valence et Adriatique)[END_REF], the last two by adding a dense grid in the Valencia basin. Over the years the dataset has grown, thanks to collaborations between several French and foreign institutes, such as the GDR "Margins" (Groupement de Recherches 'Marges') followed by Action Marges, which within multidisciplinary studies had the objectives to better understand the processes that control the formation and evolution of continental margins (e.g. [START_REF] Berne | The Gulf of Lions: An overview of recent studies within the French'Margins' programme[END_REF]. In the framework of this thesis, we could add some new lines to the dataset coming from the Italian institutions thanks to the close collaboration with OGS (National Institute of Oceanography and Applied Geophysics) and the University of Trieste. Since one of the main objectives is the analysis of the salt structures, we have focused on collecting all the lines at our disposal in the deep basin, in order to work on the highest-resolution dataset possible.

Figure 3.1 shows the seismic location of all lines used for the study of salt structures in the Western Mediterranean Sea. The available surveys can be differentiated from their origin (academic or industry) and their resolution. We firstly divided the seismic dataset into 4 categories according to their resolution, as shown in the legend (Fig. 3.1): very low (VL), low (L), high (H) and very high (VH) resolution. The very low resolution (VL) seismic lines image all the sedimentary column, the basement and some intra-crustal reflectors. Some examples are the ECORS, SARDINIA and CROP seismic lines (e.g. [START_REF] Gorini | Contribution to the structural and sedimentary history of the Gulf of Lions (western Mediterranean) from the ECORS profiles, industrial seismic profiles and well data[END_REF][START_REF] Finetti | CROP project: deep seismic exploration of the central Mediterranean and Italy[END_REF][START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF], acquired to investigate the deep crustal structure. The low resolution (L) profiles image the entire sedimentary column and, usually, the basement. In the deep basin, due to the high seismic energy absorption by salt structures, the basement can be dimmed. An example are the MS (Mediterranean Sea) lines, acquired from 1969 to 1973 in the Mediterranean by OGS, which allow the observation of the basement continuity and a good resolution of the base of salt (e.g. [START_REF] Finetti | Reflection seismic study of the Tyrrhenian Sea[END_REF][START_REF] Finetti | Wide scale digital seismic exploration of the Mediterranean Sea[END_REF]Finetti andMorelli, 1972, 1973;[START_REF] Finetti | CROP project: deep seismic exploration of the central Mediterranean and Italy[END_REF] understand the emplacement mechanisms of shallow sediment, as gravity events (e.g. Droz et al., 2020;[START_REF] Cattaneo | The last glacial maximum Balearic Abyssal Plain megabed revisited[END_REF]. The quality of seismic profiles, very variable between the different surveys, is mainly based on the year of acquisition and the possible processing carried out. Nevertheless, each profile has been used and has been useful for the interpretation of the salt structures or for the construction of the stratigraphic markers regional maps.

In the figure 3.2 three zooms of the main areas analysed in the Western Mediterranean Sea are shown. The zoom 3.2A represents seismic lines available in the Liguro-Provençal basin and at the transition between the Valencia basin and the Gulf of Lion. Here, the huge quantity of seismic lines allows a good resolution of seismic markers in the area, as previously described by different authors (e.g. [START_REF] Rabineau | Un modèle géométrique et stratigraphique des séquences de dépôts quaternaires sur la marge du Golfe du Lion: enregistrement des cycles climatiques de 100 000 ans[END_REF][START_REF] Bache | Evolution Oligo Miocène des marges du micro océan Liguro-Provençal[END_REF][START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF][START_REF] Pellen | Géodynamique et impact de la crise d'érosion et de salinité Messinienne sur les transferts sédimentaires (bassins de Valence et Adriatique)[END_REF]Leroux et al., 2019). In the deep basin it has been possible to observe salt morphologies variations with a very high resolution, as I will show in the next chapters. In the Western Sardinian margin (Fig.

3.2B), we have, for the first time (to our knowledge), merged all available datasets, mainly acquired by Italian and French institutions. The availability of high-resolution lines, as the WS10 lines (e.g. [START_REF] Geletti | The Messinian Salinity Crisis: new seismic evidence in the West-Sardinian Margin and Eastern Sardo-Provençal Basin (West Mediterranean Sea)[END_REF], compared to some low resolution profiles (e.g.

SARDINIA06) provides a good picture of the salt structures evolution compared to the crustal structures. Moreover, some regional transects allow to better understand the variations between the Gulf of Lion and the East Algerian basin, through the West Sardinian margin. Finally, the zoom 3.2C highlights the available seismic dataset in the Algerian basin. Here the coverage is less dense, especially on the north Algerian margin where to compel this lack of data we have integrated some published profiles from literature. The literature seismic profiles available in pdf format had to be transformed into the seg-y format, in order to be integrated in a seismic software for the interpretation (in our case, Kingdom Suite). The seg-y format is a digital format developed in the 1975's to enable the storage of seismic profiles on magnetic tape. This format includes a header of metadata including the identification of profiles (e.g. survey, year...) and a navigation part associating at each shot point a geographical coordinate in metric format. The conversion from pdf to seg-y format has been carried out using a script from Farran, (2008), with the help of Romain Pellen;

it allowed to add some new profiles to the database (Fig. Although in some areas the coverage of the seismic lines is not very dense, as for instance on the north Algerian margin, the strength of this dataset lies in its regional distribution, with many available profiles that allow a connection between the different sub-basins of the Western Mediterranean Sea. This is a key point that ties in with the main objectives of the thesis, mostly focused on a regional study of salt tectonics and its link with the deep structure of the crust.

To have a regional, more resolute, framework for the discussion of the salt tectonics mechanisms, we made some seismic marker compilations with the objective to build isobath and isopach maps. A part of this thesis work is therefore dedicated to the compilation of stratigraphic markers from the basement to the seafloor, with particular emphasis on Messinian markers and especially on the salt deposit.

As we will explain in chapter 4, salt in the Western Mediterranean Sea is mainly deposited in the deep basin and to a lesser extent in the lower slope. With the collaboration of Estelle Leroux (Ifremer) and Romain Pellen (UBO/IUEM/LGO), I integrated their interpretation and compilations [START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF][START_REF] Leroux | High-resolution evolution of terrigenous sediment yields in the Provence Basin during the last 6 Ma: relation with climate and tectonics[END_REF][START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF][START_REF] Pellen | Géodynamique et impact de la crise d'érosion et de salinité Messinienne sur les transferts sédimentaires (bassins de Valence et Adriatique)[END_REF][START_REF] Pellen | The Minorca Basin: a buffer zone between the Valencia and Liguro-Provençal Basins (NW Mediterranean Sea)[END_REF][START_REF] Pellen | The Messinian Ebro River incision[END_REF] in the Gulf of Lion (especially made in the shelf and slope) and in the Valencia basin, deriving from a very dense and high resolution dataset (Fig. 3.3). Moreover, depending on the seismic marker, we digitalized the interpretation already published in literature, in order to increase the density points in the resulting grids.

This part of the work has been the subject of a recent publication in which the compilation of the interpretation of some seismic stratigraphic markers are made public in open access.

Through a collaboration with several French and Italian institutes, it has been possible to integrate some areas where our dataset had less coverage. For more information on the publication of the data, please refer to Annexe-1.

Wide-angle refraction data

The wide-angle refraction seismic profiles allow to determine the geometry and the nature of crustal layers interpreting the velocity and the acoustic impedance between them. For this thesis the crustal segmentation is fundamental in order to compare it with the salt structures interpreted on reflection seismic profiles. The wide-angle refraction seismic is the best geophysical method to investigate the crustal structure and is often associated to gravity and magnetic techniques for a better imaging.

The first studies aimed to investigate the crust in the Western Mediterranean Sea are to refer to the work of Le [START_REF] Le Douaran | Deep structure of the north-western Mediterranean Basin: Results of a two-ship seismic survey[END_REF], [START_REF] Pascal | The ocean-continent boundary in the Gulf of Lion from analysis of expanding spread profiles and gravity modelling[END_REF] and [START_REF] Contrucci | A Ligurian (western Mediterranean Sea) geophysical transect revisited[END_REF] who In the Algerian basin the SPIRAL project leads to the acquisition of five wide-angle refraction profiles in the north Algerian margin (Fig. 3.4). These profiles, all oriented N-S, are located on the entire Algerian margin equally distributed from West to East. The results of the crustal structure modelling and seismic stratigraphy interpretation are published from 2013 by different authors, such as [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF]; [START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF], [START_REF] Medaouri | The transition from Alboran to Algerian basins (Western Mediterranean Sea): chronostratigraphy, deep crustal structure and tectonic evolution at the rear of a narrow slab rollback system[END_REF]; [START_REF] Hamai | Flexural behaviour of the north Algerian margin and tectonic implications[END_REF]; [START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF]; [START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF]; Arab et al., (2016a[START_REF] Arab | Coupling stratigraphic and petroleum system modeling tools in complex tectonic domains: case study in the North Algerian Offshore[END_REF]Aidi et al., (2018).

In the South Balearic margin two wide-angle refraction profiles were acquired during

August and September 2006 within the framework of WESTMED project. Data were collected with the German R/V Meteor from the Spanish mainland and from the Balearic

Islands into the

Algerian Basin (Fig. 3.4). These two profiles are shown in Vina Gaza 'thesis', (2016) but only the westernmost is interpreted. ). Sub-bottom seismic, gravimetry, multibeam bathymetry and magnetic data were collected in some area along the cruise track. In this work, we will describe and interpret for the first time the WMF2 heat flow data in order to better understand the regional thermal regime and the local influences which could affect it.

Old and new available heat flow measurements

Heat flow acquisition

The heat flow measurements are acquired with the MCHF (Micro-Computerized Heat Flow) instrument of IPGP. It was designed by Von Herzen R.P. [START_REF] Von Herzen | Measurement of oceanic heat flow[END_REF][START_REF] Bonneville | HFsoft: Toolbox for processing marine heat flow data acquired with MCHF instrumentation[END_REF] at Woods Hole Oceanographic Institution and upgraded significantly since 2001 at IPGP. It allows to measure the temperature and the thermal conductivity in-situ and, with a battery life of 72 hours, to acquire several measurements before to taking back the instrument on deck (pogo type of measuring). This instrument is composed of a 5-meters lance and 7 thermistors arranged in an elliptical shape and with regular intervals around the lance (Fig. 3.7).

Each sensor has a resistance and a heating wire for measuring temperature (resolution of 0.002 K) and thermal conductivity. An inclinometer situated on the lest allows to measure the angle of the instrument in relation to the vertical in order to correct the true thermistors depth.

The electronics in the container of top is controlled from the surface via a bidirectional acoustic connection at 2400 bit/s. The data is transmitted in real time to the surface but also stored in the instrument's memory. Between two measurements, the instrument is towed behind the boat at 100 meters above the sea-bottom. The instrument is inserted in the sediment under its own weight (1.5 tons). The complete sequence allows to get the temperature gradient observed between the thermistors and the thermal conductivity calculated by the heating (after [START_REF] Poort | WESTMEDFLUX cruise, RV L'Atalante[END_REF]Cruise Report).

Penetration causes heating of thermistors, and a minimum of 5 minutes of recording is needed in order to be able to extrapolate the value of the equilibrium temperature. After this step, to determinate the thermal conductivity, a constant heating is activated in the sediments (about 1W) and the instrument extrapolates the measurement by this temperature increasing [START_REF] Von Herzen | The measurement of thermal conductivity of deep-sea sediments by a needle-probe method[END_REF]. After this last step, the heating is stopped, the instrument pullet out of the sediments and towed to the next station (Fig. 3.8).

Another possibility to acquire heat flow data is with autonomous temperature loggers (type THP). The piston core used to recover sediment cores can be equipped with these high precision temperature loggers at different intervals in order to measure temperatures and thermal gradients in the sediments. A logger (S2IP NKE©) added at the top of the cores, is equally autonomous and measures water depth and tilt angle of the corer. On deck, the measures are then downloaded using an induction pencil (Data pencil NKE©). To allow heat friction dissipation, the cores have to stay at least 5-6 minutes in sediment without tensions. When the core is onboard, the thermal conductivity is measured using a needle-probe technique developed by Von [START_REF] Von Herzen | The measurement of thermal conductivity of deep-sea sediments by a needle-probe method[END_REF]. The needle, which includes a heating wire and a thermistor or a thermo-couple, is inserted transversally into the core and heated at a constant power. The temperature increase of the probe with the logarithm of time is proportional to the inverse of thermal conductivity. Usually, three values for 1 meter core section are measured.

The heat flow values are derived by multiplying the thermal gradient with the thermal conductivity. The measurement of the thermal gradient is measured between thermistors, located in the probe penetrating the sea bottom. A good number of thermistors and a sufficiently long probe is therefore necessary to have a reliable measurement. While during the WMF (1-2) surveys the POGO instrument was at least five metres long, the same cannot be said for other measurements, which were carried out mainly until the 1970s. In some cases (e.g. [START_REF] Lister | A close group of heat-flow stations[END_REF], the probe penetrating into the sediments was only 2 metres long, which may pose problems in trusting the measurements (see for instance Geli et al. EOS, 2001).

Method

Seismic interpretation

The seismic interpretation was carried out following the principles and concepts of seismic stratigraphy published by [START_REF] Vail | Seismic Stratigraphy and Global Changes of Sea Level: Part 1. Overview: Section 2. Application of Seismic Reflection Configuration to Stratigraphic Interpretation[END_REF][START_REF] Vail | Seismic stratigraphy and global changes of sea level[END_REF][START_REF] Vail | Seismic stratigraphy and global changes of sea level[END_REF] of which there are many summaries and published models (see for instance [START_REF] Rabineau | Un modèle géométrique et stratigraphique des séquences de dépôts quaternaires sur la marge du Golfe du Lion: enregistrement des cycles climatiques de 100 000 ans[END_REF][START_REF] Catuneanu | Principles of sequence stratigraphy[END_REF][START_REF] Brown | Interpretation of three-dimensional seismic data[END_REF][START_REF] Herron | First steps in seismic interpretation[END_REF]. The interpretation of salt structures was first made on paper, printing the profiles at the same scale and annotating the observations on a single map summarizing the whole dataset. These observations were then converted into numeric format for the construction of regional maps.

Interpretation of salt structures is mainly challenging because of their complex geometries and their higher velocities compared to sediments which surrounded them. The salt structures may change rapidly and progressively in space, they are often surrounded by faults networks and they modify stresses and pore pressures in surrounding rocks, changing their velocities and introducing velocity anisotropy. Generally, the top of salt can be identified by a positive reflection due to the downward sudden increase in acoustic impedance; this reflector often shows a strong amplitude and is located at the top of a seismically transparent zone (corresponding to the classical transparent seismic facies of salt). Sometimes, it is nevertheless tricky to clearly point out salt structures due to (i) the not completely transparency of salt deposits, and (ii) the seismic artefacts produced by strong variations of reflectivity. In Western Mediterranean Sea, the top of salt is always located below the Upper Unit (see chapter 4 for stratigraphy description), which is a well recognizable sequence.

The base of salt is a high amplitude reflector with a negative coefficient due to the downward sudden decrease in acoustic impedance relative to the underlying sediment layers.

Sometimes, base of salt above crystalline basement can show a positive reflection coefficient, as in some part of Gulf of Mexico [START_REF] Jackson | Salt tectonics: Principles and practice[END_REF]. It can be recognized because it is generally situated at the base of seismically transparent facies zone and at the top of a reflective subsalt sequence, even if there is no reflection from the base of salt itself. In the Western Mediterranean Sea, the base of salt often corresponds to a horizontal reflector, regionally unfaulted and undeformed which underlies a more or less transparent sequence (salt)

and overlays a thick, horizontal and regionally not deformed pre-salt sequence. It is worth to note that in this work, all the interpretations are done on time seismic sections, often migrated (especially with the Kirchhoff method; [START_REF] Yilmaz | Seismic data analysis: Processing, inversion, and interpretation of seismic data[END_REF], but not always. The most important limitation of time migration around and especially beneath the salt is that it cannot applies special velocities to salt. Thus, seismic energy cannot be properly positioned if it passed through salt. One example of this problem is the pull-up effect beneath salt, produced by the energy that travels faster through the salt and returns to the surface faster with respect the energy travelling in sediments (Fig. 3.9). The best way to solve the pull-up effect and to obtain proper imaging of salt-flank and subsalt structures is the pre-stack depth migration. This kind of processing allows to define the velocities in the salt and migrates the section before the stack, being able to change iteratively the velocities and the interpretation and finally reaches a better flattening of Common Image Gather (CIG). In any case, the interpretation of salt is a combination of these technical features and the experience and knowledge of the interpreter. Salt interpretation must be related to the evolutionary history of the stratigraphy that surrounds it.

Map construction methodology

Technically, the construction of thickness and depth maps goes through some phases that have been repeated for each reflector:

-The first step is to define and interpret the different sedimentary markers following the seismic stratigraphy concepts published in [START_REF] Vail | Seismic Stratigraphy and Global Changes of Sea Level: Part 1. Overview: Section 2. Application of Seismic Reflection Configuration to Stratigraphic Interpretation[END_REF] and [START_REF] Vail | Seismic Stratigraphy and Global Changes of Sea Level: Part 1. Overview: Section 2. Application of Seismic Reflection Configuration to Stratigraphic Interpretation[END_REF].

-The interpretation, well organized on Kingdom Suite software, has been exported in the form of geo-referenced horizons. Exporting data from Kingdom Suite (ED50 projected in UTM31) involves a transformation of geodesy: de-projection and change of datum to WGS84 via MapViewer software. These results are then introduced, re-projected, and interpolated on GMT (Generic Mapping Tool) to be mapped. The section is from offshore Brazil (Santos basin), after Herron, (2011).

123

GMT software (Wessel andSmith, 1995, 1998;[START_REF] Wessel | The generic mapping tools version 6[END_REF] provides a useful tool, among others, to map and interpolate seismic horizons. The software allows a good control of interpolation, allowing the operator to choose the interpolation step. As you will see in the results, in some cases, we have kept the interpolation step relatively low and in other cases we have deliberately increased the interpolation, so as to have a global vision, even if less truthful, of the reflector distribution. This choice depended on the significance of the reflector and its regional trend. The top of salt, for example, has a high variation in space due to the deformation of the underlying salt. Its regional interpolation would have given an untrue result because its trend is more irregular. In the case of other reflectors, a more regional interpolation could introduce fewer errors. As mentioned above, some areas are more deficient and have led us to use compilations already published in works by other authors. An example here is the northeast Algerian margin and the Alboran basin, where thanks to the work of Arab et al., (2016a) and [START_REF] Couto | Lago Mare and the Messinian salinity crisis: evidence from the Alboran Sea (S. Spain)[END_REF], it was possible to complete the missing zones (Fig. 3.10). For thickness calculation, the software allows a simple subtraction between two previously (with the same dimensions) calculated grids. At first, each operation was carried out in time (twt). This avoids any errors given by incorrect estimates of seismic velocities.

The conversion of reflectors and/or depth grids is a delicate operation because seismic velocities are not uniform in space, as well depicted and described for instance by [START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF]. A good depth conversion can only be done with proper processing, which can only be done on individual profiles. Since the primary objective of this thesis is not the calculation of sedimentary volumes, a depth conversion of all grids was not necessary. For the discussion of the main mechanisms of salt tectonics, e.g. sedimentary loading or basement influence, it is necessary to have a relative variation of thickness, which can then be left in two-ways time.

Nevertheless, in some cases the conversion in depth was necessary, as for example in the description of the base salt reflector and for the calculation of its slope. The slope surface is calculated according to the angle between the surface and the horizontal: is thus paramount to get the reflectors in the real depth (meters). In this case, the seismic velocities used for the conversion come from the work of Leroux, (2012), whose velocities were regionally averaged (Fig. 3.11). The method consists of multiplying the isopach in twt with the seismic velocity in order to have the isopach in meters. The isobath grid in meters of each of our surfaces were obtained in adding the isobaths grid (m) of the overlying surface and the isopach map separating from it. For instance, for the base salt surface, we have calculated the depth in meters of the sea bottom, the top of Messinian sequences, the top of salt and the thickness of each layer between them. This method has the advantage of averaging the velocities over short intervals, taking into account the thicknesses of the sediment from each layer above. Moreover, in the Pliocene-

Salt-bearing passive margins compilation

In chapter 6, I will illustrate a bibliographic compilation of some of passive margins in the world with the aim of understanding the relationship between the distribution of salt morphologies and the segmentation and the nature of the crust. The passive margins chosen, which differ in geodynamical setting, oceanic opening mechanism and age of salt deposition, are: the Brazilian margins (Santos and Campos basins), the Angolan margin, the northern Gulf of Mexico, the north-west African margins and the conjugate Nova Scotia margin. This study needed three main working-phases:

-Refraction seismic data collection: the choice of passive margins to be included in the compilation was also based on the availability of refraction surveys in the margins. The different methodologies used by different research groups emerged during the compilation. We had to find a common terminology among the different interpretation that remained as objective as possible.

-Reflection seismic data collection and interpretation of morphologies. This phase included a bibliography compilation of a series of regional reflection profiles published in the margins analysed. We tried to keep the salt morphology terminology defined in the Western Mediterranean Sea, though less detailed. This allowed the definition of domains with different salt morphologies that have been transposed into regional maps, in order to provide a regional view of salt deformation in these margins.

-Construction of regional maps with superposition of salt morphologies and crustal domains in order to define possible correlations.

Below, I provide all the references and works (papers, thesis and survey reports) on which we based our interpretation.

In the Santos and Campos basins, we interpreted salt morphologies from works of [START_REF] Modica | Postrift sequence stratigraphy, paleogeography, and fill history of the deep-water Santos Basin, offshore southeast Brazil[END_REF]; [START_REF] Mohriak | Sal: Geologia e Tectônica; Exemplos nas Bacias Brasileiras[END_REF]2012); [START_REF] Torsvik | A new scheme for the opening of the South Atlantic Ocean and the dissection of an Aptian salt basin[END_REF]; [START_REF] Lentini | Geodynamics of the central South Atlantic conjugate margins: implications for hydrocarbon potential[END_REF]; [START_REF] Scotchman | The breakup of the South Atlantic Ocean: formation of failed spreading axes and blocks of thinned continental crust in the Santos Basin, Brazil and its consequences for petroleum system development[END_REF]; [START_REF] Unternehr | Hyper-extended crust in the South Atlantic: in search of a model[END_REF]Zalan et al., (2011);[START_REF] Davison | Geology and tectonics of the South Atlantic Brazilian salt basins[END_REF]; [START_REF] Davison | Salt deposition, loading and gravity drainage in the Campos and Santos salt basins[END_REF]; [START_REF] Kumar | From oceanic crust to exhumed mantle: A 40 year (1970-2010) perspective on the nature of crust under the Santos Basin, SE Brazil[END_REF]; [START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF][START_REF] Peron-Pinvidic | Structural comparison of archetypal Atlantic rifted margins: A review of observations and concepts[END_REF]; [START_REF] Jackson | Enigmatic structures within salt walls of the Santos Basin-Part 1: Geometry and kinematics from 3D seismic reflection and well data[END_REF]; [START_REF] Strozyk | Comparison of the rift and post-rift architecture of conjugated salt and salt-free basins offshore Brazil and Angola/Namibia, South Atlantic[END_REF]; [START_REF] Kukla | South Atlantic salt basins-witnesses of complex passive margin evolution[END_REF]. The crustal segmentation is taken from the SanBa project [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF][START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF].

For the Angolan margin, we interpreted reflection profiles from [START_REF] Marton | Evolution of the Angolan passive margin, West Africa, with emphasis on post-salt structural styles[END_REF]; [START_REF] Tari | Examples of salt tectonics from West Africa: a comparative approach[END_REF]; [START_REF] Hudec | Regional restoration across the Kwanza Basin, Angola: Salt tectonics triggered by repeated uplift of a metastable passive margin[END_REF]; [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]; Unternher et al., (2010);[START_REF] Fort | Salt tectonics on the Angolan margin, synsedimentary deformation processes[END_REF]; [START_REF] Cowie | The palaeo-bathymetry of base Aptian salt deposition on the northern Angolan rifted margin: constraints from flexural back-stripping and reverse post-break-up thermal subsidence modelling[END_REF] and we based the crustal interpretation from the Zaiango Project (Contrucci et al., 2004a;[START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF].

In the Gulf of Mexico, we compiled salt morphologies from Wu et al., (1990a);[START_REF] Radovich | Insights into structure and stratigraphy of the northern Gulf of Mexico from 2D pre-stack depth migration imaging of mega-regional onshore to deep water, long-offset seismic data[END_REF]; [START_REF] Pilcher | Primary basin and their boundaries in the deep-water northern Gulf of Mexico: Origin, trap types, and petroleum system implications[END_REF] ; Rodriguez, (2011); Fort andBrun, (2012); Hudec andJackson, (2013a); Ismael, (2014); [START_REF] Pindell | Rapid outer marginal collapse at the rift to drift transition of passive margin evolution, with a Gulf of Mexico case study[END_REF] ;[START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF]; [START_REF] Weimer | An overview of the petroleum systems of the northern deep-water Gulf of Mexico[END_REF]; [START_REF] Curry | Extensional models for the development of passive-margin salt basins, with application to the Gulf of Mexico[END_REF]; [START_REF] Liu | Crustal structure of Mesozoic rifting in the northeastern Gulf of Mexico from integration of seismic and potential field data[END_REF]; [START_REF] Steier | Late Mesozoic gravity sliding and Oxfordian hydrocarbon reservoir potential of the northern Yucatan margin[END_REF] and from already published salt-distribution maps [START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF][START_REF] Peel | Genetic structural provinces and salt tectonics of the Cenozoic offshore US Gulf of Mexico: A preliminary analysis[END_REF]. The segmentation is interpreted from the refraction seismic project GUMBO [START_REF] Eddy | Deep crustal structure of the northeastern Gulf of Mexico: Implications for rift evolution and seafloor spreading[END_REF][START_REF] Eddy | Structure and origin of the rifted margin of the northern Gulf of Mexico[END_REF][START_REF] Christeson | Deep crustal structure in the eastern Gulf of Mexico[END_REF][START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF], located with a N-S direction in the northern Gulf of Mexico.

In the Morocco and Nova Scotia conjugated margins, the salt structures originate from works by [START_REF] Hinz | The continental margin of Morocco: seismic sequences, structural elements and geological development[END_REF]; [START_REF] Keen | The transition from a volcanic to a nonvolcanic rifted margin off eastern Canada[END_REF][START_REF] Sahabi | Evolution cinématique triasico-jurassique de l'Atlantique central: Implications sur l'évolution géodynamique des marges homologues nord ouest africaine et américaine[END_REF][START_REF] Shimeld | A comparison of salt tectonic subprovinces beneath the Scotian Slope and Laurentian Fan[END_REF][START_REF] Louden | Systematic variations in basement morphology and rifting geometry along the Nova Scotia and Morocco conjugate margins[END_REF]; [START_REF] Neumaier | Late Cretaceous to Cenozoic geodynamic evolution of the Atlantic margin offshore Essaouira (Morocco)[END_REF]; [START_REF] Tari | Salt tectonics in the Atlantic margin of Morocco[END_REF][START_REF] Tari | Examples of salt tectonics from West Africa: a comparative approach[END_REF][START_REF] Tari | Deep-water exploration in Atlantic Morocco: Where are the reservoirs?[END_REF] and the crustal segmentation from the MIRROR and SMART project in Morocco and Nova Scotia margins, respectively [START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF][START_REF] Contrucci | The crustal structure of the NW Moroccan continental margin from wide-angle and reflection seismic data[END_REF][START_REF] Funck | Crustal structure of the northern Nova Scotia rifted continental margin (eastern Canada)[END_REF][START_REF] Klingelhoefer | Crustal structure variations along the NW-African continental margin: a comparison of new and existing models from wide-angle and reflection seismic data[END_REF][START_REF] Wu | Crustal structure of the central Nova Scotia margin off Eastern Canada[END_REF].

Heat flow

Heat flow correction

In order to correctly interpret the heat flow measurements, it is necessary to correct the perturbation given by environmental effects, such as the sedimentation, the contrast of thermal conductivity and the sea-floor topography. In the next sub-chapters, I will illustrate two of the most important corrections to be taken into account when interpreting heat flow: sedimentation and refraction effects. It is worth to note that, both in terms of sedimentation and refraction correction, the fixed values must always be shown together with the surface value. A good interpretation can be made by analysing the relative relationships between these three values (surface, after sedimentary correction and after refraction correction), in order to understand possible influences in the sedimentary column (e.g. fluids) or deriving from basal flow.

Sedimentation effects are induced by the sedimentary history of the basin and, above all, the sedimentation rate. The cold thickness will tend to decrease the surface heat flow. Sediments deposits of uneven thickness will cause lateral variations in the surface heat flow [START_REF] Langseth | Crustal structure of the mid-ocean ridges: 5. Heat flow through the Atlantic Ocean floor and convection currents[END_REF]. The duration and the magnitude of this "cooling" will depend on the sedimentation and the duration of the event, which can be estimated from the thickness and age of sedimentary sequences. An erosion episode will amplify the value of the flow. A simple analytical solution has been given by Von Herzen et al., (1974) but does not include variable sedimentation rates, compaction and thermal interaction with basement for high sedimentation rates [START_REF] Hutchison | The effects of sedimentation and compaction on oceanic heat flow[END_REF][START_REF] Lucazeau | The blanketing effect of sediments in basins formed by extension: a numerical model. Application to the Gulf of Lion and Viking graben[END_REF][START_REF] Von Herzen | Heat flow and the thermal origin of hot spot swells: The Hawaiian swell revisited[END_REF]. In order to solve these problems, numerical solutions and algorithms have been proposed by [START_REF] Hutchison | The effects of sedimentation and compaction on oceanic heat flow[END_REF] and [START_REF] Lucazeau | The blanketing effect of sediments in basins formed by extension: a numerical model. Application to the Gulf of Lion and Viking graben[END_REF]. Although the two algorithms use different strategies and hypothesis, both give very similar results (within 0.5% of heat flow anomaly). At the limit where surface porosity is equal to zero (no compaction), both models are in agreement with the analytical solution provided by Von [START_REF] Von Herzen | Measurement of oceanic heat flow[END_REF]. In this work, we used the software sedcor 2.0 in order to correct every heat flow measurement of the WMF1 and WMF2 surveys.

For each heat flow measurements, we have calculated the sedimentary thicknesses on adjacent seismic profiles and we converted them to depth. The seismic velocities used for the conversion have been chosen and discussed with Estelle Leroux, following her work in the Gulf of Lion (see, for instance, [START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF][START_REF] Leroux | High-resolution evolution of terrigenous sediment yields in the Provence Basin during the last 6 Ma: relation with climate and tectonics[END_REF] and are attached at the end of the manuscript, in the Annexe-2 (see also previously paragraph). We have differentiated two main domains, the slope and the basin, in order to have the most likely velocities possible. As mentioned, the sedimentation effect is influenced by the rate of sedimentation, which means the sedimentation with respect time. Therefore, we have chosen some key reflectors on which we knew the age. When this was not possible, we relied mainly on the Messinian reflectors (base salt and top Upper Unit), seafloor and basement. In this case the velocities are averaged over longer time intervals. Then, for each measurement, we entered in the software the real sedimentary thicknesses in metres and their deposition ages. As output the software gives the correction percentages to add to each heat flow measurement. The chosen correction is under the algorithms of [START_REF] Hutchison | The effects of sedimentation and compaction on oceanic heat flow[END_REF]. In this way, as explained above, we have added the influence of the sedimentary sequence from the surface values, thus finding the heat flow value at the basement. This value is generally higher than the measured value at the surface and will always be given at the side of the surface value, to understand the sedimentary influence on the basal measurement. For more details, please refer to the tables shown in Annexes, which show the calculation made for each measurement and the assigned correction.

Facies variations generate geological heterogeneities with thermal conductivity contrasts such as at sediment/water interface. The magnitude of the disturbance on the surface heat flow value will be depending on the location of the station in relation to the interfaces, the magnitude of the difference in thermal conductivity and the geometry of the layers [START_REF] Lee | Heat-flow refraction across dissimilar media[END_REF]. The combined effects of topography and uneven sediment distribution (and thus conductivity contrasts) can explain the dispersion of heat flow data [START_REF] Langseth | Crustal structure of the mid-ocean ridges: 5. Heat flow through the Atlantic Ocean floor and convection currents[END_REF]. The correction to make corresponds to a 2D approximation of the geometry of the seafloor along the seismic profiles, which tends to minimise refraction effects. The best example in our data of refraction effect is given by rock salt. As mentioned in chapter 2, the thermal conductivity of salt is higher than the sedimentary rocks which surrounded it. For example, in the case of a salt diapir or abrupt bathymetric contrast, the correction will be positive and high as the thermal conductivity contrast is high. In our case the refraction correction is performed by modelling the heat transfer in permanent regime with the help of MARGE thermo-kinematic model, explain in the next sub-chapter. The model, based on the interpretation of the seismic section and thus to the thermal conductivities and lithology of each sequence, calculates the refraction correction by adding or subtracting from the surface flow values (Fig. 3.12).

Thermo-kinematic model

The plot represents the result given by MARGE model in percentage of correction to apply to the surface heat flow. The greater values correspond to a higher lateral variation of thermal conductivity. The model calculates it from interpretation of seismic section given by the operator as input. The y-axis represents the percentage of correction to add (if > 0) or to subtract (if < 0). In the xaxis the distance of the profile in km.

GEodynamique). MARGE is a predictive tool which is primarily born both for a rapid approach to large-scale oil system modelling (genesis and expulsion of hydrocarbons), or as a framework for structural analyses or modelling of the genesis and migration of smaller scale oil systems.

With the analysis of the evolution of heat flow along the margins we were able to determine the variations between the different types of crust and associate them with the salt deformation.

Thus, it was possible to define temperature ranges around salt deposits and their variations in space and time starting from its Messinian deposition. The numerical model, conceived by Francis Lucazeau, is a 2D extension model including many second-order phenomena and has previously been used by several authors in the analysis of passive margins in the world (e.g.

Latil- [START_REF] Brun | Subsidence, extension and thermal history of the West African margin in Senegal[END_REF][START_REF] Gernigon | A moderate melting model for the Vøring margin (Norway) based on structural observations and a thermo-kinematical modelling: Implication for the meaning of the lower crustal bodies[END_REF][START_REF] Lucazeau | Dynamic interactions between the Gulf of Guinea passive margin and the Congo River drainage basin: 2. Isostasy and uplift[END_REF][START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF].

The first objective of the model is to study the evolution of rift passive margin at both lithospheric and basin scales. As mentioned, it can take into account several second-order important mechanism, such as: i) the mantle and crustal thinning processes, ii) multiple stretching episodes of finite duration [START_REF] Jarvis | Sedimentary basin formation with finite extension rates[END_REF], iii) the sedimentation interaction on thermal regime, iv) the control of regional isostasy, the accretion oceanic process and the magmatic underplating. The model describes the thinning process basing on hypothesis of pure stretching [START_REF] Mckenzie | Some remarks on the development of sedimentary basins[END_REF]. Nonetheless, in order to account complex aspects which can influence the thermal regime evolution, it includes crustal and sediments heat production, sediment compaction and porosity, finite duration of rifting phases, thermal dependence of density and thermal conductivity, regional isostasy and level of necking, oceanic accretion and magma underplating. More information about MARGE are in Annexe-2, while some results will be shown in chapter 5.3.

Saltflu03 seismic line processing

The processing of SaltFlu03 line, located in the South Balearic margin, was carried out during a 2 months period at the OGS, in Trieste. The main objective was to convert the seismic line in depth in order to use it on the thermo-kinematic MARGE model. In fact, the model needs the real geometries of the structures and the sequences thicknesses in metres. This period was also an opportunity to test new processing techniques, developed at the Geophysics department of OGS, Trieste. With the help of Giuseppe Brancatelli and Edy Forlin we have performed for the first time the pre-stack depth migration of a line belong to the survey SaltFlu, acquired in 2012, using Echos and Geodepth software from Paradigm Geophysical. The Eurofleets project Salt deformation and sub-salt Fluid circulation -SALTFLU datasets consists of 10 multichannel seismic profiles in the South Balearic and adjacent passive margin. The profiles were acquired by R/V OGS -Explora in 2012 with the specific aim of investigating the Messinian and post-Messinian sedimentary sequences. The acquisition parameters allow a compromise between the resolution and sufficient penetration. According to the λ/4 Raylegh criterion (where λ is the seismic wavelength) [START_REF] Kallweit | The limits of resolution of zero-phase wavelets[END_REF], the maximum source frequency and an average seismic velocity of 2000 m/s -1 for post-MSC sediments, we obtained a theoretical vertical resolution of 2.5 m for the dataset.

We applied a standard time procedure in the first phase of processing, including spherical divergence correction, trace editing, velocity analysis and NMO correction, stack and trace equalization. The main objective was to define the better velocity field for sedimentary sequence other than salt. An iterative velocity analysis was performed in order to flatten the reflection events in the migrated CDP events (Fig. 3.13). Before the stack of the migrated CDP gathers, a stretching mute was applied to implement signal-to-noise ratio, especially at far offset where the wavelet is stretched. After the migration we performed a first stack to have the section in time domain. In seismic processing, migration is one of the fundamental step that leads to obtain the imaging of subsurface from the recorded data. In particular, migration moves dipping reflectors to their real subsurface positions and collapse diffractions, increasing the spatial resolution [START_REF] Yilmaz | Seismic data analysis: Processing, inversion, and interpretation of seismic data[END_REF]. With increasing geological complexity, the type of migration has to change from post-stack to pre-stack and from time to depth domains. This is the case of salt structures, characterized by abrupt laterally changes. Pre-stack time migration (PSTM) can handle reflectors with conflicting dips, but it fails in presence of lateral velocity variations (it is a 1D approximation) so, in these cases, pre-stack depth migration (PSDM) is recommended. In our case, the salt structures and the strong deformation associated do not allow a good imaging in the basin. The top of the salt is usually well imaged, but the flanks are commonly too steep to show up on seismic. Salt structures and layers absorb so much energy that sub-salt reflectors may be difficult to identify, mostly on a 2D seismic line. To solve at least in part the "problem" of salt, we performed the ray tomography.

The ray tomography technique aims at finding an interval velocity distribution which minimizes the difference between the calculated (through the ray-tracing) and the travel times observed on the data [START_REF] Yilmaz | Seismic data analysis: Processing, inversion, and interpretation of seismic data[END_REF]. The industry standard procedure is to update the velocity model by ray tomography in the migrated domain. A first PSDM (pre-stack depth migration) is performed with a first smooth velocity model, followed by a Residual Moveout Analysis (RMO) on CIGs or along selected horizons. If the reflection events within the CIGs are not flat, the velocity model is updated by the tomography and the PSDM re-runned. Three typologies of tomography are possible, depending on the parameter applied to the velocity model. The grid tomography is preferable in normal sedimentary basins, where velocities increase with depth and the lateral variations are few. Conversely, the layer-based tomography works better in the case of sharply changes at the interface of two rocks body, as in salt flanks. Finally, the hybrid tomography is a combination of both. The SF03 line exhibits strong lateral velocity variations mainly given by salt structures and the basement, which is relatively shallow in the slope domain and sharply deepens in the deep basin. For this reason, we decided to firstly building a starting velocity-depth model and then to refine it by using the horizon-based tomography.

The method requires a set of picked time horizons, an initial trial interval velocity field and the CMP time gathers. As shown in the flow in figure 3.14, we firstly interpreted the main horizons on the SF03 pre-stack time migrated section. We picked the water-bottom, the top of Messinian event, the top of the salt, the base of salt and, on the shelf, the acoustic basement. It is convenient to pick significant horizons, which are those with major changes in velocity.

Subsequently, we perform the de-migration of the picked horizon using the RMS velocity field (Fig. 3.14). In this method the interval velocity is identified whose modeled moveout curve best matches coherent reflections over some user-defined time window within the gather. In contrast to conventional velocity analysis, in coherency inversion the moveout curves along which semblance is calculated may be as non-hyperbolic as the ray tracing indicates. We used the velocity model obtained from the first velocity analysis performed during the time phase of processing (each 500 CDP). A ray tracing-based approach is used to analyze the interval velocity of each horizon. Then it is possible to pick the highest semblance value velocity on the CMP location along the picked horizon. Finally, we smoothed this velocity to avoid unrealistic oscillations cause by noisy data. This procedure is repeated for a range of constant trial velocities and the velocity that yields the highest semblance value is assigned to the nth layer below the CMP location where the coherency inversion is being performed. In the case of salt, we iteratively searched for the best velocities to set to have the flattening of the gathers. Taking as a priori the constant velocities inside the salt, we found a good horizontality of the CIGs with a constant velocities of 4200 m/s (Fig. 3.15).

Although other algorithms could be applied to implement line quality, we have achieved a satisfactory result for our objectives. The line has been completely converted in depth and the imaging has been sensibly improved compared to the previous version in available time (Fig.

3.16

). The seismic section can be import in the thermo-kinematic MARGE model (chapter 5.3) as most of the key reflectors can be interpreted in depth domain. The Pliocene-Quaternary megasequence is well resolved and the salt sequence imaging improved. An example is shown in figure 3.16, where between the lower slope and the deep basin the salt base can be followed and interpreted even below the first large salt diapir. In addition, the transition between the Upper Unit (UU) and the Mobile Unit (MU) (salt unit in Fig. 3.16), which is characterized by a chaotic facies, is clearly recognisable.

Nevertheless, some considerations must be discussed in this part of work. The length cable of SaltFlu survey acquisition is 3000m (e.g. Dal [START_REF] Dal Cin | Seismic imaging of Late Miocene (Messinian) evaporites from Western Mediterranean back-arc basins[END_REF]. If we rely on the rule saying that reliable seismic velocities can be obtained only until depth comparable to the spread length, we can realize the difficulty that processing on these types of lines can have. In the deep basin, where the salt base is estimated to be more than 4 km deep (Fig. 3.16), it will therefore be really challenging to obtain a reliable velocity field, especially in the pre-salt sequence. Furthermore, as mentioned above, the salt structures absorb most of the seismic energy making it even more difficult to imaging the structures below. If we consider that the modern petroleum seismic acquisition (in presence of salt deposits) are performed with length cable of 8 km (e.g. pre-salt Santos basin, [START_REF] Penna | Challenges in Seismic Imaging and Reservoir Characterization of Presalt Oilfields in Offshore Brazil[END_REF], the salt imaging on SaltFlu profiles may be too ambitious.

Nevertheless, processing techniques are improving and some geophysical works on SaltFlu lines seem to give the first good results [START_REF] Blondel | Image improvement of Late Miocene (Messinian) to Plio-Quaternary units in the Algero-Balearic basin[END_REF][START_REF] Blondel | Late Miocene to present-day tectonostratigraphy of the northern central Algerian Basin: Evidence of a contractional salt system from reprocessed seismic data[END_REF].

Summary chapter 3

Chapter 3 aims to illustrate the data and methodologies used in this study. The interpretation and description of the salt structures was carried out using reflection seismic data. This thesis allowed the implementation of the existing seismic dataset, by adding several lines from Italian research institutes. The dataset, to date, is the most complete and resolute existing in the Western Mediterranean Sea. The analysis of the crustal structure was carried out using the wide-angle refraction surveys already interpreted by several authors. New heat flow data acquired during the WMF2 survey, held on board the R/V l'Atalante in spring 2018, are also shown in this thesis. To constrain the thermal regime, a thermo-kinematical model was also used, whose functionalities I have briefly explained, complemented in the Annexes.

To conclude, the description of the experience carried out at the University of Trieste is represented. A depth processing of a seismic line that was subsequently used in the application of the model was carried out.

Résumé chapitre 3

Le chapitre 3 vise à illustrer les données et les méthodologies utilisées dans cette étude. L'interprétation et la description des structures salifères ont été réalisées à l'aide de données de sismique réflexion.

Cette thèse a permis de mettre à jour le jeu de données sismiques

CHAPTER 4. SALT STRUCTURES IN THE WESTERN

MEDITERRANEAN SEA

Why the Western Mediterranean Sea?

The Mediterranean margins, which are young and show a huge sedimentary record, are natural laboratories for the detailed study of the genesis and evolution of passive margins, the relationship between deep and surface processes, and the role of tectonic and thermal heritage.

The study of salt tectonics in the Western Mediterranean Sea has been developed since the 1980s (see Chapter 2), shortly after the Messinian Salinity Crisis discovery (Hsu et al., 1973).

Several studies have mainly focused on the Liguro-Provençal margin (e.g. [START_REF] Le Cann | Le diapirisme dans le bassin Liguro-Provençal (Méditerranée occidentale)[END_REF][START_REF] Gaullier | Diapirisme salifère et dynamique sédimentaire dans le bassin Liguro-Provençal. Données sismiques et modèles analogiques[END_REF][START_REF] Gorini | Géodynamique d'une marge passive: le Golfe du Lion (Méditerranée occidentale[END_REF][START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF][START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF]Dos Reis et al., 2005, 2008;[START_REF] Granado | Geodynamical framework and hydrocarbon plays of a salt giant: the NW Mediterranean Basin[END_REF][START_REF] Leroux | High-resolution evolution of terrigenous sediment yields in the Provence Basin during the last 6 Ma: relation with climate and tectonics[END_REF]Ferrer et al., 2017;Mianaekere and Adam, 2020a,b) but several works dealt with other Western Mediterranean margins, such as the western Sardinian (e.g. [START_REF] Sage | Seismic evidence for Messinian detrital deposits at the western Sardinia margin, northwestern Mediterranean[END_REF][START_REF] Geletti | The Messinian Salinity Crisis: new seismic evidence in the West-Sardinian Margin and Eastern Sardo-Provençal Basin (West Mediterranean Sea)[END_REF][START_REF] Dal Cin | Seismic imaging of Late Miocene (Messinian) evaporites from Western Mediterranean back-arc basins[END_REF], the Provençal (Obone-Zue-Obame et al., 2011) and the northern Algerian (e.g. [START_REF] Domzig | Searching for the Africa-Eurasia Miocene boundary offshore western Algeria (MARADJA'03 cruise)[END_REF][START_REF] Gaullier | Salt tectonics in the deep Mediterranean: indirect clues for understanding the Messinian Salinity Crisis. The Messinian salinity crisis from mega-deposits to microbiology-A consensus report[END_REF]Kherroubi et al., 2009 ;[START_REF] Yelles | Plio-Quaternary reactivation of the Neogene margin off NW Algiers, Algeria: the Khayr al Din bank[END_REF]Arab et al., 2016a,b) margins. Not all of these works aimed to study salt tectonics mechanisms but they dealt with salt deformation as a key component in the evolution of sedimentary basins. Nevertheless, none of these works ever set out to give a global view of salt deformation in all sub-basins. Some doubts remain concerning the main causes of salt tectonics and the relationship between observed structures and structural heritage, sedimentation and crustal segmentation. Since the work of Le Cann (1987), the authors are aware of the coincidence between the boundary of the oceanic crust and the change in salt morphologies in the Gulf of Lion (e.g. [START_REF] Pautot | Morphology and extension of the evaporitic structures of the Liguro-Provençal Basin: New Sea-Beam data[END_REF]. This coincidence seems to be clearer from refraction seismic studies that allow a better mapping of crustal segmentation limits [START_REF] Gailler | Crustal structure of a young margin pair: new results across the Liguro-Provencal Basin from wide-angle seismic tomography[END_REF][START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF]. The coincidence was so far explained as the results of Gulf of Lion structural setting and was supposed to be the result of: 1) the activation of faults inherited by rifting formation [START_REF] Pautot | Morphology and extension of the evaporitic structures of the Liguro-Provençal Basin: New Sea-Beam data[END_REF][START_REF] Le Cann | Le diapirisme dans le bassin Liguro-Provençal (Méditerranée occidentale)[END_REF] or 2) the different compaction of pre-salt sediments [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF]. Following [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF], the basement "dormant" steps arising from transfer zones (e.g. Catalan and Arlesian), below the pre-salt sediments, might explain the salt structures distribution. In this chapter we will try to understand if this coincidence, observed in the Gulf of Lion, can be extended throughout the Western Mediterranean, and with what differences and similarities. This will allow to explore whether there is a relationship between crustal segmentation (and nature) and salt morphologies, and thus to discuss the main causes of this coincidence. In addition, the compilation of the main stratigraphic markers allowed to map salt morphologies, date (at least relatively) salt deformations, and quantify and map sedimentary thicknesses, so that we can later evidence or discuss possible correlations.

A number of key questions will be answered in this chapter, including:

-What are the main sedimentary thicknesses variations and the main structural directions along the Western Mediterranean?

-What are the main salt morphologies differences?

-Can we find a relationship between crustal segmentation and salt morphologies variations in the Western Mediterranean?

-What is the timing of salt deformation in the Western Mediterranean Sea? Is there an apparent link with sedimentation (or other) processes?

The Western Mediterranean also displays some features that make it particularly interesting in the study of salt tectonics and its major influences, such as:

-(i) Abundant data and good geodynamic and stratigraphic knowledge of the area. The abundance of seismic data (Chapter 3), provides a good resolution of the salt structures. Our seismic dataset covers almost all sub-basins (except for the Ligurian basin) where Messinian salt is present. In addition, new heat flow measurements (Chapter 3) allow a tentative correlation between salt morphologies and thermal field of the margins.

-(ii) The occurrence of the Messinian Salinity Crisis: a topic widely debated by the scientific community to this day, which led to the deposition of the world's youngest Salt Giant. The particularity of deposition compared to 'classic' passive margins allows salt tectonics to be studied from different perspectives. Salt was deposited everywhere in the deep basin and on the lower slope, onlapping the pre-salt sequences, thanks to a sea-level drop of more than 1000m.

Although a very young salt deformation (~5.5 Ma), the structures are extensively developed, especially vertically, making it an interesting case study to compare with older ages of salt structures in the Gulf of Mexico (~165 Ma) or in the South Atlantic (~110 Ma). Some stratigraphic and morphological features of Western Mediterranean Sea appear to be inconsistent with the salt tectonics mechanisms classically inferred to explain the evolution of salt structures. These differences make it a unique place to study salt tectonics and its relationship to the deep crust.

(iii) The Western Mediterranean is mainly formed by two main sub-basins: the Liguro-Provençal basin and the Algerian basin. While the rotation of the Corsica-Sardinian block due to the rollback of the Tethys seems to be confirmed as the cause of the opening of the LPB basin, the Algerian basin, especially in its western part, is the subject of a lively debate on the opening mechanisms and the crustal nature that forms it (Chapter 1).

Seismic stratigraphy

In this chapter the main sedimentary markers of the Western Mediterranean considered in this study will be explained. As one of the main objectives of this work is the analysis of regional salt deformation throughout all the sub-basins, a study of the sedimentary markers is necessary to assess their role and to use them to date the salt movement: the interpreted stratigraphic markers along the available lines (cf. Chapter 3, data and method) allowed the construction of regional sediment thickness maps, useful to reconstruct the salt deformation history.

Messinian stratigraphy

The offshore stratigraphic sequence of the Western Mediterranean Sea is significantly impacted by the Messinian Salinity Crisis, which results in erosional surfaces, due to the huge lowering of the sea level, coupled with depositional units. Due to a total geometric disconnection, a direct correlation between offshore and onshore deposits is still discussed in literature (e.g. [START_REF] Ciesm | The messinian salinity crisis from mega-deposits to microbiology -a consensus report[END_REF]Roveri et al., 2014a;[START_REF] Ochoa | Synchronous onset of the Messinian evaporite precipitation: First Mediterranean offshore evidence[END_REF][START_REF] Raad | The Messinian Salinity Crisis deposits in the Balearic Promontory: an undeformed analog of the MSC Sicilian basins??[END_REF]. One of the points on which the discussion remains largely open is the stratigraphic and paleoenvironmental correspondence between the deposits of the deep domain and the so-called peripheral domains.

Offshore, major differences characterise the deep basins of the West and East Mediterranean Sea (Fig. 4.1, Lofi et al., 2018). In the West Mediterranean Sea three seismic units defined the Messinian Trilogy [START_REF] Montadert | De l'âge tertiaire de la série salifère responsable des structures diapiriques en méditerranée occidentales (nord-est des baléares)[END_REF][START_REF] Rehault | The western Mediterranean basin geological evolution[END_REF]: Lower Evaporites, Halite (salt) and Upper Evaporites. Instead, in the East Mediterranean, a clear distinction between the units is not depicted and the Messinian sequence can be divided into 5-6 evaporitic sequences (e.g. [START_REF] Bertoni | Controls on the basinwide architecture of late Miocene (Messinian) evaporites on the Levant margin (Eastern Mediterranean)[END_REF]Lofi et al., 2011a;[START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF]. Nowadays, two main nomenclatures define seismic units in the deep Mediterranean basin with the objective of defining a clear distinction between offshore and onshore units. They are based on two different approaches and interpretations of evaporitic deposits and detritic units deposited as a result of margin erosion. Lofi et al., (2011a[START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF] redefine the Messinian trilogy by adding the neutral term "units" and describe, from bottom to top: the Lower Unit (LU), composed by evaporites and detritic deposits; the Mobile Unit (MU), so defined for the typical salt viscous behaviour and the Upper Unit (UU), formed by sand and evaporites (Fig. The main difference between the two models derives from the different interpretation of the Messinian base and the consequent different calculated detritic volume [START_REF] Bache | Evolution Oligo Miocène des marges du micro océan Liguro-Provençal[END_REF][START_REF] Bache | Messinian erosional and salinity crises: view from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF][START_REF] Bache | A two-step process for the reflooding of the Mediterranean after the Messinian Salinity Crisis[END_REF][START_REF] Bache | Messinian evaporite deposition during sea level rise in the Gulf of Lions (Western Mediterranean)[END_REF][START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF][START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF] (Fig. 4.3). The first school of thought considers the base of the Messinian trilogy as the base of the LU or outlined by the BES (Bottom Erosion Surface) offshore and in the peripheral domains, respectively (Roveri et al., 2014a;Lofi et al., 2011a,b;[START_REF] Lofi | Evidence for pre-Messinian submarine canyons on the Gulf of Lions slope (Western Mediterranean)[END_REF]. Conversely, other authors interpreted the Messinian base deeper, well below the Lower Unit [START_REF] Bache | Evolution Oligo Miocène des marges du micro océan Liguro-Provençal[END_REF][START_REF] Bache | Messinian erosional and salinity crises: view from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF][START_REF] Bache | A two-step process for the reflooding of the Mediterranean after the Messinian Salinity Crisis[END_REF][START_REF] Bache | Messinian evaporite deposition during sea level rise in the Gulf of Lions (Western Mediterranean)[END_REF][START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF][START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF]. These authors define, below the LU, a unit defined as M reflector, mainly formed by two detritic sequences derived from the products of Messinian erosion. Differences in interpretation arose in the Gulf of Lion and extended in the Lofi et al., (2011a[START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF] Note also the differences between the West and the East Mediterranean markers and facies (from [START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF].

Valencia and Menorca basins [START_REF] Pellen | Géodynamique et impact de la crise d'érosion et de salinité Messinienne sur les transferts sédimentaires (bassins de Valence et Adriatique)[END_REF][START_REF] Pellen | The Messinian Ebro River incision[END_REF] lead to a different view of the magnitude and extent of the Messinian Salinity Crisis.

In this study we will not attempt to bring new elements for one or the other interpretation as the Messinian paleo-geographical event will not be discussed. Nevertheless, we will discuss in detail the salt unit, also referred as the Mobile Unit [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF] and the sequence above, the Upper Unit, sealed at the top by the Top Erosional Surface (TES, [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF] or Last [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF] and [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF], after Pellen, (2016). MES: Messinian Erosional Surface; TES: Top Erosional Surface; TS: Top Surface; BES: Bottom Erosion Surface; BS: Bottom Surface; RS: Ravinament Surface; TFRST: Top of Forced Regressive System Tracts; RSME: Regressive Surface of Marine Erosion; MES-CC*: MES Correlative Conformity after [START_REF] Posamentier | Siliciclastic sequence stratigraphy: concepts and applications[END_REF]; MES-CC**: MES Correlative Conformity after [START_REF] Hunt | Stranded parasequences and the forced regressive wedge systems tract: deposition during base-level'fall[END_REF].

marine ravinement surface (TES, [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF]. We have thus considered and regionally mapped the MUM sequence [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF], composed by MU and UU [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF][START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF]. The pre-salt Messinian sequence (LU from [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF][START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF] or MLM (Gorini et al., 2015) is difficult to interpret in the deep basin with the available seismic lines and a regional mapping of it would cause interpretation gaps. Although its basin distribution may have an influence on the morphology of the salt base (e.g. Dos [START_REF] Reis | Radial gravitacional gliding indicated by subsalt relief and salt-related structures: the example of the gulf of Lions, western Mediterranean[END_REF], we will consider a generic pre-salt sequence, composed of Messinian units deposited prior to the salt and syn and post-rift sequences, mostly of Miocene age. In the Liguro-Provençal basin, the syn-rift sequence is very thin [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF] and the basement reliefs are mainly covered by post-rift sediments.

Messinian salt distribution and thickness

The present-day distribution of the MU deposit can give important information on the palaeo-geographic conditions at the time of deposition. Changes in thickness may reveal differences in available space or subsidence during its deposition. The salt was mainly deposited in the deep Mediterranean basins with its upslope limit onlapping the pre-salt deposits on the lower slope. The initial Messinian salt limit deposition can be evidenced by the root of the uppermost fault, with a few salt remnants which indicates the pinch-out of the salt before its movement along the margin (e.g. [START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF]Lofi et al., 2011a). The salt has a viscous behaviour that leads it to be potentially deformed from its deposition to the present day. The present-day observed salt thickness variations are therefore the results of an intense salt tectonics. Salt absorbs seismic energy and often masks the sedimentary sequences beneath it.

The salt interpretation, as well as that of pre-salt sequences, is tricky mainly due to the seismic characteristics inborn of salt. The most recent published thickness map of Messinian deposits is by [START_REF] Haq | Deep Mediterranean's Messinian evaporite giant: How much salt?[END_REF], which present some regional maps of evaporite distribution in the Mediterranean, without differentiating salt and other evaporites deposition. The authors considered all the Messinian deposits, hence including the MLM and MUM (from [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF] or the LU-MU-UU (from Lofi et al., 2011a), depending on terminologies used. Haq et al. calculated the amount of evaporites in volume raising a question already known for several years now (see for instance [START_REF] Bethoux | Mean water fluxes across sections in the Mediterranean-Sea, evaluated on the basis of water and salt budgets and of observed salinities[END_REF][START_REF] Blanc | Of sills and straits: a quantitative assessment of the Messinian Salinity Crisis[END_REF] on the need for the Mediterranean to be continuously refilled several times to produce the total salt deposits. Their map (Fig. 4.5) show some regional thickness trends, with a greater thickness in the Liguro-Provençal basin and a lower thickness in the Algerian basin. However, the map focus on the evaporites distribution and thickness and not on the salt (Mobile Unit): it is therefore tricky to understand the regional salt trends induced by salt tectonics.

Generally, in the basins defined as peripheral, the Messinian salt is characterized by the absence of pure halite deposits and the presence of evaporitic, probably composed of gypsum and anhydrite (e.g. Lofi et al., 2011a). In these intermediate-depth basins the evaporites generally deposited above an erosional surface displaying a thickness spanning from 0 (pinch out on the Miocene slope) to up to 0.4 s twt. They are mostly aggrading and onlapping the margin foots. As shown in figure 4.6, their distribution (from Roveri et al., 2014a;Driussi et al., 2015a) is variable and mainly covers lower slope areas. The UU in the deep basin is always present above the MU, everywhere in the Western Mediterranean Sea. Montadert et al., 1978;[START_REF] Popp | Ultrasonic wave velocities, gas permeability and porosity in natural and granular rock salt[END_REF][START_REF] Jones | Seismic imaging in and around salt bodies[END_REF]. (After Haq et al., 2020). Note the thick deposits in the LPB and the thinner between the EAB and the WAB. Although the map gives a good framework of Messinian deposits distribution, the low resolution does not provide valuable information about the salt structures distribution.

It should be noted that this velocity best represents a pure halite deposits, which is reasonably not the case in the Western Mediterranean. Although the seismic facies highlights an almost pure salt, certainly more than in the East Mediterranean, silico-clastic or other evaporites layer (gypsum, anhydrite, dolomite…) cannot be excluded. The seismic velocities in relatively pure rock salt as well as other evaporites are well established but they can differ in mixed layers depending on the percentage of incorporated salt and litho-facies of the clastic or carbonate sediment. [START_REF] Haq | Deep Mediterranean's Messinian evaporite giant: How much salt?[END_REF] suggest a percentage of mixed layers (clastics and others) spanning from 40% in the Liguro-Provençal and 70% in the Algerian basins, which decrease the salt velocity to 4.21 and 4.03 km/s, respectively. Dal Cin et al., (2016) proposed higher velocities in the Western Sardinian margin, up to 5.1 km/s, by depth processing of seismic line in the Liguro-Provençal basin. It is worth to note that no wells in the West Mediterranean reach the salt layer and these evaluations are purely estimated. To conclude, a velocity of 4.5 km/s appears as a reasonably mean value, also used by [START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF], although slightly elevated if we consider that the salt deposited is not 100% pure.

The two thickness maps, in time and in meters (Fig. 4.6), give significant information about the thickness distribution along the Western Mediterranean sub-basins:

-The mean thickness in all sub-basins spans from 0 to 0.7 s twt, i.e., with a time-depth velocity of 4.5 km/s, between 0 and about 1600 m.

-The maximum thickness values are above salt structures, as for example in the Liguro-Provençal, where a network of salt stocks and walls is extended throughout the deep basin. As mentioned above (Fig. 4.4), the thickness can be biased by the interpretation of the structures. Differences can be observed in the different sub-basins: the Liguro-Provençal basin (LPB) shows huge differences in thickness, due to greater and lower thickness provoked by salt deformation diapirism; the East Algerian basin (EAB) does not show strong variation in thickness, apart for some local salt structures; the West Algerian basin (WAB) shows some small structures in its eastern part and some bigger structures in its western part. It is worth to note that in the Algerian basin the seismic dataset is less dense and some structures may be enlarged by interpolation algorithm. In any case, the WAB shows more thicknesses variations with respect to the EAB. Between the EAB and the WAB, the area called Hannibal Area (e.g. [START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF]Aidi et al., 2018) is characterized by thicknesses close to zero.

Based on salt thickness, in the Gulf of Lion, three domains can be defined from the upslope salt limit (NW) to the deep basin (greater salt thickness, SE) (Fig. 4.6A: domains I, II and III in the Gulf of Lion). A first proximal domain with a mean thickness from 0 to 0.3 s twt (i.e. 0 to 700 m), an intermediate domain with a mean thickness from 0.3 to 0.6 s twt (i.e. 700 to 1350 m) and a distal domain, in the deep basin, constituted by piercing salt structures with variable thicknesses.

The isobath and thickness maps that will be presented below (pre-salt and post-salt thickness and basement depth) were partially previously illustrated in [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. In this work we were able to add a considerable amount of data compared to those presented in that work, thus increasing the resolution, especially in the Algerian margin (refer to chapter 3 for details on used seismic dataset). Roveri et al., (2014a). The Central Mallorca salt is taken from Driussi et al., (2015a). The salt limit is from this study, [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF], Driussi et al., (2015a)

Pre-salt sequences

The sedimentary sequences deposited prior to the halite may influence the salt deformation.

Several works claimed for a close link between structural heritage and salt tectonics (e.g. [START_REF] Gaullier | Raft tectonics: the effects of residual topography below a salt de´ collement[END_REF]Dos Reis et al., 2008;[START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF]Evans and Jackson, 2019). In the Gulf of Lion, some authors have described the possible influences of subsalt relief on salt structures (Dos [START_REF] Reis Dos | Implications of salt-sediment interactions on the architecture of the Gulf of Lions deep-water sedimentary systems-western Mediterranean Sea[END_REF][START_REF] Reis | Radial gravitacional gliding indicated by subsalt relief and salt-related structures: the example of the gulf of Lions, western Mediterranean[END_REF]. The variable morphology of the base salt may have initially driven the movement of salt downhill. Furthermore, some authors have argued that differential compaction of the sub-salt was concomitant with basement steps inducing differences in salt morphology in the Gulf of Lion [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF]. However, the Western Mediterranean is characterised by a thick blanket of deposits separating the basement from the salt. This characteristic is similar to some of the best-known passive salt margins, such as the Angola margin, where a thick sag basin below the salt covers the basement roughness (e.g. [START_REF] Marton | Evolution of the Angolan passive margin, West Africa, with emphasis on post-salt structural styles[END_REF][START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF].

Looking at the basement depth map in figure 4.7, it can be seen that the salt is deposited in the lower slopes of the margins and in the deep basin, where the basement is currently at least 4 s twt deep. Differences in depth between the different sub-basins can also be observed:

-i) the LPB is characterised by a maximum depth of 7 s twt in the deepest part and tends to gradually decrease towards the conjugate margins (western Sardinian and Gulf of Lion margins); -ii) the Minorca basin is characterised by a shallower basement (<5 s twt), as described in [START_REF] Pellen | Géodynamique et impact de la crise d'érosion et de salinité Messinienne sur les transferts sédimentaires (bassins de Valence et Adriatique)[END_REF], and includes some volcanic structures aligned with the NBFZ (e.g. Maillard et al, 2020); -iii) the eastern Algerian basin is characterised by a basement depth of about 5-6 s twt and it shows a NNW-SSE direction alignment from the south of the Menorca block to the northerneastern Algerian margin; -iv) the South Menorca block is a shallow basement zone, interpreted as continental crust (Driussi et al., 2015a), whose geodynamic history is still under debate; its southward extension into the deep basin is characterised by structural highs, interpreted as volcanic structures [START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF] and called Hannibal High.

-v) the western Algerian basin is characterized by an almost constant basement depth (~6 s twt) with some structural highs and lows in the northern Algerian margin.

The pre-salt regional thickness map (Fig. 4.8A) shows notable differences in the Liguro-Provençal basin, which is characterised by the thickest sequences (up to 2 s twt), compared to the entire Algerian basin, with an average thickness of ~1 s twt. The eastern Algerian basin (mainly its northern part, at ~70 km from the north Algerian margin) presents a NW-SE alignment, similar to that observed in the basement depth map (Fig. Basement depth map (in s twt). The salt limit is from [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF], Driussi et al., (2015a), [START_REF] O Obone-Zue-Obame | The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the "MAURESC" cruise[END_REF] and this study. The contour lines are every 0.5 and 1 s twt. Note the shallow basement in the Hannibal High area and the deeper in the LPB.

Figure 4.8. Pre-salt sequence isopach map (in s twt). Contour every 0.5 and 1 s twt. The salt limit is from [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF], Driussi et al., (2015a), Obone-Zue-Obame et al., (2011) and this study. Note the NW-SE oriented thin thickness in the EAB and the thick sequence in the LPB.

Post-Messinian (Plio-Quaternary) distribution and thickness

Figure 4.9 shows a variable Plio-Quaternary coverage between the sub-basins in the Western Mediterranean Sea, ranging from values close to zero (e.g. Balearic Islands and West Sardinian Area) to values close to 2 s twt located in the Gulf of Lion (e.g. [START_REF] Leroux | High-resolution evolution of terrigenous sediment yields in the Provence Basin during the last 6 Ma: relation with climate and tectonics[END_REF][START_REF] Droz | On the termination of deep-sea fan channels: Examples from the Rhône Fan (Gulf of Lion, Western Mediterranean Sea)[END_REF], Badhani et al., 2020), in the Ebro Delta (e.g. [START_REF] Pellen | The Minorca Basin: a buffer zone between the Valencia and Liguro-Provençal Basins (NW Mediterranean Sea)[END_REF][START_REF] Pellen | The Messinian Ebro River incision[END_REF] and in the northern Algerian margin [START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF][START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF]Leprêtre, 2012).

The causes of high sedimentary supply can be ascribed respectively to the inputs of the Rhone, the Ebro and the tectonic inversion to which the northern Algerian margin has been subjected since the Pliocene [START_REF] Déverchère | Active thrust faulting offshore Boumerdes, Algeria, and its relations to the 2003 Mw 6.9 earthquake[END_REF][START_REF] Domzig | Searching for the Africa-Eurasia Miocene boundary offshore western Algeria (MARADJA'03 cruise)[END_REF]. Sedimentary thickening in the proximal part of the North African margin is due to the compression towards Europe, which causes tilting of the basement and sedimentary cover towards the south, creating more space for sediment accumulation. The large-scale southward increase in the sediment thickness all along the Algerian margin was already observed in the 1970's and it had been interpreted as the result of lithospheric bending related to the Algerian margin contractive reactivation (Auzende et al., 1972(Auzende et al., , 1975)). The Rhone fan, with a NW-SE direction in the Gulf of Lion, seems to extend up to, at least, the western Sardinian margin (close to parallel 40°N). The EAB is characterised by a constant sedimentary thickness (around 0.8 s twt) except for, as mentioned, the northern Algerian margin. The western Algerian margin, narrower compared to the eastern, displays a northern part characterized by a mean thickness of 0.5-1 s twt, and a southern part, in the northern Algerian margin, thicker (up to 1.5 s twt). However, here the interpolation (due to the less seismic coverage) and the great salt tectonics can be the cause of the widespread local variations in Plio-Quaternary thickness observed in the map. The black line shows the upslope salt limit and indicates, almost everywhere, a change in Plio-Quaternary thickness, from a thicker lower slope/deep basin to a thin slope/shelf area. The thin sedimentary thickness on the slope characterises the whole western Mediterranean Sea, in contrast to what is observed in other passive margins, where a thick progradational sedimentary blanket influences the salt deformation, as for example in the Santos basin [START_REF] Guerra | Role of halokinesis in controlling structural styles and sediment dispersal in the Santos Basin, offshore Brazil[END_REF][START_REF] Davison | Geology and tectonics of the South Atlantic Brazilian salt basins[END_REF].

The only area where a greater Plio-Quaternary thickness is extended in the slope is the Gulf of Lion, where the Rhone sedimentary input can be followed along the slope and shelf.

Salt morphologies analysis

In this chapter I will analyse the salt structures in all the Western Mediterranean Sea, in order to group them together according to geometric criteria. The salt domains will thus indicate the regional salt morphologies distribution. These morphologies will allow a global view of the salt deformation in order to understand the regional variations and superpose the structures to other tectonics and sedimentary elements, such as the crustal segmentation and the sedimentation.

The domains of salt morphologies are exclusively chosen according to geometric criteria such as: ratio between height and width, overburden deposits deformation, base salt characteristics and associated structures (e.g. faults, salt welds), diapirs frequency. Given the wide variability of resolution and quality of seismic data, we opted to maintain a regional [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF], Driussi et al., (2015a), Obone-Zue-Obame et al., (2011) and this study. Note the Petit Rhone fan (e.g. [START_REF] Droz | Quaternary turbidite systems on the northern margins of the Balearic Basin (Western Mediterranean): a synthesis[END_REF] in the LPB, the NW-SE oriented thinner area in the EAB and the thicker northern Algerian margin. classification, in order to have a global vision of salt structures differences in the sub-basins.

We did not focus on single salt structures but rather on macro-areas with the same structural and geometrical characteristics. et al., (2016). Thin black lines are bathymetry every 200 m (thin lines) and at 100 and 2000 m depth (thick lines). The upslope salt limit is from [START_REF] Bache | Messinian erosional and salinity crises: view from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF][START_REF] O Obone-Zue-Obame | The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the "MAURESC" cruise[END_REF], Driussi et al., (2015a) and this study.

sub-basins of the West Mediterranean, showing examples of profiles and discussing the distribution.

Listric domain

The Listric domain (dark blue colour in fig. 4.10) is so called because it is characterised by listric normal faults that develop from the base of the salt in the overlaying units, sometimes reaching the seafloor. It is characterized by salt rollers and rollover structures. The term salt rollers describes low-amplitude deflections of the upper surface of a salt layer at the lower termination of normal faults in the overlying sediments [START_REF] Bally | Thoughts on the tectonics of folded belts[END_REF]. The salt rollers are therefore formed by the action of the faults. The rollover structures are syn-sedimentary extensional structures resulting from layer bending during hanging-wall displacement above a listric normal fault (e.g. [START_REF] Brun | Rollovers in salt tectonics: the inadequacy of the listric fault model[END_REF]. The sliding of salt along its base detachment induces a sediments subsidence and thinning of salt, which is proportional to the density and thickness of the overburden and the initial salt layer thickness. This mechanism generated the so-called thin-skinned tectonics, as the base of salt is not affected by displacements, also typical of many fold and thrust belts developed in the foreland of a collisional zone. The Listric domain is situated, with variable width, along all the edges of the deep basins of the West Mediterranean basin. It is usually located on the lower slope but the distribution is variable in the different margins. In the Gulf of Lion, it occupies an area that can extend up to 50 km basinward from the upslope limit of salt while in the Algerian margin and in the east Alboran margin it is narrower, of 10-20 km. In the South Balearic and in the west Sardinian margins the extension is between 10 and 30 km.

Figure 4.11 shows a high resolution profiles in the Gulf of Lion lower slope representing the evolution of salt deformation from the upslope limit to the basin. The profile highlights a dipping slope in the order of 1.4°. The listric faults only affected the salt and the units above it, and are the cause of the salt rollers and rollover structures all along the slope. The faults can be currently active (deforming the seafloor, fig. 4.11) or inactive (buried) (Dos [START_REF] Reis Dos | Implications of salt-sediment interactions on the architecture of the Gulf of Lions deep-water sedimentary systems-western Mediterranean Sea[END_REF] and form rollovers from the lower Pliocene to present day. It is worth to note that the Upper Unit (UU) appears to retain the same thickness when displaced by faults, suggesting that the basinward-dipped listric faults only moved after the UU complete deposition. The pre-salt sequence, hampered by multiples reflectors, does no show important faults that deform the base of the salt, which is steeply sloping towards the basinward and appears as an undulating surface with an often-erosive character. The amount of salt appears to increase basinward (Fig. 4.11) probably due to the effect of induced gliding through its base, acting as a detachment surface.

In the west Sardinian and South Balearic margins, the Listric domain is narrower than in the Gulf of Lion (Fig. 4.10). It is located in the lower slope up to the limit with the deep basin and is characterized by listric faults involving the Upper Unit and the Plio-Quaternary sequences. In the west Sardinian margin (Fig. 4.12, WS10-13) the base salt detachment surface displays a strong basinward slope (about 3°) which generates a system of normal basinwarddipping normal faults and salt rollers. It is hard to decipher the timing of the faults because the limit between the Upper Unit and the Lower Pliocene is not always well interpretable and the thin Plio-Quaternary sequence does not allow a good interpretation of growth strata timing in the overburden. In the upper slope domain (towards the East), the basement is shallow and the pre-salt deposits seem thinning towards it.

In the south Balearic margin the Listric domain is located above a basement high. The basement, probably of volcanic origin, movement may have favoured the increasing of the base slope, allowing salt flowing towards the deep basin (Fig. 4.12). In the deep basin, the Plio-Quaternary and the base of salt reflectors display a sub-horizontal dip. Just above the shallow basement in the proximal domain (lower slope), the Plio-Quaternary reflectors are instead landward-dipping, which suggests a present-day continuous rising of the basement structure.

The Upper Unit and the pre-salt sequences show different thicknesses between the more proximal domain (close to the basement, SE) and the distal domain, which suggest that the basement structure rising was active during the Miocene and the Messinian deposition (Fig. 4.12). Other elements are the onlaps within the Upper Unit (Zoom in fig. 4.12). The volcanism in this area and, more generally, in all the Valencia basin and Balearic Promontory has been the subject of study and dating, showing mainly two active periods (Maillard, 1993;Marti et al., 1992): an early to middle Miocene calc-alkaline and a middle Miocene to Holocene alkaline volcanism cycle. In the south Balearic area (Emile Baudot Escarpment), other authors have interpreted younger volcanism, dated as early Pleistocene (Acosta et al., 2001a;[START_REF] Acosta | Sea floor morphology and Plio-Quaternary sedimentary cover of the Mallorca Channel, Balearic Islands, western Mediterranean[END_REF]. The basement high is located more SE of the well-known Emile Baudot Escarpment (Acosta et al., 2001a) and it can be followed along part of the margin and may have been the cause of the "perched" salt basin observed (Fig. 4.12).

Similarly, the SH73-23a profile (Fig. 4.13) shows the Listric Domain in the north Algerian margin, where the authors interpret a tectonic reactivation given by the North African convergence. In this profile the reactivation seems to be less evident than the images proposed by some authors (e.g. [START_REF] Domzig | Déformation active et récente, et structuration tectonosédimentaire de la marge sousmarine algérienne[END_REF]Deverchere et al., 2005) but, in any case, the margin is more abrupt than the Gulf of Lion margin. Likewise, the Listric Domain is narrower but it shows the same features previously described: the salt forms roller-like structures, extending in the lower slope until it reaches the deep basin where it forms wide pillows. The base of the salt, tilted in the Listric Domain, becomes more horizontal in the deep basin, as also shown by the contour lines (Insert map in fig. 4.11). The Miocene sequence generally onlaps the basement except in the presence of a structural high at the boundary with the lower slope, where it seems to accommodate it, a sign that a deformation was active during the Miocene. The base of salt does not seem to be faulted or highly deformed.

The fundamental feature of the Listric domain is the base of the salt leaning towards the basin, as observed in the depth map of the base salt (Insert map in fig. 4.11). The salt, given its viscous rheology, glides towards the deep basin through a detachment surface materialized by the contact between the salt deposit and the underlying formations. The formed structures are therefore of extensional origin, involving amounts of extension of listric normal faults. When salt is removed, a weld is formed, separated by the basinward-verging normal faults.

Thin/no salt domain

The Thin domain is so called because of the absence or low salt content. It does not show detachment listric normal faults that dislocate the salt and its overburden and the base of the salt are mostly sub-horizontal or can be influenced by basement structures. This domain is located in the Hannibal High area (Fig. 4.10), between the east and the west Algerian basin on the south of the South Minorca continental block (SMB), and is already interpreted by some authors as a volcanic area characterized by high basement structures and positive magnetic anomalies [START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF]Aidi et al., 2018), located. The Hannibal Area is an area of about 100 x 100 km characterized by absence/isolated deposits of salt. Focusing on basement depth map (Fig. 4.15A), we observed in this area a series of structural highs whose depths range between about 5-6 twt, shallower than the deep east or west Algerian basins. The salt thickness map shows an area of thin/absent salt deposits (Fig. 4.15B). With the resolution of the available profiles we cannot discriminate whether there is actually a noticeable amount of salt, whether there is no salt at all or whether some patches are present. The salt structures, where present, are "hidden" inside the Upper Unit and deform the lower part of it (zoom in fig. 4.14). The small deformation is sealed by an unconformity (red reflectors in the upper part of UU and toplaps on it, fig. 4.14) that can be followed inside the Upper Unit along the whole profile and delimits two internal sequences, the shallower being less affected by salt tectonics. Moreover, the salt does not seem to have glided from this area towards the edges, as we do not observe accumulations of salt in the close east and west domains (Fig. 4.15B). The Hannibal Area is the only one in the Western Mediterranean Sea where salt seems to be absent (or present to a lesser extent) in the deep basin. Some issues of this area remain unresolved, such as the crustal nature, its implication on Algerian basins geodynamics and the paleo-geographical context related to the Messinian deposits. On the basis of our observations, it would seem that the salt in this area was originally not deposited or deposited with a much smaller thickness than in the other Western Mediterranean basins. Unfortunately, the seismic dataset coverage does not allow a detailed interpretation of the Miocene units that would have allowed a study of the seismostratigraphic relationship between structural highs and pre-Messinian sedimentation.

Anticlinal domain

The Anticlinal domain is located basinward of the Listric domain, at the limit between the lower slope and the deep basin. It is characterized by salt-cored folds (pillow or anticlines) with concordant overburden: the overlaying strata are thus parallel to the upper salt contact. Widely described and observed in many context [START_REF] Shoemaker | Salt anticlines of the Paradox Basin[END_REF][START_REF] Cater | Geology of the salt anticline region in southwestern Colorado[END_REF][START_REF] Letouzey | Evolution of salt-related structures in compressional settings[END_REF] the authors claim that their formation and evolution is caused by halokinesis (gravity gliding), contraction forces and/or normal faults rollovers (e.g. [START_REF] Letouzey | Evolution of salt-related structures in compressional settings[END_REF]Ferrer et al., 2012;[START_REF] Jackson | Salt tectonics: Principles and practice[END_REF]. The anticlinal bases are wide (up to 5-10 km) and the length to height ratio very high (>5).

The Anticlinal salt are therefore structures with large wavelength. Generally, the limit between Listric and Anticlinal domain is concomitant with the flattening of the base of salt, from a strong tilting in the former to a gentle basinward dipping in the second. In the Algerian basin, as we will see below, the base of salt is gently dipping landward, making it a particular case in the Western Mediterranean Sea. The wide anticlinal/pillow area (in 2D section the difference cannot be depicted, [START_REF] Jackson | Salt tectonics: Principles and practice[END_REF]) displays a large-scale deformation that can deform the seafloor. Figure 4.16 shows Gulf of Lion wide salt cored folds (location in fig. 4.17). Locally, extensional faults affected the salt overlying sediments and seem to develop mainly from the Lower Pliocene to nowadays (Fig. 4.16). The reflectors within the Upper Unit are also concordant to the top salt although we can observe locally some small -scale onlaps on 2018) and [START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF]. B) Salt thickness map (zoom of figure 4.6) shows thin/absent salt deposits in the same area.

it. In chapter 4.5 I will go into detail about the terminations in this domain to determine the timing of the salt deformation. UU thickness seems to increase towards the basin (Fig. 4.16; towards SE). The salt displays typical transparent seismic facies, especially in the centre of the sequence (Fig. 4.16). Within the salt deposits we can observe some reflectors with higher amplitude, concordant with the overlying UU. These reflectors are parallel to the UU and look like artefacts given by internal multiple (peg-leg type) inside the salt (Fig. 4.16). We thus discard (at least for this line) the presence of detritic levels in the salt, often observable as high amplitude reflectors inside the salt deposits, as shown for instance by [START_REF] Bertoni | Controls on the basinwide architecture of late Miocene (Messinian) evaporites on the Levant margin (Eastern Mediterranean)[END_REF] in the Levant margin. The base of salt tilts slightly towards the basin (SE) of around 0.3° and does not present dislocations or roughness (apart from the artefact due to pull-ups below the salt structures). The pre-salt sequence (including the Lower Unit, Lofi et al., 2011a, not interpreted in this profile), is concordant and parallel with the salt base.

The example in figure 4.17 shows a profile crossing the limit between the east Alboran and the west Algerian basin characterized by a 15 km-long Listric domain, followed seaward by a 50 km-long Anticlinal domain. The Anticlinal domain is located at the lower slope-deep basin limit, towards the west Algerian basin. The Plio-Quaternary sequence displays a regional constant thickness from the lower slope to the deep basin, smaller than in the Gulf of Lion (~1.2 s twt in the Gulf of Lion and ~0.6 s twt in the west Algerian basin). The Upper Unit is concordant with the top salt and exhibits a thickness increasing basinward, ranging from 0.3 s twt in the lower slope to 0.6 s twt in the deep basin (Fig. 4.17). The limit between the lower slope and the deep basin is characterized by the absence of salt deposits (Fig. 4.17; no salt area).

The non-appearance of salt suggests a gliding along its base after the deposition, towards the deep basin, where it could have fed anticlinal structures. The timing of the relation between small listric faults in the lower slope and structures in the proximal deep domain is uncertain and hard to decipher: looking at the thickness variation of the Upper Unit in the Anticlinal domain, salt seems to move very early after its deposition, but unfortunately the listric normal faults timing is complex to depict with the low resolution data (Fig. 4.17). The base of salt in the Anticlinal domain shows a weak slope (about 0.4°) and is concordant with the pre-salt sequence. The lower slope and the deep basin are characterized by some normal faults which have displaced the basement. These faults interest only the basement and the pre-salt sequences, without involving the base of salt.

Large Diapirs domain

The main difference between Anticlinal and Large diapirs domain deformation is the concordant and discordant contacts with the overlying sediments, respectively. The pre-salt sequence is flatly layered, hampered below the salt diapirs but well recognizable below the anticlines. The basement shows corrugation but absence of strong steps, also confirmed by basement depth map (Fig. 4.7). The large Diapirs domain is characterized by salt walls and stocks structures with a wide base (up to 8 km) and piercing diapirs. The length to height ratio is between 0 and 1, given their greater vertical extension. The overlying sequences are always discordant (they onlap the salt) and they form drape fold of variable amplitude (refer to chapter 2.2.3.2).

Large Diapirs domain in the GoL

The Large Diapirs domain is located in the central deep basin of the LPB, downstream the Anticlinal domain (Fig. 4.18). It extends with a NE-SW direction, parallel to the Gulf of Lion margin, and is 20 km wide with a local 50 km width in the middle part. The structures always deform the seafloor and are so still actives. This area, characterized by wide and piercing salt structures, was already described by several authors who discussed the coincidence of this domain with the basinward appearance of oceanic crust [START_REF] Le Cann | Le diapirisme dans le bassin Liguro-Provençal (Méditerranée occidentale)[END_REF][START_REF] Pautot | Morphology and extension of the evaporitic structures of the Liguro-Provençal Basin: New Sea-Beam data[END_REF][START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF]. Crests can reach ten of meters above seafloor [START_REF] Pautot | Morphology and extension of the evaporitic structures of the Liguro-Provençal Basin: New Sea-Beam data[END_REF] and the structures can be recognized in bathymetry data (Zoom in fig. 4.18). Figure 4.18 shows the main rounded salt stocks distribution and elongated salt walls with two main directions: N-S and NW-SE. The first direction is the most common and is characterized by elongated walls structures that form mini-basins between them with the same N-S direction. The mini-basins are small depressions created between salt diapirs after the subsidence of the overlying sediments on the salt top. A mini-basin is initially surrounded and floored by salt, which then is expelled from beneath and rises around the diapir edges. Salt expulsion creates space for the mini-basin to deepen until a weld has formed at its base. It is typically characterized by synclines of sediment of few tens kilometres of diameter that sometimes can form closed topographic lows, as in Gulf of Mexico (e.g. [START_REF] Brun | Salt tectonics at passive margins: geology versus models-Reply[END_REF]. The base of salt can be mostly interpreted at the base of the mini-basin, where the salt does not hamper the signal, and it is regionally sub-horizontal. In the GoL the mini-basins evolution are closely related to the diapirs formation, and mostly take the direction of salt walls (Figs. 4.18;4.19). They are a preferential path of sediments [START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF]. The sinking of the sediments stops when the sequence above the salt comes into contact with the sequence deposited before the salt. In this case we talk about weld [START_REF] Jackson | Seismic recognition of salt welds in salt tectonics regimes. In Gulf of Mexico salt tectonics, associated processes and exploration potential[END_REF], which is a surface marking a vanished salt body. The weld structures can affect the hydrocarbon and fluids migrations, which can find a preferential path between the pre and post-salt deposits.

Large Diapirs domain in the WAB

The Large Diapirs domain in WAB shows some differences compared to the Large Diapirs in the Gulf of Lion. The bases are likewise wide but the salt stocks are more connected (Fig. 4.20). Moreover, the mini-basins are less developed and the welds are rare. Nevertheless, some structures, especially in the north Algerian margin, are similar to those seen in Gulf of Lion.

When the structures are more isolated, their size is smaller than in the GoL. The base of salt is regionally sub-horizontal as well as the Plio-Quaternary deposits, where the salt deformation did not affect them (e.g. Fig. 4.20). The limited dataset in the area did not allow to better describe the details in salt morphologies differences in the WAB, especially in the northern Algerian margin. In the next section, we will show other regional sections that will better show the regional distribution of this domain, illustrating some possible differences within the west Algerian basin.

Regular and Irregular connected domains

In the east Algerian and Liguro-Provençal deep basins the salt deforms in the form of narrow and frequent diapirs. They are closely spaced from each other and vertically extended (they can reach the seafloor).

High salt base domain

Unlike the other domains, this area is interpreted according to some structural features that we considered of primary interest with respect to salt morphologies. In west Sardinia and south Balearic margins, an area of shallower base salt is interpreted, characterized by differences in salt deformation intensity, outlined by salt diapirs in both margins (Fig. 4.23) suggest a basement rising during the last phases of the UU deposition up to the end of Messinian. This structure is therefore decidedly younger than the volcanic structures found in the Sardinian hinterland and dated concomitant to the rifting phase [START_REF] Rehault | The western Mediterranean basin geological evolution[END_REF][START_REF] Beccaluva | Geochronology in Sardinia: results and problems[END_REF] but is more consistent with the age measured in the south Balearic margin (Acosta et al., 2001a;Marti et al., 1992). During the rising of the basement the salt seems to slide towards the basin, going to feed the first two salt diapirs that are located to the north-west (Diapirs A and B in zoom fig. 4.23). The basement high, probably of volcanic origin, is recognizable in the base salt depth map (Fig. 4.22) and seems to be part of a network of volcanic structures in North West Sardinia margin.

Salt morphologies description summary

The sketch above (Fig. 4.24) shows the summary of the main salt morphologies and their main features as described in this chapter. Although in some domains we have mentioned the evolutionary processes and forces that come into play for the formation of salt structures, we have voluntarily omitted these criteria for the classification because, as mentioned, the primordial objective was to classify the structures according to their geometries, in order to correlate it directly with crustal segmentation. The distribution of salt morphologies in Western Mediterranean is variable from the lower slope to the deep basin and between the sub-basins that compose it (Fig. 4.10). We can summarize these regional differences in two main points:

-The first order of segmentation is perpendicular to the margins, from the lower slope to the deep basin, and concerns the amplitude and distribution of the Listric and Anticlinal salt domains: the Listric domain is present everywhere from the upslope salt limit, and displays a variable width, from a maximum value in the Gulf of Lion (around 50 km) to a minimum value in the east Alboran and north Algerian margins (around 10 km). Its amplitude and features (listric faults frequencies and overburden dislocation) mainly depend on margin architecture. When the margin is steeper, as the case in the north Algerian and west Sardinian margins, this domain is narrower while when the margin displays a gentle slope, this domain is wider.

Basinward of the Listric domain, the Anticlinal domain is only present in the Gulf of Lion, east Algerian and east Alboran margins. Here, the pillow structures are mainly characterized by a sub-horizontal base salt and are located in more or less wide domains.

The Anticlinal domain is not present in the western Sardinian, south Balearic, north east Algerian and east south Minorca margins, where, basinward the Listric domain, we observed directly more or less developed diapiric structures (e.g. Fig. 4.12) -Differences in salt morphologies exist in the Western Mediterranean Sea deep basins.

The most striking difference is observed between the west and the east Algerian basins, the eastern domain is characterized by less intense (less piercing) salt deformation compared to the western domain (Figs. 4.20,4.21) These regional observations raised several questions concerning the mechanisms in salt tectonics and their relationship with the crustal structure (and nature?):

-How can we explain the segmentation observed in the distribution and the extent of these salt domains? What do they derive from? -Why do we observe differences in salt structures between each sub-basin?

In the next chapter I will investigate the relationship between crustal segmentation and salt geometries.

Western Mediterranean salt morphologies and crustal segmentation comparison

In section 4.3 I have shown the salt morphologies distribution in the Western Mediterranean Sea. As explained, the salt morphologies vary perpendicular along the slope and between the sub-basins, highlighting strong differences between the Liguro-Provençal, eastern and western Algerian basins in particular (Fig. 4.25). To these salt morphologies categories we then superpose the crustal segmentation, taken from bibliography compilation (Fig. 4.25 below) (see chapter 3 for references). Some regional transect coupled with regional maps of geophysical (gravimetry and magnetic anomalies) and stratigraphic interpretations (e.g. base of salt and basement) are here presented. The Listric domain is situated in the lower slope, from the upslope salt limit to the proximal part of the deep basin and is concomitant with a necking crustal domain (Fig. 4.26), characterized by lower and upper crust thinning from 7 to 5 km and 7 to 3 km, respectively [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. The offshore limit of this domain is marked by the T-reflector [START_REF] Voogd | Twoship deep seismic soundings in the basins of the Eastern Mediterranean Sea (Pasiphae cruise)[END_REF], interpreted as a fault near the surface identified on the reflection seismic profiles [START_REF] Séranne | Structural style and evolution of the Gulf of Lion Oligo-Miocene rifting: Role of the Pyrenean orogeny[END_REF][START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF], which marks the basinward limit of the transitional crust domain [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. Moreover, this limit marks the offshore boundary between a tilting subsidence and a purely vertical subsidence, as observed and calculated from [START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF] and [START_REF] Leroux | Post-rift evolution of the Gulf of Lion margin tested by stratigraphic modelling[END_REF] (Hinge Line,fig. 4.27). Seaward this Hinge Line, the purely vertical subsidence is characterized by a mean rate of 500 m Ma -1 [START_REF] Leroux | Post-rift evolution of the Gulf of Lion margin tested by stratigraphic modelling[END_REF], using an age of 20 Ma for the end of the rifting phase [START_REF] Séranne | The Gulf of Lion continental margin (NW Mediterranean) revisited by IBS: an overview[END_REF]. The Anticlinal domain is concomitant with the transitional crust domain, with spatially variations from NE to SW (Fig. 4.26). The nature of transitional crust in the Gulf of Lion was matter of debate and several hypothesis were considered: i) highly thinned continental crust [START_REF] Pascal | The ocean-continent boundary in the Gulf of Lion from analysis of expanding spread profiles and gravity modelling[END_REF]; ii) exhumed lower continental crust [START_REF] Séranne | Structural style and evolution of the Gulf of Lion Oligo-Miocene rifting: Role of the Pyrenean orogeny[END_REF][START_REF] Séranne | The Gulf of Lion continental margin (NW Mediterranean) revisited by IBS: an overview[END_REF] or iii) exhumation of lower continental crust and mantle [START_REF] Jolivet | Continental breakup and the dynamics of rifting in back-arc basins: The Gulf of Lion margin[END_REF]. The wide-angle data shows a very thin crust (about 5 km) with relatively high velocities (from 6.0 to 6.4 km/s for the upper layer and 6.6 to 7.5 km/s for the lower layer) interpreted as exhumed lower continental crust [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]Afilhado et al., 2015) (Fig. 4.26). Whatever the nature, both internal and external limits of the transitional domain correspond to the limits of the salt morphologies, as interpreted in chapter 4. 3 (Figs. 4.25,4.27). The limit of the oceanic crust in the Liguro-Provençal basin is marked by a change in the pattern of the magnetic anomalies (see for instance [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. Thinner (5 km) than the "normal" oceanic crust (Moulin et al., 2015;[START_REF] Gailler | Crustal structure of a young margin pair: new results across the Liguro-Provencal Basin from wide-angle seismic tomography[END_REF], this "atypical" oceanic crust seems to lack the layer 2 of normal oceanic crust [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. The Moho depth and the velocity gradients are similar to those in the transitional crust, suggesting a relationship in the genesis [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. The atypical, thin oceanic crust can display analogies with the proto-oceanic crust (Schnurle et al., 2018), interpreted by some authors in other passive margins, as in Santos basin [START_REF] Klingelhoefer | Imaging proto-oceanic crust off the Brazilian Continental Margin[END_REF], in the Jequitinhonha basin [START_REF] Loureiro | Imaging exhumed lower continental crust in the distal Jequitinhonha basin, Brazil[END_REF], the Caroline Margin [START_REF] Shuck | The role of mantle melts in the transition from rifting to seafloor spreading offshore eastern North America[END_REF][START_REF] Bécel | Evidence for a prolonged continental breakup resulting from slow extension rates at the Eastern North American Volcanic Rifted Margin[END_REF] and in the Indian Ocean [START_REF] Peters | Extremely thin oceanic crust in the Proto-Indian Ocean: evidence from the Masirah Ophiolite, Sultanate of Oman[END_REF]. The oceanic LPB domain is coincident with the Connected, Irregular salt domain (Figs. 4.26,4.27). Its distribution is variable in the deep basin, with areas dominated by more irregular and vertically developed deformations and areas where diapirs are smaller (Figs. 4.26,4.27).

Western Sardinian margin

The relationship between crustal segmentation and salt morphologies in the WS has never been concretely addressed by the scientific community. The works directly dealing with the salt tectonics are sparse and mainly focused on the Messinian markers (e.g. [START_REF] Sage | Seismic evidence for Messinian detrital deposits at the western Sardinia margin, northwestern Mediterranean[END_REF][START_REF] Geletti | The Messinian Salinity Crisis: new seismic evidence in the West-Sardinian Margin and Eastern Sardo-Provençal Basin (West Mediterranean Sea)[END_REF][START_REF] Dal Cin | Seismic imaging of Late Miocene (Messinian) evaporites from Western Mediterranean back-arc basins[END_REF]. This margin exhibits some fundamental differences compared to its conjugated, the Gulf of Lion, such as (Figs. 4.26 and 4.28): i) a narrower margin characterized by steep and narrow slope, ii) a thin sedimentary cover, both pre and post-Messinian evaporites, iii) a different salt morphologies distribution perpendicular to the margin.

The salt pinches out on the lower slope in most of the margin, except in its centre (around latitude 40'30''N) where the salt upslope limit is located in the middle slope (see for instance fig. 6 in Dal Cin et al., 2016;[START_REF] Sage | Seismic evidence for Messinian detrital deposits at the western Sardinia margin, northwestern Mediterranean[END_REF]. The Anticlinal domain is not observed in WS margin, in contrast to the Gulf of Lion where it represents the widest domain (Fig. 4.25). In the WS, the Listric domain is followed by the High salt base domain, regionally characterized by connected diapirs (Fig. 4.26). The Listric domain is floored by a thinned continental crust which exhibits analogies with that of the Gulf of Lion margin but with no equivalent of T reflector (Afilhado et al., 2015) (Fig. 4.26).

In all the proximal deep basin (at the basinward limit between the lower slope and the deep basin) we interpreted an area of High salt base, characterized by a shallower base of salt. This area, which is parallel to the margin with a N-S direction, is floored by a transitional crust (Fig. 4.26) [START_REF] Gailler | Crustal structure of a young margin pair: new results across the Liguro-Provencal Basin from wide-angle seismic tomography[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF]. This domain is characterized by a strong velocity step between the two crustal layer (lower and upper) and a strong velocity gradient in the lower crust [START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF]. This domain, less wide than those observed in the conjugate Gulf of Lion margin, is interpreted as exhumed lower continental crust (Afilhado et al., 2015). The limit between the high salt base domain and the Irregular salt domain is coincident with the oceanic-transitional crust limit interpreted by refraction [START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF] and gravity data (Leroux et al., 2019) (Fig. 4.26). The deep basin, seaward of the transitional crust domain, is interpreted as formed by thin oceanic crust (4 km) and is also coincident with gravity and magnetic patterns (Fig. 4.26). As in the Gulf of Lion, the seismic velocities suggest an affinity between the oceanic and the transitional domain. The crustal nature and segmentation outlined in the Gulf of Lion-Western Sardinian margins show an overall symmetry composed by thinning and transitional domains with similar features.

Nevertheless, the upper crust in the WS margin displays slower velocities in the transitional but faster velocities in the oceanic domains [START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF] (Fig. 4.26): an asymmetric oceanic build-up, characterized by more magmatism in the WS is argued by some authors (e.g. [START_REF] Burrus | Contribution to the thermal regime of the Provençal Basin based on FLUMED heat flow surveys and previous investigations[END_REF]. Likewise, the salt domains in the conjugated margins transitional domains are different, with a wide Anticlinal domain in the Gulf of Lion and a Diapirs domain in the Western Sardinian, characterized by a shallower base of salt. Moulin et al., 2015 (GoL) and Afilhado et al., 2015 (WS).

. Reflection and wide-angle coincident profiles crossing the Gulf of Lion (A) and the Western Sardinian margin (B). The wide-angle profiles and crustal segmentation are taken from

Algerian basin

Eastern Algerian

The study of salt tectonics in the EAB has seen less interest than in the Gulf of Lion: some works are nevertheless present, mainly as a result of the exploitation of the Maradja1-2 and SPIRAL seismic campaign [START_REF] Gaullier | Salt tectonics in the deep Mediterranean: indirect clues for understanding the Messinian Salinity Crisis. The Messinian salinity crisis from mega-deposits to microbiology-A consensus report[END_REF]Thomas, M1 report 2010). Most of the works focused on the stratigraphic reconstructions and Plio-Quaternary inversion description (e.g. Arab et al., 2016a;[START_REF] Domzig | Searching for the Africa-Eurasia Miocene boundary offshore western Algeria (MARADJA'03 cruise)[END_REF][START_REF] Déverchère | Active thrust faulting offshore Boumerdes, Algeria, and its relations to the 2003 Mw 6.9 earthquake[END_REF][START_REF] Strzerzynski | Tectonic Inversion and Geomorphic Evolution of the Algerian Margin Since Messinian Times: Insights From New Onshore/Offshore Analog Modeling Experiments[END_REF] Both profiles exhibit steep and narrow thinning crust domain, outlined in surface by a steep slope. Likewise, the transitional crust domains are narrow (about 20 km in both profiles), characterized by greater velocities than in the continental crust but slower than in the oceanic crust [START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF] (Fig. 4.29D). The velocities do not exceed 7.1 km/s, which are slightly lower than the values found in the lower layer of the Gulf of Lion-West Sardinia margin (6.5-7.5; 6.8-7.25 km/s, respectively). The narrowness of this domain and the absence of high lower layer velocities suggest a narrow or absent transitional crust in that part of the northeastern Algerian margin [START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF]. The salt morphologies in this area are characterized by a narrow Listric domain at the lower slope, followed by an Anticlinal domain, characterized by connected pillows and landward-dipped base of salt (Figs. 4.29B;4.30). All the northern margin is affected by Plio-Quaternary compression related to the convergence between the African and the European plates (e.g. [START_REF] Déverchère | Active thrust faulting offshore Boumerdes, Algeria, and its relations to the 2003 Mw 6.9 earthquake[END_REF]Kherroubi et al., 2009). The salt is therefore affected by the compression, which may be the cause of the tilting of its base towards the North Algerian margin. Kinematic studies indicate that present-day NW-SE convergence between the African and European plate is about 5.1 mm yr -1 at the EAB longitude [START_REF] Nocquet | Geodetic measurements of crustal deformation in the Western Mediterranean and Europe[END_REF][START_REF] Stich | Kinematics of the Iberia-Maghreb plate contact from seismic moment tensors and GPS observations[END_REF]. The wide-angle seismic models of Annaba [START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF] and Jijel [START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF] regions show similar characteristics regarding thickness and nature of oceanic domain: the velocities and gradients of EAB deep basin crust are interpreted as coherent to the normal oceanic crust compiled by [START_REF] White | Oceanic crustal thickness from seismic measurements and rare earth element inversions[END_REF] for the Atlantic Ocean. Anyway, as in the LPB, the crust is thinned, with a thickness around 5.5 km [START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF] or even thinner, between 4.5 and 5 km [START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF] (Fig. 4.29D). [START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF], using the Poisson ratio method (e.g. Hyndman, 1979) suggest a magmatic lower layer oceanic crust, mainly composed by gabbroic rocks rather than of peridotites. A set of symmetrical, fan shaped, elongated NNW-SSE to NW-SE magnetic anomalies extend in the centre of the basin (Fig. 4.30) which probably illustrate a period of continuous and steady oceanic accretion, in contrast with other parts of the Western Mediterranean, where the anomalies are not clearly identified (as in the LPB or in the WAB).

In the oceanic domain the salt is characterized by a low intensity of salt deformation, outlined by small coalescent diapirs and a relatively flat and undeformed base of salt (Fig.

4.30B

). On the S-N transect in the eastern part of EAB basin, the northward compression is suggested by sedimentary anticlinal at the proximal deep basin and lower slope limit. The deep basin is characterized by a landward (with respect to the Algerian margin) base of salt and an area marked by tabular salt, concomitant with the supposed continuation of the NBFZ indicating the transfer zone related to the Corsica-Sardinia block movement (e.g. [START_REF] Olivet | La cinématique de la plaque ibérique[END_REF]. This area shows a rise of basement reflector and a sub-horizontal base of salt: the slope of the base of salt is in the order of 0.6°.

Hannibal area

The Hannibal Area is a narrow segment characterized by high magnetic anomalies and a relative negative gravity anomaly with respect to other segments [START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF]Driussi et al., 2015a;Aidi et al., 2018). Geographically, it is the southern extension of the South Minorca block, interpreted by gravity modelling as of continental nature (Driussi et al., 2015a).

A recent wide-angle refraction profile crossing the north-western part of the Hannibal Area is described in Aidi et al., (2018). Nevertheless, the crustal nature of this area and its geodynamic role still remains misunderstood. The Hannibal high marks the boundary between the east and the west Algerian basin, which seem to have undergone a different geodynamic history, probably of different ages, as depicted by [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF] Leprêtre et al., 2013 (C) and Mihoubi et al., 2014 (D). Location in free air anomaly map. The zoom on magnetic anomalies (f) shows the aligned anomalies testifying the oceanic crust accretion in the deep basin.

Western Algerian

The West Algerian basin, according to magnetic and gravity anomalies [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF], can be divided into two segments: a central segment south of the Emile Baudot Escarpment, (III in fig. 4.25) and a western segment, south of the Mazarron Escarpment (IV in fig. 4.25). The northern Algerian margin, as in EAB, is characterized by a steep thinned continental and transitional crust domain (Leprêtre et al., 2013, fig. 29C;[START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF].

The transitional crust is narrow, of 10 to 20 km maximum (Fig. In the central segment of the WAB, [START_REF] Hinz | Crustal structure of Balearic Sea[END_REF] proposed an oceanic crust with velocities spanning from 6.0 km/s at its top to 7.4 km/s at its base, whereas Gravemeyer et al., (2011) proposed lower velocities, up to 6.8 km/s, in the conjugated margin (South Balearic margin). [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF] found velocities of 5.5-5.6 at the top and 7.2-7.3 km/s at the base of layer 3, thus interpreting the deep basin as made by 5.5-thick oceanic crust (Fig. 4.29C). Other authors [START_REF] Roure | Alpine inversion of the North African margin and delamination of its continental lithosphere[END_REF] proposed a continental nature for the same area.

In the westernmost Algerian segment, south of the Mazarron Escarpment (segment IV of Fig. 4.25), the deep basin crust is also interpreted as of oceanic nature, with a thinner thickness (about 4 km) [START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF] It is far beyond this study to decipher between (exhumed) lower continental crust, protooceanic crust and true oceanic crust and to understand their connexion (see [START_REF] Bott | Evolution of young continental margins and formation of shelf basins[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Sibuet | Plate tectonic reconstructions and paleogeographic maps of the central and North Atlantic oceans[END_REF][START_REF] Shuck | The role of mantle melts in the transition from rifting to seafloor spreading offshore eastern North America[END_REF]Becel et al., 2020;Aslanian et al., 2021, Moulin et al, submitted): in our case the main concern is the apparent change in nature and hence the crustal segmentation.

To conclude, although an extensive discussion on the geodynamics of the Algerian basin (recently Gomez de la Pena et al., 2020;Romagny et al., 2021), there are still several doubts regarding the opening directions, the role of the Hannibal Area and the global kinematic reconstruction. In the EAB, fan-shaped magnetic anomalies suggest an oceanic crust, while in the WAB, the absence of clear magnetic anomalies leaves all doors open as to the nature of the crust. The salt morphologies interpreted in this work show, in the same way, substantial differences between the EAB, characterised by small connected diapirs, and the WAB, characterised by more or less isolated, discordant diapirs and piercing deformation. The analysis of the timing of salt tectonics in the Gulf of Lion in more detail is mainly allowed by the extensive coverage of seismic data in the area and the availability of dated horizons confirmed by previous studies. The sedimentary markers used for this purpose will be named and briefly described below. For a detailed framework of the Plio-Quaternary interpretation at a detailed scale, see the works [START_REF] Rabineau | Un modèle géométrique et stratigraphique des séquences de dépôts quaternaires sur la marge du Golfe du Lion: enregistrement des cycles climatiques de 100 000 ans[END_REF] and [START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF]. The definition and age of the horizons were defined by [START_REF] Rabineau | Un modèle géométrique et stratigraphique des séquences de dépôts quaternaires sur la marge du Golfe du Lion: enregistrement des cycles climatiques de 100 000 ans[END_REF] and [START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF] through the interpretation of sedimentary prisms in the shelf, glacio-eustatic cycles, stratigraphic modelling and dating with available wells. In this work, I considered some Plio-Quaternary reflectors and I completed the interpretation in the deep basin, starting from the existent one and extending into the uninterpreted lines. The considered Plio-Quaternary reflectors, from the oldest to the youngest, are P11, Q10 and Q5. The P11 reflector is a strong erosional discontinuities dated at 2.6 Ma due to the presence of the Atlantic Neogloboquadrina (planktonic foraminifer), used to date the base of the Gelasian (2.588 Ma; base Quaternary by [START_REF] Gibbard | Formal ratification of the Quaternary System/Period and the Pleistocene Series/Epoch with a base at 2.58 Ma[END_REF]. The Q10 is another remarkable erosional discontinuities dated at 0.9 via well correspondence [START_REF] Rabineau | Un modèle géométrique et stratigraphique des séquences de dépôts quaternaires sur la marge du Golfe du Lion: enregistrement des cycles climatiques de 100 000 ans[END_REF][START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF][START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF]. The Q5 surface is part of the last five erosional surfaces corresponding to the last five glacial maxima of 100000 cycles with preservation of the shoreline on the outer shelf. It is dated at 434 000 yr [START_REF] Rabineau | Paleo sea levels reconsidered from direct observation of paleoshoreline position during Glacial Maxima (for the last 500,000 yr)[END_REF][START_REF] Bassetti | The 100-ka and rapid sea level changes recorded by prograding shelf sand bodies in the Gulf of Lions (western Mediterranean Sea)[END_REF][START_REF] Sierro | Phase relationship between sea level and abrupt climate change[END_REF][START_REF] Leroux | High-resolution evolution of terrigenous sediment yields in the Provence Basin during the last 6 Ma: relation with climate and tectonics[END_REF].

Early salt deformation in the deep basin

In the last ~6 Ma, the salt tectonics has given rise to structures of great vertical extension, in some respects similar to those seen in some passive margins formed in the Mesozoic era (e.g. Atlantic margins or Gulf of Mexico). But when exactly did the vertical movement of salt begin?

An early salt deformation in the deep Gulf of Lion basin was first described, to our knowledge, by Gaullier et al., (EGU abstract, 2018). Indeed, the zooms (Fig. 4.33 within the Anticlinal domain in the Gulf of Lion (refer to fig. 4.10 for domain extension), show that the salt moves immediately after its deposition, as soon as the deposition of the Messinian Upper Units (UU): the profiles clearly show differences in thicknesses within the Upper Unit and onlap reflections of this unit on the salt. The onlaps appear to be located in the lower part of the Upper Unit, testifying to a deformation of the salt that began soon after its complete deposition, if not in the last stages of pure salt deposition (Fig. 4.33). The deformation is small-scale, indicating that the movement started very early but is stronger and of greater amplitude in the Plio-Quaternary phases. The early salt deformation is only well imaged in the Anticlinal domain, where the deformation is relatively small. In the Large Diapirs and Irregular/Regular Diapirs domains the early salt deformation is tricky to observe. In these salt domains, the vertical diapirs inhibit the early small-scale deformation within the UU. The Gulf of Lion is the area of the Western Mediterranean where the early salt deformation is most appreciable, due to the large amount of seismic data of different resolution. However, in other margins we observed some evidences that suggest a deformation of Messinian salt occurred early everywhere in the deep basin.

In the western Sardinian margin locally evidences of salt deformation activity since the deposition of the UU have been depicted in the lower slope and in the central basin (Del Ben et al., in Lofi et al., 2018): the UU reflectors onlap on the salt (Fig. 4.34, yellow unit), attesting an early salt movement.

In the north Algerian margin, the salt structures are widely influenced by the margin reactivation, which probably started in the (Late? Tortonian; Strzerzunsky et al., 2021) and is still active today: the salt tectonics predate and is often synchronous to the regional shortening (Strzerzunsky et al., 2021).

198

This early deformation is also observed in the Eastern Mediterranean Sea. In the Levant basin (East Mediterranean) the Messinian evaporites can be divided in six sub-units (e.g. [START_REF] Gvirtzman | Intense salt deformation in the Levant Basin in the middle of the Messinian Salinity Crisis[END_REF]Hubscher et al., 2007). The six units consist mainly of halite and more debris levels, which can decrease the seismic velocities down to 3.6 km/s. [START_REF] Gvirtzman | Intense salt deformation in the Levant Basin in the middle of the Messinian Salinity Crisis[END_REF] found an early deformation within the Messinian sequence (Fig. 4.36): the Unit 2 (whose transparent seismic facies suggests a high halite content) deformed before the end of the Messinian event but after the deposition of unit 3. The top of Unit 3 is deformed while the top of Unit 5 (top of Messinian sequence) is not, testifying an early deformation event occurred during the Messinian event. This early phase of deformation may have derived from the uplift of Mount Carmel, located landward, which triggered a south-westward gliding of salt [START_REF] Gvirtzman | Intense salt deformation in the Levant Basin in the middle of the Messinian Salinity Crisis[END_REF].

Listric faults timing activation

The Listric salt domain is characterised by extensive listric faults, which may be active [START_REF] Gvirtzman | Intense salt deformation in the Levant Basin in the middle of the Messinian Salinity Crisis[END_REF]. The M reflector represents the end of Messinian units. The yellow reflector deformed before the end of the Messinian. Although significant differences in Messinian stratigraphy compared to the Western Mediterranean, the profile shows an early deformation, coeval to the Messinian deposits similar. To reconstruct the faults evolution timing, it is necessary to recognize the growth strata, intended as geometry of strata deposited simultaneously with the formation or growth of a fold, induced in this case by the activation of faults. Profile from Dos [START_REF] Reis Dos | Implications of salt-sediment interactions on the architecture of the Gulf of Lions deep-water sedimentary systems-western Mediterranean Sea[END_REF]

201

In the western Sardinian margin, the timing of listric faults setting up is more difficult to establish due to the steeper base salt slope compared to the Gulf of Lion margin. Figure 4.39 shows a westward thicker Plio-Quaternary sequence compared to that of the more proximal slope (more on the eastern part of the profile). The UU shows different thicknesses along the profiles: as the Plio-Quaternary, it thickens towards the deep basin, in the west. Furthermore, the UU sequence seems to vary in thickness when involved in fault displacement (small growth strata, zoom A, Fig.

Salt deformation evolution: insights from the Gulf of Lion

Following the analysis of the relationship between salt-induced listric faults and deformation in the deep basin, in this sub-chapter we deal with the temporal evolution of salt structures from salt deposition to the present day. Three temporal phases have been interpreted by grouping them according to diapirs typology (active, passive), velocity and timing of deformation.

Phase 1

The salt tectonics phase 1 is the early salt deformation during the UU deposition (~5.6-5.3 Ma), just described. This deformation phase causes short wavelength folds and small salt anticlines and/or pillows. The early salt deformation is observed in the Anticlinal domain and, although not directly observed, we can also expect it in the Large Diapirs domain (Figs. 4.40,4.41). Here, the UU onlaps on the salt diapirs, which are vertical developed and often reach the seafloor (Figs. 4.40,4.41). The phase 1 deformation is not the greater and stronger salt deformation phase in the Gulf of Lion but it is enough to cause the listric faults activation since the Early Pliocene (Phase 2). Note that this deformation phase seems to be clearer in some In the Large Diapirs domain, the phase 2 reflectors onlap the salt diapirs, gently following the upward deformation (drape folding) (Figs. 4.40,4.41). The overlying sequences are here discordant and syn-deformation (variation in thickness). The Large Diapirs domain structures have probably undergone a passive (downbuilding) evolution (see Chapter 2 for explanation) during the phase 2, also according to Mianaekere and Adam, (2020a). This means that the structures were growing on the surface (or with a thin overlying sedimentary sequence) at the same time as the minibasins on the diapirs side were sinking. The difference in growth ratio between the Anticlinal domain, which is globally characterised by a quiescent phase, and the Large Diapirs domain, characterized by passive diapirs close to the surface, is remarkable (Figs.

4.40, 4.41).

Phase 3

Phase 3 is the phase with the strongest and rapid deformation in the Gulf of Lion (Figs. In the Large Diapirs domain, the diapirs growth locally changes from a passive (downbuilding) to an active type: some structures deform the seafloor but they not extruded from the sedimentation cover and they display thin roof. As in the Phase 2 reflectors (yellow colour sequence), also the phase 3 reflectors (blue sequence) are discordant with the salt diapirs, onlapping it (Figs. 4.40B, 4.41C).

In conclusion, the salt in the deep basin deformed soon after its deposition (during UU deposition), if not during its deposition (Fig. 4.40B). In contrast, in the lower slope, the faults are posterior and only activated from the Lower Pliocene onwards (Fig. 4.40A), when the salt in the deep basin is already deformed. The early deformation in the deep basin could induced a space, which was not there before, that allowed the salt to glide from the lower slope, leading to the listric fault formation. The Early Pliocene thin-skinned extension tectonics on the slope is therefore a consequence of the space created by the distal diapir formation in the deep basin.

The triggering of deformation in the deep basin (early salt deformation) seems not related to the gravity gliding but due to other factors, which we will try to examine in the next subchapter.

Salt deformation evolution: 3D analysis in the Gulf of Lion

The thickness maps of the Plio-Quaternary units in the Gulf of Lion allow both to extend the evolution of salt deformation in the basin as observed on 2D seismic profiles (looking the variations of the unit thicknesses overlying the salt) and to understand whether any major -Figure 4.42B and C correspond to the Quaternary thickness maps of unit P11-Q10 (2.6-0.9 Ma) and unit Q10-Seabottom (0.9-0 Ma), respectively. During the Pleistocene, strong turbidite sedimentation occurred and led to aggradation and progradation of thick turbidite systems linked to the main canyons on the Gulf of Lion (e.g. [START_REF] Droz | Quaternary turbidite systems on the northern margins of the Balearic Basin (Western Mediterranean): a synthesis[END_REF]Badhani et al., 2020) (Fig. 4.43). The main source is the Rhone, which mainly feeds the canyons of Sète, Marti, Petit-Rhône and Grand Rhône. From 2.6 Ma onwards, sedimentary accumulation is concentrated on Lobes 2 and 3 [START_REF] Droz | Quaternary turbidite systems on the northern margins of the Balearic Basin (Western Mediterranean): a synthesis[END_REF][START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF][START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF]fig. 4.42B). After 0.9 Ma, sedimentary accumulation in the deep basin is mainly fed by the Petit-Rhône and Marti canyons (Dos [START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF]fig. 4.42C). The doubling of sedimentary volume at 0.9 Ma seems to be due to the Mid-Pleistocene revolution, characterised by a high continental terrigeneous input (climatic reasons with installation of northern ice-caps) and a change in cyclicity and sea-level amplitude (respectively around 100ka and 100m) that facilitate connections between onshore rivers and offshore canyons [START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF] [START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF] [START_REF] Bache | Evolution Oligo Miocène des marges du micro océan Liguro-Provençal[END_REF] for the respective Plio-Quaternary and Messinian sequences. Are defined the colour, name, supposed/known ages, main features and salt tectonics phases description for each reflectors.

In the Anticlinal domain we observed an area of greater thickness (between latitude 40°-41°N and longitude 4°-5°E) where the salt thickness is around 0.4-0.5 s twt (i.e. with a velocity of 4.5 km/s: 900-1100 m) (Fig. 4.44). The anticlinal axis highlighted a NE-SW direction (perpendicular to the margin) or, when involved in the Petit Rhone Fan (Fig. 4.44), the axis directions follow the main sedimentary path (mainly N-S). The Large Diapirs domain is characterized by salt walls and stocks. The salt walls show a preferential N-S direction as well as the mini-basins between the salt structures (direction plot fig. 4.44). The mini-basins (blue colour) form preferential pathways for the sediments, confirming the mutual relationship between sedimentation pathways and salt tectonics (Dos [START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF]. These directions fit well with the Petit Rhone fan direction (e.g. [START_REF] Droz | Quaternary turbidite systems on the northern margins of the Balearic Basin (Western Mediterranean): a synthesis[END_REF]. As previously explained, in this domain the salt structures are growing and deforming the seafloor (Zoom bathymetry, fig. 4.44).

They do not extrude as salt glacier as they are roofed by a thin overburden. The large salt walls and stocks become smaller towards the SW, where we have interpreted the Connected, Irregular diapirs domain (see chapter 4.3). Here, the diapirs occasionally deform the seafloor and are more connected, making them more difficult to individually identify in the salt thickness map.

Main causes of the Gulf of Lion salt tectonics and insights from the Western

Mediterranean salt system

In this sub-chapter we will try to understand the main causes of salt tectonics in the Gulf of Lion, from the early salt deformation depicted in the deep basin to the present-day active movement. Moreover, we show some new insights from the Western Mediterranean salt system. Figure 4.45 shows the sketch of the evolution of salt structures from the lower slope to the deep basin, including the listric faults activation timing, as described in the previous sections.

Phase 1 trigger hypothesis

The salt tectonics phase 1 is the most difficult to investigate because it is the oldest and least intense of the three deformation phases described above. We will see, however, how it is fundamental in understanding the mechanisms of salt tectonics in the Gulf of Lion and more generally in all the Western Mediterranean. Some hypotheses about the triggering of this phase can be considered, including:

-An imbalance of salt flux: the difference in initial salt thickness can cause an imbalance of salt flux, creating space accommodation above the ramp which will subsequently be filled by growth sedimentation (Fig. 4.46). This difference in sedimentary thickness will then be the cause for a differential loading of forces which can evolved into a syncline ramp with monoclinal geometry of growth strata. A non-homogeneous sub-salt geometry is necessary to create an imbalance of salt flux. In the Gulf of Lion, Dos [START_REF] Reis | Radial gravitacional gliding indicated by subsalt relief and salt-related structures: the example of the gulf of Lions, western Mediterranean[END_REF] claimed that the thin-skinned salt tectonics have evolved under the influence of a variable morphology of the base of salt. If the sub-salt has topographic reliefs, the initial salt thickness could be different and can generate the imbalance mechanisms. Nevertheless, the early salt deformation phase seems to be confirmed in all the deep basins of the Western Mediterranean. Where seismic coverage has allowed a good detail, the salt base map shows an almost constant depth in the deep basin, with no significant reliefs. However, locally, slight reliefs cannot be excluded. The regional importance they have on this phase of salt tectonics remains unknown. [START_REF] Bache | Messinian erosional and salinity crises: view from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF] The squares shows the main deformation area for each phase. Note the early deformation during phase 1 and the stronger and faster growth above the oceanic crust. The Hinge line is taken from [START_REF] Leroux | Post-rift evolution of the Gulf of Lion margin tested by stratigraphic modelling[END_REF] and marks the limit between a slope tilting subsidence and a deep basin purely vertical subsidence [START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF], Leroux et al., 2015).

-Infra-UU erosional surface: an erosional surface within the Upper Unit could have created an imbalance in the early overburden, generating a differential loading which can induce an early deformation. An infra-UU unconformity named IES (Intermediate Erosion Surface) is observed in western Sardinian and south Balearic margins [START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF][START_REF] Geletti | The Messinian Salinity Crisis: new seismic evidence in the West-Sardinian Margin and Eastern Sardo-Provençal Basin (West Mediterranean Sea)[END_REF] and in the intermediate-depth basins, such as Valencia and east Corsica basins (Lofi et al., 2011a). The IES corresponds to an erosional truncation and divides the UU into two sub-units. The infra-UU erosional surface could be triggered by intermediate stages of desiccation that may have exposed evaporitic units sub-aerially. However, it is tricky to understand if the erosional surface within the UU could be the consequence for the initiation or only mark the end of the deformation event. Moreover, the character of the erosional surface can be local and it hardly explain the regionality of our observations.

-Salt impurity: impurities within the salt deposit can affect the deformation. In addition to modifying the rheology, they can cause spatial differential loading within the deposit itself. Although we do not have sufficient resolution in seismic data and there are no wells that reach deep salt deposits in the Western Mediterranean, the seismic facies appears to be that of a pure salt. No regional lithological levels are interpreted, as for instance depicted in eastern Mediterranean salt deposits [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF][START_REF] Gvirtzman | Intense salt deformation in the Levant Basin in the middle of the Messinian Salinity Crisis[END_REF]. The salt deposition was probably brief (<50000 years, [START_REF] Bache | A two-step process for the reflooding of the Mediterranean after the Messinian Salinity Crisis[END_REF] and the following dilution of waters led to the progressive deposition of the Upper Unit. The pure halite seismic facies and the rapidity of salt deposition incline us to exclude any erosive surfaces inside the salt that could induce loads variation.

-Differential sedimentary loading: as pointed out by several authors (see chapter 2), a different thickness of layers above the salt could induce a differential loading and thus trigger the salt movement. In the case described here, this would mean that the UU sequence would have been deposited with no uniform thicknesses in the deep basin.

Although this is a hypothesis to bear in mind, there is no evidence at the palaeogeographic and sedimentary level that the UU was deposited unevenly in the deep basin.

Moreover, the deformation is coeval to the UU deposition at a regional scale.

In the light of these hypotheses, the trigger for early deformation in the deep basin remains uncertain. Regionally, during the three phases of salt deformation in the Gulf of Lion, the present-day Large Diapirs domain experienced more intense, faster and earlier deformation than the Anticlinal domain. This domain, as explained in Section 4.4, coincides with the existence of oceanic crust in the deep basin. The coincidence between the limits of this domain and the underlying crustal change questions the actual driving forces for such deformation in the Large Diapirs domain.

We have seen that the salt deformation first started in the flat, horizontal deep basin, and then occurred on the slope. The first movement does not seem to be connected to sediment overload, slope gliding or tectonics. But what are their respective role in the deformation evolution?

Role of the base salt slope

The salt gliding is supposed to occur thanks to mechanically viscous behaviour along its base towards the deep basin, forming an upstream extensional domain and a downstream contractional domain. According to some authors, a few degrees of inclination of the base salt would serve to establish a gravity gliding regime (e.g. [START_REF] Duval | Raft tectonics in the Kwanza basin, Angola[END_REF][START_REF] Ings | Numerical modeling of salt tectonics on passive continental margins: Preliminary assessment of the effects of sediment loading, buoyancy, margin tilt, and isostasy[END_REF][START_REF] Albertz | An investigation of salt tectonic structural styles in the Scotian Basin, offshore Atlantic Canada: 1. Comparison of observations with geometrically simple numerical models[END_REF]. [START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF] give an order of magnitude of the angle needed for the salt to move, based on the overlying sedimentary thickness both without (in red: frictional angle Φ=30°) or with (in blue: Φ=20°) fluid pressure and the basin width (Fig. 4.47A). The authors do not precisely define the meaning of the basin width as the model is usually used for passive margins with a defined seaward salt limit and a large deeper oceanic domain without any salt layer but only small sheets, tongues and canopies. In the Liguro-Provençal basin, the salt is present everywhere from the lower slope to the deep basin, in both margins. Furthermore, the presence of pressurized fluids, which is crucial for the choice of the friction angle in the plot and thus for establishing a minimum slip angle, is poorly defined in the work of [START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF] and it is difficult to make assumptions about pressurized fluids below the salt.

Nevertheless, the plot is the only one available that quantifies the slope required to cause gravity gliding. In the Gulf of Lion, considering a sedimentary thickness above the salt of about 2 km (Fig. 4.47) and a basin width ranging from 300 km (if we consider the length from the upslope salt limit to the most seaward point in the deep basin), the angle needed would be about 0.8° Gorini et al., 2015, Fig. 4.47C). According to Brun andFort (2011, 2012) in the lower slope 1° could be sufficient to activate the salt sliding, indeed evidenced by clear basinward-dipped listric faults rooted on the base of salt. Nevertheless, the deep basin is subhorizontal, throughout all the deep basin, thus for more than 200 km seaward the hinge line 3 (Fig. 4.47C). The slope of the base salt is mainly due to the post break-up subsidence after basin opening. In the slope, this subsidence takes the form of seaward tilting whereas the deep basin subsides purely vertically [START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF][START_REF] Leroux | Post-rift evolution of the Gulf of Lion margin tested by stratigraphic modelling[END_REF]. The salt therefore is supposed to deposit regionally horizontally in the deep basin, pinching out on the lower slope.

Subsequently, given the tilting subsidence (from hinge line 3 towards the shelf) the base of the salt began to dip seaward, gradually reaching the present-day slope (around 1°). The presentday slope is therefore expected to be a maximum slope value as the base of the salt, as well as the other units, gradually deepened because of subsidence. It should also be considered that the gravity gliding model (e.g. [START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF][START_REF] Fort | Salt tectonics on the Angolan margin, synsedimentary deformation processes[END_REF][START_REF] Schultz-Ela | Excursus on gravity gliding and gravity spreading[END_REF] essentially born in the Kwanza basin (West Africa), where the salt in the compressional domain forms a zone of thrust, sheets and canopy, often sliding above the oceanic crust and therefore in an allochthonous position (e.g. [START_REF] Fort | Salt tectonics on the Angolan margin, synsedimentary deformation processes[END_REF]. In the Western Mediterranean Sea, salt is deposited everywhere in the deep basin and in the lower slope and cannot give rise to major horizontal movements above areas where it has not been primordially deposited, such as the oceanic crust in the Angolan basin. In the analogue models described in [START_REF] Vendeville | Salt tectonics driven by sediment progradation: Part I-Mechanics and kinematics[END_REF], salt in the deep basin (contractional domain) is expected to form thrust and contractional structures whereas in the LPB, the structures appear to be mainly vertically developed, with no easily recognisable direction of transport (except for the Anticlinal domain-Large Diapirs domain boundary, fig. 4.44). Furthermore, as described above, salt deformation in the deep basin predates fault formation in the lower slope: gravity gliding in the lower slope is therefore triggered by the space created by deformation in the deep basin. The movement may be enhanced by the increase of slope due to differential subsidence, after the horizontal salt deposition. Regionally, the base of salt shows a significant slope only in the Listric salt domain, which width is variable between the margins (Fig. 4.48). As we have seen, the Gulf of Lion presents a broad Listric domain characterised by several listric faults.

In the western Sardinian margin, this domain is narrower and reflects the steepness of the margin itself. Here, the Listric domain in the lower slope is characterised by salt sliding towards the basin while in the High Base salt domain the salt base is sub-horizontal. Moreover, the salt was initially deposited already in the lower slope and for this reason the Listric domain has a width of a few tens of kilometres. We suggest that here the gravity gliding component is strong only in the scarp, extending a few kilometres into the deep basin, up to the first structures.

Seaward, the gravity gliding component is secondary.

The North Algerian margin is characterised by a base of salt that slopes towards the margin due to the tectonic inversion to which it has been subjected since at least the Tortonian. Except for the central zone, (NE of Alger) the base of salt has a more or less marked onshore inclination. The lower slope and proximal deep basin are characterized by kilometre-scale wavelength folds. The slope is steep alternating with perched basins [START_REF] Dan | Quantifying the role of sandy-silty sediments in generating slope failures during earthquakes: example from the Algerian margin[END_REF][START_REF] Domzig | Searching for the Africa-Eurasia Miocene boundary offshore western Algeria (MARADJA'03 cruise)[END_REF] and blind reverse faults affecting the Plio-Quaternary units and propagating towards the abyssal plain (e.g. Kherroubi et al., 2009;[START_REF] Domzig | Searching for the Africa-Eurasia Miocene boundary offshore western Algeria (MARADJA'03 cruise)[END_REF]. Here, gravity gliding seems of minor importance compared to the impact of regional tectonics. In the western part of the WAB some salt walls with an ENE-SWS direction are interpreted by [START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF]. Indeed, despite the lower seismic coverage available, it appears that the base salt is less dipped towards the landward than in the EAB.

The South Balearic margin shows an escarpment perhaps even steeper than in the north-Algerian margin (Emile Baudot and Mazarron Escarpments): the salt is deposited mainly in the deep basin and only for a few kilometres in the lower escarpment. The base of salt in the proximal deep basin is sub-horizontal (high salt base domain) and the gravitational salt slip is therefore local, limited to the last few kilometres of the continental slope.

We therefore suggest that gravity gliding is a mechanism limited to the Listric domain, whose amplitude is strongly dependent on the steepness of the margin. In conclusion, we believe that in the Western Mediterranean sea, given its geomorphological characteristics that differentiate it from other passive salt margins of the world, gravity gliding is a secondary mechanism, which may help to nourish the salt structures in the deep basin (e.g. Gulf of Lion) but only in a second phase of deformation, or be the cause of some local structures near the escarpment. [START_REF] Jolivet | Continental breakup and the dynamics of rifting in back-arc basins: The Gulf of Lion margin[END_REF].

Role of the sedimentary input

According to models (see chapter 2), the gravity spreading causes motion of the material toward the basal surface, requiring deformation of the spreading body. The upper surface of the sedimentary input must dip in the movement direction but the dip of the basal surface (e.g. base of salt) can be horizontal or even be opposite to the direction of motion. The major components of a system dominated by gravity spreading is the relative sedimentary thickness (i.e. the difference in sedimentary thickness above the salt): the salt moves seaward if the proximal (the slope) domain is at least three times thicker than the distal (the deep basin) domain (Rowan et al., 2012).

At the Western Mediterranean scale, the present-day PQ thickness map shows a sedimentary thickness relatively consistently thick throughout the LPB while thins considerably In the Gulf of Lion, the sedimentary input into the deep basin is significant since the Messinian [START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF], as observed in the thickness map between the top MSC and P11 The different intensity of deformation between LPB and EAB could be explained by a different sedimentary thickness between the two basins (greater deformation and thicker PQ deposits in LPB compared to the EAB). However, this would not explain the significant differences between EAB and WAB in terms of salt deformation (see chapter 4.3). Furthermore, as stated above, although there is a thick sedimentary layer in the Anticlinal domain in the GoL, the salt formed only pillows and not salt stocks and walls. Although there is no doubt that sedimentary input plays a key role in salt deformation, it cannot explain all the observations made so far, especially when looking at the successive steps or phases of salt deformation and detailed sedimentary input variations (Fig. 4.42). Regional mapping of PQ thickness also highlights sedimentation depocenters that follows crustal domains, thus confirming the close relationship between deep and surface processes (e.g. Cloetingh andWillett, 2013a, Leroux et al, 2015).

Role of tectonics

The role of tectonics on salt deformation is predominant in certain contexts. Salt, if deposited directly in contact with basement or above a thin sedimentary thickness, may be involved in tectonic movement syn and/or post deposition. In addition, as in the case of the Morocco margin, salt is deposited in structural lows, in half-grabens, and therefore with different initial thicknesses depending on the morphology of the basement. In other cases, such as the Zechstein salt basins (e.g. [START_REF] Harding | Salt on the move: multi stage evolution of salt diapirs in the Netherlands North Sea[END_REF], the salt may be involved in a thickskinned deformation (i.e. with the base of salt displacement). Examples of salt systems in which tectonic activation has influenced or still influences salt deformation are numerous, such as: the Moroccan margin (e.g. [START_REF] Tari | Salt tectonics in the Atlantic margin of Morocco[END_REF]2003) and North Sea (e.g. [START_REF] Karlo | Triassic-age salt tectonics of the Central North Sea[END_REF]Rowan and Lindso, 2017). In the Western Mediterranean, as shown in chapter 4.2, a thick layer of sediment separates the basement from the salt. The salt was deposited when all the sub-basins (LPB, EAB and WAB) were completely formed. The pre-salt sequence is especially thick in the LPB, where it can be more than 2 km thick. This blanket covered the roughness of the basement, with onlaps over it. After the oceanic opening of the basin, the basement has not undergone any notable tectonic movements, except for the north-Algerian margin.

Role of tectonics in the LPB

In the LPB, Le Cann, (1987) proposed a basement post-rift reactivation to explain the geographical coincidence between salt morphologies and crustal segmentation. [START_REF] Pautot | Morphology and extension of the evaporitic structures of the Liguro-Provençal Basin: New Sea-Beam data[END_REF] in their conclusions said: "In summary, it is proven that the surface expression of the evaporitic domes is not the result of chance, but rather the triggering element is, in this area, the tectonic activity". However, the tectonics activity involved in the basin opening is Oligo-Miocene in age while the salt deformation started during the Messinian, far after the oceanictype crustal accretion. Syn-rift faults reactivation are observed by some authors (e.g. [START_REF] Mauffret | Structural geometry in the eastern Pyrenees and western Gulf of Lion (Western Mediterranean)[END_REF][START_REF] Maillard | Transfer zones and associated volcanic province in the eastern Valencia Basin: Evidence for a hot rifted margin?[END_REF] [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF]. Note the ratio between the basement step and the initial silicone thickness (representing the salt). could be the case for example of the Moroccan salt margin, but is not the case of the LPB: here the salt deposited above a flat pre-salt sequence, far from the basement.

The second and the third physical experiments included as an initial condition a pre-salt sequence of non-constant thickness covering the roughness of the basement, above which lies the silicon (salt) (Fig. 4.51). This situation is indeed the most likely to occur in the Gulf of Lion, however, we note that the proportions between basement step height, silicone thickness and pre-salt thickness are completely unscaled compared to the reality. A basement step three times (Experiment 3) or five times (Experiment 2; fig. 4.51) the thickness of the silicone (Fig. 4.50) is simply not coherent compared to the basement map described in chapter 2. Although the deep basin of the Gulf of Lion shows a basement deepening, it is far from the parameters set by [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF]. Furthermore, in experiment 2, a basement step 5 times as high as the initial thickness of the salt , does not seem to create structures of the type seen in the Large Diapirs domain (salt stocks and walls) (Fig. 4.51). Similarly, in experiment 3, in addition to a basement step "only" 3 times as high as the initial thickness of the salt, the authors add a slope of about 3° for the whole system (both basement and overlying sediments including salt) (Fig. [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF]. The basement step height is 5 times the silicone (salt) thickness. Note the effects of a differential compaction (monoclinal flexure) above the step. This type of structure is far from being equivalent to the structures seen in the Gulf of Lion.

Role of tectonics in the north Algerian margin

In our opinion, the most significant observation shown in this work regarding salt deformation in the Algerian basin is the difference in salt structures between the EAB and the WAB. In the EAB, the diapirs are small, interconnected, and rarely deform Quaternary reflectors. In the WAB, on the other hand, the diapirs can deform the seafloor, are well developed vertically, and display squeezed-like stocks and/or walls with some allochthonous salt tops (chapter 4.3). As shown, the setting of sedimentary depocenters is very similar between the two basins as well as the trend of the base of salt (Figs. 4.48,4.49), which therefore exclude a differential regional gravity gliding and/or spreading causes. So far, this difference in deformation between the two basins has not yet found a reasonable explanation. The north Algerian margin represents a good example of present-day inversion of a passive margin in its early stages. Several studies confirmed the crustal shortening and the tectonic inversion that this margin is undergoing, possibly leading to subduction inception (e.g. [START_REF] Déverchère | Active thrust faulting offshore Boumerdes, Algeria, and its relations to the 2003 Mw 6.9 earthquake[END_REF][START_REF] Hamai | Flexural behaviour of the north Algerian margin and tectonic implications[END_REF][START_REF] Strzerzynski | Tectonic Inversion and Geomorphic Evolution of the Algerian Margin Since Messinian Times: Insights From New Onshore/Offshore Analog Modeling Experiments[END_REF][START_REF] Yelles | Plio-Quaternary reactivation of the Neogene margin off NW Algiers, Algeria: the Khayr al Din bank[END_REF]. All the north-Algerian margin is very narrow, characterized by steep scarps and perched basins [START_REF] Domzig | Searching for the Africa-Eurasia Miocene boundary offshore western Algeria (MARADJA'03 cruise)[END_REF][START_REF] Yelles | Plio-Quaternary reactivation of the Neogene margin off NW Algiers, Algeria: the Khayr al Din bank[END_REF]Leprêtre, 2012). Recently, [START_REF] Strzerzynski | Tectonic Inversion and Geomorphic Evolution of the Algerian Margin Since Messinian Times: Insights From New Onshore/Offshore Analog Modeling Experiments[END_REF] proposed a two stages inversion characterized by popup structures onshore and subsequently piggy-back basins offshore. Moreover, although the onset of the inversion seems to have started during the Tortonian, the main offshore shortening (around 2 mm/yr) and uplift (0.5 mm/yr) are post-Messinian [START_REF] Strzerzynski | Tectonic Inversion and Geomorphic Evolution of the Algerian Margin Since Messinian Times: Insights From New Onshore/Offshore Analog Modeling Experiments[END_REF]. Other authors suggested that the oblique convergence between Africa and Europe (~5 mm/yr; [START_REF] Calais | Evidence for a post-3.16-Ma change in Nubia-Eurasia-North America plate motions?[END_REF][START_REF] Nocquet | Geodetic measurements of crustal deformation in the Western Mediterranean and Europe[END_REF]) is accommodated onshore for 50% by the Tell-Atlas systems [START_REF] Meghraoui | Earthquake-induced flooding and paleoseismicity of the El Asnam, Algeria, fault-related fold[END_REF].

One of the plausible hypotheses for describing the strong deformation in the WAB could be the compression that the salt undergoes since its Messinian deposition, which, although accommodated partly onshore, could have consequences for structures in the deep basin.

However, this hypothesis cannot explain the difference in salt structures between EAB and WAB. In fact, because the pole of rotation is towards the Alboran basin, the easternmost basin has suffered more shortening (in distance, km) than the western basin (see difference between present-day and 5 Ma ago coastline in WAB and EAB, figure 4.52). Although there has been greater shortening since the Messinian, salt tectonics in the EAB is less intense. In addition, there is little information on how this shortening is distributed in time and space, and important local variations would be expected. Conversely, the salt structure in the EAB are regionally less deformed. Pellen et al., submitted). The arrows indicate the NW direction of Africa movement (5mm/yr, from [START_REF] Serpelloni | Kinematics of the Western Africa-Eurasia plate boundary from focal mechanisms and GPS data[END_REF]. Below, the line-drawing crosses the Algerian basin from the South Balearic to the north Algerian margins highlighting the narrowness of the WAB. The profile zooms (in depth, from Blondel Simon, unpublished) shows the salt structure close to the Emile Baudot Escarpment. Note the squeezed diapirs suggesting contractional events.

Summary of observations

The Western Mediterranean is a key area for studying the mechanisms underlying salt tectonics. In this chapter we presented some clues of Western Mediterranean salt system that are summarized here:  An early deep salt deformation is depicted, which predates the listric faults activation: the salt gliding is a consequence of the free space created by the early deep basin movement together with the increase of slope due to subsidence.


 The salt strongly deforms since its deposition, in a relatively short period. The salt tectonics started very early, during the UU deposition (phase 1), still belonging to the Messinian Salinity Crisis period in all the Mediterranean. In the Gulf of Lion, the Plio-Quaternary salt movement can be divided in two more main phases (phase 2 and 3), the first of small amplitude in the Pliocene and the second much stronger, in the Pleistocene.

The sedimentary thickness variations may explain the salt tectonics timing but not the coincidence with the crustal segmentation.

 A correlation exists between salt morphologies and the structural segmentation and nature of each sub-domain of the Western Mediterranean area. In the Liguro-Provençal basin the Listric domain is located on the edges of the margins, where the authors interpret a transitional and/or a thinned crust, as well as all along the north Algerian margin and at the transition between the WAB and the Alboran basin. In the western Sardinian margin, the boundaries of the High salt base domain match well with the transitional crust. In the deep Liguro-Provençal basin the Connected, Irregular salt morphology corresponds to a proto-oceanic and/or oceanic crust following the interpretation of refraction data. Instead, a Connected, Regular domain is interpreted in the EAB, which seems to be constituted of thin oceanic crust, as evidenced by refraction data and clearly aligned magmatic anomalies. The WAB, whose crustal structure is still a matter of debate, is characterized by generally more deformed salt structures, with differences in the eastern and north-western sectors: in the southwest of the South Menorca Block, the salt structures are connected and the salt base is shallower while the deep basin is characterized by the deepening of salt and larger morphologies. The transition between continental and oceanic domains in the Alboran-WAB limit corresponds to a change in salt morphologies, between an Anticlinal to a Large/Connected domain. The sharp and quick transition from a thinned continental crust to a thin or atypical oceanic crust along the north Algerian margin is associated with a sudden transition in salt morphologies.

 Classical models of salt tectonics (gravity gliding, spreading and tectonics influence) hardly explain the coincidence between crustal segmentation and salt morphologies.

The only hypothesis that remains to be evaluated is a thermal influence from the different crustal natures that could have influenced the salt deformation.

To test the hypothesis of thermal influence on salt tectonics, in the next chapter we will analyse the thermicity of the Western Mediterranean. We will try to understand if regional variations exist between sub-basins and the different crustal natures. To do so, we will analyse heat flow data, the only possible direct measure of subsurface thermicity, thanks to recent acquisition surveys.

Summary chapter 4

This chapter aims to analyse salt tectonics in the Western Mediterranean and its relationship with crustal segmentation. In order to analyse the regional salt deformation throughout all the subbasins, a study of the stratigraphy markers was necessary to assess the stratigraphical role and the salt movement chronology. Some regional compilations of the main stratigraphic markers in the Western Mediterranean are therefore presented. Furthermore, an analysis of the salt structures in all the Western Mediterranean Sea was carried out, in order to group them according to geometric criteria. The choice of these morphologies allowed a global view of the salt deformation.

The morphologies vary perpendicular along the slope and between the sub-basins, highlighting strong differences between the Liguro-Provençal, eastern and western Algerian basins in particular. The structures described and regionally categorised are then related to the crustal structure, showing that a correlation exists between salt morphologies and the structural segmentation and nature of each subdomain of the Western Mediterranean Sea. In order to understand the importance of the mechanisms and causes of salt tectonics and the relationship with the crustal segmentation, a detailed analysis of the timing of deformation was necessary. A better knowledge of the timing can give temporal indications of the salt movement triggers, such as sedimentary input or variation of base salt slope evolution. An early deep salt deformation is depicted everywhere, which predates the listric faults activation on the slope. In the Gulf of Lion, salt movement occurred during two main phases, the first of small amplitude in the Pliocene and the second much stronger, in the Quaternary. Finally, regional mechanisms that could be responsible for the salt structures were analysed. Each margin is characterised by an intrinsic coexistence of gravity gliding, spreading and tectonics influence that depends mainly on its evolutionary, geomorphological and sedimentary history. Nevertheless, these mechanisms hardly explain the observed coincidence between crustal segmentation and salt morphologies. We then proposed to evaluate a thermal hypothesis, which could be related to crustal segmentation and thus have a different influence on regions delimited by different salt morphologies.

Résumé chapitre 4

Ce chapitre vise à analyser la tectonique salifère en Méditerranée

Objectives

Chapter 4 has highlighted the geometric relationship between salt morphologies and crustal structure. We also pointed out how the classical mechanisms of salt tectonics do not seem to work in the Western Mediterranean Sea, mainly given by its morpho-structure that makes it different from other salt passive margins. We have concluded the previously chapter by putting forward the hypothesis of a thermal influence, given by the crustal segmentation, which could influence salt deformation.

In this chapter we will therefore try to figure out the thermal regime of the Western Mediterranean, thanks to the new heat flow data recently acquired during the WestMedFlux surveys (2016 and 2018). The new data, combined with the existing ones, will help to observe possible regional thermal differences associated with different crustal natures. In the first part of the chapter we will examine the present-day surface heat flow while in the second part, through thermo-kinematic modelling (see Chapter 3 to details), we will try to understand the temperature variation in the past and the temperature evolution within the salt deposits.

The chapter 5.2 is the follow-up to the paper [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF] published in Marine Geology of which I am co-author (in Annexe-1). [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF] paper focuses on the analysis of present-day heat flow in the Western Mediterranean, analysing the regional and local scale influence variations. New measurements from WMF1 are published, while those acquired during the second survey (WMF2-2018) are shown in this manuscript. The chapter 5.2 is built in the form of a paper (Bellucci et al., in prep) and focuses on the local heat flow analysis and the relationship between crustal segmentation and thermal regime in some transects of the Western Mediterranean Sea. The references will be shown at the end of the manuscript, in the References chapter.

5.2

understanding their causes can provide some clues on the regional thermal regime related to crustal segmentation. We proposed to explain the small-scale anomalies in the South Balearic margin as a fluid circulation system characterized by an upslope recharge area concomitant with the mid-slope Formentera basin and a discharge domain downslope the Emile Baudot Escarpment. In the Gulf of Lion, several positive surface HF anomalies are clearly associated to the presence of shallow salt structures, derived by the intense salt deformation. In the deep basin, fluid circulation appears to be inhibited by the thick sedimentary blanket separating the basement from the surface. The regional signature in all the sub-basins confirm an overall increase from the eastern to the western Algerian basin. In the Liguro-Provençal basin, the greater variation is observe between the transitional and the oceanic crustal domains, while in the South Balearic the transitional domain shows similar HF to the oceanic crust domain. This work give several new insights to understand the shallow and deep thermal regime in the transitional crust domain of young passive margins.

Introduction

The Western Mediterranean basins are surrounded by a variety of passive continental margins. The formation of these passive margins is still a debated topic in the scientific community and heat flow occupies a prominent position in their study as well as the sedimentary basins evolution. The quantification of the mantle contribution, the sedimentary basin thermal regime and the thermal segmentation are major issues that are still unclear. A particular focus should be given on heat flow (HF) in the ocean-continent transition (OCT) domain. In this domain, roughly situated between the continental domain (unthinned or thinned) and the oceanic crust, the lithosphere rheology is transitional and the thermo-mechanical behaviour different. Several authors found anomalous heat flow in the transitional domain, as in the Eastern Gulf of Aden [START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF], Australia margins (Goutorbe et al., 2008a), South China Sea [START_REF] Nirrengarten | The thermal imprint of continental breakup during the formation of the South China Sea[END_REF] and in South Gabon basin [START_REF] Dupré | Seafloor geological studies above active gas chimneys off Egypt (Central Nile Deep Sea Fan)[END_REF]. [START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF], in the young passive margin in Gulf of Aden, showed clearly contrasted thermal regime between crustal domains. A post break-up persistent thermal anomaly at mantle level [START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF] and a mantle contribution increasing (Goutorbe et al., 2008a) are two hypothesis argued to explain the anomalies in the OCT. Moreover, the hydrothermal circulation in young continental margins affects the surface HF, both in oceanic [START_REF] Lister | On the thermal balance of a mid-ocean ridge[END_REF][START_REF] Langseth | The hydrogeological regime of isolated sediment ponds in mid-oceanic ridges[END_REF][START_REF] Hutnak | Hydrothermal recharge and discharge guided by basement outcrops on 0.7-3.6 Ma seafloor east of the Juan de Fuca Ridge: Observations and numerical models[END_REF][START_REF] Hasterok | Oceanic heat flow: Implications for global heat loss[END_REF][START_REF] Hasterok | A heat flow based cooling model for tectonic plates[END_REF] and continental [START_REF] Lucazeau | Post-Rift volcanism and high heat-flow at the ocean-continent transition of the eastern Gulf of Aden[END_REF][START_REF] Lucazeau | Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden[END_REF] domains. Understanding thermal processes related to the OCT domain also involves understanding the influence of the effect of fluid circulation in young margins.

The Western Mediterranean Sea is characterized by a thin, young and hot lithosphere. The presence of a relatively thin oceanic crust (around 5 km; e.g. [START_REF] Gailler | Crustal structure of a young margin pair: new results across the Liguro-Provencal Basin from wide-angle seismic tomography[END_REF][START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]Afhilado et al., 2015;[START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF] and several open questions about the nature and segmentation of the OCT domain [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]Afhilado et al, 2015;[START_REF] Jolivet | Continental breakup and the dynamics of rifting in back-arc basins: The Gulf of Lion margin[END_REF][START_REF] Dannowski | Seismic evidence for failed rifting in the Ligurian Basin, Western Alpine domain[END_REF]Lepretre et al., 2013;[START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF]Medaouiri et al., 2014;Aidi et al., 2018) make the Western Mediterranean an excellent case study for understanding deep and surface thermal processes related to continental margin formation.

Since the 1980s, several HF acquisition campaigns have taken place in Western

Mediterranean. Nevertheless, the measurements were regionally sparse and mainly focused in the marginal basins of Alboran, Valencia and Ligurian (Della [START_REF] Vedova | Dati di flusso di calore nei mari italiani[END_REF][START_REF] Foucher | Heat flow in the Valencia trough: geodynamic implications[END_REF][START_REF] Polyak | Heat flow in the Alboran Sea, western Mediterranean[END_REF][START_REF] Gueguen | On the post-25 Ma geodynamic evolution of the western Mediterranean[END_REF]. Recently, new measurements acquired during WestMedFlux-1 survey are focused on the poorly constrain OCT domains in Liguro-Provençal and Algero-Balearic basins [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF]. Several authors [START_REF] Foucher | Heat flow in the Valencia trough: geodynamic implications[END_REF][START_REF] Vedova | Dati di flusso di calore nei mari italiani[END_REF][START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF] pointed out a large influence of local phenomena on surface HF anomalies, including heat redistribution by fluids and heat refraction by a strongly deformed Messinian salt deposit. Discriminating these local anomalies and understanding their significance is therefore a major challenge to figure out regional anomalies arising from different crustal natures. We propose here the discussion of new WestMedFlux2 survey carried out in 2018 on R/V L'Atalante (Ifremer). The new data are mainly focused on the South Balearic margin crossing the continental slope, the OCT and the deep oceanic basin.

We show the presence of local heat flow anomalies on different heat flow transects and try to interpret the processes that source them.

Geological setting

The Western Mediterranean Sea is considered to be composed by the Liguro-Provençal basin bordered by the Gulf of Lion and Western Sardinian conjugated margins, and the Algero-Balearic basin, delimitated at the north by the South Balearic margin and at the south by the North Algerian margin (Fig. 5.1). Both basins are considered to be formed by Oligo-Miocene back-arc system due to the roll-back of the Tethys subducted oceanic crust [START_REF] Olivet | La cinématique de la plaque ibérique[END_REF][START_REF] Rehault | The western Mediterranean basin geological evolution[END_REF][START_REF] Jolivet | From mantle to crust: Stretching the Mediterranean[END_REF].

Liguro-Provençal basin

The rifting process in Liguro-Provençal basin is the result of the counter clockwise rotation of the Corso-Sardinia block with respect to the Ibero-European plate since the Late Eocene (Priabonian, 33.7 Ma). This range period, dated thanks to the sediments drilled in the Gulf of Lion [START_REF] Gorini | Géodynamique d'une marge passive: le Golfe du Lion (Méditerranée occidentale[END_REF], is followed by a drifting period dated from 19 to 15-16 Ma, according to paleomagnetic data and kinematic reconstructions [START_REF] Vigliotti | When did Sardinia stop rotating? New palaeomagnetic results[END_REF][START_REF] Olivet | La cinématique de la plaque ibérique[END_REF][START_REF] Speranza | Age of the Corsica-Sardinia rotation and Liguro-Provençal Basin spreading: new paleomagnetic and Ar/Ar evidence[END_REF][START_REF] Gattacceca | Miocene rotation of Sardinia: New paleomagnetic and geochronological constraints and geodynamic implications[END_REF][START_REF] Advokaat | Eocene rotation of Sardinia, and the paleogeography of the western Mediterranean region[END_REF]. Although the [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF], in the Algerian basin doubts about the basin opening lead to different segmentation interpretation. Wide-angle segmentation is taken from [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]; Afhilado et al., 2015;[START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF]Aidi et al., (2018); [START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF]; [START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF]; [START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF]. Gravity modelling segmentation is from [START_REF] Driussi | Evidence for transform motion along the South Balearic margin and implications for the kinematics of opening of the Algerian basin[END_REF]. Gravity and magnetic segmentation is from [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. Free-air anomaly map is from [START_REF] Smith | Global sea floor topography from satellite altimetry and ship depth soundings[END_REF]. Black squares and white circles represent the heat flow measurements acquired during WestMedFlux 1 ( 2016 general mechanisms of margin formation are widely accepted in literature [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF], there is still a debate on amplitude and timing of the rotation and in the extent of oceanic crust.

The crustal segmentation in the Liguro-Provençal basin is constrain by wide-angle seismic, gravity and magnetic data and is defined by interpretations of several authors [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF][START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF][START_REF] Dannowski | Seismic evidence for failed rifting in the Ligurian Basin, Western Alpine domain[END_REF].

The defined domains show a general symmetrical distribution between the western Sardinian and Gulf of Lion conjugated margins, with the exception of a wider OCT domain in the French margin (Fig. 5.1). The transitional crust is interpreted as made by exhumed lower continental crust [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF] or exhumed lower crust and upper mantle [START_REF] Jolivet | Continental breakup and the dynamics of rifting in back-arc basins: The Gulf of Lion margin[END_REF]. The oceanic crust in the LPB is thinner compared to the "classic" Atlantic type (e.g. [START_REF] White | Oceanic crustal thickness from seismic measurements and rare earth element inversions[END_REF], showing a 5 km thick crust of oceanic nature [START_REF] Gailler | Crustal structure of a young margin pair: new results across the Liguro-Provencal Basin from wide-angle seismic tomography[END_REF].

Algero-Balearic basin

The opening of the Algero-Balearic basins is still controversial regarding the kinematic evolution and the nature of the margins. In the early Miocene, the stretching of the European plate is assumed to have caused the drifting, spreading, and finally the collision of parts of a continental block, the Internal Zones, called AlKaPeCa (for Alboran, Kabylies, Peloritan, and Calabria; [START_REF] Bouillin | Betic-Rifian and Tyrrhenian arcs: distinctive features, genesis and development stages[END_REF], with the African continent. At the present day, those internal blocks are scattered around the Western Mediterranean basin, part of them having been accreted along the Algerian margin, such as the Kabylian blocks. The disagreement stems first from the interpretation of the opening direction of the oceanic Algerian Basin with two successive "schools of thought": i) a first one assuming a dominant N-S opening leading to a presently inactive slab under the North African margin (e.g. [START_REF] Carminati | The role of slab detachment processes in the opening of the western-central Mediterranean basins: some geological and geophysical evidence[END_REF][START_REF] Wortel | Subduction and slab detachment in the Mediterranean-Carpathian region[END_REF][START_REF] Gelabert | A new proposal for the late Cenozoic geodynamic evolution of the western Mediterranean[END_REF][START_REF] Rosenbaum | Reconstruction of the tectonic evolution of the western Mediterranean since the Oligocene[END_REF][START_REF] Rosenbaum | Formation of arcuate orogenic belts in the western Mediterranean region[END_REF][START_REF] Schettino | Plate kinematics of the Western Mediterranean region during the Oligocene and Early Miocene[END_REF]. The westward rollback in the Gibraltar region is thus accommodated with no significant displacement (i.e., less than 200 km) of the Alboran block [START_REF] Faccenna | Lateral slab deformation and the origin of the western Mediterranean arcs[END_REF][START_REF] Jolivet | From mantle to crust: Stretching the Mediterranean[END_REF], ii) a second one assuming a dominant E-W opening inducing a westward migration of the Alboran block [START_REF] Gutscher | Evidence for active subduction beneath Gibraltar[END_REF][START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF][START_REF] Duggen | Magmatic evolution of the Alboran region: The role of subduction in forming the western Mediterranean and causing the Messinian Salinity Crisis[END_REF][START_REF] Duggen | Post-collisional transition from subduction-to intraplate-type magmatism in the westernmost Mediterranean: evidence for continental-edge delamination of subcontinental lithosphere[END_REF][START_REF] Camerlenghi | Morphogenesis of the SW Balearic continental slope and adjacent abyssal plain, Western Mediterranean Sea[END_REF]. Recent evolution [START_REF] Etheve | Extensional vs contractional Cenozoic deformation in Ibiza (Balearic Promontory, Spain): Integration in the West Mediterranean back-arc setting[END_REF]Lepretre et al., 2018) favours a two-step opening scenario including a first westward migration and a second one towards the edges of the basin, which is accompanied by detachment or delamination. Last, whilst the rollback process is the most widely accepted mechanism to explain the coincidence of compression and expansion in this region, others such as the collapse of the previously thickened continental crust during the Alpine stage (Dewey, 1989;[START_REF] Platt | Extensional collapse of thickened continental lithosphere: A working hypothesis for the Alboran Sea and Gibraltar arc[END_REF] or lithospheric delamination [START_REF] Roure | Alpine inversion of the North African margin and delamination of its continental lithosphere[END_REF] are also proposed. While the presence of a thin oceanic crust in the East Algerian seems to be confirmed by aligned magnetic anomalies testifying the oceanic accretion [START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF][START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF], in the Western Algerian basin the different geodynamics interpretation led to uncertainties on crustal nature in deep and OCT domains.

Messinian salt distribution

The Western Mediterranean is characterised by the presence of evaporites caused by the Messinian Salinity Crisis (MSC), which led to the deposition of a thick salt blanket in all present-day sub-deep basins. The salt, also called Mobile Unit (MU) (Lofi et al., 2011a), is underlain by the Upper Unit (UU), unit still belonging to the MSC, formed by evaporits and clastic sediments (Lofi et al., 2011a). The only area in the deep basin characterised by the absence/scarce salt is the Hannibal Area (HA, fig. 5.1), located between the East Algerian (EAB) and the West Algerian (WAB) basins marked by structural highs and suggested volcanism (Aidi et al., 2018;[START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF]. The Liguro-Provançal basin shows a sedimentary thickness overlying the basement generally higher than that of the Algerian basin, mainly due to the sedimentary arrival of the Rhone [START_REF] Leroux | High-resolution evolution of terrigenous sediment yields in the Provence Basin during the last 6 Ma: relation with climate and tectonics[END_REF][START_REF] Badhani | Morphology of retrogressive failures in the Eastern Rhone interfluve during the last glacial maximum (Gulf of Lions, Western Mediterranean)[END_REF][START_REF] Dal Cin | Seismic imaging of Late Miocene (Messinian) evaporites from Western Mediterranean back-arc basins[END_REF][START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF].

Dataset and method

Heat flow data acquisition in the Western Mediterranean has a long history that started in the early 1960's, when the first marine type heat flow instruments were under development [START_REF] Lister | A close group of heat-flow stations[END_REF][START_REF] Burrus | Contribution to the thermal regime of the Provençal Basin based on FLUMED heat flow surveys and previous investigations[END_REF][START_REF] Lucazeau | Heat flow, heat production and fission track data from the Hercynian basement around the Provençal Basin (western Mediterranean)[END_REF][START_REF] Vedova | Heat flow in the tectonic provinces crossed by the southern segment of the European Geotraverse[END_REF][START_REF] Polyak | Heat flow in the Alboran Sea, western Mediterranean[END_REF]. Recently (2015, 2016 and 2018), new surface HF were acquired in the Western Mediterranean Sea, during three main surveys: MEDSALT (R/V Explora -OGS, Italy) and WESTMEDFLUX 1 and 2 (R/V L'Atalante -Ifremer, France). The WESTMEDFLUX surveys had the objective to investigate the thermal regime of the margins in the sub-basins of the Western Mediterranean Sea, in order to further constrain models of crustal structure and margin evolution. The WESTMEDFLUX 1 (WMF1) survey took place in 2016 and allowed the acquisition of 143 new heat flow measurements [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF]. The WESTMEDFLUX 2 (WMF2) survey took place in 2018 as a direct consequence of the WMF1 survey. The objectives remaining the same, this survey has allowed the acquisition of 56 new heat flow measurements, the recovering of 11 sediment cores and hard rocks from 2 dredging sites, mainly located in the Algerian basin and South Balearic margin. Sub-bottom seismic, gravimetry, multi-beam bathymetry and magnetics data were also collected along the cruise track.

In this work, we will describe and interpret the WMF2 heat flow data. Measurements are acquired above several seismic profiles located both on the margin and in the deep basin. We discuss new WMF2 and old surface HF above 4 seismic profiles in the Western Mediterranean (Fig. 5.1): i) seismic low resolution Sardinia-01 profile crossing the Gulf of Lion, ii) seismic low resolution SH-23A in the eastern South Minorca Block margin, iii) seismic low resolution SH-37B crossing the Hannibal Area between the west and east Algerian deep basins and iv) seismic high resolution MEDS-07D and SaltFlu-03 profiles in the South Balearic margin.

During both the WMF-1 and WMF-2, the heat flow acquisition was carried out using two different methods: i) the MCHF (Micro-Computerized Heat Flow) instrument and ii) sediment corer. The two types of acquisition give mutually consistent results (Le [START_REF] Gal | Traçage thermique et géochimique des systèmes hydrothermaux: exemple d'un domaine océanique jeune et d'une marge continentale[END_REF]Lucazeau et al., 2010).

MCHF instrument (pogo type measurement)

The MCHF instrument was designed by Von Herzen R.P. [START_REF] Von Herzen | Measurement of oceanic heat flow[END_REF][START_REF] Bonneville | HFsoft: Toolbox for processing marine heat flow data acquired with MCHF instrumentation[END_REF] at Woods Hole Oceanographic Institution and upgraded significantly since 2001 at IPGP. It allows to measure the temperature and the thermal conductivity in-situ and, with a battery life of 72 hours, to acquire several measurements before to taking back the instrument on deck (pogo type of measuring). This instrument is composed of a 5-meters lance and 7 thermistors arranged in an elliptical shape and with regular intervals around the lance. Each sensor has a resistance and a heating wire for measuring temperature (resolution of 0.002 K) and thermal conductivity. An inclinometer situated on the lest allows to measure the angle of the instrument in relation to the vertical in order to correct the true thermistors depth. The electronics in the container of top is controlled from the surface via a bidirectional acoustic connection at 2400 bit/s. The data is transmitted in real time to the surface but also stored in the instrument's memory. Between two measurements, the instrument is towed behind the boat at 100 meters above the sea-bottom. The instrument is inserted in the sediment under its own weight (1.5 tons). Penetration causes heating of thermistors, and a minimum of 5 minutes of recording is needed in order to be able to extrapolate the value of the equilibrium temperature.

After this step, to determinate the thermal conductivity, a constant heating is activated in the sediments (about 1W) and the instrument extrapolates the measurement by this temperature increasing [START_REF] Von Herzen | The measurement of thermal conductivity of deep-sea sediments by a needle-probe method[END_REF]. After this last step, the heating is stopped, the instrument pullet out of the sediments and towed to the next station.

Sediment coring heat flow

The sediment coring includes the acquisition of HF with the autonomous temperature loggers (THP on the core) equipment. The piston used to recover sediment cores can be equipped with these high precision temperature loggers at different intervals in order to measure temperatures and thermal gradients in the sediments. A logger (S2IP NKE©) added at the top of the cores is equally autonomous and measures water depth and tilt angle of the corer. On deck, the measures are then downloaded using an induction pencil (Data pencil NKE©). To allow heat friction dissipation, the cores have to stay at least 5-6 minutes in sediment without tensions. When the core is on-board, the thermal conductivity is measured using a needle-probe technique developed by Von Herzen and Maxwell, (1959). The needle, which includes a heating wire and a thermistor or a thermo-couple, is inserted transversally into the core and heated at a constant power. The temperature increase of the probe with the logarithm of time is proportional to the inverse of thermal conductivity. Usually, three values for 1 meter core section are measured (Fig. 5.2).

Correction

In order to correctly interpret the heat flow measurements, it is necessary to correct the heat flow perturbation given by environmental effects, such as the sedimentation, the contrast of thermal conductivity and the sea-floor topography. It is worth to note that, both in terms of sedimentation and refraction correction, the resulting values must always be shown together with the surface value.

Sedimentation effects are induced by the sedimentary history of the basin and, above all, by the sedimentation rate. A high sedimentation rate will tend to decrease the surface heat flow and sediments deposits of uneven thickness will cause lateral variations in the surface heat flow [START_REF] Langseth | Crustal structure of the mid-ocean ridges: 5. Heat flow through the Atlantic Ocean floor and convection currents[END_REF]. The duration and the magnitude of this "cooling" will depend on the sedimentation and the duration of the event, which can be estimated from the thickness and age of sedimentary sequences. When sedimentation ceases, the system rebalances itself with a time which depends on the thermal response of the entire lithosphere [START_REF] Hutchison | The effects of sedimentation and compaction on oceanic heat flow[END_REF]. Conversely, an erosion episode will amplify the value of the flow. In order to include variable sedimentation rates, compaction and thermal interaction with basement for high sedimentation rates, numerical solutions and algorithms have been proposed by [START_REF] Hutchison | The effects of sedimentation and compaction on oceanic heat flow[END_REF] and [START_REF] Lucazeau | The blanketing effect of sediments in basins formed by extension: a numerical model. Application to the Gulf of Lion and Viking graben[END_REF]. Although the two algorithms use different strategies and hypothesis, both give very similar results (within 0.5% of heat flow anomaly). In this work we referred to the sedimentary correction according to [START_REF] Hutchison | The effects of sedimentation and compaction on oceanic heat flow[END_REF].

Heat flow description

Previous HF surface dataset

Thanks to the new acquisition surveys we enhance the Heat Flow Density (HFD) in the Western Mediterranean Sea (Fig. 5.1). Most of the available measurements (WMF1 and WMF2 surveys) are acquired above seismic profiles. The remaining HF measurements (~516 measures) come from earlier work. The first devices were relatively short (2-3 m only) with only a few temperature sensors, often lacking a tilt measurement and thus vulnerable for misinterpretations. Some old measurements were omitted based on a lack of basic quality control (refer to [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF]. Nevertheless, the majority of the existing marine data points were obtained between 1982 and 2000, with equipment appropriate to evaluate data quality (tilt sensor, reasonably number of thermistors..). The old existing measurements are widely distributed, with a major concentration in the Alboran [START_REF] Polyak | Heat flow in the Alboran Sea, western Mediterranean[END_REF][START_REF] Marzan | Régimen térmico en la Península Ibérica. Estructura litosférica a través del macizo ibérico y el margen surportugués[END_REF], Valencia (Albert-Beltran, 1979;[START_REF] Foucher | Heat flow in the Valencia trough: geodynamic implications[END_REF], Ligurian (Della [START_REF] Vedova | Dati di flusso di calore nei mari italiani[END_REF][START_REF] Jemsek | Heat flow and lithospheric thinning in the Ligurian Basin (NW Mediterranean)[END_REF] basins and one transect from the Gulf of Lion to the conjugated western Sardinian margin [START_REF] Burrus | Contribution to the thermal regime of the Provençal Basin based on FLUMED heat flow surveys and previous investigations[END_REF]) (Fig. 5.1).

In the Liguro-Provençal basin, [START_REF] Burrus | Contribution to the thermal regime of the Provençal Basin based on FLUMED heat flow surveys and previous investigations[END_REF], found an asymmetrical HF increase from the Gulf of Lion to the western Sardinia margin. Onshore, the Hercynian basement appears hotter in Corsica (76 mW/m 2 ) than in Provence (50-60 mW/m 2 ) [START_REF] Lucazeau | Heat flow, heat production and fission track data from the Hercynian basement around the Provençal Basin (western Mediterranean)[END_REF]). In the deep basin, a mean value of 100 mW/m 2 is in agreement with the oceanic cooling age model [START_REF] Burrus | Contribution to the thermal regime of the Provençal Basin based on FLUMED heat flow surveys and previous investigations[END_REF]. The lack of resolution and the scarce knowledge of the crustal structure have left various hypothesis opened to explain the heat flow asymmetry, such as: i) a more recent oceanic opening to the east [START_REF] Rehault | The western Mediterranean basin geological evolution[END_REF][START_REF] Jemsek | Heat flow and lithospheric thinning in the Ligurian Basin (NW Mediterranean)[END_REF]; ii) post-rift magmatic intrusions [START_REF] Burrus | Contribution to the thermal regime of the Provençal Basin based on FLUMED heat flow surveys and previous investigations[END_REF]; iii) post-rift tectonic activity (Della [START_REF] Vedova | Heat flow in the tectonic provinces crossed by the southern segment of the European Geotraverse[END_REF]; iv) asymmetric rifting [START_REF] Pasquale | Rifting and thermal evolution of the Northwestern Mediterranean[END_REF]. Recently, [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF] confirmed the heat flow asymmetry suggesting, despite a regional symmetry in the basin opening (Afhilado et al., 2015;[START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF], difference in OCT crustal nature between the Western Sardinian and Gulf of Lion margins. The coverage data in the Algerian basin is less dense compared to the Alboran and Liguro-Provençal basins (Fig. 5.1).

Here, the available heat flow data are sporadic and focused only on the extreme western part (Alboran basin, [START_REF] Polyak | Heat flow in the Alboran Sea, western Mediterranean[END_REF] or in the south Sardinia (Della [START_REF] Vedova | Heat flow in the tectonic provinces crossed by the southern segment of the European Geotraverse[END_REF]. In the Alboran basin the observed heat flow are relatively high, with a mean values between 80-145 mW/m 2 . [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF] added 148 HF measurements mainly located in the South Balearic margin and deep Algerian basin. The authors found an overall surface HF increase from W to E in the Provençal basin and an E to W in the Algero-Balearic basin. Moreover, different HF anomalies are identified in both basins, which will be further analysed in this work.

WMF heat flow analysis

Sedimentation correction on WMF1-2 data

In the Western Mediterranean Sea, variations in sedimentary thickness are mainly due to: i) sedimentary arrivals of the major attributes, such as the Rhone in the Gulf of Lion (e.g. [START_REF] Droz | Quaternary turbidite systems on the northern margins of the Balearic Basin (Western Mediterranean): a synthesis[END_REF][START_REF] Leroux | High-resolution evolution of terrigenous sediment yields in the Provence Basin during the last 6 Ma: relation with climate and tectonics[END_REF][START_REF] Badhani | Morphology of retrogressive failures in the Eastern Rhone interfluve during the last glacial maximum (Gulf of Lions, Western Mediterranean)[END_REF] and the Ebro [START_REF] Pellen | The Messinian Ebro River incision[END_REF][START_REF] Garcia-Castellanos | Interplay between tectonics, climate, and fluvial transport during the Cenozoic evolution of the Ebro Basin (NE Iberia)[END_REF] in the Valencia basin; ii) the evolution of crustal segments since the formation of the basins; iii) the tectonics, as the inversion to which the North Algerian margin is subject (e.g. [START_REF] Déverchère | Active thrust faulting offshore Boumerdes, Algeria, and its relations to the 2003 Mw 6.9 earthquake[END_REF][START_REF] Domzig | Searching for the Africa-Eurasia Miocene boundary offshore western Algeria (MARADJA'03 cruise)[END_REF][START_REF] Serpelloni | Kinematics of the Western Africa-Eurasia plate boundary from focal mechanisms and GPS data[END_REF]. The sedimentary corrections presented in this paper belong to the HF acquired during the MedSalt CHAPTER 5. THERMAL REGIME IN THE WESTERN MEDITERRANEAN SEA 247 and WestMedFlux 1-2 oceanographic campaigns. Old acquired HF could not be corrected as they were not acquired above available seismic profiles.

The sediment blanketing effect is strongest in the deep sea basins with a slightly higher effect in the Liguro-Provençal basin than in the Algero-Balearic basin (respectively 15-20% and 10 15%) (Fig. 5.3). On and near slope, deposits often generate a surface heat flow decrease of < 8%. The highest correction values are found in the Gulf of Lion, due to the high sedimentary thickness. Here, basement heat flow could be more than 20% higher than the surface measured value (Fig. 5.3). Minor correction percentages are calculated in the South Balearic margin, with an average of less than 10% in the slope and around 12% in the deep basin (Fig. 5.3). [START_REF] Lucazeau | The blanketing effect of sediments in basins formed by extension: a numerical model. Application to the Gulf of Lion and Viking graben[END_REF] found an average sedimentation correction of about 32% in the Gulf of Lion, significantly higher than that in this work. Nevertheless, the authors calculated the values basing on uniform and widely averaged lithology while in this work the abundant geophysical data allowed a better improvement of stratigraphy ages and thickness (according to seismic stratigraphy compilation by Bellucci et al., 2020).

Gulf of Lion

On the Gulf of Lion margin, we focus on the WMF1 heat flow data collected along the SARDINIA01 seismic profile (Fig. 5.1). This is more 50 km south than the transect shown along the Geotraverse [START_REF] Burrus | Contribution to the thermal regime of the Provençal Basin based on FLUMED heat flow surveys and previous investigations[END_REF]), but has the advantage that the seismic reflection profile is coincident with the wide-angle profile shown in [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF], which well-constrained the deep crustal segmentation and nature. The basement is covered with at least 7-8 km of Oligocene to Quaternary sediments (Fig. 5.4). The pre-salt sequence includes thin syn-rift sediments overlaid by Oligo-Miocene post-rift sediments characterized by discontinuous low-amplitude horizontal reflections (e.g. [START_REF] Gorini | Géodynamique d'une marge passive: le Golfe du Lion (Méditerranée occidentale[END_REF][START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF], Messinian pre-salt deposits including the Messinian Lower Unit (LU, [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF] and Messinian turbidites and evaporites (Fig. 5.4). The Messinian salt in the Gulf of Lion shows three morphological domains based on the salt geometry structures: i) an upslope Listric salt domain in the lower slope, characterized by salt rollers and basinward-dipped listric faults, ii) a tabular/anticlinal domain characterized by large pillows and anticlines, iii) a diapirs domain in the distal deep basin, divided in a Large diapirs domain and a connected, irregular diapirism in the Liguro-Provençal deep basin (Bellucci et al., submitted). In the Large diapirs domain, the salt stocks and walls often deformed the seafloor and show a preferential N-S/NW-SE direction. The thick Plio-Quaternary deposits includes the Rhone fan, deposited after Rhone river discharge mainly through the Petit Rhône canyon during the Pleistocene [START_REF] Droz | Quaternary turbidite systems on the northern margins of the Balearic Basin (Western Mediterranean): a synthesis[END_REF][START_REF] Leroux | Post-rift evolution of the Gulf of Lion margin tested by stratigraphic modelling[END_REF][START_REF] Badhani | Morphology of retrogressive failures in the Eastern Rhone interfluve during the last glacial maximum (Gulf of Lions, Western Mediterranean)[END_REF].

In the Gulf of Lion, about 150 surface heat flow measurements are available (Fig. 5.1), most of them located above the OCT (about 70 measurements) or continental thinned crust. In figure 5.4 we present the major heat flow trends perpendicular to the margin along the selected SARDINIA 01 profile from the new data and including older data projected from a maximum distance of 50 km. The lower slope domain is characterized by HF values from 44 to 60 mW/m 2 , with a slightly rise towards the deep basin domain (from 44 to 62 mW/m 2 ). From the lower slope all along the deep basin (in the OCT and oceanic domains), most of the values are in the range between 50 and 70 mW/m 2 (Fig. 5.4). The most basinward part of the OCT domain shows an increase of surface HF values [START_REF] Burrus | Contribution to the thermal regime of the Provençal Basin based on FLUMED heat flow surveys and previous investigations[END_REF], reaching an average of around

East Minorca slope

The profile SH73-23A (Fig. 5.5A) is located in the South-East of Menorca Island, in the lower slope of the South Menorca Block (SMB), interpreted as continental in nature (Driussi et al., 2015a) (Fig. 5.1). The SMB shows a deeper basement than the Balearic Promontory, characterized by a NE-SW structural direction connecting the Balearic Islands. The acoustic basement is irregular and affected by several phases of extension and volcanism [START_REF] Driussi | Evidence for transform motion along the South Balearic margin and implications for the kinematics of opening of the Algerian basin[END_REF]Acosta et al., 2001a). Some normal faults affect the basement and the Miocene sequence in the lower slope (Fig. 5.5A). The Messinian salt only characterizes the deep basin, where, at the lower slope limit, it onlaps the pre-Messinian sequence (Fig. 5.5A; km 80). In the distal part of the slope the salt deformation is characterised by an extensional domain of about 10 km showing listric faults rooted in the base of salt and Upper Unit (80-90 km); this area is followed by a transitional domain outlining a base of salt sloping towards the deep basin (90-110 km) and a basinward domain characterised by small vertical diapirism (110-130 km) (Fig. 5.5A).

The heat flow values along the SH73-23a profile were acquired during the WMF2 survey while, [START_REF] Burrus | Contribution to the thermal regime of the Provençal Basin based on FLUMED heat flow surveys and previous investigations[END_REF], at a maximum distance of 50 km. Thin lines above seafloor indicate the HF measurements location. Thickness in meters of Miocene pre-salt is from [START_REF] Bache | Evolution Oligo Miocène des marges du micro océan Liguro-Provençal[END_REF]. Crustal segmentation is taken from [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. The HF measurements are from WMF1 survey. in [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF]. In the upper continental part of the profile (km 30-45), the HF average is 72.1 +-14 mW/m 2 . Towards the deep basin, in the lower slope (km 45-75), the average of measurements is around 94.3 mW/m 2 with maximum peaks at 126 and 139 mW/m 2 . A relatively low value (56 mW/m 2 ) was measured on a seafloor and basement escarpment (around km 45 in the profile). Higher measurements are instead measured at the lower limit of the lower slope (km 80), where some listric faults given by the basinward movement of salt are interpreted. In the deep basin, the average measured value is around 78.4 +-5 mW/m 2 , coherent with the average values of the East Algerian basin (82.1 mW/m 2 ; Della Vedova and Pellis, 1984;[START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF]. It is still tricky to isolate the possible surface HF influences of salt diapirs in the deep basin, which do not seem to have a significant impact. The salt, unlike the deep domain of the Gulf of Lion, displays less piercing deformation: the structures can deform the Pliocene deposits but they do not impact the seafloor. In the SE margin of SMB, the values seem to be highest in the lower slope area, close to the deep basin, at the upslope edge of the margin. The positive and negative anomalies are mainly located at the edge of a basement deepening (Fig. [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF] and fig. 5.5A (km 45 and 80). These zones could be more subject to the refraction phenomenon given by the sudden change in thermal conductivity in the abrupt zones.

1). HF are indicated in plot above with black (measured value), blue (after refraction correction) and red (after sedimentation correction) points. The dashed lines represent the higher HF values above the two salt walls. Empty circles are projected HF from

5.5b in

Hannibal area

The profile SH73-37b is located in the deep Algero-Balearic basin, between the EAB and the WAB, crossing the Hannibal Area (Figs 5.1, 5.5B). The Hannibal Area is characterized by structural highs, scarce salt and suggested volcanism [START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF]Aidi et al., 2018).

The profile crosses it from NE to SW and is floored, according to wide-angle survey interpretation (Aidi et al., 2018), by oceanic crust (Fig. 5.5B). The basement shows two structural highs around 110 and 150 km, showing a pre-salt thickness variation all along the profile. Some pre-salt onlaps on the basement are observable, especially when the latter has risen up, also deforming the base of the salt. The base of salt is flat in the EAB and WAB sectors while is deformed in the Hannibal Area. The thickness of salt in the Hannibal Area is thinner than EAB and WAB nearby basins. Apart from a single diapir at km 110 the salt does not deform as usually observed in the Western Mediterranean deep basins. The UU is less deformed and presents some faults that dislocate internal reflectors within the unit. Faults are also found in the Plio-Quaternary sequence (e.g. km 150, 180, 210). The seabottom all along the profile is convex. Despite a good depth resolution, it is tricky to decipher if the salt pinch-out on the pre- Driussi et al., (2015a), Aidi et al., (2018) and [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF]. The HF are from WMF2 survey.

1). Free-air gravity anomaly was acquired during WMF2 survey. B) HF variation along the SH73-37B profile, crossing from NE to SW the Hannibal Area. HF are indicated in plots above the profiles with black (measured value), and red (after sedimentation correction) points. Thin lines above seafloor indicate the HF measurements location. Crustal segmentation is taken from

CHAPTER 5. THERMAL REGIME IN THE WESTERN MEDITERRANEAN SEA 252

Here, the seafloor is deformed by some faults. The higher HF are more located towards the WAB, where fluids rising are interpreted (locally transparent and more chaotic facies) (zoom in fig. 5.5B). Here, although the low seismic resolution, some faults propagating from the UU are observed and can act as preferential pathway to fluid circulation. In this area, the structural high signal is also visible on magnetic anomaly where a positive peak is measured at km 110 (Fig. 5.5B). The fluids could be originated from the basement (probably locally faulted) and rise through the pre-salt and Upper Unit sequence. The salt welds (absence of salt) could favour the rising across the pre and post-salt deposits.

South Balearic margin

The South Balearic margin is considered to be the southern margin of the Balearic Promontory, going from south Menorca to the Mazarron Escarpment in the south-western part (e.g. Acosta et al., 2003). The Emile Baudot Escarpment is steeper in the north-eastern sector (south Menorca Island, 6.5-7.9° of slope, Acosta et al., 2001a). In this work we focused on the south-western part of the Escarpment, in the margin connecting the slope of the Ibiza and Formentera Islands continental domain to the deep Algerian basin, separated by the intra-slope Formentera basin. All the South Balearic margin is characterized by a widely presence of volcanic seamounts (Rovere and Wurtz, 2015), as the southwest Mallorca Volcanic Field, an area of more than 118 volcanic pinnacles (Acosta et al., 2001a). The volcanic activity in the Balearic Promontory, including its southern margin, show two cycles: an early to middle Miocene (Maillard, 1993;Marti et al., 1992) and a Miocene to Holocene [START_REF] Acosta | Sea floor morphology and Plio-Quaternary sedimentary cover of the Mallorca Channel, Balearic Islands, western Mediterranean[END_REF].

Most of the volcanic structures are located upslope the Emile Baudot Escarpment.

The intra-slope South Formentera basin is located between the south Ibiza margin and Emile Baudot Escarpment, which upslope limit in our area of study is marked by two volcanic seamounts (Riba and Los Martines; [START_REF] Canals | Toponímia de la mar catalano-balear[END_REF]Rovere and Wurtz, 2005)

(Fig. 5.6A).
The two seamounts show high faulted basement and thin sedimentary cover and they mark the southern edge of the Formentera basin, characterized by thin Plio-Quaternary sequence and probably a thin perched Messinian salt deposit (Driussi et al., 2015a;[START_REF] Raad | The Messinian Salinity Crisis deposits in the Balearic Promontory: an undeformed analog of the MSC Sicilian basins??[END_REF][START_REF] Blondel | Late Miocene to present-day tectonostratigraphy of the northern central Algerian Basin: Evidence of a contractional salt system from reprocessed seismic data[END_REF]. All the Formentera basin shows low HF values, from maximum of 63.9 to a minimum of 0.8 mW/m 2 (average of 25.8 mW/m 2 ) (Fig. 5.6). The measurements were acquired at 3 km maximum distance of MEDS-07D seismic profile as during the acquisition the subbottom profile warned on the hard penetrating sediments just above it. The values exhibit their minimums at the Los Martines Seamount while they appear to increase in the sedimentary basin towards the SW and in the deep basin (Fig. 5.6A,B). The multi-beam data allowed to point out for the first time the presence of a large pockmark (350-400 m in diameter) north of Los Martines Seamount (Zoom A in fig. 5.6A). KF09 core (4-5 m length) highlighted clay to siltyclay sediments inside the pockmark. The heat flow measurement does not reveal a thermal gradient anomaly (HF of 30.9 mW/m 2 ), which remains consistent with neighbouring measurements. Moreover, the acoustic water column survey over the pockmark did not highlight any flare.

HF increase in the deep basin to values between 90 and 100 mW/m 2 where the sea floor flattens out (Fig. 5.6B). A positive HF peak (139 mW/m 2 ; HF07-14) and a relatively low peak (HF07-17) are also recorded. The values then seem to increase again towards the deep basin (average value of 94.4 mW/m 2 ), which is characterised by strong salt deformation. The socalled "perched" basin is formed by a basement high located basinward the Emile Baudot Escarpment: the structural high can be followed in multi-beam data and seems to be shallower towards SW (multi-beam inset in fig. 5.6). The pre-salt sequence onlaps on the basement and its thickness variation suggest a basement volcanic activity since the Miocene age, which probably was still active during the Messinian (Fig. 5.6B). The "perched" basin area is also characterized by small-offset, fractures and faults propagating from the upper part to the UU to the Plio-Quaternary sequence (also according to [START_REF] Wardell | Seismic evidence for Messinian salt deformation and fluid circulation on the South Balearic margin (Western Mediterranean)[END_REF]. The polygonal fault (e.g. [START_REF] Cartwright | The genesis of polygonal fault systems: a review[END_REF]Bertoni and Cartwright, 2005a) pattern affecting the UU (km 60-65; fig. 5.6B) has been interpreted as caused by the volumetric change induced by gypsumanhydrite transformation and dewatering which could affect the overlying sediments [START_REF] Wardell | Seismic evidence for Messinian salt deformation and fluid circulation on the South Balearic margin (Western Mediterranean)[END_REF][START_REF] Dal Cin | Seismic imaging of Late Miocene (Messinian) evaporites from Western Mediterranean back-arc basins[END_REF]. Moving towards the deep basin, the basement and the overlain sequence, including the salt, deepening suddenly. The Plio-Quaternary deposits thickens as well as the UU sequence. The salt shows squeezed, vertical and close structures deforming all the Plio-Quaternary and sometimes the seafloor, suggesting a still active strong deformation. The base salt is sub-horizontal and overlain the Miocene pre-salt deposits and basement, masked by the salt seismic energy. In the deep basin the HF show values from 90 and 120 mW/m 2 with a negative anomaly at the limit between the "perched" and the deep basin (62.9 mW/m 2 ; fig.

5.6B

). Unlike the Gulf of Lion, in the South Balearic margin the salt diapirism refraction effect is hard to isolate: for instance, the WMF1 07-19 measurement seems to be exactly above the first upslope salt diapir (forming a NE-SE directed salt walls observable in multi-beam data) but it shows a value consistent with the nearby HF measurements. Driussi et al., (2015a) and [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF]. The HF are from WMF1 and WMF2 survey. Inset top right: multi-beam bathymetry acquired during WMF1-2 surveys showing the available HF measurements in the South Balearic margin. Position of Riba and Los Martines seamounts are from Rovere and Wurtz, (2015).

1). B) HF variation along the Pre-Stack Depth Migration (PSDM) SaltFlu-03 profile, crossing from NW to SE the South Balearic margin. HF are indicated in plots above the profiles with black (measured value), blue (after refraction correction) and red (after sedimentation correction) points. Thin lines above seafloor indicate the HF measurements location. Crustal segmentation is taken from

Discussion

We have detailed the heat flow variation along five seismic profiles crossing the South-Balearic and the Gulf of Lion margins, and in the deep basin of the Hannibal Area. Along the margins, locally, we pointed out strong surface HF anomaly, as earlier observed by [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF]. In the deep basin, however, the surface HF do not show the same short-wavelength anomalies. We have shown that sedimentation has an important effect on the surface heat flow in the Western Mediterranean (up to 20%), but it does not allow to explain most of the observed anomalies. In the deep basins where the sedimentary infill is thick and rather uniform, the observed heat flow variation are of long-wavelength scale (Gulf of Lion and Hannibal area profiles). When corrected for sedimentation, different heat flow regimes are pointed out for the deep Liguro-Provencal, Algerian and West Algeria basins. These could be interpreted as expression of crustal level heat flow. The age of the underlying oceanic crust could explain different heat flow levels. The higher heat flow in the West Algerian basins compared to the East Algerian and Provencal basin corresponds to the younger age of opening of this part of the Western Mediterranean. On the other hand, the short-wavelength heat flow anomalies can often be correlated to variations in sedimentary thickness, deformations of the Messinian salt layer or basement highs.

In the following paragraphs we discuss the main processes that seem to play an important role in the observed surface heat flow anomalies on the Western Mediterranean margins.

Salt refraction

The deep basin in the Gulf of Lion is characterised by several vertically evolved salt structures deforming the seabottom. The KF-25 measurement was acquired above a large salt diapir that deforms the seabed for about two kilometres in width and about five kilometres in length in an approximate N-S direction (Fig. 5.7). The HF value reaches 153 mW/m 2 , which is significantly higher than the average HF in the Gulf of Lion (about 66 mW/m 2 ). In addition, Anomalous thermal structure around salt is well documented (e.g. [START_REF] Corrigan | Heat flow and gravity responses over salt bodies: A comparative model analysis[END_REF][START_REF] Nagihara | Geothermal heat flow in the northeast margin of the Gulf of Mexico[END_REF]. Near-surface heat flow anomalies are generally associated with salt bodies as a result of the higher thermal conductivity of halite relative to that of other sedimentary rocks. Given its quasi-impermeability, the thermal conductivity for salt range between about 5.0 and 8.0 W/mK (e.g. Roberston, 1988). The salt channelizes the heat along diapirs or other salt structures, affecting the surface HF measurements. Surface HF measurements may suggest the presence of a buried salt structures but at the same time bias the understanding of deep crustal thermal regime. The positive anomaly in the Gulf of Lion (Fig. 5.7) is therefore interpreted as the consequence of the high thermal conductivity of the salt structure, which therefore acts as a heat pumping towards the surface. Precisely below the anomalously low values (Fig. 5.7), we do not have any seismic profiles that might suggest a salt influence.

Nevertheless, according to several authors (e.g. [START_REF] Nagihara | High heat flow anomalies over salt structures on the Texas continental slope, Gulf of Mexico[END_REF][START_REF] Mello | Role of salt in restraining the maturation of subsalt source rocks[END_REF] the low anomalies could still be due to the influence of the salt diapir, which cools the sedimentary sequences around it. This effect would be especially noticeable in the case of vertical structures, such as salt stocks and walls. In the case of anticlinal structures we would expect a smaller amplitude of temperature variations. The magnitude of the surface influence from salt refraction is thus mainly given by: i) the depth of the salt structure, ii) the geometry of the structure (size, shape..), iii) the basal thermal regime [START_REF] Nagihara | High heat flow anomalies over salt structures on the Texas continental slope, Gulf of Mexico[END_REF]. In the case of the Western Mediterranean, the measurements where the salt structures influence is well constrained are few. The salt diapirs deforming the seabottom are mostly located in the western Algerian and Gulf of Lion basins. However, no clearly anomalous surface HF values have been recorded other than those described above in the Gulf of Lion.

Hydrothermal fluids circulation

In the Gulf of Lion, from the lower slope all along the deep basin (in the OCT and oceanic domains), most of the values are in the range between 50 and 70 mW/m 2 (Fig. 5.4). In the OCT domain, the basement is never outcropping and remains buried for more than 5 km of sediment deposited since the Oligo-Miocene (Figs. 5.4, 5.8). Furthermore, the basement does not present marked roughness and apart from a few recent episodes of volcanism interpreted at the SE of the Menorca basin (e.g. [START_REF] Pellen | The Minorca Basin: a buffer zone between the Valencia and Liguro-Provençal Basins (NW Mediterranean Sea)[END_REF][START_REF] Maillard | Transfer zones and associated volcanic province in the eastern Valencia Basin: Evidence for a hot rifted margin?[END_REF] it does not present any noticeable uplift or outflow of volcanic material. There are no surface heat flow anomalies, except above the salt structures (Fig. 5.4).

The South Balearic margin shows local variations of the order of 10-20 km between measurements, with minimum and maximum values (0.8-163 mW/m² along the SaltFlu 03 profile) often very close to each other (Figs. 5.5, 5.6). In the SMB margin (Fig. 5.5A), the OCT domain is narrow (from Driussi et al., 2015a) and the transition between continental and transitional domain is marked by a high positive anomaly (WMF2 02-05; 126.3 mW/m 2 ). This area is also associated with the presence of listric faults rooted on the base salt caused by the salt gliding towards the deep basin (gravity gliding mechanism). The basinward-dipped listric faults dislocate the seabed and may act as preferential directions for fluid upwelling. In addition, early salt sliding (Lower Pliocene) creates salt weld zones where pre-salt sediments are in direct contact with the UU. In the continental domain, two anomalously low values (WMF2 01-06 and 02-01; 56 and 65.3 mW/m 2 , respectively) are recorded near a step of the seafloor and the underlying basement, interpreted about 400 m below (Fig. 5.5A; km 50). Similar values are recorded close to this structural high by [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF]. This area, characterised by thin sedimentary cover (plot on fig. 5.8), can be interpreted as recharge area because of the low HF, the shallow basement and the thin sedimentary cover. The discharge area, however, is more difficult to observe: it could be located about 30 km downstream and use the listric faults as a preferential direction of flow rising (Fig. 5.5A; km 80-90). Moreover, the pockmark-like structure observed (Fig. 5.9) confirms an active interaction between shallow fluid and seafloor in this area. Pockmarks are circular to elliptical depressions at the seafloor that result from the vertical focused venting/expulsion of fluids from shallow reservoirs [START_REF] Judd | Seabed fluid flow: the impact on geology, biology and the marine environment[END_REF][START_REF] Moss | Evidence for fluid migration following pockmark formation: Examples from the Nile Deep Sea Fan[END_REF]. These kind of structures can be buried [START_REF] Bertoni | Messinian evaporites and fluid flow[END_REF] or at the seafloor and can be connected to the source regions via pipes.

The discharge area in the South Balearic margin could be situated along the slope and/or in the OCT domain (Fig. 5.6B). According to [START_REF] Gal | Traçage thermique et géochimique des systèmes hydrothermaux: exemple d'un domaine océanique jeune et d'une marge continentale[END_REF], in this area refraction effects from structural highs in the basement do not seem to affect surface HF measurements. A significant uplift of the basement is recorded in the lower slope, at the boundary with the deep basin (Figs.

5.6, 5.10). The basement dislocated at various points, the thin pre-salt and the several welds suggest a basement to surface fluid transfer possible. This correlation of low and high heat flow anomalies with potential recharge and discharge area suggest a heat redistribution by a regional hydrothermal fluid circulation system.

Hydrothermal circulation models are well known in the ocean at the ridge flanks. In the oceans the low heat flow measured on young ridge flanks compared to the predictions based on plate cooling models has been the basic proxy that has led to the interpretation of a rigorous hydrothermal circulation near the ridges [START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF][START_REF] Hasterok | Oceanic heat flow: Implications for global heat loss[END_REF]. Several studies attest the presence of recharge and discharge areas where fluids can flow into the uppermost part of the basaltic basement which is considered more permeable than the sediments and travel tens of kilometres laterally [START_REF] Davis | FlankFlux: An experiment to study the nature of hydrothermal circulation in young oceanic crust[END_REF]Fisher et al., 2003a;[START_REF] Langseth | Heat transfer in the oceanic crust of the Brazil Basin[END_REF][START_REF] Hutnak | Hydrothermal recharge and discharge guided by basement outcrops on 0.7-3.6 Ma seafloor east of the Juan de Fuca Ridge: Observations and numerical models[END_REF][START_REF] Lucazeau | Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden[END_REF]. The most important factors influencing hydrothermal circulation are the thickness of the sedimentary cover [START_REF] Davis | FlankFlux: An experiment to study the nature of hydrothermal circulation in young oceanic crust[END_REF][START_REF] Lister | On the thermal balance of a mid-ocean ridge[END_REF], the density of structural highs in the basement outcropping (or approaching) the surface and the presence of fractures [START_REF] Lucazeau | Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden[END_REF][START_REF] Hasterok | Oceanic heat flow: Implications for global heat loss[END_REF]. [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF], Afhilado et al., (2015), Driussi et al., (2015a), [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF], Aidi et al., (2018). The yellow colour in the profile indicates the sedimentary thickness above basement. The plot represents the surface measured HF with respect the sedimentation thickness above basement for each profile. The dashed ellipse represents the HF variations in areas of thin sedimentary thickness, so more likely to be affected by fluid circulation. The dashed horizontal black lines represent, for each crustal segment, the average measured surface HF with the corresponding value noted. Note the very low HF values on the South Balearic associated with a low sedimentary thickness. The map in the centre represents all the available surface HF in the Western Mediterranean Sea superposed to the crustal segmentation taken from [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. The scale is the same for all the profiles.

In the Western Mediterranean Sea, we are not in a context of oceanic crust formation, as the last formed oceanic crust is found in the Western Algerian basin (whether it is oceanic crust) dating back at least 8 Ma [START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF] or more (e.g. [START_REF] Van Hinsbergen | Origin and consequences of western Mediterranean subduction, rollback, and slab segmentation[END_REF], 2014). However, we have shown how in the OCT domain, several scenarios could also make this area prone to hydrothermal circulation, such as basement outcrops, basaltic intrusions or recent volcanism. The direction of fluids transport is difficult to estimate: although there is a clear difference in heat flow between the upslope and lower slope domains (Fig. 5.6) that suggests a preferential fluid direction towards the SE, we have no clues to estimate whether the discharge of the flows could also be further north, in the northern Formentera basin. A fluid upwelling towards the upper slope domain has been interpreted by [START_REF] Lucazeau | Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden[END_REF] in the Gulf of Aden. Here, a basement high in the deep domain is interpreted as a recharge zone (very anomalous low HF) while the discharge zone appears to be located towards the continental domain, in the lower slope. Although discharge zones are often more difficult to interpret, the South Balearic margin proves to be an area largely affected by fluid circulation. Pockmarks, mud volcanoes and recent volcanic activity (Pleistocene, [START_REF] Acosta | Sea floor morphology and Plio-Quaternary sedimentary cover of the Mallorca Channel, Balearic Islands, western Mediterranean[END_REF] could play a role in the fluid distribution pattern of this margin.

In the deep basin of the Western Mediterranean, where crustal nature is probably oceanic, sedimentary thickness is on average greater than 1 km (Fig. 5.3), which makes fluid circulation difficult to influence surface HF (Fig. 5.4). In the deep Algerian domain, [START_REF] Gal | Traçage thermique et géochimique des systèmes hydrothermaux: exemple d'un domaine océanique jeune et d'une marge continentale[END_REF] discarded the hypothesis of regional hydrothermal circulation: the analysed fluid collected during WMF1 show only brines fluid flowing on the surface. In addition, salt deposited in the Messinian age throughout the whole deep basin and covering the oceanic crust everywhere, acts as an additional impermeable layer that separates the basement from the seafloor. Although the salt is not completely impermeable and is subject to faults and fractures that aid the fluid migration [START_REF] Davison | Faulting and fluid flow through salt[END_REF]Schoenherr et al., 2007b;Bertoni and Cartwright, 2015a;[START_REF] Warren | Evaporites through time: Tectonic, climatic and eustatic controls in marine and nonmarine deposits[END_REF][START_REF] Dale | The Messinian Salinity Crisis as a trigger for high pore pressure development in the Western Mediterranean[END_REF], its permeability is significantly lower than the sediments surrounding it. In the deep basin, the sedimentary (including thick salt) blanketing probably play a major role in equalising surface HF. The sedimentary thickness above the basement may inhibit the cooling through fluid circulation of the underlying crust, affecting the subsidence and thus the current basement geometry (e.g. [START_REF] Lizarralde | Variation in styles of rifting in the Gulf of California[END_REF][START_REF] Lucazeau | Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden[END_REF][START_REF] Marton | Evolution of the Angolan passive margin, West Africa, with emphasis on post-salt structural styles[END_REF].

Gypsum dehydration

Along the SaltFlu profile, in the OCT domain, several polygonal faults are rooted on the UU and Early Pliocene sequences (Zoom B,fig. 5.10). This area has previously been interpreted as suffering from gypsum dehydration in the UU [START_REF] Wardell | Seismic evidence for Messinian salt deformation and fluid circulation on the South Balearic margin (Western Mediterranean)[END_REF][START_REF] Bertoni | Messinian evaporites and fluid flow[END_REF]. The gypsum-anhydrite transition can cause brine release and is mainly temperaturepressure dependant [START_REF] Jowett | Predicting depths of gypsum dehydration in evaporitic sedimentary basins[END_REF]. Recently, [START_REF] Dale | The Messinian Salinity Crisis as a trigger for high pore pressure development in the Western Mediterranean[END_REF] discussed in the same area the dehydration of gypsum with the aid of a 1-D model. According to the authors, the fluids released from evaporitic dehydration is possible only with heat flow exceeding 105 mW/m 2 and low thermal conductivities of the UU (1-1.5 W/m/). Although the thermal conductivity remains uncertain at this depth, this work shows that the thermal gradients (113.2, 90.1, 78.1 °C/km) and the heat flow (126.8; 103.6; 86.8 mW/m 2 ) above the polygonal faults are high well above the thermal gradient used by [START_REF] Dale | The Messinian Salinity Crisis as a trigger for high pore pressure development in the Western Mediterranean[END_REF] in their models (36 °C/km). Whether this area is affected by gypsum-anhydrite transformation or by disequilibrium compaction-related hydro fracturing [START_REF] Dale | The Messinian Salinity Crisis as a trigger for high pore pressure development in the Western Mediterranean[END_REF], the brine released could aid dissolution and migration of fluids to the surface through fractures and faults in Plio-Quaternary deposits (Fig. 5.10). Moreover, the Messinian evaporites may be crossed by fluids from the pre-salt once the threshold pressure is exceeded: dissolution and diagenesis will subsequently guide the path migration of these fluids up to the post-Messinian deposits [START_REF] Bertoni | Messinian evaporites and fluid flow[END_REF].

Volcanism

We have shown how the basement highs seem to play a key role on create pathways and aid the fluid circulation, especially when the structures are buried by thin sediment thickness as in the South Balearic margin. Instead, in the oceanic crustal domain, the sedimentary thickness above the basement is usually thick. The only area where the basement is shallow due to the action of suggested volcanic structures (Aidi et al., 2018;[START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF] is the Hannibal Area (Fig. 5B). Here, several high basement structures deform all the sedimentary sequence overlying basement. Despite the profile low resolution, some faults displacing the Upper Unit and Plio-Quaternary sequences are depicted in the western sector of the Hannibal Area. This area is characterised by a shallow volcanic structure deforming the Messinian units: there appears to be little or no salt, which could favour the rising of fluids through salt welds (Fig.

5.5B

). Nevertheless, the even more piercing eastern structure (km 150, fig. 5.5) does not seem to influence the HF values at the surface. To generate surface heat flow variations of at least 40-50 mW/m 2 , volcanism must be very recent (<0.1-0.2 Ma) and at crustal depth of < 5-10 km [START_REF] Rikitake | Intrusion and Cooling of Magma Comparison between 2D and 3D Analyses[END_REF][START_REF] Ritter | Heat flow in the Vøring Basin, mid-Norwegian shelf[END_REF]. However, the emplacement of volcanic structures can cause overpressure and thus heating the basement and the surrounding sediments. This event can generate gas due to the thermal cracking of organic matter or reduce the intensity of the fluids which then rise to the surface [START_REF] Berndt | Rifting under steam-How rift magmatism triggers methane venting from sedimentary basins[END_REF]Kjoberg et al., 2017). The volcanic structures, later than the margin formation, could therefore, through welds in the salt and fractures in the Plio-Quaternary sequence, generate warm fluid circulation which reach the surface and increase surface heat flow. However, the density of measurements in the Hannibal Area is still too sparse to allow a suggestion of active deep fluid circulation, as observed in ridge systems in the Pacific Ocean (e.g. Hutnak et al., 2008;[START_REF] Wheat | Cool seafloor hydrothermal springs reveal global geochemical fluxes[END_REF] or in the mid-Atlantic (e.g. [START_REF] Becker | Leg 174B synopsis: revisiting Hole 395A for logging and long-term monitoring of off-axis hydrothermal processes in young oceanic crust[END_REF][START_REF] Gal | Heat flow, morphology, pore fluids and hydrothermal circulation in a typical Mid-Atlantic Ridge flank near Oceanographer Fracture Zone[END_REF].

Crustal segmentation

Considering the heat flow variation discussed above, we can try to estimate an average regional basement heat flow for the different crustal segmentation. Despite the newly acquired heat flow measurements, the density of the measurements is still too weak to allow a detailed study of crustal thermicity. Nevertheless, some trends can be discussed using the new and old available measurements (Figs. 5.8,5.11). We considered all available values, including the previously described anomalies, discarding in one case only the positive anomalous values related to the presence of salt structures. The small-scale wavelength anomalies previously described are included in the regional heat flow analysis: the presence of large areas with positive or negative anomalies may be characteristic of a certain crustal nature and should be included in the average values. In contrast, positive anomalies given by salt structures in the LPB are easily discriminated. In this case an average by considering the values and an average by discarding them has been showed.

The average values in the continental crust seem to be relatively similar between the Gulf of Lion and the South Balearic margin (around 65 Mw/m 2 ), while they are higher in the Sardinian margin (79 mW/m 2 ) (Figs. 5.8,5.11) confirming the measurements observed by [START_REF] Lucazeau | Heat flow, heat production and fission track data from the Hercynian basement around the Provençal Basin (western Mediterranean)[END_REF]. The Sardinian margin is also warmer in the continental and OCT domains, as observed by [START_REF] Burrus | Contribution to the thermal regime of the Provençal Basin based on FLUMED heat flow surveys and previous investigations[END_REF] and [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF]. The OCT domain shows anomalously high values only in the South Balearic margin, where we previously suggested a discharge zone of upslope fluids. In the Liguro-Provençal basin, a heat flow segmentation is hardly interpretable: between the thinning continental crust and the OCT domains, the averaged values are similar, both in the Gulf of Lion and in the Western Sardinian (Fig. 5.8 and 5.11). In oceanic crust, the values increase by about 15% and 28% for the Western Sardinian and Gulf of Lion margin, respectively. The average values at the basement ( 79Mw/m 2 ) are lower than those predicted by the plate cooling model for an oceanic crust of LPB age, although it should be noted that the available corrected values are few and scattered (5.11).

The oceanic crust in LPB shows similarities with the proto-oceanic crust interpreted in the Santos basin [START_REF] Klingelhoefer | Imaging proto-oceanic crust off the Brazilian Continental Margin[END_REF], formed at the onset of the seafloor spreading at subdued spreading rates. The proto-oceanic crust could be formed before a more typical oceanic crust and associated to the lower crust/mantle exhumation process occurred in the transitional domain [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF]Aslanian et al., 2019).

In the South Balearic margin the averaged values between OCT and oceanic crust are similar, while the values in the continental domain are lower (Fig. 5.8). The similar thermal regime between the two domains could be associated with a similar crustal nature between the two domains or, as shown above, the effect of regional discharge zone close to basement highs.

The basement HF values compared with the plate cooling model confirms a younger west

Algerian basin compared to the EAB [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF]. The OCT domain of the Gulf of Lion is interpreted by some authors as made by lower continental crust and/or mantle exhumation [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Jolivet | Continental breakup and the dynamics of rifting in back-arc basins: The Gulf of Lion margin[END_REF]. During passive margin formation, the exhumation phase [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF] can be characterised by the outcrop of mantle peridotite at the surface, which once hydrated form serpentine (e.g. [START_REF] Manatschal | New models for evolution of magma-poor rifted margins based on a review of data and concepts from West Iberia and the Alps[END_REF][START_REF] Lucazeau | Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden[END_REF].

In addition to being an exothermic chemical processes, the serpentinization seems to be accompanied by a large hydrothermal heat loss due to the role of meteoric fluid circulation In the case of the uncorrected measurements (for sedimentation), we were able to retain all available measurements, both old and newly acquired. In the case of the corrected measurements, we were forced to retain only the new measurements in which the sedimentation correction was made (refer to map in Fig. 5.3). [START_REF] Cannat | Oceanic corrugated surfaces and the strength of the axial lithosphere at slow spreading ridges[END_REF]. However, where the serpentinized mantle is locally dredged (e.g. Iberian margin, [START_REF] Boillot | Undercrusting by serpentinite beneath rifted margins[END_REF], the present-day HF seems to be unaffected both by the serpentinization process itself and by hydrothermal circulation associated [START_REF] Louden | Variations in heat flow across the oceancontinent transition in the Iberia abyssal plain[END_REF].

The lower continental crust exhumation [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Bott | Evolution of young continental margins and formation of shelf basins[END_REF][START_REF] Huismans | Depth-dependent extension, two-stage breakup and cratonic underplating at rifted margins[END_REF] process is still poor known as well as its thermal regime implication. This process would imply a hot, weak lower crust exhumation towards the rift axis (e.g. [START_REF] Huismans | Depth-dependent extension, two-stage breakup and cratonic underplating at rifted margins[END_REF]. In the Gulf of Lion, heat flow in the OCT domain do not appear to record influences from exhumation prior to the break-up and/or by hydrothermal circulation.

Fluids from the exhumation of lower continental crust and/or mantle in the OCT may be trapped by the Messinian salt resulting in an increase in pressure and temperature at the base of this level. Overpressures below salt is a well-known phenomenon in petroleum engineering (e.g. [START_REF] O'brien | Understanding subsalt overpressure may reduce drilling risks[END_REF][START_REF] Dale | The Messinian Salinity Crisis as a trigger for high pore pressure development in the Western Mediterranean[END_REF]. The effect that these overpressures and temperature anomalies have on salt tectonics, however, is a topic that is still little debated by the scientific community.

Conclusion

The newly acquired data (WMF2) have allowed to add a total of 54 heat flow measurements, mostly distributed in the south Balearic margin. The analysis of the detailed new and old surface heat flow measurements allowed us making the following conclusion on the thermal regime in the Western Mediterranean:

1. Small-wavelength surface HF anomalies, thin sedimentary cover, nearly outcropping basement, pockmarks structures, recent volcanic activity, gypsum dehydration phenomena and seismic signatures in the South Balearic margin (continental and OCT crustal domains) suggest the presence of fluids circulation and percolation systems in the sedimentary column and probably upper basement. Further geochemical analysis could confirm this hypothesis. Firstly, between the South Formentera basin, characterized by very low HF (0.8-57 mW/m 2 ), and the Emile Baudot Escarpment, characterized by higher measurements (63-127 mW/m 2 ),where basement outcrop and young volcanism prevail, a possible fluid circulation systems is interpreted. Secondly, we showed some heat flow anomalies (127; 104, 87 mW/m 2 ) at the foot of the Emile Baudot Escarpment coincident with the area previously interpreted as affected by gypsum-anhydrite dehydration.

2. Some local very high anomalies are associated to salt diapirism (153, 130 mW/m 2 ). This is well shown in the OCT of the Gulf of Lion, but could also explain some anomalies in the OCT and oceanic domains of the South Balearic margin.

3. In the deep basins (Provencal and Algerian basins), fluid circulation appears to be inhibited by the thick sedimentary blanket separating the basement from the surface.

Longer wavelength variation are believed to express here crustal levels processes (Algerian: 71-113 mW/m 2 ; Provençal: 66-89 mW/m 2 ).

4. An attempt has been made to define the regional basement heat flow levels for the different crustal segmentations. In the Liguro-Provençal basin a clear variation is only observed between the continental/transitional domain and the oceanic crust. The latter is also colder (LBP mean of 89 mW/m 2 , not corrected) than expected from plate cooling model, which could be characteristic of the proto-oceanic nature. In the South Balearic margin, a well thermal segmentation is observed between the continental and the transitional-oceanic domains, suggesting both a similar crustal nature between the two domains or a transitional domain largely affected by fluid circulation.

Evolution of thermal regime in a kinematic 2D approach

In the previous chapter we discussed the present-day surface heat flow measurements in the Western Mediterranean Sea. We have seen how the crustal thermal regime can be influenced by surface and local processes such as fluid upwelling, salt tectonics and basement morphology.

An understanding of the deep thermal regime, thus linked to crustal segmentation, has been tricky by its interaction with more shallow phenomena. In this chapter we apply the opposite approach by predicting the thermal regime (present but also past) from a basin modelling study.

We will focus on two transects in the Liguro-Provençal and Western Algerian basins (Fig. 5.12)

with the help of the thermo-kinematic model MARGE (description in chapter 3). The model has been applied on two profiles perpendicular to the Gulf of Lion and the South Balearic margins (Fig. 5.13) and it could give information about the temperature variation during the evolution of the margin and at different sedimentary units, including Messinian salt level.

The main addressed question were:

• • What is the temperature range at the base of salt from its deposition to present-day? Are there temperature differences between transitional and oceanic domains in the salt layer?

The numerical model MARGE is a 2D extension model including many second-order phenomena designed to reconstruct the evolution of rift basins and passive margins at both lithospheric and basins scales. MARGE reconstructs the evolutionary history of the margin based mainly on the present-day bathymetry, the given lithospheric parameters and the interpreted stratigraphic sequence.

MARGE is constrained by a set of input parameters and laws that can be set by the operator according to the observations. The main input data are the sedimentary layers, their physical properties and age constrain. For the initial crustal configuration and associated physical parameters (in particular the thermal ones: heat production and thermal conductivity) common values are used which will be further fine-tuned in the modelling. The so-called "control"

parameters are mainly the mean square error between the calculated and observed bathymetry and the crustal thinning, compared to that obtained by refraction seismic (when available). In

Gulf of Lion model

Input parameters

The stratigraphy of the Gulf of Lion and the Liguro-Provençal basin has been widely investigated, highlighting syn-rift (e.g. [START_REF] Gorini | Géodynamique d'une marge passive: le Golfe du Lion (Méditerranée occidentale[END_REF][START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF], Oligo-Miocene [START_REF] Mauffret | Tectonics and deep structure of the northwestern Mediterranean Basin[END_REF][START_REF] Bache | Evolution Oligo Miocène des marges du micro océan Liguro-Provençal[END_REF], Messinian and Plio-Quaternary sequences (Lofi et al., 2003;[START_REF] Droz | Quaternary turbidite systems on the northern margins of the Balearic Basin (Western Mediterranean): a synthesis[END_REF][START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF][START_REF] Leroux | High-resolution evolution of terrigenous sediment yields in the Provence Basin during the last 6 Ma: relation with climate and tectonics[END_REF] (see also chapter [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. For lithosphere parameters references refer to the text.

The age and the limits of the sequences are interpreted based on the previously works of [START_REF] Leroux | Post-rift evolution of the Gulf of Lion margin tested by stratigraphic modelling[END_REF][START_REF] Leroux | High-resolution evolution of terrigenous sediment yields in the Provence Basin during the last 6 Ma: relation with climate and tectonics[END_REF], carried out from the shelf to the deep basin of Gulf of Lion, and on this work. The radioactive minerals that cause the highest heat flow production are unevenly distributed in the stratigraphic sequences. Since wells reaching the basement are not available in the deep basin, an approximation was necessary. In the sedimentary sequences, the heat production spans from 0.1 uW/m 3 for the salt to 5.5 uW/m 3 for shale mudrocks [START_REF] Rybach | Amount and significance of radioactive heat sources in sediments[END_REF], also accordingly to other works (e.g. [START_REF] Mckenna | Radiogenic Heat Production in Sendimentary Rocks of the Gulf of Mexico Basin, South Texas[END_REF][START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF][START_REF] Gernigon | A moderate melting model for the Vøring margin (Norway) based on structural observations and a thermo-kinematical modelling: Implication for the meaning of the lower crustal bodies[END_REF]. Similarly, the lithospheric heat production values (divided into upper crust, lower crust, upper mantle and oceanic crust) chosen are in agreement with [START_REF] Schatz | Thermal conductivity of earth materials at high temperatures[END_REF]; [START_REF] Norden | Heat flow and lithospheric thermal regime in the Northeast German Basin[END_REF]; [START_REF] Majorowicz | Thermal properties of the crust and the lithosphereasthenosphere boundary in the area of Poland from the heat flow variability and seismic data[END_REF]; [START_REF] Beaumont | On the evolution of rifted continental margins: comparison of models and observations for the Nova Scotian margin[END_REF] highlighting an higher heat production in the upper continental crust compared to the lower continental crust and upper mantle (Fig. 5.15). The initial lithospheric crustal structure and thickness is taken by the unthinned continental crust described by wide-angle refraction data in the profile shown in [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF], which is coincident with the reflection seismic profile used.

The model need the setting of the basal temperature, which is the temperature at the base of lithosphere at the boundary with the asthenosphere. We have referred to the value of 1333 °C, defined by Parlson and Sclater, (1977) and [START_REF] Sclater | The heat flow through oceanic and continental crust and the heat loss of the Earth[END_REF] using observational data of oceanic crust bathymetry in various area. This values correspond to three quarters of the pyrolite melting temperature [START_REF] Mckenzie | Some remarks on the development of sedimentary basins[END_REF][START_REF] Hantschel | Fundamentals of basin and petroleum systems modeling[END_REF]. Several authors agree on basal temperature lithosphere ranging from 1250 to 1350 °C [START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF][START_REF] Jaupart | The thermal structure and thickness of continental roots[END_REF][START_REF] Mckenzie | The volume and composition of melt generated by extension of the lithosphere[END_REF]. The sea-bottom temperature is set at 13 °C after direct measurements during WMF surveys [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF]. Effect of regional isostasy in the Gulf of Lion transect have been tested. We tried the regional isostasy (see Annexe-2) but the predicted subsidence and crustal structure was not better than those predicted by local isostasy (also in agreement with [START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF].

Since the variation in heat flow was minimal, a local isostasy (Airy) was maintained for the other tests.

The rifting phases that led the present-day structure and thickness of the crust are other input parameters to be set. There is a good agreement on the Liguro-Provençal rifting period as well as the present-day crustal structure. The rifting period was therefore set, as required by MARGE, as followed: -30-20.4 Ma (rifting period); -20.4-16 (oceanisation) and 16-0 Ma (relaxation) according to (e.g. [START_REF] Gorini | Géodynamique d'une marge passive: le Golfe du Lion (Méditerranée occidentale[END_REF][START_REF] Séranne | The Gulf of Lion continental margin (NW Mediterranean) revisited by IBS: an overview[END_REF]Réhault et al., 1984;Gattacceca et al., 2007) (Fig. 5.15).

A difference in depth between the continental and oceanic domains (150 and 90 km, respectively) (Fig. 5.16) is set, as depicted for instance in the Angolan margin [START_REF] Lucazeau | Dynamic interactions between the Gulf of Guinea passive margin and the Congo River drainage basin: 2. Isostasy and uplift[END_REF]. Between the two domains, a zone of transition has been imposed where thickness decrease linearly towards the oceanic domain. The thinning of the lithosphere occurred during the rifting phases, linearly, until the beginning of the formation of the oceanic crust, where the lithosphere reached a set thickness of 90 km. As previously observed [START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF] the temperature consequences are not important enough but this helps to increase buoyancy in the OCT domain.

Results for reference model -Gulf of Lion

The best fit with the reconstructed bathymetry, gravimetry and crustal thickness was found in the reference model (Fig. 5.17). The measured heat flow are not used as a control parameter but they are subsequently compared to the thermal model outputs. From the reference model [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. Note the good fitting concomitant with the thinnest crustal domain.

we carried out several further tests with the aim of understanding which parameters (that can be changed as input) influence the surface HF. These tests, not presented in the manuscript, are briefly explained in the Annexe-2 as they are not strictly related to the objective of this thesis. ). The difference in heat flow between the oceanic and transitional domains is more pronounced immediately after the end of oceanic crust formation, while it is more uniform at present-day and 5.9 Ma. At the Messinian epoch, heat flow appear to be about 20 % higher than today. Note also the difference between surface and basement HF: at 16 Ma the difference is small because there is little sedimentation, while today the difference can be higher especially in the continental domain, where heat production is more significant. The values calculated at 0 Ma compared to the average values measured at the surface (not corrected for sedimentation, refer to fig. 5.11, chapter 5.2), show higher measured values in the continental domain, slightly higher values (5-10 Mw/m 2 ) in the transitional domain and significantly higher values in the oceanic domain (20 mW/m 2 ).

Results for partial melting and serpentinization

Following some authors [START_REF] Mckenzie | The volume and composition of melt generated by extension of the lithosphere[END_REF][START_REF] Wilson | Magmatism and the geodynamics of basin formation[END_REF], during the evolution of rifting to oceanic spreading, if stretching is rapid, the pressure within the lithosphere may drop below the melt solidus, with the result of a mantle partial melting. The melt formed in the mantle will then be located below the Moho as a result of low crustal density. The thermo- kinematic model makes possible to inhibit this phenomenon, thus assuming that there is no partial melting in the mantle or, using the model of [START_REF] Mckenzie | The volume and composition of melt generated by extension of the lithosphere[END_REF], allowing magma to form during stretching. We performed some tests to understand the magma formation impact on surface heat flow (Annexe-2). The extreme thinning of the transitional crust associated with magma emplacement is not in agreement with the crustal structure described in [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF] after refraction data. Moreover, the model allows to test the serpentinization process, described as an exothermic process subsequent to the mantle exhumation given by water circulation (e.g. [START_REF] Boillot | Ocean-continent boundary off the Iberian margin: a serpentinite diapir west of the Galicia Bank[END_REF][START_REF] Le Douaran | Deep structure of the north-western Mediterranean Basin: Results of a two-ship seismic survey[END_REF][START_REF] Chamot-Rooke | Constraints on Moho depth and crustal thickness in the Liguro-Provençal basin from a 3D gravity inversion: geodynamic implications[END_REF]. Nevertheless, the serpentinization process does not impact present-day surface heat flow (Annexe-2) and is thus discarded in the reference model.

South Balearic margin

As carried out in the Gulf of Lion transect, several parameters have been tested in the South Balearic margin in order to get the result that best fits the available geophysical parameters in the area.

Input parameters

The seismic sections stratigraphy has been constrain by several studies in the Western Algerian basin. The major uncertainty lies in the resolution of the SaltFlu profile, which allows good imaging of Plio-Quaternary and Messinian sequences but highlights low resolution of deeper sequences (Fig. 5.13). For the interpretation, we therefore relied on profiles that cross the entire basin from north to south, also referring to several works by other authors [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF][START_REF] Blondel | Image improvement of Late Miocene (Messinian) to Plio-Quaternary units in the Algero-Balearic basin[END_REF].

As made in the Gulf of Lion, the heat production in the sediments is calculated by the model based on the average lithological and physical properties characteristic of each stratigraphic sequence (Figs. 5.19,5.20). The lithology for the Plio-Quaternary sequence is referred to the closest well available (DSDP 371, in the Hannibal Area, SE to the SaltFlu transect; [START_REF] Erickson | Down-hole temperature measurements, Deep Sea Drilling Project[END_REF]. Despite the relative remoteness of the well and the uncertainty on the pre-salt sedimentary sequences, the quality of the profile in depth and the studies carried out in this area have allowed us to be confident about the stratigraphy.

Conversely, the crustal segmentation is still uncertain in the western Algerian basin as well as the nature of the deep basin crust. The input continental crustal thickness in pre-rift situation CHAPTER 5. THERMAL REGIME IN THE WESTERN MEDITERRANEAN SEA 274 comes from work of [START_REF] Schettino | Plate kinematics of the Western Mediterranean region during the Oligocene and Early Miocene[END_REF] and Diaz and Gallart, (2009) while the oceanic crust thickness from wide-angle refraction data from [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF]. The basal ( 1333°C) and the seabottom (13°C) temperatures are set as boundary conditions temperature limits (see references above) (Figs. 5.19,5.20). In the case of regional isostasy, the flexural strength of the lithosphere is controlled by the 450 °C isotherm [START_REF] Burov | The effective elastic thickness (T e) of continental lithosphere: What does it really mean?[END_REF]Reemst and Cloething, 2000;[START_REF] Gernigon | A moderate melting model for the Vøring margin (Norway) based on structural observations and a thermo-kinematical modelling: Implication for the meaning of the lower crustal bodies[END_REF]. Using a regional isostasy, the model allows to modify the depth of necking, intended as the virtual level in the lithosphere that induces restoring forces to recover isostatic equilibrium, but, as seen in the Gulf of Lion transect, no major changes in surface heat flow were detected (see Annexe-2). For the reference model, a local isostasy (Airy) was therefore set (Fig. 5.20). The OCT limit in the South Balearic margin is still uncertain and, as well as the segmentation, the opening model are different. Our model is referred on a NW-SE transect, perpendicular to the margin. The opening model considered is therefore that of a passive margin with an opening axis parallel to the profile, NE-SW, according to some authors (e.g. [START_REF] Gelabert | A new proposal for the late Cenozoic geodynamic evolution of the western Mediterranean[END_REF]. We made several tests with the aim to observe the heat flow variations setting different crustal segmentation limits (see Annexe-2).

The best fitting with the gravimetry, present-day bathymetry and crustal thickness as shown in Vina Gaza, ( 2016), is found in the reference model, with an OCT limit according with Leroux separate points) for two ages: at the present day and at 5.3 Ma, i.e. the end of the Messinian Salinity Crisis. The aim was to understand whether, especially at the level of the base salt, the temperature could change between different crustal domains. In addition, the comparison of ages can reveal the temporal evolution of temperatures.

Results for reference model -South Balearic

In the Gulf of Lion we considered an imaginary well in the transitional crust and one in the oceanic crust (Fig. 5.13). The temperatures at the base of the salt, as shown in the graph at the present day (Fig. 5.22), are about 30 °C higher in the oceanic crust compared to the well in the transitional domain. Note also that the temperature curve in the oceanic crust has a higher gradient (blue line) than in the transitional crust (red line). At 5.3 Ma, the salt deposit is shallower as it is only underlain by the UU (still belonging to the Messinian). The temperature difference between the oceanic and transitional domains is smaller here as well as the difference in temperature gradient between the oceanic and transitional domains (Fig. 5.22).

In the South Balearic margin the difference in temperature at the base of the salt between the transitional and oceanic domains is smaller than in the Gulf of Lion (around 8°C), both at where the salt base in the oceanic domain is modelled about 500 m lower than the salt base in the transitional domain (Fig. 5.23). This reliably causes the temperature to be higher because the base salt reflector is deeper. However, this difference in base salt depth between the oceanic and transitional domains is not confirmed by the seismic data explained so far in this work (see chapter 4.2). Where the base salt depth is the same (Fig. 5.23), the temperature difference between the two crustal domains is close.

MARGE thermo-kinematic model limitations

The configure separately the thinning of the continental crust with that of the upper mantle (by varying the Beta factor), to account the heat production in the crust and sediments and to add the sedimentation processes (compaction, change in porosity..). In the oceanic crust, the thermal regime on MARGE is based on the classical plate cooling model [START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF], which is based on the age of the oceanic crust. In the transitional crust domain the basic model of lithospheric cooling depends mostly on crustal thinning and thus on crustal Beta Factor. Higher beta factor means higher heat flow. However, several studies in passive margins [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF][START_REF] Labails | Crustal structure of the SW Moroccan margin from wide-angle and reflection seismic data (the Dakhla experiment). Part B-The tectonic heritage[END_REF][START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Péron-Pinvidic | The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view[END_REF][START_REF] Geoffroy | Volcanic passive margins[END_REF][START_REF] Huismans | Complex rifted continental margins explained by dynamical models of depth-dependent lithospheric extension[END_REF], 2011) have revealed inconsistencies between Mckenzie's model of rifting formation and observations. One of the biggest differences is based on subsidence. Tectonic subsidence appears to be much smaller than post-break-up thermal subsidence, as observed in the Gulf of Lion, Iberian and Angolan margin (see chapter 1), which goes against the uniform stretching model. Nevertheless, we have seen how, especially in the Gulf of Lion transect, the calculated crustal thinning is coherent with wide-angle studies. As the thermal regime is mainly influenced by crustal thinning, a good fitting of crustal thicknesses would mean a reliable regional thermal regime at the present-day situation.

Another observation that seems to be inconsistent with the McKenzie model concerns a minimal extension of the system during rifting and subsequent oceanic drifting: the presence of few listric faults on the continental slope and the geodynamic reconstructions suggest that the system underwent far less extension than described in the models. Furthermore, an interaction of the mantle in the process of crustal thinning seems argued by different authors (e.g. Huismans andBeaumont, 2008, 2011). MARGE allows to model the thermal impact of some aspects of serpentinization and partial melting, but we observed that the long term impact is generally small. Also, the dynamics of these processes during the rifting phases and their impact on heat flow are still poorly understood by the scientific community. Some authors pointed out how these processes could be linked to fluid circulation which necessarily has an impact on the thermal regime of the margin (e.g. [START_REF] Cannat | Oceanic corrugated surfaces and the strength of the axial lithosphere at slow spreading ridges[END_REF][START_REF] Louden | Variations in heat flow across the oceancontinent transition in the Iberia abyssal plain[END_REF][START_REF] Boillot | Undercrusting by serpentinite beneath rifted margins[END_REF].

As fluid circulation and the associated advective heat transport is not implemented in the MARGE code, the impact of these processes could not be estimated during our modelling study.

As noted above, the temperatures obtained at the base of the salt are mostly influenced by the depth and the crustal thinning and not directly by the crustal nature itself. In fact, in MARGE model the crustal nature only plays a major role in heat production and, as far as oceanic crust is concerned, by the age of its formation. Moreover, mantle and/or lower crust exhumation [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Jolivet | Continental breakup and the dynamics of rifting in back-arc basins: The Gulf of Lion margin[END_REF] cannot be modelled by MARGE. We could therefore not study the impact of these processes.

The temperatures found by MARGE reflect the influence of several parameters that are taken into account by the model, but cannot analyse others. The temperatures are therefore a first step from which to discuss the difference of the thermal regime according to the crustal segmentation. The model confirms that crustal thinning is a fundamental parameter in the study of the thermal regime. The influence of other processes, such as exhumation and crustal nature processes associated (as fluids circulation), are still poorly understood and the model does not help to resolve them.

Thermal regime segmentation and impact on salt deformation

In chapter 5.2 we described the new heat flow measurements acquired during the WMF2 Balearic margins. However, we also discussed that the used thermo-kinematic model does not allow to take into account some of the processes involved in rifting formation that may have influenced the temperature (e.g. lower continental crust/mantle exhumation). In the following, I will summarise and discuss the main clues extracted from this chapter.

Main observations in the Liguro-Provençal basin and Gulf of Lion-Western Sardinian conjugated margins:

-Hotter continental and transitional domains in the Western Sardinian margin compared to the Gulf of Lion. This confirms the statement of several authors, including [START_REF] Burrus | Contribution to the thermal regime of the Provençal Basin based on FLUMED heat flow surveys and previous investigations[END_REF] and Della [START_REF] Vedova | Heat flow in the tectonic provinces crossed by the southern segment of the European Geotraverse[END_REF].

predicted by the plate cooling model for the LPB oceanic formation age (Fig. 5.24).

Several hypotheses may coexist, including a colder nature of the proto-oceanic crust or a more significant influence of sedimentation effect than predicted and calculated.

-Fluids appear to be inhibited by the thick sedimentary blanket (including at least one km of halite) and a regional homogeneity of the basement. In the deep basin, surface [START_REF] Carlson | On modeling the thermal evolution of the oceanic upper mantle: An assessment of the cooling plate model[END_REF].

heat flow are mainly disturbed by refraction of salt diapirs, especially when the salt structures deform the seafloor and are of significant size.

-The continental and OCT domains show similar thermal regime, both in GoL and WS (64/77 for the continental and 66/75 mW/m 2 for the OCT domain, for the Gulf of Lion/western Sardinia, respectively) (Fig. 5.24).

In the South Balearic margin:

-A regional difference between EAB and WAB deep basins is confirmed (from Poort et al., 2020), showing mean values of 82 mW/m 2 in the first and 105 mW/m 2 in the second.

-The OCT and oceanic domains have similar calculated and observed HF. While in the former domain some positive anomalies could be related to a discharge zone (high surface HF and nearly outcropping basement), in the deep oceanic domain the HF could be related to the deep crustal nature (deep basement and thick sediment coverage). The effect of salt diapirs is difficult to quantify and observe but, given the often outcropping diapirs, they could impact the surface HF.

-Small-wavelength surface HF anomalies, thin sedimentary cover, nearly outcropping basement, pockmarks structures, recent volcanic activity, gypsum dehydration phenomena and sub-bottom seismic signatures in the South Balearic margin (continental and transitional crustal domains) suggest possible fluids circulation and percolation in the sedimentary column and probably upper basement. Further geochemical analysis may confirm this hypothesis.

Salt tectonics-temperature relationship:

The temperatures at the base salt level found by the model in the Gulf of Lion and South Balearic do not seem to show significant differences between the crustal segments (30°C and 8°C between OCT and oceanic crust in the Gulf of Lion and South Balearic, respectively).

Some phenomena that the model does not take into account could affect them. We have seen how some anomalies could be explained by fluids rising from the basement under conditions of basement highs and thin sedimentation. Although this phenomenon has been mainly observed in oceanic crust (e.g. [START_REF] Davis | FlankFlux: An experiment to study the nature of hydrothermal circulation in young oceanic crust[END_REF], Fisher et al., 2003a;[START_REF] Langseth | Heat transfer in the oceanic crust of the Brazil Basin[END_REF][START_REF] Hutnak | Hydrothermal recharge and discharge guided by basement outcrops on 0.7-3.6 Ma seafloor east of the Juan de Fuca Ridge: Observations and numerical models[END_REF], this study seems to confirm that even in transitional crust the circulation of fluids are possible (as also shown in [START_REF] Lucazeau | Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden[END_REF]. Salt, when present, acts as a seal on the fluids and we can expect an accumulation of them at its base. This could CHAPTER 5. THERMAL REGIME IN THE WESTERN MEDITERRANEAN SEA 283 lead to an increase in temperature and pressure at the base of the salt and thus have an impact on salt tectonics. Although these are only speculations and the phenomenon, although significant, would be local in nature, it would need to be tested numerically to understand how it might affect salt tectonics. At the regional level, both calculated and measured values agree that there is a high difference in thermal regime between the WAB and EAB. As seen in Chapter 4, the salt morphologies in the EAB are characterised by small diapirs, not piercing, which only deform the early Pliocene deposits. In the WAB, salt structures are characterised by salt stocks, walls and squeezed piercing diapirs. Is this correlation a coincidence or do the corresponding mean heat flow differences could have played a role in moulding the salt morphologies?

In the GoL, the calculated and observed heat flow and temperature do not show regional strong differences between the salt morphologies domains.

In conclusion, we have shown that surface heat flow data combined with thermal modelling studies on different scales allow to constrain to a certain level the subsurface thermal regime.

However, we have to note that in order to better understand the role of the thermal regime and the different processes that are affected by it, the need for more detailed surface heat flow data is necessary. A better thermal constrain could results from adapted thermo-kinematic models that can incorporate crustal processes such as lower crustal exhumation combined with sedimentary infill history and fluid circulation.

Summary chapter 5

Chapter

Résumé chapitre 5

Le chapitre 5 a exploré la thermicité de la Méditerranée occidentale.

L'objectif principal a été de comprendre si la thermicité peut être liée In the chapter 4 we showed the relationship between crustal segmentation and salt morphologies in the Western Mediterranean. It was shown for the first time that there is a regional correspondence between the types of morphologies and the limits of the underlying crust. We have also shown that the Mediterranean Sea can be considered a special case among the world's salt basins. Nevertheless, some of its margins present characteristics very similar to the passive margins that have been studied at a global level. Our objective in this chapter will therefore be to understand if the correspondence found in the Western Mediterranean is also observe on other passive margins. To do this, we have compiled the crustal and salt features of different margins, such as the Santos basin (Brazil), the Angolan margin, the Gulf of Mexico and the Morocco-Nova Scotia margins (Fig. 6.1). The choice of the South and Central Atlantic segment stemmed from the IFREMER experience on the study of these margins. The segmentation and crustal nature have been constrained by several wide-angle refraction surveys through techniques and modus operandi sharpened by years of seismic acquisition. In the Gulf of Mexico, on the other hand, we have relied on a refraction campaign acquired by American institutes (references in chapter 3). In the first part of this chapter we will summarise the main geodynamic and crustal characteristics of the margins analysed, while later we will correlate the authors' interpretations with the salt morphologies. We will then discuss the relationship between salt tectonics and crustal structure in these passive margins, trying to understand what are the differences and similarities of this coincidence, also with respect to the Western Mediterranean.

Brief summary of analysed passive margin crustal segmentation

In this chapter we will recapitulate the formation of each analysed passive margin and their current crustal segmentation. We will begin with an analysis of the passive margins of the South Atlantic (Santos and Angolan margin) and then the Gulf of Mexico basin and conclude with the conjugated Morocco-Nova Scotia margins. We will not dwell on the still debated points of passive margin genesis but we will attempt only to outline the interpretation of the crustal segmentation in order to compare it with the interpretation of salt structures.

Brazilian margin: the Santos São Paulo plateau System (SSPS)

The Brazilian salt basins belong to the Central Segment of the South Atlantic Ocean, located between the Ascension Fracture Zone (north of the study area, near 7°S latitude) and the Florianopolis (or Rio Grande) Fracture Zone (FFZ). While oceanic spreading in the Austral Segment started between 139.5 and 130 Ma (e.g. [START_REF] Rabinowitz | The Mesozoic South Atlantic Ocean and evolution of its continental margins[END_REF][START_REF] Curie | Ouverture de l'Atlantique Sud et discontinuités intra-plaques: une nouvelle analyse[END_REF][START_REF] Moulin | A new starting point for the South and Equatorial Atlantic Ocean[END_REF], the Central Segment opened more than 18 Ma later, (e.g. [START_REF] Torsvik | A new scheme for the opening of the South Atlantic Ocean and the dissection of an Aptian salt basin[END_REF][START_REF] Moulin | A new starting point for the South and Equatorial Atlantic Ocean[END_REF], at the end of evaporite deposition (~112 Ma, [START_REF] Pautot | Morphology, limits, origin, and age of salt layer along South Atlantic African margin[END_REF].

The largest Aptian salt occurrence is located in the offshore area and covers almost the entire Brazilian coast from the Santos Basin-São Paulo Plateau System (SSPS) to Camamu triple junction (north of the study area, at 12°S) with some smaller occurrences northwards, in the Sergipe-Alagoas basins. The salt distribution and thickness in the Brazilian margin increase southward, reaching the maximum extension in SSPS [START_REF] Mohriak | Sal: Geologia e Tectônica; Exemplos nas Bacias Brasileiras[END_REF][START_REF] Mohriak | Salt: geology and tectonics of selected Brazilian basins in their global context[END_REF]. Similarly to the Liguro-provençal Basin, the SSPS is a sort of closed basin, but in the Santos case it aborted at about the time of salt deposition [START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF][START_REF] Davison | Salt deposition, loading and gravity drainage in the Campos and Santos salt basins[END_REF]. The SSPS is bordered by Capricornio and Cruzeiro do Sul NW-SE trending lineaments (Fig. 6.2)

representing the trajectories of the relative movement and the opening of the basin [START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF]. The latter, associated with the Cabo Frio High (Fig. 6.2), separates the SSPS from the Campos Basin and is characterized by a decrease in salt thickness [START_REF] Demercian | Style and pattern of salt diapirs due to thin-skinned gravitational gliding, Campos and Santos basins, offshore Brazil[END_REF].

To the north, the volcanic Vitoria Trindade Chain (Fig. 6.2) marks the limit with the Espirito Santo Basin, which extends up to the Abrolhos Volcanic High. The salt extension in SSPS basin reaches over 500 km and its average thickness is around 2 km, but can reach 3 km in the presence of diapirs and walls [START_REF] Kukla | South Atlantic salt basins-witnesses of complex passive margin evolution[END_REF].

The gravity, magnetic and the seismic studies show a segmentation of the SSPS, which strongly suggests an oblique opening in respect to the rest of the South Atlantic Ocean. On the base of GXT lines interpretation, two divergent conclusions to each other appeared at the same period. Zalán et al., (2011) claim that a strong continuous reflector, the Conrad discontinuity, separates the crust between a rigid, highly fractured upper part and a ductile lower part. The São Paulo Plateau is described as a 15 km thick continental crust topped by about 4 km of volcanic material. By analogy with the Iberian Margin, they interpret the easternmost part of the SSPS as exhumed mantle. This exhumed mantle is further supposed to surround the entire SSPS, including the São Paulo ridge, as well as the Campos and Espírito Santo basins. [START_REF] Kumar | From oceanic crust to exhumed mantle: A 40 year (1970-2010) perspective on the nature of crust under the Santos Basin, SE Brazil[END_REF], on the other hand, do not notice evidence of exhumed mantle, except, maybe, along the Florianópolis Fracture Zone, as it was described along other fracture zones such as the São Paulo (Romanche) Fracture Zone in the Equatorial Segment [START_REF] Seyler | Regional-scale melt-rock interaction in lherzolitic mantle in the Romanche Fracture Zone (Atlantic Ocean)[END_REF].

Though [START_REF] Kumar | From oceanic crust to exhumed mantle: A 40 year (1970-2010) perspective on the nature of crust under the Santos Basin, SE Brazil[END_REF] agree with Zalán et al. ( 2011) on the continental nature of the SSPS, they suggest, following [START_REF] Thybo | Magma-compensated crustal thinning in continental rift zones[END_REF] and [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF], that extension might have been partly accomplished by volcanic intrusions and extrusions.

The SanBa Experiment, a joint project between Ifremer, IUEM, Lisbon's faculty of Science, the University of Brasilia and Petrobras which collected six multichannel (MCS) and coincident wide-angle seismic profiles in the Brazilian margin gave some precision on the crustal segmentation: profiles SB01 and SB02 run in a NW-SE direction, separated from each other by less than a hundred kilometres (Fig. 6.2); profiles SB03, SB04, SB06 and SB07 cross these two principal lines.

The velocity models enabled the authors [START_REF] Klingelhoefer | Imaging proto-oceanic crust off the Brazilian Continental Margin[END_REF][START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF] to

propose a new precise crustal segmentation interpretation composed by seven distinct domains (Fig. 6.2), also coherent with the observations of gravity and magnetic data:

-Domain CC: unthinned continental crust domain with a 35-40 km thick crust and velocities between 5.6 an 7.0 km/s.

-Domain N: the necking domain, characterized by thinning, is wide less than 100 km.

The Moho rises and the basement deepens.

-Domain A: thin crust with velocities between 6.0 and 7.0 km/s. Towards the deep basin (SE), the Moho and the top of the basement rise slowly. This domain corresponds to a low gravity anomaly and a high magnetic anomaly and is interpreted as continental in nature [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]Zalan et al., 2011;[START_REF] Kumar | From oceanic crust to exhumed mantle: A 40 year (1970-2010) perspective on the nature of crust under the Santos Basin, SE Brazil[END_REF][START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF].

The high upper crustal velocity can be interpreted as an exhumation of middle/lower crust zone [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. (after Evain et al., 2015;[START_REF] Klingelhoefer | Imaging proto-oceanic crust off the Brazilian Continental Margin[END_REF]. The crustal limit are from [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Reflection and refraction seismic data used in this study are referenced in chapter 3. B) Maps showing the crustal segmentation from the wide angle interpretation in the Santos Basin. Left: on the magnetic map. Center: On the gravity map. Right: with the crustal thickness. The hinge line and the Capricornio and Cruzeiro do Sul lineaments are from [START_REF] Moulin | Kinematic keys of the Santos-Namibe basins[END_REF].

-Domain B: very thin crust that shows the most heterogeneous crustal structure. The basement deepens by 1-2 km and the area is characterized by a large and mostly negative magnetic anomaly and a relatively high gravity anomaly. Large lateral variations in crustal velocities are observed between the two profiles. This domain is interpreted either as very thin exhumed lower continental crust intruded by magmatism or as atypical oceanic crust, overlying altered mantle [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Whatever the nature of domain B in the central part of the SSPS, it is characterized by a Moho rise, an extremely thin crust (7 to 11 km thick from [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF] and a lower layer characterized by high velocity (7.0-7.8 km/s).

-Domain C: 11 to 17 km thick crust with a pattern similar to Domain A except for the lower upper crust velocity (5.2 km/s).

-Domain D: 5 km thick atypical crust with a triangular shape characterized by a step in bathymetry, low gravity and magnetic anomalies. [START_REF] Klingelhoefer | Imaging proto-oceanic crust off the Brazilian Continental Margin[END_REF] describe this domain characterized by anomaly velocities as proto-oceanic crust.

-Domain OC: Oceanic crust

Angolan margin

The Angolan margin belongs to the Central Segment of the South Atlantic Ocean, which started opening 140 Ma ago, during the Lower Cretaceous, in the Gondwana break-up context.

As in the conjugated Brazilian margin, the central segment of the South Atlantic is characterized by the presence of thick deposits of salt. In Aptian time, for a duration of 5 million years (117-112 Ma) [START_REF] Doyle | Angiosperm pollen from the pre-Albian Lower Cretaceous of equatorial Africa[END_REF] evaporites were deposited, forming a salt basin whose maximum thicknesses is close to 1 km. The Aptian salt along the West African margin extends from the Gabon basin in the north to the Namibe Basin in its southern part.

The crustal segmentation is constrained by the ZaïAngo wide-angle project, led by Ifremer and TotalFinaElf. Seven MCS and refraction profiles were acquired between the Lower Congo and the Angolan basins (Fig. 6.3). On the base of these new data, Contrucci et al., (2004a) and [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF] interpreted the Angolan margin formed by four domains (Fig. 6.3), also coherent with gravity and magnetic data: -T1: refers to the proximal region of transitional domain characterized by a thin crust of about 16-8 km thick, and an anomalous velocity zone below (7.2 to 7.5 km/s). This layer is interpreted partly in the necking zone and it reaches a maximum thickness when the basin displays the maximum depth.

-T2: refers to the basinward region of transitional domain, characterized by a slightly thinning crust and the absence of the high velocity lower layer seen in T1. The transitional domain is bounded to the west by a basement high. Crust thickness does not exceed 5 km.

293

-OC: the oceanic crust is 6-7 km thick. [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF] highlighted that the transitional crust seems to be divided into two parts, called 'Type 1' and 'Type 2' crust. The anomalous velocity layer in domain T1 can be interpreted as lower continental crust because of its velocities [START_REF] Holbrook | The seismic velocity structure of the deep continental crust[END_REF] or as serpentinized mantle (Contrucci et al., 2004a). The velocity model in the upper crustal layer of segment T2 does not seem to be coherent with an oceanic nature and, at the same time, shows velocity and thickness that appear to be different to those of a "typical" continental crust (Contrucci et al., 2004a). For [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF] T2 could be an atypical oceanic crust, serpentinized mantle, lower continental crust or intruded continental crust. On the base of industrial ION GXT profiles and following the model of [START_REF] Manatschal | New models for evolution of magma-poor rifted margins based on a review of data and concepts from West Iberia and the Alps[END_REF], Unternher et al. Contrucci et al., (2004a) and [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]. Reflection and refraction seismic data used in this study are represented (references in chapter 3). Bottom: wide-angle refraction seismic profile showing the crust velocity model in Zaiango03 (Z03) profile (after Contrucci et al., 2004a). Dashed black lines represent the lower and upper limit of the crust.

(2010) propose the presence of exhumed serpentinized mantle in that segment. On the other hand, based on kinematic studies, wide-angle and multichannel seismic analysis, Aslanian et al. (2009) propose a three-phase model of evolution of the conjugate passive margins, where domain T2 is allochthonous and could represent the exhumation of the lower continental crust from the autochthonous T1 domain.

Gulf of Mexico

The Gulf of Mexico (GOM) was formed in two rifting phases: the first phase started in the Triassic, when the supercontinent Pangea started opening in a NW-SE direction and led to the separation of South & North America [START_REF] Salvador | Triassic-Jurassic. The Gulf of Mexico Basin: Boulder, Colorado[END_REF][START_REF] Marton | Jurassic reconstruction of the Gulf of Mexico Basin[END_REF] while the second phase began in the Late Jurassic with the counter-clockwise rotation of the Yucatan Block [START_REF] Pindell | Tectonic evolution of the Gulf of Mexico, Caribbean and northern South America in the mantle reference frame: an update[END_REF]. From the Callovian to the Oxfordian (Hudec et al., 2013a;[START_REF] Nguyen | Gravity and magnetic constraints on the Jurassic opening of the oceanic Gulf of Mexico and the location and tectonic history of the Western Main transform fault along the eastern continental margin of Mexico[END_REF], the deposition of a thick-salt sequence occurred in a relatively short period (~3Ma after [START_REF] Pindell | Rapid outer marginal collapse at the rift to drift transition of passive margin evolution, with a Gulf of Mexico case study[END_REF]. After the Oxfordian, the seafloor spreading separated the GOM basin into two distinct conjugated margins and salt provinces, named Louann in the north and Campeche and Yucatan in the south (Fig. 6.10). By the Berriasian [START_REF] Nguyen | Gravity and magnetic constraints on the Jurassic opening of the oceanic Gulf of Mexico and the location and tectonic history of the Western Main transform fault along the eastern continental margin of Mexico[END_REF] or the Valanginian time [START_REF] Pindell | Tectonic evolution of the Gulf of Mexico, Caribbean and northern South America in the mantle reference frame: an update[END_REF], seafloor spreading ceased and the Yucatan block reached its present-day location. The GOM northern margin is characterized by a 9 to 18 km thick [START_REF] Sawyer | The crust under the Gulf of Mexico Basin. The Gulf of Mexico Basin: Geological Society of America[END_REF][START_REF] Peel | Genetic structural provinces and salt tectonics of the Cenozoic offshore US Gulf of Mexico: A preliminary analysis[END_REF] sedimentary sequence that covers the Jurassic structures. The pre-salt sequences are locally observed and represent the deposits formed in the late stages of rifting, which are not deformed and are parallel to the salt base (Rowan, 2018). The crustal segmentation was interpreted as part of the GUMBO Marine Seismic Experiment which consisting of four wide-angle profiles in the northern GOM margin (Fig.

6

.4). The continental crust is between 36 km (Offshore Florida, [START_REF] Eddy | Structure and origin of the rifted margin of the northern Gulf of Mexico[END_REF] and 40 km [START_REF] Huerta | Wilson cycles, tectonic inheritance, and rifting of the North American Gulf of Mexico continental margin[END_REF] thick and it gets thinner along about 200 km (Gumbo3, [START_REF] Eddy | Deep crustal structure of the northeastern Gulf of Mexico: Implications for rift evolution and seafloor spreading[END_REF]. In the transitional domain, the crust stretched to a thickness of less than 10 km (GUMBO1 offshore Texas, [START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF]fig. 6.4), and 6-7 km offshore Florida [START_REF] Christeson | Deep crustal structure in the eastern Gulf of Mexico[END_REF]. In the north-western GOM, concomitant to GUMBO3 and GUMBO4 profiles, the authors interpreted high-velocity lower crust as syn-rift magmatic intrusion into the lower crust [START_REF] Eddy | Deep crustal structure of the northeastern Gulf of Mexico: Implications for rift evolution and seafloor spreading[END_REF] while offshore Texas, the low velocity is not consistent with magmatic underplating [START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF]. Here, a 45 km-wide zone of low-velocity and thin crust might be associated with exhumed mantle, locally serpentinized. The downward limits and width of the transitional crust are still debated in literature (Fig. 6.4). The oceanic crust has a thickness ranging from 6 km (offshore Florida, GUMBO4) to 8 km. Many interpretations of the nature of the transitional crust domain in the north GOM are proposed: thinned continental crust [START_REF] Roberts | Regional geologic and geophysical observations basinward of the Sigsbee Escarpment and Mississippi Fan fold Belt, Central deep-water Gulf of Mexico[END_REF]; oceanic and proto-oceanic crust [START_REF] Imbert | The Mesozoic opening of the Gulf of Mexico: Part 2. Integrating seismic and magnetic data into a general opening model[END_REF][START_REF] Mickus | Potential field evidence for a volcanic rifted margin along the Texas Gulf Coast[END_REF]; serpentinized mantle or thin oceanic crust [START_REF] Kneller | Plate kinematics of the Gulf of Mexico based on integrated observations from the Central and South Atlantic[END_REF]; hyperextended continental crust with exhumed mantle in central and north-western sectors and proto-oceanic crust in the east [START_REF] Rowan | Salt tectonics at passive margins: Geology versus models-Discussion[END_REF]. Whatever the interpretation, the velocity models show a wide transitional domain characterized by a Moho rise (Fig. 6.4) (up to 16 km depth, GUMBO3) and crustal thinning (up to 7 km, GUMBO4), associated with high velocity in the lower layer (Fig. 6.4).

Morocco -Nova Scotia margins

The Morocco -Nova Scotia conjugated margins formed after the rifting in the central Atlantic Ocean that started at the Late Triassic-Early Jurassic limit (e.g. [START_REF] Michard | Continental evolution: The geology of Morocco: Structure, stratigraphy, and tectonics of the Africa-Atlantic-Mediterranean triple junction[END_REF] or during the Sinemurian period [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF], thereby making it one of the oldest existing passive margins in the world. They formed during the break-up of the Pangea supercontinent [START_REF] Scotese | A continental drift flipbook[END_REF], which coincided with high volcanic activity in the Central Atlantic Magmatic Province (CAMP) [START_REF] Hames | The Central Atlantic Magmatic Province: Insights from Fragments of Pangea[END_REF]. The Nova Scotia and Morocco margins are bordered by two magnetic anomalies, the East Coast Magnetic Anomaly (ECMA)

and the West African Coast Magnetic Anomaly (WACMA) (Fig. 6.5), which can be considered as conjugated [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF]. The ECMA extends from Georgia to Nova Scotia [START_REF] Drake | Continental margins and geosynclines: the east coast of North America north of Cape Hatteras[END_REF], and is strong and continuous. The WACMA, also called S1 in its northern part, runs from Senegal to northern Morocco; its amplitude is lower than the ECMA. Both mark the continentocean transition on the African margin [START_REF] Hinz | The continental margin of Morocco: seismic sequences, structural elements and geological development[END_REF][START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF].

The crustal segmentation is constrained by MIRROR [START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF], SISMAR [START_REF] Contrucci | The crustal structure of the NW Moroccan continental margin from wide-angle and reflection seismic data[END_REF] and SMART [START_REF] Funck | Crustal structure of the northern Nova Scotia rifted continental margin (eastern Canada)[END_REF][START_REF] Wu | Crustal structure of the central Nova Scotia margin off Eastern Canada[END_REF] reflection-refraction experiments for, respectively, the Morocco (the former two) and Nova-Scotia margins (Fig. and an oceanic domain. The thinning domain is less than 90 km wide and, at the limit with the oceanic domain, the crust is approximately 13 km thick. The oceanic domain is characterized by an area with high lower crust velocities (atypical oceanic crust from [START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF] and an oceanic crust thickness of 8 km in the most distal part. In the Nova Scotia margin (Fig. 6.5), [START_REF] Funck | Crustal structure of the northern Nova Scotia rifted continental margin (eastern Canada)[END_REF] (SMART1) and [START_REF] Wu | Crustal structure of the central Nova Scotia margin off Eastern Canada[END_REF] (SMART2) interpreted a 36 km-thick continental crust, which thins seawards to 5-6 km, mostly over the slope region. To the north (SMART1 and SMART2), the authors propose a wide area of partially serpentinized upper mantle rocks, characterized by high lower-crustal velocities (up to 7.6 km/s). Further south (SMART3) [START_REF] Louden | Systematic variations in basement morphology and rifting geometry along the Nova Scotia and Morocco conjugate margins[END_REF] interpreted a thicker oceanic crust (7 km) and an area of magmatic underplated bodies. The comparison between the two conjugated profiles (SMART1 and MIRROR1), following the kinematic reconstitution of [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF], shows structural and crustal similarities in the area of the necking zone and a thinning of continental crust. However, the presence of a transitional domain in the Canadian margin proposed as an exhumed serpentinized mantle and a West African domain formed by intruded oceanic crust led the authors to favour the hypothesis of a symmetrical rifting followed by an asymmetrical oceanic accretion [START_REF] Klingelhoefer | Crustal structure variations along the NW-African continental margin: a comparison of new and existing models from wide-angle and reflection seismic data[END_REF][START_REF] Biari | Opening of the central Atlantic Ocean: implications for geometric rifting and asymmetric initial seafloor spreading after continental breakup[END_REF], although there are other hypothesis, including an age difference between the two oceanic crusts imaged by refraction profiles or a greater thickness of the oceanic crust on the African side due to the influence of the Canary hot spot [START_REF] Biari | Structure profonde de la marge Nord-Ouest Africaine[END_REF]. [START_REF] Funck | Crustal structure of the northern Nova Scotia rifted continental margin (eastern Canada)[END_REF] and [START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF], respectively. Black lines represent seismic profile used in this study (references in chapter 3). ECMA and WACMA are from [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF].

Salt morphologies domains and crustal segmentation coincidence

The definition of salt morphologies domains is not a simple task as each passive margin may differ in main salt tectonics mechanisms and resulting structures. We have grouped the salt morphologies into 3 main domains, so that they can be regionally compared with the crustal segmentation previously described. We have referred the salt structures interpretation to the wide salt tectonics literature present, using published profiles (References in chapter 3) and salt isopach maps (e.g. [START_REF] Kukla | South Atlantic salt basins-witnesses of complex passive margin evolution[END_REF][START_REF] Mohriak | Salt tectonics, volcanic centers, fracture zones and their relationship with the origin and evolution of the South Atlantic Ocean: geophysical evidence in the Brazilian and West African margins[END_REF]. The 3 domains are so-defined based to their main geometric characteristics and associated structures, as done in the Western Mediterranean Sea, in order to give a global and homogenous view, and are named: -Raft characterized by thickening of salt deposits, thrust, folds and "compressional" diapirs. This domain can be characterized by massive thicken salt and/or canopy structures. The term canopy describes salt that is emplaced at stratigraphic levels above the autochthonous evaporites and comprises sub-horizontal or moderately dipping structures [START_REF] Mrazec | Despre cute cu simbure de strapungere [On foldswith piercing cores[END_REF][START_REF] Jackson | A glossary of salt tectonics[END_REF][START_REF] Hudec | Advance of allochthonous salt sheets in passive margins and orogens[END_REF]. The salt moved vertically from a single or multiple autochthonous feeder forming a salt sheet which, after coalescence of numerous structures, can form a canopy. The canopy salt is often interpreted as allochthonous salt which includes several geometrical styles of structures such as: bulbs, salt-stock canopies, salt tongues, sheet, nappes and wings. In many cases, these structures are formed when the salt supply is great and thus moves laterally, overhanging the sediments. Due to the high absorbance of thick halite deposits, it is sometimes tricky to interpret the base of salt and thus claim for an autochthonous or allochthonous salt structure. Since the objective is a regional interpretation of salt structures in several passive margins, we often interpreted this domain as characterized by massive salt deposits that could evolve in canopies. The main difference with the Diapir domain is that the structures are coalescent, close together, and hardly ever form welds and mini-basins.

In the Western Mediterranean Sea the canopy salt structures are not observed: the structures can be close together or isolated but they rarely occupy stratigraphic positions above their initial location and are rarely detached from their basal source. Apart from a few hard-to-discriminate local examples, the salt structures in the Western Mediterranean Sea can be considered as autochthonous, so connected to their bases.

Santos basin

As quoted before, the largest salt occurrence is located in the offshore area and cover almost the entire Brazilian coast from the Santos to Sergipe-Alagoas basin and, more widely spread on the Equatorial sector, from Bacia Potiguar to Cassipore. As mentioned before, some authors suggested a younger Santos basin salt deposition with respect the other South Atlantic salt basins [START_REF] Davison | Geology and tectonics of the South Atlantic Brazilian salt basins[END_REF][START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF]. The salt isopach maps proposed by several authors (e.g. [START_REF] Mohriak | Sal: Geologia e Tectônica; Exemplos nas Bacias Brasileiras[END_REF][START_REF] Mohriak | Salt: geology and tectonics of selected Brazilian basins in their global context[END_REF][START_REF] Guerra | Role of halokinesis in controlling structural styles and sediment dispersal in the Santos Basin, offshore Brazil[END_REF] show that the salt distribution and thickness increase to the south, reaching the maximum extension in SSPS basin (up to 2 Km of thickness). Salt can exceed 3000m in presence of diapirs and walls [START_REF] Kukla | South Atlantic salt basins-witnesses of complex passive margin evolution[END_REF].

The isopach map already highlights a subdivision from the upper slope to the deep basin. Zoom A in figure 6.6 shows a salt thickness map in a square area of Santos basin, made by Guerra and Underhill, (2012) interpreting a 3D seismic dataset. The same authors interpreted the area as outlined by a proximal extensional area (E) and a basinward contraction area (C). Likewise, the zoom B is mainly located in the Campos basin and shows a similar pattern distribution of salt thickness than in the zoom A, with a basinward thicken and a proximal thinner areas. The boundaries between the two domains (extension and contraction) well correspond with the limit between the Raft and the Diapirs domain of this study. The Raft Salt domain presents similar structures to those of the Mediterranean, such as rollover and salt-cored normal faults and saltcored anticlines, and is located all along the slope (Fig. 6.6). The Salt Diapir domain begins at the lower slope and is characteristic of a region with huge salt diapirs and salt walls that form mini-basins and welds (Fig. 6.6), filled with Late Cretaceous-Late Tertiary sediments [START_REF] Kukla | South Atlantic salt basins-witnesses of complex passive margin evolution[END_REF]. These mini-basins are characterized by synclines of sediments that weight on underlying salt, which is mobilized and evacuated into adjacent salt highs. Salt is expelled on the sides, rises around its margin and in turn creates space for new sediments to accumulate. If the expulsion of salt is complete, a "weld structure" [START_REF] Jackson | Seismic recognition of salt welds in salt tectonics regimes. In Gulf of Mexico salt tectonics, associated processes and exploration potential[END_REF]) is formed and the pre-salt deposits are discordant with post-salt successions. The Diapir domain is wider in the SSPS than in the Campos basin (142 km in SB01 profile, Fig. 6.6). In the SSPS, it is subdivided into Isolated and Narrow diapirs, interpreted in a restricted area on the Sao Paulo Plateau (max 100 km wide). Narrow diapirism seems to disappear towards both the NW and the Capricornio Lineament where it is no longer visible on the SB02 profile (Fig. 6.6). Note also that the present-day base of the salt is highly variable in depth in both areas due to postdeposition differential subsidence or basement structures highs (e.g. [START_REF] Guerra | Role of halokinesis in controlling structural styles and sediment dispersal in the Santos Basin, offshore Brazil[END_REF]. The Canopy-Massive Salt domain is located in the deep basin and is characterized by salt walls, pop-up structures, reverse faults and canopy salt that affect the seafloor. It extends further in the SSPS (159 km in SB01, Fig. 6.6) than in the Campos basin (Fig. 6.6). It is characterized by a fairly constant and remarkable thickness of salt, which can reach 2 km [START_REF] Kukla | South Atlantic salt basins-witnesses of complex passive margin evolution[END_REF]. The vertical diapir deformation is not well developed and does not shows evolved mini basins and weld structures as in the Diapir Salt domain. The base can only be interpreted locally and looks to be pseudo-horizontal, like the slightly deformed pre-salt layers (Fig. 6.6).

The seafloor displays sub-horizontal inclination and even, locally, landward dips. The salt base is evidently interpretable except in the Massive-Canopy domain, where seismic imaging is hampered by absorption and scattering of salt deposits. In the Large Diapir domain, the salt base shows a landward vergence (Fig. 6.6; [START_REF] Davison | Geology and tectonics of the South Atlantic Brazilian salt basins[END_REF][START_REF] Guerra | Role of halokinesis in controlling structural styles and sediment dispersal in the Santos Basin, offshore Brazil[END_REF][START_REF] Strozyk | Comparison of the rift and post-rift architecture of conjugated salt and salt-free basins offshore Brazil and Angola/Namibia, South Atlantic[END_REF], probably due to the Sao Paulo Plateau basement tectonic influence. Following the interpretation of [START_REF] Pichel | Base-salt relief controls salt-tectonic structural style, São Paulo Plateau, Santos Basin, Brazil[END_REF] the sag basin underlain the salt deposits is largely dislocated by high angle faults. The sag basin is mainly composed by syn-rift sediments [START_REF] Kumar | From oceanic crust to exhumed mantle: A 40 year (1970-2010) perspective on the nature of crust under the Santos Basin, SE Brazil[END_REF] of about 2 km thick [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Looking at the relationship between crustal segmentation, previously introduced, and the salt morphologies we noticed how the boundaries interpreted by [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF] often match with a change in regional salt geometries (Fig. In the Canopy-Massive domain (crustal domain B) the base of salt is tricky to detect with reflection seismic data but the refraction data show a deep, irregular basement topography. The SSSP represents a buffer zone of the South Atlantic Ocean [START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF] with its two conjugate margins and a failed ridge in its centre [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Therefore, in the southern [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Volcanic structures are from Mohriak, (2001). The hinge line and the Capricornio and Cruzeiro do Sul Lineaments are from [START_REF] Moulin | Kinematic keys of the Santos-Namibe basins[END_REF]. Black lines represent seismic profile interpreted (references in the chapter 3). (B) From top to bottom, Sanba01 (SB01) time-migrated reflection seismic line uninterpreted and interpreted (location in the maps above). The interpreted salt morphologies are represented, showing their evolution from the lower slope to the deep basin. Sanba01 wide-angle profile (SB01), coincident with the reflection seismic line showing crust segmentation along SSPS (from [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Dashed black lines represent the lower and upper limit of the crust.

part of the basin, the salt onlaps the Sao Paulo Ridge (Fig. 5.7), interpreted as of continental nature [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. In the Angolan margin, the salt deposition timing with respect the rifting phase is still debated. Some authors claim for a pre-break-up salt deposition (e.g. [START_REF] Brice | Tectonics and sedimentation of the South Atlantic Rift Sequence: Cabinda, Angola: rifted margins: field investigations of margin structure and stratigraphy[END_REF] while other for a post-break-up deposition (e.g. [START_REF] Marton | Evolution of the Angolan passive margin, West Africa, with emphasis on post-salt structural styles[END_REF]. [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF] showed that the salt was deposited in shallow depositional environments on the platform and all over the transitional domain, above a pre-salt sediment layer with a homogeneous thickness of about 3-4 km. On the shelf, pre-salt sediments mostly vary from continental to lacustrine and the earliest marine sediment layer is thin and was deposited immediately prior to the Aptian salt layer: there is no thick, significant marine sequence pre-dating the salt deposition [START_REF] Brognon | Oil and geology in Cuanza Basin of Angola[END_REF][START_REF] Brice | Tectonics and sedimentation of the South Atlantic Rift Sequence: Cabinda, Angola: rifted margins: field investigations of margin structure and stratigraphy[END_REF]. The depositional context of salt deposits can have a direct influence on the evolution of salt tectonics, influencing initial salt thickness and pre-salt topography (e.g. [START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF][START_REF] Rowan | The South Atlantic and Gulf of Mexico salt basins: crustal thinning, subsidence and accommodation for salt and presalt strata[END_REF]. Figure 6.8 shows the salt morphologies domains interpreted in the Angolan passive margins, after compilation of previously study and seismic reflection available in literature. The margin perpendicular distribution of the domains is similar to that of the Santos basin, highlighting a proximal Raft domain, a mid-slope Diapirs Domain and a distal Canopy-Massive domain. The Raft domain exhibits typical extensional structures well described by [START_REF] Duval | Raft tectonics in the Kwanza basin, Angola[END_REF], and is located on the upper slope part of the margin. The structures are very similar to those interpreted in the SSPS, Campos and Gulf of Lion margins (Listric salt domains). We included, without differentiation, the mini and mega rafts interpreted by [START_REF] Marton | Evolution of the Angolan passive margin, West Africa, with emphasis on post-salt structural styles[END_REF], who sub-divided it basing on age of structures development. The Diapir domain is the wider salt domain (about 120 km) and includes huge diapirs, pillows, minibasins and weld structures. It is located between the lower slope and down to about 160 km from the coastline to the deep basin, above the pre-salt sag basin (Fig 6.9-T1 domain). The Canopy-Massive domain also lies on the sag basin (according to refraction data, Fig. 6.9-T2 domain). It is the thickest salt domain and presents features similar to those of the Brazilian margin. Basinward, salt sheets rise above a structural high which marks the boundary between transitional and oceanic crust (Fig. 6.9). These structures are typical in passive margins and highlighted the rise of allochthonous salt above the oceanic crust as a result of basinward gravitational and sedimentary forces.

Angolan margin

Gulf of Mexico

The Gulf of Mexico is probably the best studied salt basin in the world. The oil and gas industry acquired thousand km and km2 of 2D and 3D seismic data in this petroleum prolific Contrucci et al. (2004a) and [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]. Black lines represent seismic profile interpreted in this study (references in the text). (B) From top to bottom, time migrated reflection profile (Z-03) and line-drawing interpretation (modified after [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]; location on maps above) showing salt morphologies domains. Z-03 wide-angle coincident profile showing crust segmentation by Contrucci et al., (2004a). Dashed black lines represent the lower and upper limit of the crust.

basin. However, the seismic data are mainly private, making their availability in un-interpreted format difficult. Nevertheless, several publications show seismic transects along the margin, especially in the Louann Salt area in the northern Gulf of Mexico (references in Chapter 3). The salt deposition context is still debated (see chapter 1; [START_REF] Pindell | Rapid outer marginal collapse at the rift to drift transition of passive margin evolution, with a Gulf of Mexico case study[END_REF]Hudec et al., 2013b;[START_REF] Rowan | The South Atlantic and Gulf of Mexico salt basins: crustal thinning, subsidence and accommodation for salt and presalt strata[END_REF][START_REF] Galloway | Depositional evolution of the Gulf of Mexico sedimentary basin[END_REF]. The main factors influencing salt tectonics is the result of different interpretations of the original salt thickness. Several authors (e.g. [START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF]Rowan, , 2018;;Hudec et al., 2013b) claimed that the differences of present-day salt distribution can be the consequence of the variations of rifting and spreading timing and consequently the distribution of related crustal segments. At the basinward limit of sag basin, a landward high 1 to 4 km ramp (Barker and Mukherjee 2011) could marks the oceanic crust limit (Hudec et al., 2013b), as observed in the Angolan margin [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Moulin | A new starting point for the South and Equatorial Atlantic Ocean[END_REF] or in the Central Atlantic Ocean [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF]. The autochthonous salt is thus placed lower than the oceanic crust [START_REF] Pindell | Rapid outer marginal collapse at the rift to drift transition of passive margin evolution, with a Gulf of Mexico case study[END_REF][START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF][START_REF] Curry | Extensional models for the development of passive-margin salt basins, with application to the Gulf of Mexico[END_REF], increasing unresolved questions about margin evolution. As shown in figure 6.10, the salt morphologies are different with respect the other salt passive margins, including the Western Mediterranean. Isolated diapirs, as observed for example in the Gulf of Lion, are rare and are replaced by small deformed diapirs that break away and form sheets occupying higher stratigraphic positions. The Massive Canopy domain is mostly composed of evolved sheets and allochthonous salt that migrates basinward and can be located above the oceanic crust in the deep basin. Base of salt is subhorizontal throughout the margin and does not show a similar wide Raft domain. The pre-salt sag basin is difficult to observe in reflection seismic data due to the high absorbance of the salt structures, thus giving no information about its slope and topography. Salt detachment levels can be many, often being detached from the autochthonous salt base (Fig. 6.10). Moreover, in the deep basin, allochthonous sheets can climb the ramp dividing, following some authors (e.g. Hudec et al., 2013a), the transitional to the oceanic crust and continued to advance until, at least, the middle Cretaceous (Hudec et al., 2013a).

In this work we have relied primarily on regional interpretations made by several authors (references in chapter 3) who, often with the help of not sharable datasets, have grouped salt morphologies throughout the northern Gulf of Mexico. We then compared the interpretations with the groups of salt morphologies interpreted in the other passive margins, attempting to standardise terminologies. [START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF]. Fault trends are from [START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF][START_REF] Stephens | Basement controls on subsurface geologic patterns and near-surface geology across the northern Gulf of Mexico: a deeper perspective on coastal Louisiana[END_REF].

The salt morphologies boundaries are modified from previous interpretation of [START_REF] Seni | Evolution of salt structures during burial of salt sheets on the slope, northern Gulf of Mexico[END_REF]. Salt structural domains map is from P. Bourges (personal communication); original salt distribution is from [START_REF] Karlo | Classifications of syndepositional Systems and Tectonic Provinces of the Northern Gulf of Mexico[END_REF]; the profiles are modified from [START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF] [START_REF] Schuster | Deformation of allochthonous salt and evolution of related salt-structural systems, eastern Louisiana Gulf Coast[END_REF].

Thus, although differences in salt structures may differ, we essentially divided the Gulf of Mexico into two domains (Fig. 6.10): i) the Diapirs domain, which is proximal and can shows some Raft, less developed, salt structures and ii) the Canopy-Massive domain, showing irregular, well canopy and sheet structures, coalescent, with a basinward vergence. [START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF]. Salt morphologies boundary are redrawn from Seni, (1992). The oceanic domain boundaries from Hudec et al., (2013a); [START_REF] Sawyer | The crust under the Gulf of Mexico Basin. The Gulf of Mexico Basin: Geological Society of America[END_REF], [START_REF] Christeson | Deep crustal structure in the eastern Gulf of Mexico[END_REF] and [START_REF] Curry | Extensional models for the development of passive-margin salt basins, with application to the Gulf of Mexico[END_REF] are represented. Black lines represent Gumbo wide-angle survey profiles (references in chapter 3). Fault trends are from [START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF][START_REF] Stephens | Basement controls on subsurface geologic patterns and near-surface geology across the northern Gulf of Mexico: a deeper perspective on coastal Louisiana[END_REF]. Black lines represent seismic profile, interpreted in this study (references in the text). (B) PSDM ION GulfSPAN 2450 profile from [START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF]Dickinson, (2017) approximately in the location of GUMBO 1 profile (location in (A) maps). The salt morphologies are from this study. Below, the GUMBO1 wide-angle profile. Crustal segmentation in black is from this study and discussion in [START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF]. Dashed black lines represent the lower and upper limit of the crust.

In the Gulf of Mexico the crustal segmentation is more uncertain compared to the other passive margins. Although a recent refraction wide-angle survey (GUMBO survey), the crustal segmentation is not well constrain as well as the nature of each segment. The velocity models proposed by the authors give a good constrain on Moho depth, crustal thinning and lithospheric thickness. However, they fail to be sufficiently conclusive on basement depth (and hence sedimentary thickness), velocity anomalies (positive or negative), boundary between lower and upper crust, and the nature of transitional crust. Moreover, from the NW to NE GoM margins, the interpretations also differ on the amount of magma involved in the rifting-drifting processes (see [START_REF] Eddy | Deep crustal structure of the northeastern Gulf of Mexico: Implications for rift evolution and seafloor spreading[END_REF][START_REF] Eddy | Structure and origin of the rifted margin of the northern Gulf of Mexico[END_REF][START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF]. A detailed comparison between crustal segmentation and salt morphologies, as carried out in the other passive margins, has been more complicated. However, some information can be derived from the position of salt morphologies along the margin and the crustal depth -thinning of the Moho in the Gulf of Mexico. The Diapirs domain lays all along the crustal thinning domain, as already observed for instance in the Angolan margin. Instead, the Canopy salt domain lays on extremely thinned transitional crust, probably exhumed [START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF](Rowan, , 2018) ) and intruded, and on oceanic crust.

Where the Moho is shallower (up to 8 km) and the crust thinner, the salt outlines canopy, coalescent sheet structures (Fig. 6.11).

Morocco-Nova Scotia margins

The evaporite sequences were deposited in the Central Atlantic Ocean from the Rhaetian to the Sinemurian [START_REF] Jansa | Upper Triassic salt deposits of the western North Atlantic[END_REF] in syn-rift half-grabens. They are discontinuous along the Central Atlantic margins, mainly present offshore Nova Scotia and Morocco, but also in the Carolina Basin, offshore Mauritania and in the continental basin of Senegal [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF] Chapter 2). On the Nova Scotia margin, [START_REF] Shimeld | A comparison of salt tectonic subprovinces beneath the Scotian Slope and Laurentian Fan[END_REF], and on the Moroccan margin, Tari and Jabour, (2013), subdivided the salt basin into five tectono-stratigraphic sub-provinces, parallel to the margin from NE to SW. These salt segmentations show a salt structures distribution from north to south, with a parallel and not perpendicular direction to the margins.

In the SW segment of the Nova Scotia margin, the salt distal limit coincides with the ECMA (Fig. 6.13) while to the NE the salt has probably moved to occupy an allochthonous basinward position (Sahabi et al., 2004 on Keen andPotter, 1995 profile). On the Moroccan margin, the WACMA boundary generally corresponds to the salt distal limit and the salt is considered to be mainly autochthonous. The seaward movement is limited [START_REF] Holik | Effects of Canary hotspot volcanism on structure of oceanic crust off Morocco[END_REF]Maillard et 2006), except in the Tafelney Plateau (Fig. 6.12), where some salt canopies may have locally mobilized over a distance up to 20 km. 2004) ;[START_REF] Sahabi | Evolution cinématique triasico-jurassique de l'Atlantique central: Implications sur l'évolution géodynamique des marges homologues nord ouest africaine et américaine[END_REF] and [START_REF] Tari | Salt tectonics in the Atlantic margin of Morocco[END_REF]. Black lines represent the seismic profiles used in this study (references in chapter 3). Canopy (allochthonous) salt in Nova Scotia is from Sahabi, (2004) interpretation. Tafelney canopy area is from interpretation of [START_REF] Tari | Salt tectonics along the Atlantic margin of Morocco[END_REF]. Nova Scotia seismic profile is modified from Louden et al., (2012). Mirror01 profile is taken from Biari, (2015) (salt structures interpretation is taken from his work).

314

We defined three regional salt morphologies domains (Fig. 6.12): i) Raft salt domain, ii)

Diapir salt domain and iii) Canopy salt domain. The Raft Salt and Diapir Salt domains characterize both margins, occupying the entire slope domain up to the upslope limit (Fig. 6.12).

The Canopy salt domain is interpreted in the NE limit of Nova Scotia margin and in the Tafelney Plateau. It is formed by salt that was remobilized after its deposition, which derives from the more landward domain: in the Nova Scotia margin, the Massive-Canopy salt domain is characterized by salt derived from the Diapir Domain, which glided towards the deep basin after its deposition [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF]. ). WACMA and ECMA are from [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF]. (B) Mirror01 reflection and wide-angle associated profiles (location in map above (A)). Modified after [START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF].

The salt tectonics system of Morocco-Nova Scotia conjugated margins exhibits some differences with respect the Gulf of Mexico and South Atlantic margins. The Diapir salt domain is mainly centred on the Necking Zone domain, where the crust is of continental nature and thinned (Fig. 6.13; [START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF] and the deformation seems to be affected by the initial salt thickness and the underlying basement structures [START_REF] Ings | A new conceptual model for the structural evolution of a regional salt detachment on the northeast Scotian margin, offshore eastern Canada[END_REF][START_REF] Krézsek | Mechanics of fault and expulsion rollover systems developed on passive margins detached on salt: insights from analogue modelling and optical strain monitoring[END_REF]. The latter domain is therefore not overlying a sag basin as in the Gulf of Mexico or South Atlantic basins but is mostly located in the lower slope, where it shows less extensive horizontal structures 6.4 Summary of crustal segmentationsalt morphologies coincidence, also including the

Western Mediterranean margins

Despite a difference in quality and resolution between the studied seismic profiles which could locally modify our classification, the previously sub-chapter shows that, whatever the morphologies and the crustal nature interpreted by the authors, their boundaries correspond to those of the crustal segmentation constrained by refraction data (Fig. 6.14).

We divided the salt deposition context in pre-syn oceanic spreading salt deposition, including the passive margins analysed in this chapter, and the post-oceanic spreading salt deposition, referring to the Western Mediterranean margins (Fig. 6.14). Moreover, we differentiated the presence and the absence of the "sag" basin. The sag basin, as referred in this thesis, is the thick sedimentary sequence between the salt and the basement which is characterized by flatly layered sedimentation (e.g. [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]Karner and Gamboa, 2007;[START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF]. For the time being, we do not attribute a particular genesis to the sag basin as part of the rifting formation, but only a stratigraphic feature.

Regionally, the Raft Salt domain is located above the continental crust, which gradually becomes thinner towards the deep basin (Necking zone domain), associated with a gradual rise of the Moho, as clearly visible on the Angolan or Santos margins (Figs. 6.7, 6.9). Whilst the Canopy Salt domain has been interpreted only in pre/syn-oceanic spreading salt margins that show a sag basin and are located above an extremely thin or transitional crust (Fig. 6.14), all profiles present a strong change in salt morphologies when crossing the landward limit of both the transitional (Angola, Santos, Gulf of Mexico), and the proto-oceanic or oceanic crust (West Mediterranean Sea) (Fig. notable horizontal movement. In the case of margins with the presence of a sag basin, the coincidence between crustal segmentation and salt morphologies seems to be even clearer.

The next step is to understand whether a specific crustal nature can be associated with a specific salt morphology. As explained in chapter 2, salt tectonics is the result of several forces that play together in the construction and evolution of salt structure. The parameters that come into play are mostly structural, understood as relationships of forces, mostly gravitational, that cause a direct reaction on the salt. The compilation made in figure 6.16 aims to understand whether certain geophysical and structural characteristics (magnetic and gravity anomaly, crustal thickness, Moho depth, crustal velocities) are associated with certain salt morphologies.

The compilation shows how the Canopy-Massive domain is present where the crust is thinner and exhibiting anomalous velocity and the Moho is shallower. The transitional crust nature still presents many doubts about its composition (see chapter 1) and its process of genesis is still debated. As a matter of fact, the nature is still misunderstood and the velocity anomalies found within it (in the upper and/or lower layer) have different interpretations. The Diapirs salt domain, which presents different variations within it (e.g. in the Western Mediterranean), is mostly located above thinned continental crust or, in the Mediterranean, above proto-oceanic or atypical oceanic crust. The Raft salt domain is mainly centred on unthinned and thinned crust, continental in nature, in the proximal margin. We would certainly not have expected a direct relationship between salt morphologies and crustal nature since the parameters that come into play in salt tectonics, as mentioned, are multiple. Nevertheless, it seems to be clear that coincidence is confirmed everywhere, although with variable differences.

In conclusion, we have seen how the coincidence between crustal segmentation and salt morphologies is also confirmed in other salt-bearing passive margins, albeit with differentiation. Here, we have not analysed in detail the mechanisms of salt tectonics as it is not the direct objective of this thesis. However, we have pointed out that this coincidence should be analysed with more interest by the scientific community, also in view of that observed in the Western Mediterranean where a detailed analysis of salt structures seems to exclude classical mechanisms from explaining this relationship. The thermal regime, although its influence is not yet confirmed, could play a role in shaping the passive margins, thus affecting the salt level and its deformation.

Summary chapter 6

Chapter 6 aims to explore the coincidence of crustal segmentation and salt morphologies in some of the world's best known passive margins, such as the Santos Basin (Brazil), the Angolan margin, the Gulf of Mexico and the Morocco-Nova Scotia margins. Despite a difference in quality and resolution between the studied seismic profiles which could locally modify our classification, this chapter shows that, whatever the morphologies and the crustal nature interpreted by the authors, their boundaries correspond to those of the crustal segmentation constrained by wide-angle refraction data. It has been shown that crustal thinning, often concomitant with an exhumation domain, coincides with more mature salt deformation. The presence of a sag basin seems to coincide with a canopy domain while where the margin is more abrupt, the salt sheets are rarer. Although a direct relationship between particular salt morphologies and crustal nature is tricky to observe, since the parameters that come to play a role in the deformation are multiple, this chapter shows how the geometrical coincidence should not be overlooked and deserves a more in-depth study of its relationship, as initiated in the Western Mediterranean Sea.

Résumé chapitre 6

Le chapitre 6 a pour objectif d'explorer la concordance entre la segmentation crustale et les morphologies salifères dans certaines des marges passives les plus connues au monde, telles que le bassin de Santos (Brésil), la marge angolaise, le golfe du Mexique et les marges Maroc-Nouvelle-Écosse. Malgré une différence de qualité et de résolution entre les profils sismiques étudiés qui pourrait localement modifier notre classification, ce chapitre montre que, quelles que soient les morphologies et la nature crustale interprétées par les auteurs, leurs limites correspondent à celles de la segmentation crustale contrainte par les données de réfraction grand-angle. Il a été montré que l'amincissement crustal, souvent concomitant à un domaine d'exhumation, coïncide avec une déformation salifère plus mature. La présence d'un bassin sag semble correspondre à un domaine de sel en canopée tandis que là où la marge est plus abrupte, les salt sheets sont plus rares. Bien qu'une relation directe entre les morphologies particulières du sel et la nature de la croûte soit délicate à observer, puisque les paramètres qui entrent en jeu dans la déformation sont multiples, ce chapitre montre comment la correspondance géométrique ne doit pas être négligée et mérite une étude plus approfondie de leur relation, comme cela a été initié en Méditerranée occiden

CONCLUSIONS AND PERSPECTIVES

Salt in the Western Mediterranean was deposited during the Messinian Salinity Crisis, around 5.6 Ma. This makes it the youngest salt giant on earth. Unlike the other salt-bearing passive margins, in the Western Mediterranean certain characteristics make it a privileged study area for the study of salt tectonics and its relationship with the deep crust:

 Salt deposition takes place around ~5.6 Ma, in the deep basin, showing a pinch-out on pre-salt marine deposits on the slope, in a context of regional sea level lowering (the debate is still raging) which created strong erosion in the channels both onshore and offshore. Given the purely vertical subsidence in the deep basin, evidenced by previous studies and a global horizontality of Plio-Quaternary deposits, we can suggest that salt was deposited uniformly in space and with constant thickness. At the basins edge in the slopes, where subsidence is in the form of tilting, the salt deposits may showed lower thickness.

 Between the basement and the salt, a thick blanket of predominantly Miocene sediments is widespread in the escarpments and deep basins. This marine sediment blanket, around 1 km thick, fills the basement roughness and is regionally unfaulted.

 Horizontal movements due to plate motion are almost non-existent since the Messinian.

The only active zone since, at least, the Tortonian, is the northern Algerian margin, characterised by a tectonic compressional inversion. The other basins do not show tectonic movements since 16 Ma (8 Ma for the western part of the Algerian basin).

Keeping in mind the specificities of the Western Mediterranean Sea, the first objective was to describe and to map the salt structures using exclusively geometric criteria. From this first part of the work, two orders of segmentation of salt morphologies have been observed:

1) The first is perpendicular to the margins, from the lower slope to the deep basin and mainly concerns the amplitude and distribution of the Listric and Anticlinal salt domains and the limits of the Diapirs domains. When the margins are steeper, the Listric and Anticlinal domains are narrower while when the margin displays a gentle slope the domains are wider.

2) The second order of segmentation concerns the differences depicted within the deep Western Mediterranean sub-basins which show a distinctive morphology for each.

Strong differences are depicted between the Liguro-Provençal, the west and the east Algerian basins. In the Algerian basin, the eastern domain is characterized by less intense (less piercing) salt deformation compared to the western domain.

Subsequently, the different salt domains were related to the crustal segmentation as defined by the authors based on interpretations of wide-angle seismic refraction, gravity and magnetic anomalies. The main objective was to investigate the relationship between the distribution of salt morphologies and crustal segmentation. Some insights have been made:

 A correlation exists between salt morphologies and the structural segmentation and nature of each sub-domain. In the Liguro-Provençal basin, the Listric domain is located on the edges of the margins, where the authors interpret a transitional and/or a thinned crust, as well as all along the north Algerian margin and at the transition between the WAB and the Alboran basin. In the western Sardinian margin, the boundaries of the High salt base domain match well with the transitional crust. In the deep Liguro-Provençal basin the Connected, Irregular salt morphology corresponds to a proto-oceanic and/or oceanic crust following the interpretation of refraction data. Instead, a Connected, Regular domain is interpreted in the EAB, which seems to be constituted of thin oceanic crust, as evidenced by refraction data and clearly aligned magmatic anomalies. The WAB, whose crustal structure is still a matter of debate, is characterized by generally more deformed salt structures, with differences in the eastern and north-western sectors: in the southwest of the South Menorca Block, the salt structures are connected and the salt base is shallower while the deep basin is characterized by the deepening of salt and larger morphologies.

The transition between continental and oceanic domains in the Alboran-WAB limit corresponds to a change in salt morphologies, between an Anticlinal to a

Large/Connected domain. The sharp and quick transition from a thinned continental crust to a thin or atypical oceanic crust along the north Algerian margin is associated with a sudden transition in salt morphologies.

 Given the different mechanisms involved in moulding the shape of salt structures, a direct relationship between crustal nature and specific salt morphology has not been found. However, it is clear that a change in crustal nature (segmentation) coincides with a change in salt morphology.

The natural consequence of these considerations was to try to understand why this coincidence occurred. We have therefore analysed in detail the aspects involved in deformation as described by previous models. To do this, we have analysed the elements and mechanisms involved in salt tectonics and defined their role and dominance in the system. A detailed analysis of the chronology of deformation was carried out mainly in the Gulf of Lion, where the large dataset available, a chronological calibration of the reflectors and previous sedimentary knowledge allowed to discuss in more detail the main mechanisms. Concerning the main causes and mechanisms involved in salt tectonics, several points are depicted:

 The Plio-Quaternary deposits are regionally thin in the lower slope and thick in the deep basin and the depocenters follow the margin segmentation. It thus excludes a regional sedimentation spreading as for instance described in [START_REF] Vendeville | Salt tectonics driven by sediment progradation: Part I-Mechanics and kinematics[END_REF] or observed in the Santos basin (e.g. [START_REF] Guerra | Role of halokinesis in controlling structural styles and sediment dispersal in the Santos Basin, offshore Brazil[END_REF], except for the Gulf of Lion.

Sedimentation differences between the LPB and the Algerian basins are confirmed, whilst no difference between the WAB and EAB are seen. The entire north-Algerian margin is characterised by a considerable sedimentary thickness, which would confirm the foreland basin caused by the active African compression tectonics.

 The thin-skinned salt tectonics is well developed only in the lower slope-proximal deep basin (Listric salt domain). The width of this domain is indirectly proportional to the steepness of the margin. The main mechanism involved in this domain would be the gravity gliding, driven by the slope of the salt base.

 The north Algerian margin undergoes a thick-skinned salt tectonics due to the tectonic compression induced by the North African convergence, as already shown by some authors. The north Algerian basin shows locally a landward-dipped base of salt which preclude a regional gravity gliding towards the deep basin.

 The basement and the tectonic influence play only a minor (if not completely absent) role in the salt deformation of the LPB. Instead, the compression that affects and has affected the salt deposits in the north Algerian margin, may have an influence on the observed morphologies, especially in the closest part to the margin.

 The salt started to deform in the deep basin during the deposition of the Messinian Upper Unit. The listric faults located in the lower slope activated only in the Lower Pliocene to now-days. This means that the gravity gliding mechanism is not the cause of the initial salt deformation trigger in the deep basin, except locally. The salt gliding is therefore a consequence of the free space created by the early deep basin salt movement and acts as an aid to nourishing structures, especially near the margin. Its role is amplified over time by thermal subsidence.

 In the Gulf of Lion, we proposed an evolution of salt tectonics consisting of three main phases, starting with its deposition (~5.6 Ma) to the present-day: Phase 1) an early salt deformation occurred only in the deep basin; Phase 2) basinward-dipped listric faults activation, quiescence in the transitional crust domain and strong passive diapirism deformation in the oceanic domain; Phase 3) strong deformation both above transitional and oceanic crust.

 In the Gulf of Lion, the Rhone input is a major factor in shaping the salt structures, especially in the Quaternary. Gliding acts in the margin edge, where the slope can be more than one degree, and in the proximal Anticlinal domain. In the deep domain, characterised by a horizontal base of salt, we consider its secondary effect. The influence of tectonics is non-existent. Nevertheless, the deformation rate above the oceanic crust is much higher than above the transitional crust. Moreover, classical models of salt tectonics (gravity gliding, spreading and tectonics influence) hardly explain the coincidence between crustal segmentation and salt morphologies. The only hypothesis that remains to be evaluated is a thermal influence from the different crustal natures that could have influenced the salt deformation.

To test the thermal influence hypothesis we used two main techniques, consisting of observation of present-day surface heat flow measurements -the only direct measure of subsurface thermicity -and in the calculation of past thermal field, using the thermo-kinematical model. Thanks to the acquisition of new heat flow measurements during the WestMedFlux1-2 (WMF1-2) campaigns in 2016 and 2018, the density of HF measurements has been increased, especially in the Gulf of Lion and in the South Balearic margin. In this thesis, surface HF measurements from the WMF2 campaign are described for the first time and related to the old measurements. The main results show both short-wavelength variations -in the order of 10-20 km -and regional-scale variations. The most significant local variations were observed in the South Balearic margin, where the thin sedimentary cover, basement highs and strongly positive and negative HF anomalies could indicate a fluid circulation system, and in the Gulf of Lion, where salt diapirs act as a heat pump, significantly increasing the heat flow measured at the surface. Our observations confirm the South Balearic margin as an area affected by important fluid circulation, probably also related to recent volcanic processes.

The transitional and oceanic crust domain is often characterised by a thick blanket of sediments of kilometre thickness with a thick salt blanket within it. The sediments thus sealed the upwelling of fluids at the surface, which are only locally visible. The heat production supposed to be produced during the exhumation phase (mantle and/or lower crust) does not seem to affect the surface, where large differences in surface HF between the transitional and oceanic domains have not been observed.

The thermo-kinematic model allowed to find a good fit between the calculated sections and the present-day crustal structure, which therefore allowed to find a plausible temperature range in the salt deposit. Nevertheless, the model cannot predict phenomena such as exhumation and upwelling of fluids from the basement in the transitional domain, which are still poorly understood but could play a key role in salt deformation.

The analysis of the correlation between salt morphologies and crustal domains in the some passive margins confirms the coincidence observed in the Western Mediterranean. The main differences are in the sag basin passive margins (Brazilian, West African and Gulf of Mexico margins) compared to the more abrupt margins where salt was deposited non-uniformly during continental opening (Morocco-Nova Scotia margins). Although the causes of salt tectonics are multifaceted here and have not been analysed in the same way as in Western Mediterranean, we have shown that the coincidence between crustal segmentation and salt morphologies should not be overlooked.

In conclusion, this study has for the first time regionally described the structures and causes of salt tectonics in the Western Mediterranean. The coincidence with crustal segmentation seems to be explained only by an indirect influence, such as temperature, and not by existing classical models of salt tectonics.

More questions than answers emerge from this thesis. The most important concerns the role of the thermal regime in the evolution of passive margins and thus its influence on salt tectonics.

The direct perspective of this work is to study in more detail the regional thermal regime in order to identify possible differences between the various crustal segments. A first approach could be to acquire more heat flow data in these areas. We have seen that heat flow measurements are easily influenced by surface processes (e.g. fluids, salt...) and only a large point density can give us trustful information about the deep thermal state. A second approach could be numerical modelling. Important steps have been taken since the first McKenzie models on lithospheric stretching. Nevertheless, the diatribe is as open as ever, especially on the transitional domain where different hypotheses coexist.

Another field of research that needs to be explored directly is the relationship between salt tectonics, temperature and fluids. Although some rheological studies propose a direct relationship, a geological application is an approach that has never been addressed. What impact does the temperature-dependent decrease in salt viscosity have on structures? Does the deformation rate increase as the temperature rises? These are just a few of the questions raised after this study. Here again, two complementary approaches would be required:

Analogue modelling: the processes of salt tectonics are often modelled using analogue models, where salt is replaced by silicon and sediments by more or less fine sands. In order to understand the relationship of salt with temperature in a dynamic system, one would need to know the rheological properties of silicon and how it reacts to increases in temperature.

Numerical modelling: several numerical modelling studies of salt tectonic processes are available in the literature (e.g. [START_REF] Ings | Numerical modeling of salt tectonics on passive continental margins: Preliminary assessment of the effects of sediment loading, buoyancy, margin tilt, and isostasy[END_REF][START_REF] Pichel | The impact of pre-salt rift topography on salt tectonics: A discrete-element modeling approach[END_REF]. In the final phase of this thesis, a principle of collaboration with the University of Mainz was born (Tobias Baumann), in which the objective will be to test with a numerical model carried out in the Gulf of Lion (Sardinia profile) the influence of temperature variation in the system. The model takes into account the rheology of the salt and its thermal properties. Although for the moment the work is only a project, it could give insights into the role of temperature, which is still neglected in the literature.

Various modelling tests (both numerical and analogue) could then be carried out. One example would be to carry out two tests of the same regional salt system, such as the classic extension-translation-contraction, at different temperatures. Another test could be to vary the temperature at the basement according to the crustal domain to which it belongs: continental, transitional, proto-oceanic, and oceanic. In this way, it would be possible to understand whether temperature actually plays a role in deformation or whether it is a secondary parameter with respect to classical models.

In addition to modelling, other future perspectives could extend the observation of the relationship between crustal segmentation and salt morphologies to other global margins, such as the Red Sea, a young and warm margin [START_REF] Cochran | Effects of finite rifting times on the development of sedimentary basins[END_REF]. Furthermore, as far as the Mediterranean Sea is concerned, this thesis shows that the presence of a well that reaches at least the salt (if not the underlying crust) is increasingly desired, in order to have a concrete reference and to allow the comparison of seismic imaging with well sampling (as it was proposed within the GOLD drilling project). [START_REF] Cochran | Effects of finite rifting times on the development of sedimentary basins[END_REF]. Par ailleurs, en ce qui concerne la Méditerranée, cette thèse montre que la présence d'un puit atteignant au moins le sel (sinon la croûte sous-jacente) est de plus en plus souhaitée, afin d'avoir une référence concrète et de permettre la comparaison de l'imagerie sismique avec l'échantillonnage (comme cela a été proposé dans le cadre du projet de forage GOLD).

CONCLUSIONS ET PERSPECTIVES

LIST OF FIGURES

Chapter 1.

Figure 1.1. Not exhaustive and simplification of magma-rich (red segments) and magma-poor (green segments) passive margins (after Geoffroy, 2005;Aslanian, personal communication;[START_REF] Reston | The structure, evolution and symmetry of the magma-poor rifted margins of the North and Central Atlantic: A synthesis[END_REF][START_REF] Haupert | Upper-plate magma-poor rifted margins: Stratigraphic architecture and structural evolution[END_REF].

Yellow stars and hexagons indicate Type I and Type II margin example, respectively (from [START_REF] Huismans | Depth-dependent extension, two-stage breakup and cratonic underplating at rifted margins[END_REF].To note that in some magma-poor passive margins may be present evidences of volcanic deposits. 21 et al., (2011) and the absence following [START_REF] Kumar | From oceanic crust to exhumed mantle: A 40 year (1970-2010) perspective on the nature of crust under the Santos Basin, SE Brazil[END_REF]. 27

Figure 1.7. Opening models: A) pure shear [START_REF] Mckenzie | Some remarks on the development of sedimentary basins[END_REF] and B) simple shear [START_REF] Wernicke | Uniform-sense normal simple shear of the continental lithosphere[END_REF] models.

28

Figure 1.8. Conservative model versus kinematic approaches describing the continental crust thinning process.

A) In the conceptual approach (conservative) model the area of continental crust is equal to the initial area, therefore the continental crust thinning can be converted in the horizontal movement. B) In the kinematic approach the horizontal movement is given by kinematic reconstruction. A wide thinned basin remains in that case. The quantity of missing lower continental crust depends on the nature of the allochthonous domain (see text). The sketch comes from Angola and Espirito Santos conjugated margins case study (after [START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF].

31

Figure 1.9. The three phases of thinning processes described in [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF] considering seismic, gravity and kinematic reconstructions data (from [START_REF] Moulin | Etude géologique et géophysique des marges continentales passives: exemple du Zaïre et de l'Angola[END_REF]. To note the vertical subsidence of the sag basin and the relatively shallow position of the system before the break-up. [START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF] and Parson and Sclater, (1977). Points are measured heat flow and lines are modelled ones. The plot on the left represents the heat flow variations compared to the age whilst the plot on the right the ocean depth against the age (modified after [START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF]. 34

Figure 1.11. Plate cooling model from [START_REF] Hasterok | Oceanic heat flow: Implications for global heat loss[END_REF] after filtering results with >400 m sediment cover and more than 60 km far away to the nearest seamount. a) Heat flow versus age. Open circles contain <10 sites, full circles >10 sites. Squares are from [START_REF] Hasterok | Oceanic heat flow: Implications for global heat loss[END_REF] (1978) to account heat production for different stretching factors (1.25, 2.00, 3.50). The red line shows the plate cooling oceanic model (from [START_REF] Jaupart | Treatise on Geophysics. Temperatures, Heat and Energy in the Mantle of the Earth[END_REF]. 36

Figure 1.13. Seismic profile and heat flow measurements in the Gulf of Aden, after [START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF]. The grey area corresponds to the range of values expected for the age of the oceanic floor according to [START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF] [START_REF] Jolivet | Lithospheric-scale geodynamic context of the Messinian salinity crisis[END_REF], 2009[START_REF] Roure | Alpine inversion of the North African margin and delamination of its continental lithosphere[END_REF]and Leroux et al., 2019). 39 angle refraction, reflection, gravity and magnetic data (from [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF]Leroux et al., 2019). With red lines are indicated the SARDINIA wide-angle and coincidents reflection seismic lines. In the Algerian basin the dashed lines indicate the segmentation from gravity and magnetic data from [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. In the North Algerian basin, the black dashed lines indicate the interpretation of crustal domains from SPIRAL wide-angle survey (from [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF][START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF][START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF][START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF]Aidi et al., 2018). SPIRAL lines are indicated with red solid lines. WESTMED refraction survey in South Balearic margin is shown with red lines (from Vina Gaza, 2016;Gomez de la Pena et al., 2018) but is not considered in segmentation interpretation. The segmentation in the Valencia and Menorca segments is from [START_REF] Pellen | The Minorca Basin: a buffer zone between the Valencia and Liguro-Provençal Basins (NW Mediterranean Sea)[END_REF] and [START_REF] Etheve | Extensional vs contractional Cenozoic deformation in Ibiza (Balearic Promontory, Spain): Integration in the West Mediterranean back-arc setting[END_REF]. The South Minorca block position and interpretation is from Driussi et al., [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. The first profile on the top is the SARDINIA01 crossing NW-SE the Gulf of Lion whilst the other two cross it with a NE-SW direction. B) West

Sardinian margin profiles with a WNW-ESE direction, from [START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF]. The profiles are at the same scale. 47 except for the profile E, acquired in a NW-SE direction (after [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF][START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF][START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF][START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF], Mihoubi et al., 2015, Aidi et al., 2018). The profiles are at the same scale. 49

Chapter 2. hemisphere due to the dominance of landmasses across the Permian to recent periods (after [START_REF] Ziegler | Detection of intensification in global-and continental-scale hydrological cycles: Temporal scale of evaluation[END_REF].

60

Figure 2.5. Phanerozoic volume of deposited evaporites against time (Phanerozoic) (after [START_REF] Hay | Evaporites and the salinity of the ocean during the Phanerozoic: Implications for climate, ocean circulation and life[END_REF]. Baltimore Canyon;21. Berrechid;23. Bohai Basin;24. Bonaparte (Petrel); 25.

Brazilian Aptian Basin (Camamu); 26. Brazilian Aptian Basin 27. Brazilian Aptian Basin (Ceara);28. Brazilian Aptian Basin (Cumuruxatiba);31. Canning Basin;33. Carnarvon Basin (Yaringa);34. Carpathian foredeep;35. Carson Basin (Grand Banks);39. Cuban;40. Danakil;41. Dead Sea;44. Eastern Alps;45. Ebro Basin;46. Flemish Pass Basin (Grand Banks);47. Georges Bank;48. Green River Basin;49. Gulf of Mexico [START_REF] Lofi | Erosional processes and paleo-environmental changes in the Western Gulf of Lions (SW France) during the Messinian Salinity Crisis[END_REF] showing the trilogy depicted in the deep basin. Salt, in yellow, is called Mobile Unit (MU). D) sketch from the Levant basin (Bertoni and Cartwright, 2005a) showing the Mobile Unit, which can be in turn subdivided in 6 subunits (after Roveri et al., 2014a). 73 shows little changes in density with the depth while the other rocks, subjected to the compaction, increase their density (after [START_REF] Jackson | External shapes, strain rates, and dynamics of salt structures[END_REF]. 75

Figure 2.16. Rock salt viscosity compared to other rocks/substances (modified after Weijemers et al., 1993).

76

Figure 2.17. Thermal conductivity of typical rocks, included rock salt (last row). Note the higher thermal conductivity of about 5.5 W/m*k, which depends also on the temperature. 77 [START_REF] Jackson | Salt tectonics: Principles and practice[END_REF].

80

Figure 2.20. Steady state deformation map of rock salt from [START_REF] Khaledi | Recent and active deformation pattern off the easternmost Algerian margin, Western Mediterranean Sea: New evidence for contractional tectonic reactivation[END_REF] who modified the original plot from [START_REF] Munson | Preliminary deformation-mechanism map for salt (with application to WIPP)[END_REF] and [START_REF] Urai | Weakening of rock salt by water during long-term creep[END_REF] [START_REF] Cornet | Long term creep closure of salt cavities[END_REF]. 82 . Time to reach 10% strain at different strain rates is shown on the right side of the graph (after [START_REF] Schléder | Microstructural evolution of deformation-modified primary halite from the Middle Triassic Röt Formation at Hengelo, The Netherlands[END_REF]. 83

Figure 2.23. Coarse grain halite at 30-200 °C. Strain rate versus differential stress. [START_REF] Li | Rheology of rock salt for salt tectonics modeling[END_REF].

84

Figure 2.24. Stress strain curves for dry Avery Island rock salt at constant strain rates over 3.5 years, after [START_REF] Carter | Rheology of rocksalt[END_REF]. 85 (after Van Keken et al., 1993). 86

Figure 2.26. Typical stress-strain curves showing the effect of temperature on the behaviour of wet polycrystalline halite at strain rate of 5-7 10 -7 s -1 . For comparison, two stress-strain curves for dry polycrystalline halite (grey curves) are included [START_REF] Watanabe | Electrical impedance measurement of plastically deforming halite rocks at 125 C and 50 MPa[END_REF]Ter Heege, 2002). To note the temperature influence on strain.

86

Figure 2.27. Review of rock salt viscosity values from different authors [START_REF] Mukherjee | Viscosity estimates of salt in the Hormuz and Namakdan salt diapirs, Persian Gulf[END_REF]. (after Carter et al., 1993). 88 [START_REF] Hudec | Terra infirma: Understanding salt tectonics[END_REF]. 94

Figure 2.33. Interpreted seismic section in the Gulf of Lion from Dos [START_REF] Reis | Radial gravitacional gliding indicated by subsalt relief and salt-related structures: the example of the gulf of Lions, western Mediterranean[END_REF] showing an example of thin-skinned tectonics. To note the listric faults that not dislocate the base of salt and the Miocene sequence. [START_REF] Jackson | A glossary of salt tectonics[END_REF]. 96

Figure 2.36. Summary of the three stages of diapir piercement through pre-kinematic overburden. (A) after [START_REF] Jackson | Structural dynamics of salt systems[END_REF]; (B) after Jackson and Vendeville, (1991a). 97

Figure 2.37. Downbuilding process and passive diapir evolution (after [START_REF] Ribes | Interaction entre la tectonique salifère et la sédimentation dans des mini-bassins: Exemple de l'Oligo-Miocène du bassin de Sivas[END_REF][START_REF] Barton | Mechanics of formation of salt domes with special reference to Gulf Coast salt domes of Texas and Louisiana[END_REF]. 98 [START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF][START_REF] Jackson | Salt tectonics: Principles and practice[END_REF]. [START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF]. [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]. 104

Figure 2.42. The differential compaction above a basement step during gravitational gliding is shown. The regional slope is of 3°. To note, in figure c, the differential compaction effect above the basement step and the graben formed above the updip part (after [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF]. Note the scale in the experimental set-up, which involved a basement step 2-3 times greater than the silicone (salt) thickness. 105 [START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF]. 109

Chapter 3. warming of the instrument due to the penetration in the sediments; during the third phase the thermistors are heated with a constant energy and the conductivity is calculated; in the last phase the instrument is pulled-out.

The complete sequence allows to get the temperature gradient observed between the thermistors and the thermal conductivity calculated by the heating (after [START_REF] Poort | WESTMEDFLUX cruise, RV L'Atalante[END_REF]Cruise Report). 123 Lofi et al., (2011a[START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF] Note also the differences between the West and the East Mediterranean markers and facies (from [START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF]. 12: Pliocene Quaternary contourites (after [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF]. 146

Figure 4.3. Nomenclature comparison between the model of [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF] and [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF], after [START_REF] Pellen | Géodynamique et impact de la crise d'érosion et de salinité Messinienne sur les transferts sédimentaires (bassins de Valence et Adriatique)[END_REF] [START_REF] Hunt | Stranded parasequences and the forced regressive wedge systems tract: deposition during base-level'fall[END_REF]. 146 the salt structures are rare. The offshore evaporitic distribution is after Roveri et al., (2014a). The Central Mallorca salt is taken from Driussi et al., (2015a). The salt limit is from this study, [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF]), Driussi et al., (2015a) and [START_REF] O Obone-Zue-Obame | The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the "MAURESC" cruise[END_REF]. In Basement depth map (in s twt). The salt limit is from [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF], Driussi et al., (2015a), [START_REF] O Obone-Zue-Obame | The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the "MAURESC" cruise[END_REF] and this study. The contour lines are every 0.5 and 1 s twt. Note the shallow basement in the Hannibal High area and the deeper in the LPB. 154

Figure 4.8. Pre-salt sequence isopach map (in s twt). Contour every 0.5 and 1 s twt. The salt limit is from [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF], Driussi et al., (2015a[START_REF] O Obone-Zue-Obame | The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the "MAURESC" cruise[END_REF] [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF], Driussi et al., (2015a[START_REF] O Obone-Zue-Obame | The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the "MAURESC" cruise[END_REF] and this study. Note the Petit Rhone fan (e.g. [START_REF] Droz | Quaternary turbidite systems on the northern margins of the Balearic Basin (Western Mediterranean): a synthesis[END_REF] et al., (2016). Thin black lines are bathymetry every 200 m (thin lines) and at 100 and 2000 m depth (thick lines).

The upslope salt limit is from [START_REF] Bache | Messinian erosional and salinity crises: view from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF][START_REF] O Obone-Zue-Obame | The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the "MAURESC" cruise[END_REF], Driussi et al., (2015a) and this study. 158 (2018) and [START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF] Here, the base of salt is landward dipping, probably due to the tectonic reactivation which could landward tilted the basement. Below, the MUM (nomenclaute from [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF] Moulin et al., 2015 (GoL) and Afilhado et al., 2015 (WS). 186 The wide-angle seismic profiles are taken from Leprêtre et al., 2013 (C) and Mihoubi et al., 2014 (D). Location in free air anomaly map. 192 [START_REF] Bache | Messinian erosional and salinity crises: view from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF] The squares shows the main deformation area for each phase. Note the early deformation during phase 1 and the stronger and faster growth above the oceanic crust. The Hinge line is taken from [START_REF] Leroux | Post-rift evolution of the Gulf of Lion margin tested by stratigraphic modelling[END_REF] and marks the limit between a slope tilting subsidence and a deep basin purely vertical subsidence [START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF], Leroux et al., 2015). 218 [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF].

Note the ratio between the basement step and the initial silicone thickness (representing the salt). 229 movement (5mm/yr, from Serpelloni et al., 2007). Below, the line-drawing crosses the Algerian basin from the South Balearic to the north Algerian margins highlighting the narrowness of the WAB. The profile zooms (in depth, from Blondel Simon, unpublished) shows the salt structure close to the Emile Baudot Escarpment. Note the squeezed diapirs suggesting contractional events. 232 Chapter 5.

Figure 5.1. Regional setting of the Western Mediterranean Sea. The present-day segmentation is the result of plate and blocks geodynamical history. While there is a consensus about segmentation and geodynamic in the Liguro-Provençal basin [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF], in the Algerian basin doubts about the basin opening lead to different segmentation interpretation. Wide-angle segmentation is taken from [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]; Afhilado et al., 2015;[START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF]Aidi et al., (2018); [START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF]; [START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF]; [START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF].

Gravity modelling segmentation is from [START_REF] Driussi | Evidence for transform motion along the South Balearic margin and implications for the kinematics of opening of the Algerian basin[END_REF] Gravity and magnetic segmentation is from [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. Free-air anomaly map is from [START_REF] Smith | Global sea floor topography from satellite altimetry and ship depth soundings[END_REF] [START_REF] Pellen | The Minorca Basin: a buffer zone between the Valencia and Liguro-Provençal Basins (NW Mediterranean Sea)[END_REF]. 244 [START_REF] Burrus | Contribution to the thermal regime of the Provençal Basin based on FLUMED heat flow surveys and previous investigations[END_REF], at a maximum distance of 50 km. Thin lines above seafloor indicate the HF measurements location. Thickness in meters of Miocene pre-salt is from [START_REF] Bache | Evolution Oligo Miocène des marges du micro océan Liguro-Provençal[END_REF]. Crustal segmentation is taken from [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. The HF measurements are from WMF1 survey. 253 segmentation is taken from Driussi et al., (2015a), Aidi et al., (2018) and [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF]. The HF are from WMF2 survey. 255 Thin lines above seafloor indicate the HF measurements location. Crustal segmentation is taken from Driussi et al., (2015a) and [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF] Mediterranean. From I to V, the Gulf of Lion, Western Sardinian, Hannibal Area, SMB and South Balearic margins are represented, respectively. The crustal segmentation is taken from [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF], Afhilado et al., (2015), Driussi et al., (2015a), [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF]), Aidi et al., (2018) [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. The scale is the same for all the profiles. 263 [START_REF] Smith | Global sea floor topography from satellite altimetry and ship depth soundings[END_REF]. Thin black solid and dashed lines represent the crustal segmentation (from [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF].270 Below: initial crustal setting showing the same parameters than above but on the crust level. Initial and final (oceanic crust) crustal thicknesses are taken from [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. For lithosphere parameters references refer to the text. 273 [START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF]. 275

Figure 5.17. Final (output) crustal structure of the reference model in the Gulf of Lion. Dashed line represents top basement and Moho depth from wide-angle refraction model [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. Note the good fitting concomitant with the thinnest crustal domain. 275 [START_REF] Carlson | On modeling the thermal evolution of the oceanic upper mantle: An assessment of the cooling plate model[END_REF]. 285

Chapter 6. (after Evain et al., 2015;[START_REF] Klingelhoefer | Imaging proto-oceanic crust off the Brazilian Continental Margin[END_REF]. The crustal limit are from [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Right: with the crustal thickness. The hinge line and the Capricornio and Cruzeiro do Sul lineaments are from [START_REF] Moulin | Kinematic keys of the Santos-Namibe basins[END_REF]. 294 Figure 6.3. From top to bottom: map showing the crustal segmentation in the Angolan margin. The crustal limits are from Contrucci et al., (2004a) and [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]. Reflection and refraction seismic data used in this study are represented (references in chapter 3). Bottom: wide-angle refraction seismic profile showing the crust velocity model in Zaiango03 (Z03) profile (after Contrucci et al., 2004a) (references in the chapter 3). Bottom: Smart1 and Mirror1 profiles are from [START_REF] Funck | Crustal structure of the northern Nova Scotia rifted continental margin (eastern Canada)[END_REF] and [START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF], respectively. Black lines represent seismic profile used in this study (references in chapter 3). ECMA and WACMA are from [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF]. 302 [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF].

Volcanic structures are from [START_REF] Mohriak | Salt tectonics, volcanic centers, fracture zones and their relationship with the origin and evolution of the South Atlantic Ocean: geophysical evidence in the Brazilian and West African margins[END_REF]. The hinge line and the Capricornio and Cruzeiro do Sul Lineaments are from [START_REF] Moulin | Kinematic keys of the Santos-Namibe basins[END_REF]. Black lines represent seismic profile interpreted (references in the chapter 3). Wide-angle profile location and crust segmentation are from Contrucci et al. (2004a) and [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF].

Black lines represent seismic profile interpreted in this study (references in the text). (B) From top to bottom, time migrated reflection profile (Z-03) and line-drawing interpretation (modified after [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]; location on maps above) showing salt morphologies domains. Z-03 wide-angle coincident profile showing crust segmentation by Contrucci et al., (2004a). Dashed black lines represent the lower and upper limit of the crust. 311 Figure 6.10. Map showing salt morphologies distribution along the northern Gulf of Mexico. Salt structures outline are from [START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF]. Fault trends are from [START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF] and [START_REF] Stephens | Basement controls on subsurface geologic patterns and near-surface geology across the northern Gulf of Mexico: a deeper perspective on coastal Louisiana[END_REF]. The salt morphologies boundaries are modified from previous interpretation [START_REF] Seni | Evolution of salt structures during burial of salt sheets on the slope, northern Gulf of Mexico[END_REF]. Salt structural domains map is from P. Bourges (personal communication); original salt distribution is from [START_REF] Karlo | Classifications of syndepositional Systems and Tectonic Provinces of the Northern Gulf of Mexico[END_REF]; the profiles are modified from [START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF][START_REF] Schuster | Deformation of allochthonous salt and evolution of related salt-structural systems, eastern Louisiana Gulf Coast[END_REF]. 313 shown only the crustal segmentation while on the right the superposed salt morphologies. Outlined in red the salt structures from [START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF]. Salt morphologies boundary are redrawn from Seni, (1992). The oceanic domain boundaries from Hudec et al., (2013a); [START_REF] Sawyer | The crust under the Gulf of Mexico Basin. The Gulf of Mexico Basin: Geological Society of America[END_REF], [START_REF] Christeson | Deep crustal structure in the eastern Gulf of Mexico[END_REF] and [START_REF] Curry | Extensional models for the development of passive-margin salt basins, with application to the Gulf of Mexico[END_REF] are represented. Black lines represent Gumbo wide-angle survey profiles (references in chapter 3).

Fault trends are from [START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF] and [START_REF] Stephens | Basement controls on subsurface geologic patterns and near-surface geology across the northern Gulf of Mexico: a deeper perspective on coastal Louisiana[END_REF]. Black lines represent seismic profile, interpreted in this study (references in the text). (B) PSDM ION GulfSPAN 2450 profile from [START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF] and Dickinson, (2017) approximately in the location of GUMBO 1 profile (location in (A) maps). The salt morphologies are from this study. Below, the GUMBO1 wide-angle profile. Crustal segmentation in black is from this study and discussion in [START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF]. Dashed black lines represent the lower and upper limit of the crust. 314 Figure 6.12. Map showing salt morphologies of Nova Scotia-Morocco conjugated margins. Salt structures are from Shimeld, (2004);[START_REF] Sahabi | Evolution cinématique triasico-jurassique de l'Atlantique central: Implications sur l'évolution géodynamique des marges homologues nord ouest africaine et américaine[END_REF] and [START_REF] Tari | Salt tectonics in the Atlantic margin of Morocco[END_REF]. Black lines represent the seismic profiles used in this study (references in chapter 3). Canopy (allochthonous) salt in Nova Scotia is from Sahabi, (2004) interpretation.

Tafelney canopy area is from interpretation of [START_REF] Tari | Salt tectonics along the Atlantic margin of Morocco[END_REF]. Nova Scotia seismic profile is modified from Louden et al., (2012) (references in the chapter 3). WACMA and ECMA are from [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF]. (B) Mirror01 reflection and wide-angle associated profiles (location in map above (A)). Modified after [START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF]. closed system, formed several Ma before the deposition, horizontally in the entire deep basins, above a homogenous multi-kilometre pre-Messinian thickness. The subsidence is purely vertical in the deep basin, implying a regional constant initial salt thickness, the post-salt overburden is homogenous and the distal salt deformation occurred before the mid-lower slope normal faults activation. Instead, the compilation of MCS and wide-angle seismic data highlighted a clear coincidence between crustal segmentation and salt morphology domains.

The salt structures change morphology at the boundary between different crustal natures. Lower evaporites are considered less ductile than the pure halite, as anhydrite creeps slowly than gypsum which in turn creeps slowly than halite [START_REF] Jackson | Salt tectonics: Principles and practice[END_REF]. In most cases, they brittly accommodated the underlying salt deformation.

The Messinian units are deposited above a thick Miocene sedimentary sequence characterized by thickness variations between the Western Mediterranean sub-basins. The Oligocene syn-rift to Miocene post-rift sedimentary units are composed, by analogy with onshore drill (e.g. onshore Kabyle, Algeria, [START_REF] Géry | Definition d'une série type de l'Oligo-Miocene Kabyle[END_REF]Onshore Camargue, France, Triat and Truc, 1983), by silty marl, conglomerates and sandstones, showing facies from shallow water to deep marine. In seismic, these deposits onlaps the acoustic basement reflector and fill the hollows in the relief. At present day, they are at basin scale sub-horizontal, parallel to the base of salt and mostly unfaulted.

Salt is ductile and, in the Western Mediterranean Sea, is always deposited as flat horizontal layer above the pre-Messinian units. The present-day slope of this surface thus gives the postdeposition movement, mainly caused by differential subsidence. In the Gulf of Lion, first [START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF] with a 2D dataset and then [START_REF] Leroux | Post-rift evolution of the Gulf of Lion margin tested by stratigraphic modelling[END_REF] with a 3D grid calculated using sedimentary geometries the subsidence up to present day. They define three subsidence domains, from the shelf to the deep basin, which fit with the hinge lines defined by refraction studies by [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF] (see chapter below) and by interpretation by [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF]. On the platform and on the slope, they observed a seaward tilting of different amplitudes, varying from the Miocene (0.06° Ma -1 -0.12° Ma -1 ) to the Plio-Quaternary age (0.16° Ma -1 ) [START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF][START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF]. Instead, in the central deep basin, they calculated a purely vertical post-rift subsidence, with a mean rate of 500 m/Ma since 20 Ma, supposedly to be the end of rifting age [START_REF] Séranne | The Gulf of Lion continental margin (NW Mediterranean) revisited by IBS: an overview[END_REF]. The Gulf of Lion therefore acts as a sag basin, with features similar to those of the Angolan margin [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF] and Santos basin (Klingelhoefer et al., 2015;[START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. In this work, the term "sag basin" refers to the sedimentary sequence below the salt, characterized by flatly layered sedimentation [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]Karner and Gamboa, 2007;[START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF] and purely vertical subsidence.

The post-Messinian series (Pliocene and Quaternary deposits) in the Algerian basin has a lower thickness than in the Liguro-Provençal (0.8 km and 2 km, respectively; from [START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF], whereas it is roughly similar between the eastern and western Algerian basins and western Sardinian margins [START_REF] Dal Cin | Seismic imaging of Late Miocene (Messinian) evaporites from Western Mediterranean back-arc basins[END_REF].

Dataset and method

We compared salt morphologies and crustal domains in Western Mediterranean Sea margins, Brazilian margin (Santos and Campos basins), Angolan margin, northern Gulf of Mexico margin, north-west African margin and Nova Scotia margin.

Salt morphologies interpretation

In the Western Mediterranean Sea, we interpreted a large dataset composed of different resolution seismic lines, collected through the French GDR Marges and Action Marges programs, with additional recent seismic data from OGS and Ifremer (Fig. 1). Reflection seismic lines have different resolution and quality allowing a good interpretation of deep and shallow reflectors.

In the Santos and Campos basins, we interpreted salt structures from published seismic profiles (Fig. 9) from [START_REF] Modica | Postrift sequence stratigraphy, paleogeography, and fill history of the deep-water Santos Basin, offshore southeast Brazil[END_REF]; [START_REF] Mohriak | Sal: Geologia e Tectônica; Exemplos nas Bacias Brasileiras[END_REF]2012) [START_REF] Kukla | South Atlantic salt basins-witnesses of complex passive margin evolution[END_REF].

For the Angola margin, we interpreted profiles (Fig. 10) from [START_REF] Marton | Evolution of the Angolan passive margin, West Africa, with emphasis on post-salt structural styles[END_REF]; [START_REF] Tari | Examples of salt tectonics from West Africa: a comparative approach[END_REF] ; [START_REF] Hudec | Regional restoration across the Kwanza Basin, Angola: Salt tectonics triggered by repeated uplift of a metastable passive margin[END_REF] ; [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF] ; Unternher et al., (2010) ; [START_REF] Fort | Salt tectonics on the Angolan margin, synsedimentary deformation processes[END_REF]; [START_REF] Cowie | The palaeo-bathymetry of base Aptian salt deposition on the northern Angolan rifted margin: constraints from flexural back-stripping and reverse post-break-up thermal subsidence modelling[END_REF].

For the Gulf of Mexico, we compiled salt morphologies from several published seismic profiles (Fig. 11) [START_REF] Wu | Allochthonous salt, structure and stratigraphy of the northeastern Gulf of Mexico. Part I: Stratigraphy[END_REF][START_REF] Radovich | Insights into structure and stratigraphy of the northern Gulf of Mexico from 2D pre-stack depth migration imaging of mega-regional onshore to deep water, long-offset seismic data[END_REF][START_REF] Pilcher | Primary basin and their boundaries in the deep-water northern Gulf of Mexico: Origin, trap types, and petroleum system implications[END_REF][START_REF] Rodriguez | Regional structure, stratigraphy, and hydrocarbon potential of the Mexican sector of the Gulf of Mexico[END_REF][START_REF] Fort | Kinematics of regional salt flow in the northern Gulf of Mexico[END_REF]Hudec and Jackson, 2013a;[START_REF] Ismael | Tectonostratigraphic Stages in the Mesozoic Opening and Subsidence of the Gulf of Mexico Based on Deep-Penetration Seismic Reflection Data in the Salt-Free Eastern Part of the Basin[END_REF][START_REF] Pindell | Rapid outer marginal collapse at the rift to drift transition of passive margin evolution, with a Gulf of Mexico case study[END_REF][START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF][START_REF] Weimer | An overview of the petroleum systems of the northern deep-water Gulf of Mexico[END_REF][START_REF] Curry | Extensional models for the development of passive-margin salt basins, with application to the Gulf of Mexico[END_REF][START_REF] Liu | Crustal structure of Mesozoic rifting in the northeastern Gulf of Mexico from integration of seismic and potential field data[END_REF] and from already published saltdistribution maps [START_REF] Seni | Evolution of salt structures during burial of salt sheets on the slope, northern Gulf of Mexico[END_REF][START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF][START_REF] Peel | Genetic structural provinces and salt tectonics of the Cenozoic offshore US Gulf of Mexico: A preliminary analysis[END_REF] In the Morocco and Nova Scotia conjugated margins (Fig. 12), the salt structures originate from works by [START_REF] Hinz | The continental margin of Morocco: seismic sequences, structural elements and geological development[END_REF]; [START_REF] Keen | The transition from a volcanic to a nonvolcanic rifted margin off eastern Canada[END_REF][START_REF] Sahabi | Evolution cinématique triasico-jurassique de l'Atlantique central: Implications sur l'évolution géodynamique des marges homologues nord ouest africaine et américaine[END_REF][START_REF] Shimeld | A comparison of salt tectonic subprovinces beneath the Scotian Slope and Laurentian Fan[END_REF]; [START_REF] Neumaier | Late Cretaceous to Cenozoic geodynamic evolution of the Atlantic margin offshore Essaouira (Morocco)[END_REF]; [START_REF] Tari | Salt tectonics in the Atlantic margin of Morocco[END_REF][START_REF] Tari | Examples of salt tectonics from West Africa: a comparative approach[END_REF][START_REF] Tari | Salt tectonics along the Atlantic margin of Morocco[END_REF]

Crust segmentation

The crustal segmentation is constrained by wide-angle profiles from ECORS and SARDINIA Experiments [START_REF] Pascal | The ocean-continent boundary in the Gulf of Lion from analysis of expanding spread profiles and gravity modelling[END_REF][START_REF] Gailler | Crustal structure of a young margin pair: new results across the Liguro-Provencal Basin from wide-angle seismic tomography[END_REF][START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF] in the Liguro-Provençal basin and by Spiral Project [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF] structure is the result of processes interaction, we tried to discriminate them only by their geometrical characteristics. The salt morphologies groups are then plotted on map, showing wide variations between the proximal and distal domains and between the sub-basins composing the Western Mediterranean Sea (Fig. 5).

Salt morphologies description and distribution

In this chapter we will describe the main present-day salt morphologies characteristics (Fig. 4) and their spatially distribution along the Western Mediterranean Sea (Fig. 5). Figure 6 2001) and are located at the mid-lower slope of the margins. The sliding of salt along its base detachment induces a sediments subsidence and thinning of salt, which is proportional to the density and thickness of the overburden and the initial salt layer thickness [START_REF] Vendeville | Salt tectonics driven by sediment progradation: Part I-Mechanics and kinematics[END_REF], and does not affect the pre-salt sequence (thin-skinned tectonics). The structures formed by the salt movement are the results of extensional process, which involves salt and overburden basinward movements. This domain is located at mid-lower continental slope of the margins (Figs. 6; 7) and is always present albeit with some differences in amplitude, mainly given by base of salt steepness and wideness of the margin (Fig. 5): in the Gulf of Lion it occupies an area that can extend up to 50 km basinward from the upslope limit of salt (Fig. 6A) while in the Algerian margin and in the east Alboran margin is narrower, of 10-20 km (Figs. 6B,D; 7I). In the south Balearic and in the western Sardinian margins is between 10 and 30 km (Figs. 6C,E; 7F,G,H). As mentioned above (Fig. 2a), the listric faults activated after the deposition of the Upper Unit and are mainly active in the Pliocene but they can reach the seafloor (Badhani et al., 2020).

• The Anticlinal salt domain (Fig. 4) is characterized by the absence of normal faults rooted at the base of salt and it consists of anticlinal salt-cored and sparsely distributed normal faults at the top. The outer-arc extension faults are mainly located at the top of Upper Unit affecting the Lower Pliocene sequence. The base of salt can be sub-horizontal (Gulf of Lion; Fig. 3) or even dipping landward, as in the north Algerian margin (Fig. 6B,D). The base of anticlines is large and the ratio between length and height is greater than five. The Anticlinal domain is located in the proximal deep basins (Fig. 5), characterized by a purely vertical subsidence (as shown in Gulf of Lion by [START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF][START_REF] Leroux | Post-rift evolution of the Gulf of Lion margin tested by stratigraphic modelling[END_REF] as also attested by sub- • The Large Isolated Diapir (GoL) (Fig. 4) and the Large/Connected (WAB) domains exhibit piercing diapirism affecting the seafloor. In Gulf of Lion (Fig. 5), diapir crests can rise to 250 m above the seafloor [START_REF] Pautot | Morphology and extension of the evaporitic structures of the Liguro-Provençal Basin: New Sea-Beam data[END_REF] and the structures are isolated, forming wide mini-basins and welding together (Fig. 3). In the western Algerian deep basin the structures are less spaced-apart and generally smaller in size (Figs. 5; 7I). In both basins the overburden is discordant except for the Upper Quaternary sequence, which is concordant to the top of structures. The overburden deposits could form narrow and steep or, less frequently, gentle drape-folds geometries on diapirs flanks, typical of hook and wedge halokinetic sequences described by [START_REF] Giles | Concepts in halokinetic-sequence deformation and stratigraphy[END_REF] (see also [START_REF] Mianaekere | Halo-kinematic'sequence stratigraphic analysis adjacent to salt diapirs in the deepwater contractional province, Liguro-Provençal Basin, Western Mediterranean Sea[END_REF]. Both salt stocks and walls are present: in the Gulf of Lion the salt walls have a dominantly N-S direction while in the north Algerian margin they are parallel to the margin, as also described by [START_REF] Badji | Structure Profonde de la croûte et potentiel pétrolier des bassins sédimentaires à l'ouest de l'Algérie[END_REF] and Leprêtre, (2012). In the Gulf of Lion they grew far from the upslope salt limit (at least 100 km basinward; figs. 5; 6A) while in the west Algerian basin they appear closer to the margin (about 10 km, just basinward the Listric domain; fig. 5) and dominate the deep basin. The structures show an initial active growth history early after the deposition followed by a passive down-building which characterized mostly all the Plio-Quaternary diapirs growing.

• The Small, Regular and the Narrow, Irregular domains (Fig. 4) are interpreted in the deep basins (Fig. 5) and are characterized by different-sized connected diapirs (Figs. 6,7). The Connected, Regular domain is characterized by closely-spaced diapirs that deform the Pliocene but very rarely the Quaternary sequences (Fig. 6B,C). The overburden reflectors are mainly concordant and the width to height ratio is close to one. This domain is located in the EAB, where a maximum salt thickness of 0.5 s twt and a regional sub-horizontal base characterize the entire basin (Figs 5; 6B,C). The Plio-Quaternary sedimentary thickness is more or less constant in all basin, except in the north eastern Algerian margin, with a mean thickness of 0.8 s twt. The Connected, Irregular domain is characterized by close and frequent diapirs (Figs. 6A; 7F). The overburden is mostly discordant and the structures are smaller and narrower than in the Large Diapirs domain previously described: they have developed more in height than in width (Fig. 4) and can deform the seafloor.

In addition to the salt morphologies domains described above, we interpreted two areas where the base of salt is around 500 m shallower than in the deep basin (Fig. 5). In the western Sardinian and south Balearic margins (Figs. 6B,C,D,E; 7F,G,H) the base of salt extends for 50 km (western Sardinian) to 20-100 km (south Balearic) from the Listric domain, located in the lower slope, and is low basinward tilted. The diapirs structures are close and connected. In the south Balearic margin (Fig. 6E) the sudden deepening of the salt base could be provoked by southward basement tilting associated with the compressive reactivation of the Algerian margin (Leprêtre, 2012).

We also observed an area of thin or absent salt (hard to decipher with our seismic data resolution), concomitant with the Hannibal Area between the east and west Algerian basins (Figs. 5; 6C). Here the salt is not deformed and, where present, has a maximum thickness of 0.2 s twt. The Hannibal Area is characterized by positive magnetic anomalies (Aidi et al., 2018) and basement highs [START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF], which suggest the presence of magmatic structures (Fig. 6C).

Crustal segmentation and nature

During the SARDINIA Experiment, three wide-angle profiles in the Gulf of Lion [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF] and three in the Western Sardinian margin [START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF] were acquired (Fig. 1). The authors interpreted each margin in three domains, with possible subdomains, as also described by Bache et al., 2010 (Figs. 3;5). These domains are similar between the conjugate margins, showing a symmetrical distribution [START_REF] Gailler | Crustal structure of a young margin pair: new results across the Liguro-Provencal Basin from wide-angle seismic tomography[END_REF], except for the dimensions of the transitional domain, which is wider in the Gulf of Lion (Fig. 5). The first domain, which follows the onshore unthinned continental crust domain, is the "crustal thinning" domain, area characterized by the main thinning of the crust, mainly focused on the lower crust where, in the Gulf of Lion, thickness decreases from 15 to 7 km (Fig. 3). Basinward, the transitional domain is characterized by a relatively high crustal velocity, varying between 6.0 and 6.4 km/s for the upper layer, and 6.6-7.5 km/s, 6.8-7.25 km/s for the lower layer, in the Gulf of Lion and West Sardinian, respectively. The lower layer is interpreted as exhumed lower continental crust [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF] or exhumed lower crust and upper mantle [START_REF] Jolivet | Continental breakup and the dynamics of rifting in back-arc basins: The Gulf of Lion margin[END_REF]. The central domain is characterized by a decrease in velocity and velocity gradient in the lower crust [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF] and presents an "atypical" relatively thin (5 km) oceanic crust (e.g. Le [START_REF] Le Douaran | Deep structure of the north-western Mediterranean Basin: Results of a two-ship seismic survey[END_REF][START_REF] Gailler | Crustal structure of a young margin pair: new results across the Liguro-Provencal Basin from wide-angle seismic tomography[END_REF][START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF].

The oceanic crust is thinner than the Atlantic type but the velocity and gradients confirm the oceanic nature [START_REF] Gailler | Crustal structure of a young margin pair: new results across the Liguro-Provencal Basin from wide-angle seismic tomography[END_REF] and its close relationship with the transitional domain, regarding the velocities and the Moho discontinuity depth [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF]. The segmentation is confirmed by gravimetric (Sandwell and [START_REF] Smith | Global sea floor topography from satellite altimetry and ship depth soundings[END_REF] and aeromagnetic [START_REF] Galdeano | Assemblage à altitude constante des cartes d'anomalies magnétiques couvrant l'ensemble du bassin occidental de la Méditerranée[END_REF] data [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF].

Whilst in the EAB a well-organized set of N-S to NW-SE magnetic anomalies suggests an oceanic nature for this basin (e.g. [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF], in the WAB the absence of clear aligned magnetic anomalies testifies for a clear oceanic crust, leaving open all questions concerning the crustal nature and consequently the geodynamic models of the area. The north Algerian margin was surveyed during the SPIRAL survey (Groupe SPIRAL, 2014) and five wide-angle profiles were acquired with a more or less N-S direction, from the west to the east ends of the Algerian basin (Fig. 1). The results show a narrow thinning continental crust domain (from 20 to 60 km wide) (Fig. 5) along the entire Algerian margin with possible heterogeneous thinning between upper and lower crust in some transects (Lepretre et al., 2013;Arab et al., 2016a;Aidi et al., 2018). Likewise, the transitional domain is narrow (Fig. 5), often associated with graben structures at the surface and interpreted by some authors as the surface expression of the subduction-transform edge propagator (STEP) fault [START_REF] Govers | Lithosphere tearing at STEP faults: Response to edges of subduction zones[END_REF] with several accretion axes [START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF]Aidi et al., 2018). The SPIRAL refraction results show a central part of the Algerian basin characterized by a 5.5 km thick crust with velocity differences between the sub-basins that lead the authors to interpret their nature as follow: (i) the EAB is composed of magmatic thin crust [START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF][START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF]; (ii) the Hannibal High could have undergone a magmatic reworking during the second phase of basin opening (Aidi et al., 2018); (iii) in the WAB the presence of some mantle serpentinization is possible (Aidi et al., 2018). Recently, heat flows suggested different formation ages (Poort et al., 2020), confirming the differences in geodynamic sub-basin history.

Discussion

Geometrical correlation between salt morphologies and crustal segmentation

A correlation exists between salt morphology and the structural segmentation and nature of each sub-domain of the Western Mediterranean area (Figs. 5; 6; 7). In the Liguro-Provençal basin the Listric domain is located on the edges of the margins, where the authors interpret a transitional and/or a thinned crust [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF], as well as all along the north Algerian margin (Lepretre et al., 2013;[START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF][START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF][START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF]Aidi et al., 2018) and at the transition between the WAB and the Alboran basin [START_REF] Medaouri | The transition from Alboran to Algerian basins (Western Mediterranean Sea): chronostratigraphy, deep crustal structure and tectonic evolution at the rear of a narrow slab rollback system[END_REF]. In the western Sardinian margin, the boundaries of the high salt base domain match well with the transitional crust interpreted by [START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF]. In the deep Liguro-Provençal basin the Connected, Irregular salt morphology corresponds to a proto-oceanic and/or oceanic crust following the interpretation of refraction data by [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF] and [START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF]. Instead, a Connected, Regular domain is interpreted in the EAB, which seems to be constituted of thin oceanic crust, as evidenced by refraction data [START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF][START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF] and clearly aligned magmatic anomalies [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. The WAB, whose crustal structure is still a matter of debate, is characterized by generally more deformed salt structures, with differences in the eastern and north-western sectors: in the southwest of the South Menorca Block, the salt structures are connected and the salt base is shallower while the deep basin is characterized by the deepening of salt and larger morphologies. The transition between continental and oceanic domains in the Alboran-WAB limit corresponds to a change in salt morphologies, between an Anticlinal to a

Large/Connected domain. The sharp and quick transition from a thinned continental crust to an oceanic crust along the north Algerian margin is associated with a quick transition in salt morphologies.

Salt morphologies segmentation hypotheses

We have mentioned some peculiar features of the Western Mediterranean which making it a particular area for the salt tectonics study in passive margin context. Here, the salt was deposited during the Messinian Salinity Crisis (about 6 million years ago) in a closed system where all sub-basins considered in this paper were already formed, well after the rifting phases Following [START_REF] Bache | A two-step process for the reflooding of the Mediterranean after the Messinian Salinity Crisis[END_REF] the evaporites in Mediterranean deep basin deposited during a relatively moderate and slow sea-level rise. The salt deposition was probably brief (<50 000 years, [START_REF] Bache | A two-step process for the reflooding of the Mediterranean after the Messinian Salinity Crisis[END_REF] and the following dilution of waters led the progressive deposition of the Upper Unit. The pure halite seismic facies and the rapidity of salt deposition in a relatively constant sea level rise inclines us to exclude any erosive surfaces inside the salt that could have triggered differential spatial loading. Moreover, the seismic facies seems typical of pure halite and no regional lithological levels are interpreted, as for instance depicted in eastern Mediterranean salt deposits [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF][START_REF] Gvirtzman | Intense salt deformation in the Levant Basin in the middle of the Messinian Salinity Crisis[END_REF].

The main issue still unresolved is the geometrical coincidence between the salt morphologies and the crustal segmentation (Figs. 3,5,6,7). As mentioned, the salt is deposited above a thick (up to 2.5 km in Liguro-Provençal basin), regionally unfaulted, pre-salt sequence.

The base of salt is also unfaulted and do not shows regionally spatially depth variations (Figs.

6; 7). The only margin affected by thick-skinned tectonics is the north Algerian margin, which undergo to tectonic inversion caused by the NW-SE convergence between the African and European plates (e.g. Kherroubi et al., 2009). The still present-day shortening causes the base of salt offset by low angle south-dipping reverse faults (e.g. [START_REF] Domzig | Searching for the Africa-Eurasia Miocene boundary offshore western Algeria (MARADJA'03 cruise)[END_REF]Leprêtre, 2012;Deverchère et al., 2005) and the salt involving in the play of active ramps and flats (Fig. 6B,D,E). The north Algerian margin is however a particular case in the Western Mediterranean Sea, not observed in other sub-basins. An active tectonic influence is thus to discard for a possible cause of crustal segmentation-salt morphologies coincidence.

As mentioned above, Le Cann, (1987) and [START_REF] Pautot | Morphology and extension of the evaporitic structures of the Liguro-Provençal Basin: New Sea-Beam data[END_REF] claimed for the reactivation of rifting-involved faults which could influence the salt structures distribution and [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF] for a differential pre-salt sediments compaction influence. However, there are no main faults system that could have affect the base of salt, since that the pre-Messinian sediments are thick and mostly unfaulted in the deep basin. The majority of inherited rifting faults are no longer actives and there is no correlation between salt deformation and faults activation timing.

We then agree on basement steps relevance, even below a thick sedimentary sequence which filled any rugosity but, unless probably for the North Balearic Transfer Zone (Fig. 5), there are no significant step in the basement that could explain such a difference. Moreover, the physical experiments of [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF] are unrealistic scaled, with a basement steps three times the silicone thickness and a simulated base salt tilt of 3°, not observed in the deep basin. As highlighted in figure 3, at the transitional-oceanic crust boundary, the basement has small depth variations, the pre-salt is mostly unfaulted and the base of salt is sub-horizontal. Moreover, the observations of [START_REF] Pautot | Morphology and extension of the evaporitic structures of the Liguro-Provençal Basin: New Sea-Beam data[END_REF] and [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF] are mainly localized in the Gulf of Lion deep basin, while the crustal segmentation-salt morphologies coincidence seems to be present in all the Western Mediterranean sea.

It is well-known that the sedimentary loading may be a dominant mechanism on passive margin salt tectonics (e.g. [START_REF] Vendeville | Salt tectonics driven by sediment progradation: Part I-Mechanics and kinematics[END_REF][START_REF] Rowan | Salt tectonics at passive margins: Geology versus models-Discussion[END_REF][START_REF] Warsitzka | Salt diapirism driven by differential loading-Some insights from analogue modelling[END_REF][START_REF] Gaullier | Salt tectonics and crustal tectonics along the Eastern Sardinian margin, Western Tyrrhenian: New insights from the "METYSS 1[END_REF]. The progradation of a brittle sedimentary wedge over a buoyant salt layer induces pressure gradient differences caused by differential loading (e.g. [START_REF] Vendeville | Salt tectonics driven by sediment progradation: Part I-Mechanics and kinematics[END_REF]. In the Gulf of Lion, the Quaternary Rhône Fan represents a large turbidite system which comprises a 1500-thick accumulation of turbidites and mass-transport deposits (e.g. [START_REF] Leroux | High-resolution evolution of terrigenous sediment yields in the Provence Basin during the last 6 Ma: relation with climate and tectonics[END_REF][START_REF] Droz | On the termination of deep-sea fan channels: Examples from the Rhône Fan (Gulf of Lion, Western Mediterranean Sea)[END_REF][START_REF] Cattaneo | The last glacial maximum Balearic Abyssal Plain megabed revisited[END_REF][START_REF] Badhani | Morphology of retrogressive failures in the Eastern Rhone interfluve during the last glacial maximum (Gulf of Lions, Western Mediterranean)[END_REF]. The strong salt deformation in the deep Gulf of Lion basin occurred in the Quaternary is often put in relation with this sedimentary fan, which would be pushed and squeezed the salt toward the distal basin, forming salt stocks and walls (Large Diapirs domain, Fig. 5). Nevertheless, once again, this phenomenon cannot explain the coincidence between crustal segmentation and salt morphologies observed everywhere in Western Mediterranean Sea. Moreover, the Plio-Quaternary sedimentation is variable in the deep sub-basins. It can reaches 2 km in the Gulf of Lion basin but is, with smaller thicknesses, almost equal in the EAB and in the WAB (less than 1 km). As described (Figs. 5; 6; 7), the salt morphologies in the EAB and WAB differ considerably, questioning the role of sedimentary loading in both deep basins.

We propose that, despite being deposited above a thick sedimentary column, the salt layer could be affected by a crustal and mantle thermal anomaly. The main causes of salt tectonics, which have been discussed here and which have been known until now, seem to be unable to explain the coincidence between crustal nature and salt morphology. The thermal segmentation seems to be the only hypothesis that could explain the observed correlation. Below, we will try to give some elements to discuss our hypothesis which has still to be proved and quantified, but which should not overlooked.

The potential role of thermicity on salt deformation

Since the hypothesis of thermal convection argued by [START_REF] Talbot | Halokinesis and thermal convection[END_REF] the heat influence on salt deformation has intrigued the salt tectonics scientific community. Following this author, the geothermal gradients can add an extra component to the classical salt tectonics mechanisms.

Salt rheology is mainly described by creep equations, strongly affected by grain salt properties, water content and temperature (e.g. [START_REF] Li | Rheology of rock salt for salt tectonics modeling[END_REF]. Temperature plays an important role, causing a decrease in viscosity [START_REF] Urai | Weakening of rock salt by water during long-term creep[END_REF][START_REF] Urai | Flow and transport properties of salt rocks. Dynamics of complex intracontinental basins: The central European basin system[END_REF][START_REF] Carter | Rheology of rocksalt[END_REF][START_REF] Van Keken | The effective viscosity of rocksalt: implementation of steady-state creep laws in numerical models of salt diapirism[END_REF][START_REF] Li | Rheology of rock salt for salt tectonics modeling[END_REF][START_REF] Marketos | Impact of rock salt creep law choice on subsidence calculations for hydrocarbon reservoirs overlain by evaporite caprocks[END_REF][START_REF] Peach | Effect of confining pressure on dilatation, recrystallization, and flow of rock salt at 150 C[END_REF][START_REF] Jackson | Salt tectonics: Principles and practice[END_REF].

For instance, [START_REF] Carter | Rheology of rocksalt[END_REF] found a strong decrease of salt viscosity (up to 4 orders of magnitude) from a temperature of 0°C to 100°C. A high temperature can be localized adjacent to a rise of magma which may be the main cause of its movement [START_REF] Schofield | Mobilizing salt: Magma-salt interactions[END_REF]. In seem to change near the sill-complex: where the sills are located, salt rollers are formed whilst far from the sill, the area is characterized by diapiric deformation [START_REF] Magee | Salt-magma interactions influence intrusion distribution and salt tectonics in the Santos Basin, offshore Brazil[END_REF]. The post-rift volcanic activity is observed in several margins, as in the oceanic crust of Gulf of Aden [START_REF] Leroy | Contrasted styles of rifting in the eastern Gulf of Aden: A combined wide-angle, multichannel seismic, and heat flow survey[END_REF] and in Newfoundland and Labrador margins [START_REF] Karner | Basalt sills of the U reflector, Newfoundland Basin: A serendipitous dating technique[END_REF]. In the Gulf of Aden, [START_REF] Lucazeau | Post-Rift volcanism and high heat-flow at the ocean-continent transition of the eastern Gulf of Aden[END_REF] measured very high heat flow concomitant to a volcanic structure, whose activity lasted well beyond the rifting phase. The magma transfer is close related to fault-zones [START_REF] Georgen | Plume-transform interactions at ultra-slow spreading ridges: Implications for the Southwest Indian Ridge[END_REF] which could be inherited from the rifting period and can channelize the heat distribution. Volcanic activity and magmatic intrusions can somehow influence salt morphologies, but they are local phenomena and do not fully explain the coincidence between crust and salt, observed at a regional level. More regional thermal anomalies can be produced by a pronounced crustal heat segmentation. An extremely thinned crust with exhumed mantle or lower crust can, with the help of fluids, affect the thermal regime in a large transition zone and lead to regional variations in temperature at the base of the salt.

The passive margin genesis is a complex process, where the lower continental crust and the upper mantle play a crucial role. The discovery of serpentinized mantle in a few transitional domains [START_REF] Boillot | Ocean-continent boundary off the Iberian margin: a serpentinite diapir west of the Galicia Bank[END_REF], the role of lower continental crust exhumation [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF][START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF][START_REF] Loureiro | Imaging exhumed lower continental crust in the distal Jequitinhonha basin, Brazil[END_REF], the anomalous heat flow in the transitional domain [START_REF] Dupré | Integrated tectonic study of the South Gabon Margin. Insights on the rifting style from seismic, well and gravity data analysis and numerical modelling[END_REF], Lucazeau et al., 2008, Goutorbe et al., 2008a[START_REF] Goutorbe | Global heat flow trends resolved from multiple geological and geophysical proxies[END_REF], the role of mafic intrusion in the lower continental crust (Thybo &[START_REF] Thybo | Magma-compensated crustal thinning in continental rift zones[END_REF][START_REF] Thybo | Moho and magmatic underplating in continental lithosphere[END_REF][START_REF] Tozer | Crustal structure, gravity anomalies, and subsidence history of the Parnaíba cratonic basin, Northeast Brazil[END_REF][START_REF] Aslanian | Deep structure of the Pará-Maranhão/Barreirinhas passive margin in the Equatorial Atlantic (NE Brazil)[END_REF], the fact that the passive margins remain in a high position, close

to the sea-level, until the break-up and even much later [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Labails | Crustal structure of the SW Moroccan margin from wide-angle and reflection seismic data (the Dakhla experiment). Part B-The tectonic heritage[END_REF][START_REF] Péron-Pinvidic | The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view[END_REF][START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF] provide insights into crustal and mantle thermal segmentation and its role on subsidence. The replacement of the continental mantle by hot asthenosphere produces an important thermal anomaly that affects the subsidence of the transitional domain (Huismans andBeaumont, 2011, 2014). These thermal anomalies can be persistent in time due to edge-driven convection in the mantle and bring episodically heat to the surface by magmatic intrusions (King andAnderson, 1998, Lucazeau et al., 2008). Analysis from heat flow in the transitional crust domains estimates that these processes can lead to an increased mantle heat flow input of 20-30 mW/m² [START_REF] Goutorbe | Surface heat flow and the mantle contribution on the margins of Australia[END_REF] and a doubling of the surface heat flow [START_REF] Lucazeau | Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden[END_REF]. This equally means higher temperatures at the top of basement crust that will be transferred to the salt deposits. Moreover, also regional hydrothermal circulations are known to occur in margins and can redistribute heat in specific margin segments [START_REF] Lucazeau | Heat-flow and hydrothermal circulation at the ocean-continent transition of the eastern gulf of Aden[END_REF][START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF].

Although the direct link between salt morphology segmentation and the thermal regime remains speculative, we argue that the hypothesis of a relationship between temperature and salt deformation at regional level should not be overlooked. Only more in-depth work on the thermal regime in passive margins can help in quantifying the temperature variations needed to affect the salt flow.

Other salt passive margins

In the previous section we have described the coincidence between crustal segmentation and salt morphologies in Western Mediterranean Sea. Although we have listed some of the potential hypothesis that could explain this coincidence, the discussion is still open and a clear answer is still unclear. In the next section, we will explore others, well-known, passive margins in the world (Fig. 8) in order to understand if this correlation can be observed in other saltbearing margins context. We will not go into detail about the discussion of salt tectonics in every margin as is not the objective of this paper. Nevertheless, we will try to summarize the key information and the analogies with the Western Mediterranean Sea, in order to discuss the salt morphologies-crustal segmentation relationship. We compared regional salt morphologies and crustal segmentation in the South-Atlantic margins (Angolan and Santos basins), Gulf of Mexico, Morocco and Nova Scotia margins.

Salt morphologies

The definition of salt morphology domains is not a simple task as each passive margin differs in main salt tectonics mechanisms and resulting structures. We have grouped the salt morphologies into 3 main domains, so that they can be regionally compared with the crustal domains constrain by refraction seismic data. We have referred the salt structures interpretation to the wide salt tectonics literature present in the different passive margins, using published profiles (References in chapter 3.1) and salt isopach maps (e.g. and allochthonous salt as well as basinward listric faults [START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF][START_REF] Fort | Kinematics of regional salt flow in the northern Gulf of Mexico[END_REF]. The Massive-Canopy domain is located in the downdip part of the salt basins and is characterized by thickening of salt deposits, thrust, folds and compressional diapirs. This domain can be characterized by massive thicken salt and/or canopy structures. The term canopy describes salt that is emplaced at stratigraphic levels above the autochthonous evaporites and comprises sub-horizontal or moderately dipping structures [START_REF] Hudec | Advance of allochthonous salt sheets in passive margins and orogens[END_REF]. The salt moved vertically from a single or multiple autochthonous feeder forming a salt sheet which, after coalescence of numerous structures, can form a canopy. The spatial distribution of the three domains just described shares characteristics with passive margins kinematically linked zones already described by different authors (e.g. [START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF][START_REF] Hudec | Regional restoration across the Kwanza Basin, Angola: Salt tectonics triggered by repeated uplift of a metastable passive margin[END_REF][START_REF] Jackson | Structural dynamics of salt systems[END_REF][START_REF] Peel | How do salt withdrawal minibasins form? Insights from forward modelling, and implications for hydrocarbon migration[END_REF][START_REF] Vendeville | Salt tectonics driven by sediment progradation: Part I-Mechanics and kinematics[END_REF][START_REF] Rowan | Salt tectonics at passive margins: Geology versus models-Discussion[END_REF], characterized by and updip extension, a mid-slope translation and a downdip contraction domain. We have not used the terminology already proposed in the literature because we consider it interpretative with regard to the processes of salt tectonics involved. The Raft domain in the passive margins present similarities with the Listric salt domain interpreted in the Western Mediterranean Sea.

The Diapirs domain has the main similarities with the Large Diapirs domain in the Algerian and Gulf of Lion deep basin (Figs. 6A and 10). Instead, the Canopy-Massive domain is not interpreted in Western Mediterranean salt basins, where the salt is mainly autochthonous.

Passive margins crustal segmentation

The crustal segmentation and nature of each margin is described in this small paragraph, listing the interpretation proposed in literature. As in Western Mediterranean sea, the segmentations is constrain by wide-angle seismic data with the complementation of gravity and magnetic data.

In SSPS (Santos Sao Paulo plateau System) we have considered the SanBa Experiment, a joint project between Ifremer, IUEM, Lisbon's faculty of Science, the University of Brasilia and Petrobras which collected six multichannel (MCS) and coincident wide-angle seismic profiles in the in the Brazilian margin: profiles SB01 and SB02 run in a NW-SE direction, separated from each other by less than a hundred kilometres (Fig. 9a); profiles SB03, SB04, SB06 and SB07 cross these two principal lines. The velocity models enabled the authors [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF] to present a new segmentation composed of seven distinct domains (Figs. 9), also coherent with the observations of gravity and magnetic data:

-Domain CC: unthinned continental crust domain with a 35-40 km thick crust and velocities between 5.6 and 7.0 km/s.

-Domain N: the necking domain, characterized by thinning, is wide less than 100 km.

The Moho rises and the basement deepens.

-Domain A: thin crust with velocities between 6.0 and 7.0 km/s. Towards the deep basin (SE), the Moho and the top of the basement rise slowly. This domain corresponds to a low gravity anomaly and a high magnetic anomaly and is interpreted as exhumed lower continental crust [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF].

-Domain B: very thin crust that shows the most heterogeneous crustal structure. The basement deepens by 1-2 km and the area is characterized by a large and mostly negative magnetic anomaly and a relatively high gravity anomaly. Large lateral variations in crustal velocities are observed between the two profiles. This domain is interpreted either as very thin exhumed lower continental crust intruded by magmatism or as atypical oceanic crust, overlying altered mantle [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Whatever the nature of domain B in the central part of the SSPS, it is characterized by a Moho rise, an extremely thin crust (7 to 11 km thick from [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF] and a lower layer characterized by high velocity (7.0-7.8 km/s) (Fig. 9b).

-Domain C: 11 to 17 km thick crust with a pattern similar to Domain A except for the lower upper crust velocity (5.2 km/s).

-Domain D: 5 km thick atypical crust with a triangular shape characterized by a step in bathymetry, low gravity and magnetic anomalies. [START_REF] Klingelhoefer | Imaging proto-oceanic crust off the Brazilian Continental Margin[END_REF] describe this domain as characterized by anomaly velocities as proto-oceanic crust.

-Domain OC: Oceanic crust

In the Angolan margin we have considered the crustal nature interpreted after the ZaïAngo wide-angle project, led by Ifremer and TotalFinaElf. Seven MCS and refraction profiles were acquired between the Lower Congo and the Angolan basins (Fig. 10). Contrucci et al., (2004a) and [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF] interpreted the Angolan margin formed by four domains (Fig. 10), also coherent with gravity and magnetic data:

ANNEXE-1. SCIENTIFIC PRODUCTION

424

-CC: corresponds to the unthinned continental crust, 30-35 km thick (based on gravity data)

-N: refers to the 50 km-wide necking zone, with an abrupt thinning of crust of about 20 km.

-T1: refers to the landward region of transitional domain characterized by a thin crust of about 16-8 km thick, and an anomalous velocity zone below (7.2 to 7.5 km/s). This layer is interpreted partly in the necking zone and it reaches a maximum thickness when the basin displays the maximum depth.

-T2: refers to the basinward region of transitional domain, characterized by a slightly thinning crust and the absence of the high velocity lower layer seen in T1. The transitional domain is bounded to the west by a basement high. Crust thickness does not exceed 5 km.

-OC: the oceanic crust is 6-7 km thick.

The velocity model in the upper crustal layer of segment T2 does not seem to be coherent with an oceanic nature and, at the same time, shows velocity and thickness that appear to be different to those of a "typical" continental crust (Contrucci et al., 2004a). The anomalous velocity layer in domain T1 can be interpreted as lower continental crust because of its velocities [START_REF] Holbrook | The seismic velocity structure of the deep continental crust[END_REF] or as serpentinized mantle (Contrucci et al., 2004a). Based on kinematic studies, wide-angle and multichannel seismic analysis, [START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF] propose a three-phase model of evolution where domain T2 is allochthonous and could represent the exhumation of the lower continental crust from the autochthonous T1 domain.

In Gulf of Mexico, the crustal segmentation interpreted as part of the GUMBO Marine Seismic Experiment consists of four wide-angle profiles in the northern GOM margin (Fig. 11).

The continental crust is between 36 km (Offshore Florida, [START_REF] Eddy | Structure and origin of the rifted margin of the northern Gulf of Mexico[END_REF] and 40 km [START_REF] Huerta | Wilson cycles, tectonic inheritance, and rifting of the North American Gulf of Mexico continental margin[END_REF] thick and it gets thinner along about 200 km (Gumbo3, [START_REF] Eddy | Deep crustal structure of the northeastern Gulf of Mexico: Implications for rift evolution and seafloor spreading[END_REF]. In the transitional domain, the crust stretched to a thickness of less than 10 km (GUMBO1 offshore Texas, Van Avendonk et al, 2015; Fig. 7b), and 6-7 km offshore Florida [START_REF] Christeson | Deep crustal structure in the eastern Gulf of Mexico[END_REF]. In the north-western GOM, concomitant to GUMBO3 and GUMBO4 profiles, the authors interpreted high-velocity lower crust as syn-rift magmatic intrusion into the lower crust [START_REF] Eddy | Deep crustal structure of the northeastern Gulf of Mexico: Implications for rift evolution and seafloor spreading[END_REF] while offshore Texas, the low velocity is not consistent with magmatic underplating [START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF]. Here, a 45 km-wide zone of low-velocity and thin crust might be associated with exhumed mantle, locally serpentinized. The oceanic crust limit (OCT) is still debated in literature (Fig. 11). The oceanic crust has a thickness ranging from 6 km (offshore Florida, GUMBO4) to 8 km. Many interpretations of the nature of the transitional crust domain in the north GOM are proposed: thinned continental crust [START_REF] Roberts | Regional geologic and geophysical observations basinward of the Sigsbee Escarpment and Mississippi Fan fold Belt, Central deep-water Gulf of Mexico[END_REF]; oceanic and proto-oceanic crust [START_REF] Imbert | The Mesozoic opening of the Gulf of Mexico: Part 2. Integrating seismic and magnetic data into a general opening model[END_REF][START_REF] Mickus | Potential field evidence for a volcanic rifted margin along the Texas Gulf Coast[END_REF]; serpentinized mantle or thin oceanic crust [START_REF] Kneller | Plate kinematics of the Gulf of Mexico based on integrated observations from the Central and South Atlantic[END_REF]; hyperextended continental crust with exhumed mantle in central and north-western sectors and proto-oceanic crust in the east [START_REF] Rowan | Salt tectonics at passive margins: Geology versus models-Discussion[END_REF]. Whatever the interpretation, the velocity models show a wide transitional domain characterized by a Moho rise (Fig. 11) (up to 16 km depth, GUMBO3) and crustal thinning (up to 7 km, GUMBO4), associated with high velocity in the lower layer (Fig. 11b).

In Morocco-Nova Scotia conjugated margins, we considered crustal segmentation using MIRROR [START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF], SISMAR [START_REF] Contrucci | The crustal structure of the NW Moroccan continental margin from wide-angle and reflection seismic data[END_REF] and SMART [START_REF] Funck | Crustal structure of the northern Nova Scotia rifted continental margin (eastern Canada)[END_REF][START_REF] Wu | Crustal structure of the central Nova Scotia margin off Eastern Canada[END_REF] reflection-refraction experiments for, respectively, the Morocco (the former two) and Nova-Scotia margins (Fig. 12). The Moroccan margin segmentation is divided into three crustal domains (Fig. 12, from [START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF]: unthinned continental crust of 36 km thick, a thinning continental crust domain and an oceanic domain. The thinning domain is less than 90 km wide and, at the limit with the oceanic domain, the crust is approximately 13 km thick. The oceanic domain is characterized by an area with high lower crust velocities (atypical oceanic crust from [START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF] and an oceanic crust thickness of 8 km in the most distal part. In the Nova Scotia margin (Fig. 12), [START_REF] Funck | Crustal structure of the northern Nova Scotia rifted continental margin (eastern Canada)[END_REF] a thicker oceanic crust (7 km) and an area of magmatic underplated bodies. The comparison between the two conjugated profiles (SMART1 and MIRROR1), following the cinematic reconstitution of [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF], shows structural and crustal similarities in the area of the necking zone and a thinning of continental crust. However, the presence of a transitional domain in the Canadian margin characterized by an exhumed serpentinized mantle and a West African domain formed by intruded oceanic crust led the authors to favour the hypothesis of a symmetrical rifting followed by an asymmetrical oceanic accretion [START_REF] Klingelhoefer | Crustal structure variations along the NW-African continental margin: a comparison of new and existing models from wide-angle and reflection seismic data[END_REF][START_REF] Biari | Opening of the central Atlantic Ocean: implications for geometric rifting and asymmetric initial seafloor spreading after continental breakup[END_REF], although there are other hypothesis, including an age difference between the two oceanic crusts imaged by refraction profiles or a greater thickness of the oceanic crust on the African side due to the influence of the Canary hot spot [START_REF] Biari | Structure profonde de la marge Nord-Ouest Africaine[END_REF].

Geometrical correlation between salt morphologies and crustal segmentation in other passive margins and potential explanations

The spatial salt morphologies distribution variation (Figs. 9;10;11;12) suggests a relationship with crustal segmentation of each margin.

In Santos margin, the salt base is evidently interpretable except in the Massive-Canopy domain, where seismic imaging is hampered by absorption and scattering of salt deposits. In the Large Diapir domain, the salt base shows a landward vergence (Fig. 9b; [START_REF] Davison | Geology and tectonics of the South Atlantic Brazilian salt basins[END_REF][START_REF] Guerra | Role of halokinesis in controlling structural styles and sediment dispersal in the Santos Basin, offshore Brazil[END_REF][START_REF] Strozyk | Comparison of the rift and post-rift architecture of conjugated salt and salt-free basins offshore Brazil and Angola/Namibia, South Atlantic[END_REF]. Moreover, it is largely unfaulted in the proximal to distal domains and underlain by similarly unfaulted sag sequence [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]Karner and Gamboa, 2007;Unternher et al., 2010;[START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF], composed of syn-rift sediments [START_REF] Kumar | From oceanic crust to exhumed mantle: A 40 year (1970-2010) perspective on the nature of crust under the Santos Basin, SE Brazil[END_REF] of about 2 km thick [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Salt deformation is entirely thin-skinned, without involvement or reactivation of pre-salt structures [START_REF] Guerra | Role of halokinesis in controlling structural styles and sediment dispersal in the Santos Basin, offshore Brazil[END_REF]. The transition between the continental domain (Domain A and A') and Domain B coincides with a change in salt morphology, from a Diapir Salt Domain to a Canopy-Massive Domain (Fig. 9). In domain B the wide-angle profile shows an irregular top of the crust (Fig. 9; dashed black line) but do not seems to have a structural influence on the salt. The SSSP represents a buffer zone of the South Atlantic Ocean [START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF] with its two conjugate margins and a failed ridge in its centre [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Therefore, in the southern part of the basin, the salt onlaps the Sao Paulo Ridge (Fig. 9), interpreted as of continental nature [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF].

In the Angolan margin (Fig. 10), the slope exhibits a Raft extensional domain, described by different authors (e.g. [START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF][START_REF] Marton | Evolution of the Angolan passive margin, West Africa, with emphasis on post-salt structural styles[END_REF][START_REF] Duval | Raft tectonics in the Kwanza basin, Angola[END_REF], basinward followed by the Diapir domain in the proximal sag basin, characterized by salt stocks, weld structures and wide pillows. In the Canopy-Massive domain, as in Santos basin, the salt is thick, stands above the sag basin and the base of salt is hampered. It can extends over the oceanic crust, forming nappe geometries (Fig. 10). Whatever the crustal nature of the different segments in the transitional domain, there is a strong coincidence between: 1) crustal domain T1 and the overlaying Large Diapir Domain, 2) crustal domain T2 and the Canopy-Massive Salt domain (Fig. 10b). In the Santos and Angolan margin, the limit between the Diapirs domain to the Massive-Canopy domain corresponds to a shallower Moho depth (from ~20 km to ~15 km) and a thinning of crust (from ~12-15 to ~5-8 km).

In the Gulf of Mexico, the crustal segmentation incertitude (Fig. 11) and the wide spatial distribution of salt structures make difficult the comparison between crustal nature and salt morphologies. Nevertheless, the canopy structures in the Sigsbee Escarpment lays on extremely thinned transitional crust, probably exhumed [START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF](Rowan, , 2018)), and on oceanic crust. The crust below the wide canopy domain thins (up to 8 km) and the Moho rises and could be characterized by mantle exhumation [START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF].

The salt tectonics system of Morocco-Nova Scotia conjugated margins exhibits some differences with respect the Gulf of Mexico and South Atlantic margins. The Diapir salt domain is mainly centred on the Necking Zone domain, where the crust is of continental nature and thinned (Fig. 12; [START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF] and the deformation is affected by the initial salt thickness and the underlying basement structures [START_REF] Ings | A new conceptual model for the structural evolution of a regional salt detachment on the northeast Scotian margin, offshore eastern Canada[END_REF][START_REF] Krézsek | Mechanics of fault and expulsion rollover systems developed on passive margins detached on salt: insights from analogue modelling and optical strain monitoring[END_REF]. The Massive-Canopy salt domain occupies a vast area only in the Nova Scotia margin and is characterized by salt derived from the Diapir Domain, which glided towards the deep basin after its deposition [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF]) (Fig. 12). In the Moroccan margin, the seaward movement is limited [START_REF] Holik | Effects of Canary hotspot volcanism on structure of oceanic crust off Morocco[END_REF], except in the Tafelney Plateau (Fig. 12), where some salt canopies may have locally mobilized over a distance up to 20 km.

In contrast to the Western Mediterranean Sea, several mechanisms may be at the origin of the crustal segmentation-salt morphologies coincidence. The salt passive margin segmentation caused by interaction between gliding-spreading mechanisms (e.g. [START_REF] Ge | Kinematics and dynamics of salt tectonics driven by progradation[END_REF][START_REF] Vendeville | Salt tectonics driven by sediment progradation: Part I-Mechanics and kinematics[END_REF][START_REF] Hudec | Terra infirma: Understanding salt tectonics[END_REF][START_REF] Gaullier | Role of thick-skinned tectonics on thin-skinned salt tectonics in the Western Mediterranean: A comparison between the Algerian and North-Balearic basins[END_REF][START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF][START_REF] Rowan | Salt tectonics at passive margins: Geology versus models-Discussion[END_REF] likely explain the downdip succession of salt morphologies domains but does not fully demonstrate their spatially coincidence with the crustal domains. The present-day salt structures distribution could be related to the salt deposition timing with respect the rifting phases [START_REF] Jackson | Structural dynamics of salt systems[END_REF][START_REF] Tari | Examples of salt tectonics from West Africa: a comparative approach[END_REF][START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF]Rowan, , 2018;;[START_REF] Jackson | Salt tectonics: Principles and practice[END_REF][START_REF] Hudec | A critical review of models for deposition of the Louann Salt, and Implications for Gulf of Mexico evolution[END_REF]. The crustal structure controls the topography at the time of salt deposition and thus exerts a primary control on the initial salt thickness. The salt thickness can govern the evolution of the salt morphologies, which derived, among other causes, by the salt supply (e.g. [START_REF] Hudec | Terra infirma: Understanding salt tectonics[END_REF]. A good examples are the Morocco-Nova Scotia conjugated margins, considered as a syn-rift [START_REF] Tari | Examples of salt tectonics from West Africa: a comparative approach[END_REF][START_REF] Tari | Salt tectonics along the Atlantic margin of Morocco[END_REF] or syn-stretching [START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF] salt basins.

Here, the salt was deposited during the last stage of rifting, prior to the break-up, in the Upper Triassic/Lower Jurassic [START_REF] Hafid | Triassic-early Liassic extensional systems and their Tertiary inversion, Essaouira Basin (Morocco)[END_REF][START_REF] Tari | Examples of salt tectonics from West Africa: a comparative approach[END_REF]. The salt structures are thus attributed to the underlying basement structure, which determined the initial configuration of the basins and influenced the salt initial thickness [START_REF] Ings | A new conceptual model for the structural evolution of a regional salt detachment on the northeast Scotian margin, offshore eastern Canada[END_REF][START_REF] Krézsek | Mechanics of fault and expulsion rollover systems developed on passive margins detached on salt: insights from analogue modelling and optical strain monitoring[END_REF]. In Gulf of Mexico and South Atlantic salt basins, several authors claimed for significant variations in initial salt thickness (Gulf of Mexico: [START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF][START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF]Hudec et al., 2013a) while others (Angolan margin: [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF] for a roughly constant thickness and no post-deposition horizontal movements. As a matter of fact, the salt deposition context is still debated as well as its impact on present-day salt structures.

Conclusion

We have showed that due to its peculiar characteristics, in the Western Mediterranean the classical salt tectonics models fail to explain the regional differences in salt morphologies distribution, the early deformation in the deep basin and the spatial coincidence with the crustal segmentation.

A Further heat flow analysis are needed to correlate the salt deformation timing with the thermal regime evolution in passive margin. Moreover, analogical and/or numerical modelling might be useful to isolate the temperature parameter impact and understand how the salt may changes the morphology and timing with different temperature regime at its base.

L'Atalante 2016, https://doi.org/10.17600/16000600) and WESTMEDFLUX2 (R/V L'Atalante 2018, https://doi. org/10.17600/18000402).

Contributions

The study was conceived by DA. MB has re-interpreted and compiled the different salt morphologies with the help of RP, DA, MM, MR, EL, CG, ADB. The compilation and analysis of the published wide-angle data were done by MB, MM, DA. The thermal data were provided by JP. AC provided new seismic data. All authors provided critical feedback and helped shape the research, analysis and manuscript. (B) Zoom on low-resolution seismic profile (Fig. 3; location Fig. 2) showing early salt deformation syn-deposition of Upper Messinian Unit (green). The Lower Unit limit is from [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF]. et al., 2015). Dashed black lines represent the lower and upper limit of the crust. Western Mediterranean Sea. The contour lines represent the base of MUM unit [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF] in the deep basin and the BES (Basal erosional surface) and MES (Messinian erosional surface) [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF][START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF] in the slope and shelf. In the deep basin, within the red dashed lines, the base of MUM unit represents the base of salt. Dashed red line represents salt upslope limit before this work, taken from [START_REF] Bache | Messinian erosional and salinity crises: view from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF][START_REF] O Obone-Zue-Obame | The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the "MAURESC" cruise[END_REF][START_REF] Driussi | Evidence for transform motion along the South Balearic margin and implications for the kinematics of opening of the Algerian basin[END_REF]. Contour every 500 m. The categories associated with the different colours are described in Fig. 4. Solid black lines correspond to the crustal segmentation from [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF] (Gulf of Lion), Afhilado et al., (2015) (West Sardinia)

and [START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF][START_REF] Medaouri | The transition from Alboran to Algerian basins (Western Mediterranean Sea): chronostratigraphy, deep crustal structure and tectonic evolution at the rear of a narrow slab rollback system[END_REF][START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF][START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF][START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF]Aïdi et al., 2018 (north Algerian margin). Dashed lines represent segmentation interpretation from gravity and magnetic data [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. Transfer zones are from [START_REF] Jemsek | Heat flow and lithospheric thinning in the Ligurian Basin (NW Mediterranean)[END_REF] and [START_REF] Pellen | The Minorca Basin: a buffer zone between the Valencia and Liguro-Provençal Basins (NW Mediterranean Sea)[END_REF]. 2004) and [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF].

Black lines represent seismic profile interpreted in this study (references in the text). (B) From top to bottom, time migrated reflection profile and line-drawing interpretation (modified after [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF] showing salt morphologies domains. Z-03 wide-angle coincident profile showing crust segmentation by [START_REF] Contrucci | Deep structure of the West African continental margin (Congo, Zaïre, Angola), between 5 S and 8 S, from reflection/refraction seismics and gravity data[END_REF]. Location in Fig. 10a. Dashed black lines represent the lower and upper limit of the crust. et al., (1995). Salt morphologies boundary are redrawn from Seni, (1992). The oceanic domain boundaries from Hudec et al., 2013a;[START_REF] Sawyer | The crust under the Gulf of Mexico Basin. The Gulf of Mexico Basin: Geological Society of America[END_REF], Christeson et al., 2014[START_REF] Curry | Extensional models for the development of passive-margin salt basins, with application to the Gulf of Mexico[END_REF] represented. Black lines represent Gumbo wide-angle survey profiles (references in the text).

Fault trends are from [START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF][START_REF] Stephens | Basement controls on subsurface geologic patterns and near-surface geology across the northern Gulf of Mexico: a deeper perspective on coastal Louisiana[END_REF]. Black lines represent seismic profile, interpreted in this study (references in the text). (B) PSDM ION GulfSPAN 2450 profile from [START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF]Dickinson, (2017) approximately in the location of GUMBO 1 profile (location in Fig. 11a). The salt morphologies are from this study. Below, the GUMBO1 wide-angle profile. Crustal segmentation in black is from this study and discussion in [START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF]. Dashed black lines represent the lower and upper limit of the crust. [START_REF] Sahabi | Evolution cinématique triasico-jurassique de l'Atlantique central: Implications sur l'évolution géodynamique des marges homologues nord ouest africaine et américaine[END_REF] and [START_REF] Tari | Salt tectonics in the Atlantic margin of Morocco[END_REF]. Black lines represent the seismic profile, interpreted in this study (references in the text). Canopy (allochthonous) salt in Nova Scotia is from Sahabi, (2004) interpretation. (B) Mirror01 reflection and wide-angle associated profiles (location in Fig. 12a). Modified after [START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF]. Dashed black lines represent the lower and upper limit of the crust. positive polarity (SEG normal polarity) reflector in the sedimentary column. It separates the chaotic seismic facies of the substratum from the stratified seismic facies of the sedimentary column (Fig. 2). In the Alboran and Valencia basins it corresponds to the Base of the Tertiary, or Oligocene unconformity (e.g. [START_REF] Couto | Lago Mare and the Messinian salinity crisis: evidence from the Alboran Sea (S. Spain)[END_REF][START_REF] Pellen | The Minorca Basin: a buffer zone between the Valencia and Liguro-Provençal Basins (NW Mediterranean Sea)[END_REF][START_REF] Etheve | Extensional vs contractional Cenozoic deformation in Ibiza (Balearic Promontory, Spain): Integration in the West Mediterranean back-arc setting[END_REF].

The Base of salt marker is interpreted only in the deep basin, where the MSC Salt is observed (Fig. 4). It corresponds to the base MU (Mobile Unit), from [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF] and base MUM (Messinian upper megasequence) in the deep basin, from [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF]. The MU is absent elsewhere in our study area (i.e. Valencia and Alboran basins). It is imaged as a strong reflector characterized by high amplitude and negative polarity (Fig. 2).

The Top of salt marker is interpreted only in the deep basin, where the Messinian Salt is observed (Fig. 5). It corresponds to the top MU from [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF] and [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF].

It is imaged as a strong reflector characterized by high amplitude and positive polarity overlying a usually transparent or chaotic (depends on seismic resolution) seismic facies unit interpreted as salt (Fig. 2).

The Base of the Plio-Quaternary (PQ) sequence marker is interpreted in all the geomorphological domains, from the shelf to the deep basin (Fig. 6). It corresponds, according

to [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF], to the MES (Marginal Erosional Surface) on the shelf and upper margin where no MSC units are present, to the TES/TS on the slope and margin and to the top of UU in the deep basin. According to [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF], it corresponds to the top MUM (Fig. 2).

In the Gulf of Lion margin, we consider the base of the PQ unit as the Top M2 reflector (from [START_REF] Bache | Evolution Oligo Miocène des marges du micro océan Liguro-Provençal[END_REF] and in the Valencia and Menorca basins the S30 reflector (from [START_REF] Pellen | Géodynamique et impact de la crise d'érosion et de salinité Messinienne sur les transferts sédimentaires (bassins de Valence et Adriatique)[END_REF]. It is imaged as a strong reflector characterized by high amplitude and positive polarity. It corresponds to the end of the Messinian Salinity Crisis, dated at 5.33 Ma (Krijgsman et al., 1999a) (Fig. 2).

The seafloor marker is interpreted in all the available dataset (Fig. 7). It is imaged as a strong reflector characterized by high amplitude and positive polarity (Fig. 2).

Isobath maps

Below, we show the data distribution as provided in xyz format, illustrating the isobath map for each stratigraphic marker. The maps are projected in Mercator, using GMT software [START_REF] Wessel | New version of the generic mapping tools[END_REF]. The data come from interpretation of seismic lines and digitalization from published isobath maps. [START_REF] Arab | Analyse des systèmes pétroliers de l'offshore algérien oriental: Quantification, modélisation stratigraphique et thermique[END_REF]. Upslope salt (MU) limit is from Bellucci et al., (submitted).

Mean velocity Mean velocity

Table 2.4. Table representing the seismic velocity used for the sedimentary sequences conversion in depth used for the heat flow correction. The velocity chosen differ from the margin to the basin and are taken and simplified from work [START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF].

Annexe 2.2.2 -Other tests

This part of work, still in progress, aims to exploit the thermo-kinematic MARGE model to understand how the initial and evolutionary variables (defined as input paramters) of a passive margin can influence the heat flow. I provide the tests carried out and comparisons with the reference model, explained in the chapter 5.4. The results will not be discussed but only summarize with the help of two tables showing the tests carried out in the Gulf of Lion and South Balearic margins and the heat flow variations plotted in graphs. Rifting periods (Myr) 30-20.4-16 30-20.4-16 30-20.4-16 30-20.4-16 30-20.4-16 30-20.4-16 30-20.4-16 30-20.4-16 Heat production Plioquaternary sequence (µW m -3 ) 0.915 Conductivity continental crust (W m -1 K -1 )

ANNEXE

3 3 3 3 3 3 3
Conductivity of mantle (W m -1 K -1 )

3 3 3 3 3 3 3
Seabottom temperature (°C) 13 13 13 13 13 13 13

Rifting periods (Myr) -The general trend shows a phase of no deformation (phase 1) followed by a phase of shortening (phase 2). ANNEXE-2. HEAT FLOW MEASUREMENTS, MODELS AND RHEOLOGY EXPERIMENT

471

-The duration of the phase 1 depends on the temperature. The higher is the temperature, shorter will be the phase 1.

-Phase 2 and the shortening depend on the temperature. The higher the temperature, greater will be the shortening of the specimen.

Phase 1 is described as a period of a few hours in which salt accumulates energy, called "energy activation of salt". This period is closely related to temperature, as shown in figure 2.4.

Phase 2 and therefore the shortening also depends on the temperature. The maximum measured shortening is 1.10% at 130 °C. This sample is the most interesting and showed more deformation. The author noted a regular increase in deformation every five minutes. The evolution of the curve is linear, with a fairly gentle slope (between 8696 and 14416 s) before moving to a steeper slope (between 14416 and 24000 s).

The test conducted at 25°C during 13h did not show a change in deformation.

The test at 90 °C shows a maximum shortening of 0.1 % of the sample. At this temperature, the slope is smooth, linear and uniform. On a more detailed scale, it is possible to observe levels where the acceleration seems to grow and periods of slowing deformation at regular intervals.

In conclusion, the author claimed that the salt deformation (shortening in his case) is strongly affected by temperature. This study was preliminary and the results could have been a starting point for a deeper analysis. Unfortunately, this research presents some fundamental problems regarding the approach and, as will be explained in the next session, the results.

First, the lack of data describing the samples does not allow a correct interpretation of the deformation. It could be interesting to notice the volume variation before and after the experiment. Second, the pressure applied above the sample during all the tests is neglected. The pressure, indicated as weight in Kilos and not in Pascal, is not deliberately part of the experiment and not calculated as part of the behaviour of the sample. If we calculated the MPa involved during the experience the maximum value is 0.01, probably too small to have an influence on the deformation. Third, the test has no end. It has been very well described the onset of the deformation but we do not know until when it could continue and it is unlikely that a hyperbolic curve of deformation is possible in nature. To conclude, the purpose behind the experience is still appreciable, but without basic knowledge of the subject is difficult to approach it. In the next chapter will be described the method, the problems and the results of the new tests, carried out during my period in Lyon. The support is designed using two carbon plates, resistant to the temperature and therefore to the deformation. They allow a mobile movement of the upper wall and a perfect balance when setting up the weight. The space above the upper wall is restricted and, to keep a good balance of the structure, is possible to put weights up to 2.4 Kg. Measurements are taken every 15 seconds and recorded automatically through an external computer. The temperature range of the experiments varied from 18 to 140°C and these temperatures are quickly reached by the oven. The deformation is measured only in one direction (along the main axis).

We measured the water content (in percentage) in our halite samples, to better compare our halite samples with the ones discussed in literature. We weighed the samples before and after the heating, which it lasted at least 12 hours at 110 °C. Before putting the rock in the oven, we crushed it so as to eliminate the traces of water among the grains. We found a medium water content of 3-5 %, which is quite high compared to the literature data (e.g. [START_REF] Urai | Weakening of rock salt by water during long-term creep[END_REF].

The importance of the water content in the evaporite deformation is well known in literature.

For instance, [START_REF] Urai | Weakening of rock salt by water during long-term creep[END_REF] and, more recently, [START_REF] Li | Rheology of rock salt for salt tectonics modeling[END_REF] confirmed that one of two mechanisms in the evaporite deformation is the solution-precipitation creep, implying the crystal grain sliding along the boundaries (see chapter 2). To allow this phenomenon a sufficient water content in grain boundaries is fundamental, allowing a fluid-assisted migration.

We performed a total of 11 tests with the halite samples (Fig. 2.6). The duration of the experiments was variable, from a minimum of 32775 s (Exp11) to 235770 s (Exp4). The purpose was to observe how the time could influence the magnitude of the deformation and if there was a threshold from which the behaviour of rock could be modified. The general trend that we observed can be summarised as follow:

-Step 1 (heating phase): rapid increase of the extension since the oven turned on. The duration and the amplitude of this phase depend on the temperature and the applied stress.

-Step 2 (heating phase): a steady-state phase that, in the most case, it is not disturbed until the oven is switched off.

-Step 3 (stop heatingcooling phase): the extensional deformation returns to the initial condition after a sudden pick of extensional deformation that lasts a few seconds. In some cases, the extension, after reaching the zero, turns in shortening that seems to be permanent.

These three steps were observed in all the 11 samples tested, not without differences. We focus the interpretation on the amplitude and time of the first step and we discuss the third step, trying to understand what could happen in the cooling phase. The experimental temperature varies between room temperature (Exp11) to 140 °C (Exp5). We tested the samples with the temperature gap closest to the natural condition, in which the salt might deform in our area of study. The dimension of the samples ranges from 12 mm to 52 mm and, usually, they have a cylindrical shape. In order to increase the differential stress, we added 1.4 Kg, thus reaching the maximum weight of 2.4 Kg. Moreover, we polished the samples to have a smaller surface possible and we reached maximum stress of about 2Mpa (Exp7). In this case, the surface was of some mm 2 and, in a test, has created a structural problem and the measures were no consistent.

It is risky to reduce the surface too much because could make it structural problems that induce a consistency loss of the data. It is important to notice that the only differential stress is not enough to induce a deformation, as shown in Exp11, where with differential stress of 1MPa and room temperature there has not been deformation. On the contrary, in the Exp3 (Figure 2.7), we detected a small elongation (0.03 %) with a temperature of 50 °C and small differential stress applied. In this case, the stress does not seem to induce greater deformation but, instead, could reduce the elongation. The small elongation detected in this experience is given only by the temperature, which induces the deformation. In general, it is difficult to find a linear and coherent interpretation of what concerns the differential stress applied. For instance, if we consider two experiences with the same temperature (Exp 7 and Exp10, 80 °C), we found the greater extension in the sample where the lowest stress is applied, which is Exp10. Here, the greater differential stress seems to reduce the elongation. On the contrary, if we consider another couple of tests with the same temperature (Exp1 and Exp6, 130 °C) the greater extension is, in this case, in the sample with the greater stress applied, which is Exp6. Could the temperature be important in this change in behaviour or do the characteristics of the sample taken simply change, such as the water content and the grain size?

The temperature has a greater influence on the deformation. The maximum elongation range varies from 0.03 % at 50 °C to 3.66 % at 140 °C. Considering only the temperature as variable and keeping aside the differential stress we found an increase of deformation by increasing the temperature. The Exp5 has an impressive elongation, hard to explain without other tests but could give us the magnitude of the maximum elongation. Without this extreme value, the mean deformation is about 1%, which means, in a Salt Giant deposits, an elongation in the order of tens of meters.

The cooling phase starts when we turned off the oven and opened it. The temperature decreases rapidly and the volume of the sample change accordingly. We observed, just after the beginning of the cooling phase, an extensional pick, which lasts a few seconds. The pick is not observable in all the experiences and the amplitude seems to be correlated to the temperature.

This maximum is followed by a brutal and rapid decrease of the elongation until it is reached the initial condition, the point zero. Sometimes, as in Exp6, the curve exceeds this point and the sample seems to undergo shortening, subsequently stabilizing in a steady state. The shortening behaviour after the heating could be related to the deformations of the microstructures at the intra-granular level induced by the increase of the temperature. When the temperature decreases rapidly, the grains, in some cases, could reposition themselves differently from the initial situation. This phenomenon seems to be independent of temperature magnitude, as shown by the difference in Exp5 and Exp9, and more dependent by the position and size of the grains and by water content, which influence the pressure solution deformation. Abstract : Some of the world's most prolific petroleum system are located in salt-bearing passive margins. Due to its rheoligical characteristics, salt largely affects the sedimentary basins. In the Western Mediterranean Sea, salt was deposited during the Messinian Salinity Crisis (MSC, 5.96-5.32 Ma), mainly in the deep sub-basins and lower slope. Using an extensive seismic dataset, a regional description and categorisation of salt structures is presented. The salt structures change morphology at the boundary between different crustal natures. The compilation of crustal segmentation and salt morphologies in different salt-bearing margins, such as the Santos (Brazil), Angolan, Gulf of Mexico, Morocco and Nova Scotia margins, seems to confirm this correspondence. In the Western Mediterranean, the constant initial salt thickness, the horizontal salt base in the deep basin, the homogenous multikilomètre pre-Messinian sequence, the early deformation above transitional and oceanic crust and a weak sedimentary cover in the slope (except for the Gulf of Lion) seem to call into question the classical mechanisms of salt tectonics, which hardly explain the crustal segmentationsalt morphologies coincidence. The hypothesis of a thermal influence on deformation is therefore evaluated. The thermal regime was investigated by analysing and interperting surface heat flow (HF) data recently acquired during the WestMedFlux1-2 surveys (2016-2018) with the complement of a thermo-kinematic model. Among the small-wavelength HF influenced by local phenomena, a regional thermal segmentation is observed. The role of temperature on salt deformation remains the only plausible hypothesis for the explanation of the observed correspondence and deserves further investigation.

Figure

  Figure 1.1. Not exhaustive and simplification of magma-rich (red segments) and magma-poor (green segments) passive margins(after Geoffroy, 2005; Aslanian, personal communication;[START_REF] Reston | The structure, evolution and symmetry of the magma-poor rifted margins of the North and Central Atlantic: A synthesis[END_REF][START_REF] Haupert | Upper-plate magma-poor rifted margins: Stratigraphic architecture and structural evolution[END_REF]. Yellow stars and hexagons indicate Type I and Type II margin example, respectively (from[START_REF] Huismans | Depth-dependent extension, two-stage breakup and cratonic underplating at rifted margins[END_REF].To note that in some magma-poor passive margins may be present evidences of volcanic deposits.

Figure 1 . 4 .

 14 Figure 1.4. Sketch of Type II rifted margin and associated profiles below. To note, among other features, the presence of well-developed sag basins and salt structures. The natural examples of TypeI I margin are the margins in the Central segment of South Atlantic, as the Angola margin. The numbers represent the features described in the text (modified from[START_REF] Huismans | Depth-dependent extension, two-stage breakup and cratonic underplating at rifted margins[END_REF].

Figure 1 . 5 .

 15 Figure 1.5. Example of GXT profile acquired by ION-GXT in the Santos basin and published by Zalan, (2013). To note the deep imaged crustal reflectors and the base of salt, well-resolved in the left part of the profile and hampered on the right, where the salt deposits is thicker.

  et al., (2011) and the one of Kumar et al., (2013) (Naresh Kumar was working for ION at that time) (Fig. 1.6).

Figure 1 . 6 .

 16 Figure 1.6. Two different interpretations in the Santos basin coming from the same dataset. Note the exhumed mantle interpretation from Zalan et al., (2011) and the absence following[START_REF] Kumar | From oceanic crust to exhumed mantle: A 40 year (1970-2010) perspective on the nature of crust under the Santos Basin, SE Brazil[END_REF].

  Figure 1.7. Opening models: A) pure shear[START_REF] Mckenzie | Some remarks on the development of sedimentary basins[END_REF] and B) simple shear[START_REF] Wernicke | Uniform-sense normal simple shear of the continental lithosphere[END_REF] models.

Figure 1 .

 1 Figure 1.10. Plate cooling model from[START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF] andParson and Sclater, (1977). Points are measured heat flow and lines are modelled ones. The plot on the left represents the heat flow variations compared to the age whilst the plot on the right the ocean depth against the age (modified after[START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF].

Figure 1 .

 1 Figure 1.11. Plate cooling model from[START_REF] Hasterok | Oceanic heat flow: Implications for global heat loss[END_REF] after filtering results with >400 m sediment cover and more than 60 km far away to the nearest seamount. a) Heat flow versus age. Open circles contain <10 sites, full circles >10 sites. Squares are from[START_REF] Hasterok | Oceanic heat flow: Implications for global heat loss[END_REF] data. In grey the standard deviation. b) Number of available data before (grey) and after (black) filtering.

Figure 1 .

 1 Figure 1.12. Heat flow versus continental margin age. The model is modified from the homogenous extension model of McKenzie,(1978) to account heat production for different stretching factors(1.25, 2.00, 3.50). The red line shows the plate cooling oceanic model (from[START_REF] Jaupart | Treatise on Geophysics. Temperatures, Heat and Energy in the Mantle of the Earth[END_REF].

Figure 1 .

 1 Figure 1.14. Map of Mediterranean area outlining the major structural features. The map plots the different formation ages of Mediterranean sub-basins, highlighting fundamental differences between the East Mediterranean (Mesozoic age) and the Western Mediterranean (Cenozoic age) (modified from[START_REF] Jolivet | Lithospheric-scale geodynamic context of the Messinian salinity crisis[END_REF], 2009[START_REF] Roure | Alpine inversion of the North African margin and delamination of its continental lithosphere[END_REF] and Leroux et al., 2019).

Figure 1 .

 1 Figure 1.15. Sketch showing the two main scenario proposed in literature illustrating the effects in subduction zone configurations.A) N-S extension with roll back of the slab that goes from Gibraltar to Corsica, B) E-W extension in theAlgerian basin with roll back confined to the Balearic-Corso-Sardinian segments(after Van Hinsbergen et al., 2014).

  favours a two-step opening scenario including a first westward migration and a second one towards the edges of the basin, which is accompanied by detachment or delamination. The reconstruction in figure 1.16B shows in detail this scenario, at 20 and 16 Ma. To note the initial position of the AlKaPeCa blocks, more grouped together, which implies a huge westward movement of the Alboran block, generating, as mentioned, lateral deformation. The third scenario in fig. 1.16C represents another possible option where the position of the AlKaPeCa blocks are different at 20 Ma. If it is assumed that the Alboran, Kabylides and Galite blocks are further

Figure 1 .

 1 Figure 1.16. Kinematic reconstructions of the Western Mediterranean Sea from Pellen and Aslanian, (personal communication). The sketches represent three different models of Algerian basin opening and show the situations at 20 and 16 Ma. 20 Ma is the onset of oceanisation in the Liguro-Provençal basin while 16 Ma represents the end of Corso-Sardinian and Kabyle blocks movement. The three scenarios are closely related to the initial position of the AlKaPeCa blocks.

Figure 1 .

 1 Figure1.17. Segmentation of the Western Mediterranean Sea. Gravity map on the left and magnetic map on the right. In the Liguro-Provençal basin the solid lines and the arabic numerals indicate the segmentation from wide-angle refraction, reflection, gravity and magnetic data (from[START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF][START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. With red lines are indicated the SARDINIA wide-angle and coincidents reflection seismic lines. In the Algerian basin the dashed lines indicate the segmentation from gravity and magnetic data from[START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. In the North Algerian basin, the black dashed lines indicate the interpretation of crustal domains from SPIRAL wide-angle survey (from[START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF][START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF][START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF][START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF] Aidi et al., 2018). SPIRAL lines are indicated with red solid lines. WESTMED refraction survey in South Balearic margin is shown with red lines(from Vina Gaza, 2016; Gomez de la Pena et al., 2018) but is not considered in segmentation interpretation. The segmentation in the Valencia and Menorca segments is from[START_REF] Pellen | The Minorca Basin: a buffer zone between the Valencia and Liguro-Provençal Basins (NW Mediterranean Sea)[END_REF] and[START_REF] Etheve | Extensional vs contractional Cenozoic deformation in Ibiza (Balearic Promontory, Spain): Integration in the West Mediterranean back-arc setting[END_REF]. The South Minorca block position and interpretation is fromDriussi et al., (2015a). NBFZ: North Balearic Fracture Zone. CFZ: Central Fracture Zone. Gravity map from[START_REF] Smith | Global sea floor topography from satellite altimetry and ship depth soundings[END_REF]; magnetic map from[START_REF] Galdeano | Assemblage à altitude constante des cartes d'anomalies magnétiques couvrant l'ensemble du bassin occidental de la Méditerranée[END_REF].

Figure 1 .

 1 Figure 1.18. The SARDINIA wide-angle profiles are represented as well as their position in the Liguro-Provençal basin. A) Gulf of Lion profile and refraction segmentation from[START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. The first profile on the top is the SARDINIA01 crossing NW-SE the Gulf of Lion whilst the other two cross it with a NE-SW direction. B) West Sardinian margin profiles with a WNW-ESE direction, from[START_REF] Afilhado | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-II. Sardinia's margin[END_REF]. The profiles are at the same scale.

  South Balearic margin was surveyed during the WESTMED survey in 2006 (GEOMAR Institute and University of Barcelona) (Fig. 1.19F-G). To date there are no published works on these two lines other than Vina Gaza's thesis, (2016) and an abstract focused on the western domain (Gomez de la Pena et al., 2018). Vina Gaza, (2016), whose thesis was not really focused on the modelling and interpretation of wide-angle data, made some considerations on the South Balearic margin, in the sector corresponding to the segment III (South Ibiza) and IV (Mazarron Escarpment) (Fig. 1.19). The transitional domain is narrow, with velocities that are neither clearly continental nor oceanic. No kinematic indicators has been observed in the data (also seismic reflection lines) indicating transtensional or trasnspressional movements that would suggest a strike-slip deformation of the margin. Nevertheless, no normal faults are depicted in the area would suggest extensional movement. The author have interpreted

Figure 1 .

 1 Figure 1.19. The SPIRAL wide-angle refraction profiles are represented as well as their position in the Algerian basin,from east (A) to west (E). The profiles A and B cross the East Algerian basin (segment I), the profile C crosses the north-western part of the Hannibal Area (segment II), the profile D crosses the Central Algerian basin (segment III) and the profile E crosses the West Algerian basin (segment IV). All the profile have a N-S direction except for the profile E, acquired in a NW-SE direction (after[START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF][START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF][START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF][START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF], Mihoubi et al., 2015, Aidi et al., 2018). The profiles are at the same scale.

  differences and interpretation problems of continental passive margins. Salt deposits are present in many passive margins, except those defined as typically volcanic. It is deposited during the formation of passive margins by evaporation, which are so called 'salt-bearing passive margins'. The debate on the formation of passive margins is still active since the first models of[START_REF] Mckenzie | Some remarks on the development of sedimentary basins[END_REF] and Wernicke,(1985). Geodynamic reconstructions, newly available geophysical data and different interpretations have led the scientific community to agree on the inadequacy of these conservative models in explaining some observations, such as: i) the relatively elevated position of the margin until, at least, the break-up; ii) the absence of numerous widely extensive faults in the margins, iii) the anomalous heat flow in the transitional domain; iv) the presence of a strong reflector in the lower crust and the interpretation of exhumed lower crust and/or serpentinized mantle. A key role in the passive margin evolution seems to be the heat mantle segmentation. The thermal regime in passive margins is, however, mainly still misunderstood in the transitional crustal domain, related to the doubts on the nature and evolutionary processes of this zone. In the Western Mediterranean Sea, several recent wide-angle refraction seismic surveys and geodynamic reconstruction seem to have resolved the evolution and partly the nature of the Liguro-Provençal basin. The discussion remains largely open on the segmentation and geodynamics of the Algerian basin.

Figure 2 . 1 .

 21 Figure 2.1. Sketch representing the percentage of evaporites formed by evaporating 1 km of seawater column[START_REF] Warren | Evaporites: sediments, resources and hydrocarbons[END_REF]

Fig. 2

 2 Fig. 2.3 (Warren, 2010) plots the Quaternary continental lacustrine evaporitic deposits against the Koeppen climate zone[START_REF] Kottek | World map of the Köppen-Geiger climate classification updated[END_REF], latitude and elevation of the basin floor. The Koeppen Climate Zone are mainly divided with respect the seasonal precipitation and temperature patterns. It is pointed out that arid climate and topographic relief are the two more important environment conditions for the deposition of non-marine evaporitic

Figure 2 . 2 .

 22 Figure 2.2. Nonmarine and marine evaporites comparison from Warren, (2006).

Figure 2 . 3 .

 23 Figure 2.3. Sketch representing the Quaternary continental lacustrine deposits in relation to their Koeppen climate zone and latitude during the deposition. The brown shade indicates "horse latitude"[START_REF] Oliver | Encyclopedia of world climatology[END_REF], characterized by light winds and fine, clear weather.

  , are thick basin-filling evaporite units which extend across large areas of the central part of sedimentary basins. In these basins, the evaporites play a primary role in the sedimentary sequence and can reach kilometric thicknesses, typically composed of halite beds. Some examples of these salt giants are the Zechstein Basin in north Europe, the Louann Salt Basin in Gulf of Mexico, the South Atlantic basins and the Mediterranean Messinian Salt (Fig. 2.6).

Figure 2 .

 2 Figure 2.4 is not an evaporite volume plot but it only counts the evaporite occurrence in each degree latitude region. Instead, figure 2.5 shows the halite volume against age (from Hayet al., 2006) in the last 600 Ma. The deposition of the evaporites is episodic and depends on the existence of restricted passages between basins and the open oceans. Moreover, as the nonmarine evaporites deposits, they require region where evaporation exceeds precipitation and runoff. Figure2.5 highlights the volume of evaporites deposited against time period, showing a relationship between plate tectonics and salt basin formation. It can be seen that there are

Figure 2 . 4 .

 24 Figure 2.4. Latitudinal distribution of evaporites from Permian to now-days. Shaded belts indicated "horse latitudes". The sketch plots latitude occurrence and not the evaporite volume. Note the dominance of northern hemisphere due to the dominance of landmasses across the Permian to recent periods (after Ziegleret al., 2003).

  these periods of salt deposition correspond to a general change in world oceanic salinity. These changes are indeed related to major extractions of salt into the young oceanic basins. For instance, the Mesozoic extraction of salt related to the formation of North Atlantic, Gulf of Mexico and South Atlantic basins led to a general decline of salinity. A plot of the world's halite basins is presented in figure 2.6, showing the spanning deposition age from Neoproterozoic to Plio-Pleistocene. The oldest halite-dominant basins are the various salt basins of central and southern Australia. In the Officer and Amadeus basins (Fig. 2.6, legend references in black) large volumes of salt dated 800 Ma years are still preserved. The youngest salt basin in the world, even one of the bigger, is the Mediterranean salt giant, with its succession of halite and other evaporites spans in several sub-basins in the Western, Central and Eastern part. In this small chapter we described the relationship between geodynamic context and evaporites world deposition, giving some evaporites basin deposition examples.

  2.7). For instance, the Ghaba Salt basin (South Oman; fig. 2.6, reference 88) is part of a series of rift basins stretching from India and Pakistan across the Arabian Shield and they formed during the Infracambrian and Lower

Figure 2 . 7 .

 27 Figure 2.7. Sketch showing plate reconstruction at 600 Ma from[START_REF] Li | Assembly, configuration, and break-up history of Rodinia: a synthesis[END_REF].

Figure 2 . 8 .

 28 Figure 2.8. Chrono-stratigraphic scale of the Permian and Triassic periods. The main salt deposition events are represented (modified after Soto et al., 2017).

  most important salt giants in the Mesozoic are related to the Central and South Atlantic Ocean, and Gulf of Mexico opening. The Triassic period is characterized by the deposition of evaporites in the Central Atlantic (Upper Triassic, Fig. 2.8) and includes the Morocco, Nova Scotia, Mauritania, Senegal, Gambia and Guinea-Bissau salt basins. In the Morocco-Nova Scotia conjugated margins, the salt deposited in the "Argo Formation", from Norian to Hettangian (~210

Figure 2 . 9 .

 29 Figure 2.9. Summary map of the Zechstein Basin in Central Europe showing salt distribution, diapirs and pillows location (after Soto et al., 2017 and references therein).

Figure 2 .

 2 Figure 2.10. Segmentation of Central Atlantic from[START_REF] Labails | La marge sud-marocaine et les premières phases d'ouverture de l'océan Atlantique Central[END_REF] showing the salt deposits distribution all along both margins before the oceanic break-up (reconstruction at 195 Ma after[START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF].

Figure 2 .

 2 Figure 2.11. Salt basins in the Gulf of Mexico region showing locations of salt structures and the oceaniccontinental crust limit interpreted from reflection seismic data(Hudec et al., 2013a).

Figure 2 .

 2 Figure 2.12. Present-day evaporites distribution in the deep and intermediate Mediterranean Sea. The outline of main deep-sea fans are indicated by dotted lined: 1) Rhone,2)Ebro, 3)Nile. In the Western Mediterranean Sea a thick evaporites deposit (more than 500 m) occupies all the present-day deep basins (after[START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF].

Figure 2 .

 2 Figure 2.13. Messinian sub-basins in the Mediterranean. The marginal basins are now-days emerged and are mainly composed of gypsum deposits (except minor areas). The deep basins are additionally characterized by salt deposition. Note the structural highs which physically disconnected the areas of deposition (after Roveri et al., 2014a).

Figure 2 .

 2 Figure 2.14. Seismic profiles zoom of Messinian seismic records: C) sketch from Gulf of Lion,[START_REF] Lofi | Erosional processes and paleo-environmental changes in the Western Gulf of Lions (SW France) during the Messinian Salinity Crisis[END_REF] showing the trilogy depicted in the deep basin. Salt, in yellow, is called Mobile Unit (MU). D) sketch from the Levant basin(Bertoni and Cartwright, 2005a) showing the Mobile Unit, which can be in turn subdivided in 6 sub-units (afterRoveri et al., 2014a).

  Figure 2.16 puts in relation the salt viscosity with other rocks, substances and the mantle, showing a mean viscosity ranging between 10 12 -10 15 Pa s. The creep of the evaporites, as I will explain in the next chapters, comes from their properties of crystallographic lattice which result in a viscous creep-type deformation using a

Figure 2 .

 2 Figure 2.15. Density versus depth plot. The density of salt is compared to other rocks. The salt, incompressible,shows little changes in density with the depth while the other rocks, subjected to the compaction, increase their density (after[START_REF] Jackson | External shapes, strain rates, and dynamics of salt structures[END_REF].

Figure 2 .

 2 Figure 2.16. Rock salt viscosity compared to other rocks/substances (modified after Weijemers et al., 1993).

Figure 2 .

 2 Figure 2.18. Temperature influence on thermal conductivity of several specimen byf different authors (references in the text). Note the higher thermal conductivity with lower temperatures.

Figure 2 .

 2 Figure2.17. Thermal conductivity of typical rocks, included rock salt (last row). Note the higher thermal conductivity of about 5.5 W/m*k, which depends also on the temperature.

  on the applied stress magnitude and the temperature, rock salt creep undergoes several mechanisms. Below, I explain the main mechanisms which occur in salt microstructures during the deformation. The discussion on the main dominant mechanism is still open in literature but there is a general consensus about the role of dislocation and pressure solution mechanisms creep on the long term deformation evolution of salt in salt-bearing basins.

Figure 2 .

 2 Figure 2.19. The general creep trend shows three stages. In the salt rock, the primary elastic creep is negligible compared with the permanent creep deformation (secondary-steady creep) (after Jackson and Hudec, 2017).

Figure 2 .

 2 Figure 2.20. Steady state deformation map of rock salt from[START_REF] Khaledi | Recent and active deformation pattern off the easternmost Algerian margin, Western Mediterranean Sea: New evidence for contractional tectonic reactivation[END_REF] who modified the original plot from[START_REF] Munson | Preliminary deformation-mechanism map for salt (with application to WIPP)[END_REF] and[START_REF] Urai | Weakening of rock salt by water during long-term creep[END_REF]. The plot shows in which temperature/pressure fields act the dislocation creep (glide and climb) and the solution precipitation creep.

Figure 2 .

 2 Figure 2.22. Differential stress -strain rate diagram summarising low temperature laboratory data for a wide range of rock salts. Broken line is extrapolation of the dislocation creep law, for temperature of 30 and 50 °C. Solid line is the room temperature (20 °C) solution-precipitation creep law for different grain sizes (0.1, 0.6, 3, 10 mm). It can be seen that for a grain size of 3 mm the two mechanisms contribute equally to the deformation at a strain rate of 10 -10 to 10 -11 s -1

Figure 2 .

 2 Figure 2.23. Coarse grain halite at 30-200 °C. Strain rate versus differential stress.[START_REF] Li | Rheology of rock salt for salt tectonics modeling[END_REF]

Figure 2 .

 2 Figure2.24. Stress strain curves for dry Avery Island rock salt at constant strain rates over 3.5 years, after[START_REF] Carter | Rheology of rocksalt[END_REF].

Figure 2 .

 2 Figure2.26. Typical stress-strain curves showing the effect of temperature on the behaviour of wet polycrystalline halite at strain rate of 5-7 10 -7 s -1 . For comparison, two stress-strain curves for dry polycrystalline halite (grey curves) are included[START_REF] Watanabe | Electrical impedance measurement of plastically deforming halite rocks at 125 C and 50 MPa[END_REF] Ter Heege, 2002). To note the temperature influence on strain.

Figure 2 .

 2 Figure 2.25. Effective viscosity derived from the two mechanisms creep (pressure solution and dislocation creep). The three plots (a,b,c) indicate three different grain sizes specimens. Bold lines indicate viscosity behaviour at 160 °C; normal lines at 20 °C. Dashed and solid lines indicate specimens deriving from different areas. Note that the behaviour of the two mechanisms depends on the strain rate(after Van Keken et al., 1993).

I

  have often mentioned the viscosity as the parameter to be taken into account when talking about fluid flow. But what is the rock salt viscosity that can be found in nature? Mukherjee et al., (2010) published a review of salt viscosity in different areas and by different authors and it results that it typically falls in the range of 10 14 to 10 20 Pa s (Fig. 2.27).

Figure 2 .

 2 Figure 2.27. Review of rock salt viscosity values from different authors[START_REF] Mukherjee | Viscosity estimates of salt in the Hormuz and Namakdan salt diapirs, Persian Gulf[END_REF].

  (Fig. 2.28) shows the relation between viscosity and temperature at constant differential stress (1 MPa), by three different equations. All of them highlight a strong decrease of viscosity with temperature increase, especially between 0 and 100°C where the viscosity changes from a maximum value over 10 21 Pa s to a value close to 10 17 Pa s or lower.

Figure 2 .

 2 Figure 2.28. Log equivalent viscosity versus temperature plot of variations in viscosity at 1 MPa differential stress by three different equations. Viscosities for solid curves and dashed curves are stress-dependent while for dotted curves are not(after Carter et al., 1993).

Figure 2 .

 2 Figure 2.29. Comparison between strain rate of Halite, Gypsum and Anhydrite (Williams-Stroud and Paul, 1997).

Figure 2 .

 2 Figure 2.30. Gravity-driven deformation: (a) gravity gliding, in which a rigid block slides down a detachment; (b) gravity spreading, in which a rock mass distorts under its own weight by vertical collapse and lateral spreading; and (c) mixed mode deformation. Shaded areas are the final stages and arrows show material movement vectors (after[START_REF] Rowan | Gravity-driven fold belts on passive margins[END_REF].

Figure 2 .

 2 Figure 2.31. Diagram showing the minimum margin tilt angle necessary to activate the dominant gliding of a salt basin with different width. The two sets of curves have been calculated for thicknesses of the initial sedimentary cover in km and for a normal frictional angle (red) and a reduced frictional angle (blue) of the sediments (after[START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF].

Figure 2 .

 2 Figure 2.32. Sketch showing the displacement loading mechanism acting on pre-existing salt structures. (a) During shortening, the horizontal displacement load forces salt to rise. Salt, in this case, would flow out, going to cover the sediments. (b) In extension, the salt subsides because of lateral movement of one or both sidewalls (after[START_REF] Hudec | Terra infirma: Understanding salt tectonics[END_REF].

Figure 2 .

 2 Figure 2.33. Interpreted seismic section in the Gulf of Lion from Dos[START_REF] Reis | Radial gravitacional gliding indicated by subsalt relief and salt-related structures: the example of the gulf of Lions, western Mediterranean[END_REF] showing an example of thinskinned tectonics. To note the listric faults that not dislocate the base of salt and the Miocene sequence.

  calculated a Rayleigh number of 768 for the Danakil Depression salt in Ethiopia, largely enough to think

Figure 2 .

 2 Figure 2.34. Interpreted section from[START_REF] Warsitzka | The timing of salt structure growth in the Southern Permian Basin (Central Europe) and implications for basin dynamics[END_REF] showing a salt diapir overlying a large-offset normal faults (thick-skinned tectonics). Zechstein salt deposits, south Permian basin. The basement tectonic has a major control on salt deformation.

Figure 2 .

 2 Figure 2.35. Sketch showing examples of salt structures depicted in nature. It is shown the evolution of structures according to their maturity and sources: a) structures growth from line source; b) structures growth from point sources (after[START_REF] Jackson | A glossary of salt tectonics[END_REF].

Figure 2 .

 2 Figure 2.36. Summary of the three stages of diapir piercement through pre-kinematic overburden. (A) after Jacksonet al., (1994); (B) afterJackson and Vendeville, (1991a).

Figure 2 .

 2 Figure 2.37. Downbuilding process and passive diapir evolution (after[START_REF] Ribes | Interaction entre la tectonique salifère et la sédimentation dans des mini-bassins: Exemple de l'Oligo-Miocène du bassin de Sivas[END_REF][START_REF] Barton | Mechanics of formation of salt domes with special reference to Gulf Coast salt domes of Texas and Louisiana[END_REF].

Figure 2 .

 2 Figure 2.38. Geometries and characteristics of the two typical halokinetic sequences (A) Hook and (B) Wedge. To note the red line dip, which indicates the angular discordance separating each halokinetic sequence. (C) the vertical stacking of hook type halokinetic sequences will form a tabular type composite sequence (D) the vertical stacking of wedge type halokinetic sequences will form a tapered composite sequence (after[START_REF] Giles | Concepts in halokinetic-sequence deformation and stratigraphy[END_REF].

Figure 2 .

 2 Figure 2.40. Sketch illustrating the dominant gliding (a,b) and pure spreading (c) end-members[START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF].

Figure 2 .

 2 Figure 2.41. Pre-break-up tectonic evolution of the Angolan margin from Neocomian (144,2 Ma) to Late Aptien(112,2 Ma). The purely vertical subsidence in the deep basin (transitional domain, crust 1 and 2) and the tilting in the continental slope domain are shown. The salt is deposited above a thick, not brittle, sag basin at nearzero water depths. During salt deposition the subsidence is approximately equal to sedimentation rate and strongly increase afterwards (after[START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF].

Figure 2 .

 2 Figure 2.43. Sketch of the three structural domains resulting from thin-skinned tectonics in passive margins (after Vendeville, 2005).

Figure 2 .

 2 Figure 2.44. Tectono-stratigraphic provinces of the Gulf of Lions basin, showing first-order salt subsystems along the extensional province[START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF]. In each of these salt-structural domains, overburden extension evolved under variable influence of progradational sediments and residual relief in the base salt.

Figure 2 .

 2 Figure 2.45. Profile crossing the north Algerian margin from S to N showing active ramps and flats which dislocated the salt base and influence the salt structures. Red reflectors are pre-salt deposits, the salt is in yellow, in brown the detrital deposits related to the Messinian Salinity Crisis and in blue the post-salt deposits (after Domzig, 2006).

Figure 2 .

 2 Figure 2.46. Low-resolution depth profile crossing from NW to SE the Gulf of Lion. Domain I and II undergo tilting subsidence while domain III and IV purely vertical subsidence. To note the horizontal base of salt in the deep basin (basinward km 180) (after[START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF].

Figure 3 . 1 .

 31 Figure 3.1. Seismic dataset used in this study for salt structures interpretation. In the legend are represented the available surveys and the resolutions: very low (VL), low (L), high (H) and very high (VH).

Figure 3 . 2 .

 32 Figure 3.2. Zooms of seismic available dataset. A) Gulf of Lion margin and Provençal deep basin. B) West-Sardinian margin and deep Provençal basin. C) Algerian basin.

Figure 3 . 3 .

 33 Figure 3.3. Global dataset used for the construction of isobath and isopach maps. The dataset includes seismic lines used in Leroux, (2012) and Pellen, (2016). The difference with respect the figure 3.1 is the higher coverage in the Valencia basin and in the Gulf of Lion shelf and upper slope.

  interpreted the ESP (Expanding Spread Profiles) in the Gulf of Lion and in the Ligurian basin. To better constrain the deep crust structure, the subsequent SARDINIA wide-angle refraction experiment was carried out by IFREMER on the R/V l'Atalante in 2006 (Fig. 3.4). Six coincident wide-angle and reflection multichannel seismic profiles were acquired in the Gulf of Lion and Western Sardinian margin. At least, each profile crosses another one and together they allow a well constrain of the two margins and the Liguro-Provençal basin. The first tomographic result published by Gailler et al., (2009) and subsequently two more detailed papers (Moulin et al., 2015 -Gulf of Lion and Afhilado et al., 2015 -Western Sardinia) well defined the segmentation of these conjugated margins.

Figure 3

 3 Figure 3.4. Wide-angle refraction profiles available in the Western Mediterranean Sea. We only considered the refraction surveys crossing salt deposits. See references in the text for the surveys description.

  Part of this work of thesis dealt with the analysis and interpretation of surface heat flow in the Western Mediterranean Sea. Recently(2015, 2016 and 2018), new heat flow were acquired in the Western Mediterranean Sea, during three main surveys: MEDSALT (R/V Explora-OGS, Italy) and WESTMEDFLUX 1 (10.17600/16000600) and 2 (10.17600/18000402) (R/V L'Atalante-Ifremer, France) conducted by J. Poort (UPMC). The WESTMEDFLUX surveys had the objectives to investigate the thermal regime of the margins in the sub-basins of the Western Mediterranean Sea, in order to further constrain models of crustal structure and margin evolution.The WESTMEDFLUX 1 survey took place in 2016 on the R/V l'Atalante and allowed the acquisition of 143 new heat flow measurements, 115 in pogo mode and 28 with a sediment corer (Fig.3.5). The data are aligned along several regional heat flow profiles crossing the transitional domains of the Provençal and the Algero-Balearic basins, covering the conjugated, divergent and oblique margins, transform faults and oceanic crust of different ages. Besides, pore water fluids are extracted on board and sub-bottom profiling, multi-beam and ADCP have been collected along most of the cruise tracks, with water column multi-beam mode for a few selected areas. The WESTMEDFLUX 2 survey, in which I participated during my thesis, took place in 2018 as a direct consequence of the 2016 survey. The objectives remaining the same, this survey has allowed the acquisition of 56 new heat flow measurements, the recovering of 11 sediment cores and hard rocks from 2 dredging sites (Fig. 3.6

Figure 3 . 5 .

 35 Figure 3.5. Navigation of WestMedFlux1 survey in the Western Mediterranean Sea. Are represented the navigation during the survey, the POGO measurements in blue dots and the sediment coring sites with temperature measurements in red dots(after Poort et al., 2016; Cruise Report)

Figure 3 . 6 .

 36 Figure 3.6. Navigation of WestMedFlux2 survey in the Western Mediterranean Sea. The navigation during the survey, the POGO measurements in yellow dots, the sediment coring sites with temperature measurements in red dots, the sediment coring without temperature measure in purple dot and the rock dredging site in green dots are represented. In orange the magnetic acquisition (after Poort et al., 2018; Cruise Report).

Figure 3

 3 Figure 3.7. MCHF instrument with main elements represented. It is constituted by a lance where are positioned in ellipse 7 thermistors (left diagram). It is also shown the lest containing the batteries, the heating system, the acquisition driver, the data storage, a pressure sensor and an inclinometer.

Figure 3 . 8 .

 38 Figure 3.8. Diagram representing the acquisition sequences in a temperature/time plot.The first phase is the recording of water temperature during the descent of the instrument; the second is the relaxation period after warming of the instrument due to the penetration in the sediments; during the third phase the thermistors are heated with a constant energy and the conductivity is calculated; in the last phase the instrument is pulled-out. The complete sequence allows to get the temperature gradient observed between the thermistors and the thermal conductivity calculated by the heating (after[START_REF] Poort | WESTMEDFLUX cruise, RV L'Atalante[END_REF] Cruise Report).

Figure 3 . 9 .

 39 Figure 3.9. Seismic section showing in time (a) and in depth (b) the presence of salt deposits. It is shown the pull-up effect and its correction. A correct input velocity model removes pull-ups in depth. The section is from offshore Brazil (Santos basin), after Herron, (2011).

Figure 3 .

 3 Figure 3.10 shows an example of the basement reflector grid interpolated with the nearneighbor method with an interpolation of 0.5 km from each interpreted point, relatively low on a regional scale throughout the Western Mediterranean Sea. The figure clearly shows the areas of uncertainty and the areas where the data are densest, such as the Valencia Basin.

Figure 3 .

 3 Figure 3.10. Example of GMT grid calculation for the basement reflector with an interpolation of 500 m. It is shown the less dense coverage in the Algerian basin and the points add from works of Arab et al., (2016) and Do Couto, (2014) (located to the East Algerian basin and Alboran domain, respectively). The visualisation allows to define uncertainities and more resolute areas.

Figure 3 .

 3 Figure 3.11. Example of seismic velocities for the Plio-Quaternary sequence used for the map depth conversion.

  This part of work was done during a three months period at the Sorbonne University with the collaboration of Jeffrey Poort and Francis Lucazeau from Sorbonne University and IPGP institution, respectively. The model setting and the discussion began during the first two years of PhD, with frequent visits to Parisian institutes. The main objective was to define the evolution of the thermal regime of some areas of the Western Mediterranean Sea with the help of a 2D thermo-kinematic model called MARGE (Méthode d'Analyse et de Restauration

Figure 3 .

 3 Figure3.12. Example of refraction correction in the SaltFlu03 profile. The plot represents the result given by MARGE model in percentage of correction to apply to the surface heat flow. The greater values correspond to a higher lateral variation of thermal conductivity. The model calculates it from interpretation of seismic section given by the operator as input. The y-axis represents the percentage of correction to add (if > 0) or to subtract (if < 0). In the xaxis the distance of the profile in km.

Figure 3 .

 3 Figure 3.13 Example of velocity analysis on CMP-supergather via coherence spectra. In the left and centralside, it is shown real data (un-corrected hyperbole and NMO-corrected reflectors). On the right it is shown the picking of maximum of coherence to get a velocity function. We performed the first velocity analysis every 500 CDP.

Figure 3 .

 3 Figure 3.14. Flowchart applied for the horizon-based tomography. To note the iterative process between the quality control and the refining of residual move-out analysis.

Figure 3 .

 3 Figure 3.15. Example of zoom in SaltFlu03 velocity field. The green colour represented the velocity set for the salt deposits (4.2 km/s). These velocities gave the best flattening in the CIGs within the salt.

  existant en ajoutant plusieurs lignes provenant d'instituts de recherche italiens. Le jeu de données, à ce jour, est le plus complet et le plus résolu existant en Méditerranée occidentale. L'analyse de la structure crustale a été réalisée en utilisant des données de sismique réfraction grand-angle, déjà interprétées par plusieurs auteurs. De nouvelles données de flux de chaleur acquises lors de la campagne WMF2, réalisée à bord du R/V l'Atalante au printemps 2018, sont également présentées dans cette thèse. Pour contraindre le régime thermique, un modèle thermo-cinématique a également été utilisé. Ses fonctionnalités ont été ici brièvement expliquées, complétées dans le chapitre Annexe-2. Pour conclure, le traitement en profondeur réalisée à l'Université de Trieste d'une ligne sismique est représenté. Cette partie du travail sera exploité pour l'utilisation du modèle thermocinématique.

  4.1). The top of the Upper Unit has been sampled during DSDP Leg XIII (Hsu et al., 1973) highlighting layers of dolomitic marls and anhydrite. The Complex Unit (CU) is described as chaotic facies units organized as fan shaped geometry in the lower slope. Gorini et al., (2015) defined a new seismic stratigraphic model in order to better describe the evolution of Messinian sedimentary sequences from the shelf to the deep basin (Fig. 4.2). They summarize the Messinian Trilogy in two Megasequences: the Messinian Lower Megasequence (MLM) composed by deeper evaporites and clastics deposits and the Messinian Upper Megasequence (MUM), composed by salt, aggradation sand and evaporites and shallowwater deposits. Compared to the offshore former model by Lofi et al., the MLM corresponds to the LU and CU units and the MUM to the MU and UU units. Likewise, the authors disagree on nomenclature, distribution and extent of erosional and conformity surfaces (Fig. 4.3).

Figure 4

 4 Figure 4.1. Schematic cross section representing the present day distribution of the MSC markers following the nomenclature ofLofi et al., (2011a[START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF] Note also the differences between the West and the East Mediterranean markers and facies (from[START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF].

Figure 4 . 2 .

 42 Figure 4.2. Model of western and eastern Mediterranean Messinian stratigraphy. 1: forced regressive deltas; 2: deep basin clastics; 3:Lower Halite in the eastern basin; 4:Top of the MLM; 5: Mobile Unit the western basin (salt in this work); 6: Upper Evaporites in the deep basin; 7a: fluvio-lacustrine sediments/incised valley fill; 7b: Marine sands and conglomerates; 8: transgressive sands and reworked evaporites; 9a Pliocene bottomsets; 9b: Pliocene prograding clinoforms; 10: Pliocene deep sea fans; 11: Pliocene-Quaternary hemipleagic sediments; 12: Pliocene Quaternary contourites (after[START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF].

Figure 4 . 3 .

 43 Figure 4.3. Nomenclature comparison between the model of[START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF] and[START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF],after Pellen, (2016). MES: Messinian Erosional Surface; TES: Top Erosional Surface; TS: Top Surface; BES: Bottom Erosion Surface; BS: Bottom Surface; RS: Ravinament Surface; TFRST: Top of Forced Regressive System Tracts; RSME: Regressive Surface of Marine Erosion; MES-CC*: MES Correlative Conformity after[START_REF] Posamentier | Siliciclastic sequence stratigraphy: concepts and applications[END_REF]; MES-CC**: MES Correlative Conformity after[START_REF] Hunt | Stranded parasequences and the forced regressive wedge systems tract: deposition during base-level'fall[END_REF].

  Figure 4.4 shows an example of three possible interpretations of a salt diapir localised in the Gulf of Lion. From A to C, the interpretation changes considerably and will affect the overall thickness interpretation of the salt deposit and the post-salt sequence. The zoom also shows the Pull-Up phenomenon, an artefact generated by the high velocities of the salt (close to 4.5 km/s, e.g. Hubscher and Netzeband, 2007) which, if not taken into account adequately through depth processing or disregarded during interpretation, literally pulls the underlain reflectors upwards and can lead to incorrect localisation of the salt base. Interpretation uncertainty is greatest with more vertically developed structures and with lower resolution seismic data.

Figure 4 . 4 .

 44 Figure 4.4. Salt diapir structure in Gulf of Lion deep basin. Three possible interpretations are represented. Note also the pull-up effect on the base of salt and pre-salt reflectors.

  Figure 4.6 shows the MU (salt) thickness map in twt (seconds) in all the Western Mediterranean basin performed in this work, with the exception of the Ligurian basin. The red line shows the salt upslope limit from previous interpretation by Bache et al., (2010), Driussi et al., (2015a) and Obone-Zue-Obame et al., (2011) and from this work. The salt distribution uniformly covers the LPB and Algerian basin (Fig 4.6), and its geographical distribution mainly depends on the structural heritage during the Messinian (e.g.[START_REF] Bache | A two-step process for the reflooding of the Mediterranean after the Messinian Salinity Crisis[END_REF]. The tectonic situation at Messinian time did not differ so much from the present-day configuration: there were no more tectonic movements due to plate tectonics as the opening has stopped around 16 Ma in the LPB as well as the movement of the Kabyle in the north Algerian margin (without considering the north-Algerian margin reactivation-see chapter 1) that could have directly influenced the salt tectonics. Thicknesses can change considerably and are mainly driven by salt tectonics. Recently, some authors(Driussi et al., 2015a;[START_REF] Raad | The Messinian Salinity Crisis deposits in the Balearic Promontory: an undeformed analog of the MSC Sicilian basins??[END_REF] have interpreted the presence of salt between Majorca and Ibiza, in the Central Mallorca Depression. Salt thickness in twt (Fig 4.6A) is then converted in meters (Fig 4.6B), with a constant velocity of 4.5 km/s. The chosen velocity is an average of salt velocities values, ranging from 4.43 to 4.75 km/s (e.g.

Figure 4

 4 Figure 4.5. Isopach map of evaporites and Messinian related sediment in the Western Mediterranean(After Haq et al., 2020). Note the thick deposits in the LPB and the thinner between the EAB and the WAB. Although the map gives a good framework of Messinian deposits distribution, the low resolution does not provide valuable information about the salt structures distribution.

Figure 4 . 6 .

 46 Figure 4.6. Thickness maps of salt in the Western Mediterranean. A) Salt thickness map in time (s twt). B) Salt thickness in km, with an average velocity of 4.5 km/s. The interpolation step is 4km and the contour every 0.2 and 0.8 s twt (A) and 0.4 and 1 km (B). Note the greater thickness in the deep Gulf of Lion and in the WAB. In the EAB, the salt structures are rare. The offshore evaporitic distribution is afterRoveri et al., (2014a). The Central Mallorca salt is taken fromDriussi et al., (2015a). The salt limit is from this study,[START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF],Driussi et al., (2015a) and[START_REF] O Obone-Zue-Obame | The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the "MAURESC" cruise[END_REF]. In figure A, I,II and III in the Gulf of Lion indicate thickness salt domains (see text).

  Figure 4.6. Thickness maps of salt in the Western Mediterranean. A) Salt thickness map in time (s twt). B) Salt thickness in km, with an average velocity of 4.5 km/s. The interpolation step is 4km and the contour every 0.2 and 0.8 s twt (A) and 0.4 and 1 km (B). Note the greater thickness in the deep Gulf of Lion and in the WAB. In the EAB, the salt structures are rare. The offshore evaporitic distribution is afterRoveri et al., (2014a). The Central Mallorca salt is taken fromDriussi et al., (2015a). The salt limit is from this study,[START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF],Driussi et al., (2015a) and[START_REF] O Obone-Zue-Obame | The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the "MAURESC" cruise[END_REF]. In figure A, I,II and III in the Gulf of Lion indicate thickness salt domains (see text).

  4.7). The Hannibal High is characterised by thinner pre-salt deposits, concomitant with the high basement. The western Algerian margin shows a NE-SW alignment of pre-salt sedimentary thickness increases, at the south of Majorca and the NW of Algeria, corresponding with slightly deeper basements (fig 4.7). With the exception of the Hannibal High area and some structural highs, the entire western Mediterranean is characterised by a pre-salt sedimentary sequence thickness of at least 0.5 s twt, which stands above the basement. The basement roughness (Fig. 4.7) is therefore covered by sedimentation (predominantly Miocene), which results in a regional horizontal base salt standing above the pre-salt sediments (Fig. 4.8B).

Figure

  Figure 4.7.Basement depth map (in s twt). The salt limit is from[START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF],Driussi et al., (2015a),[START_REF] O Obone-Zue-Obame | The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the "MAURESC" cruise[END_REF] and this study. The contour lines are every 0.5 and 1 s twt. Note the shallow basement in the Hannibal High area and the deeper in the LPB.

Figure 4

 4 Figure 4.9.Post-Messinian (Plio-Quaternary) isopach map (in s twt). Contour every 0.2 (thin black line) and 0.8 (thick black line) s twt. The salt limit is from[START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF],Driussi et al., (2015a), Obone-Zue-Obame et al.,(2011) and this study. Note the Petit Rhone fan (e.g.[START_REF] Droz | Quaternary turbidite systems on the northern margins of the Balearic Basin (Western Mediterranean): a synthesis[END_REF] in the LPB, the NW-SE oriented thinner area in the EAB and the thicker northern Algerian margin.

Figure 4 .

 4 Figure 4.10 summarises the five salt morphologies domains described, which are: i) Listric salt domain, ii) Anticlinal salt domain, iii) Connected, regular salt domain, iv) Connected, irregular salt domain, v) Large, Isolated (Gulf of Lion) salt domain, vi) Large, connected (western Algerian basin) salt domain, vii) High salt base domain.

Figure 4 .

 4 Figure 4.10. Western Mediterranean salt morphologies map. The salt morphologies domains are described in the text. The Ligurian basin, even if salt is present, is not analysed in this work for lack of data. The question marks represent areas with less seismic coverage (see dataset in chapter 3). The transfer zones outlined are from Pellenet al., (2016). Thin black lines are bathymetry every 200 m (thin lines) and at 100 and 2000 m depth (thick lines). The upslope salt limit is from[START_REF] Bache | Messinian erosional and salinity crises: view from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF][START_REF] O Obone-Zue-Obame | The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the "MAURESC" cruise[END_REF]), Driussi et al., (2015a) and this study.

Figure 4 .

 4 Figure 4.11. High resolution seismic sections in the Gulf of Lion lower slope margin. The profile shows the Listric salt domain characterized by basinward-dipping normal faults, salt rollers and rollover structures. Vertical exaggeration 1:5. Insert map: zoom of figure 4.10 on Gulf of Lion. The contours represent the base salt depth in km, every 0.5 km. Active (black) and buried (blue) listric faults are from Dos Reis, (2001).

Figure 4 .

 4 Figure4.12. High resolution seismic sections in the south Balearic (SF12-04) and western Sardinia (WS10-13) margins. The profiles show the upslope salt limit in both margins and the Listric salt domain characterized by basinward-dipping normal faults, salt rollers and rollover structures. To note in SF12-04 profile the "perched" basin with the presence of salt and the difference in Upper Unit thicknesses in the zoom sketch. Vertical exaggeration 1:5. Insert map: profiles location.

Figure 4 .

 4 Figure 4.13. Low resolution seismic profile located in the central-north Algerian margin, crossing the Listric domain and the proximal part of the Anticlinal domain from S to N. Faults often deformed the seafloor. Insert map: zoom of figure 4.10 showing the location of beside profile and in next figure (Fig. 4.14). The contours represent the base salt depth in km, every 0.5 km.

Figure 4 .

 4 Figure 4.14. Low resolution seismic profile crossing the Hannibal High area (location in fig. 4.13). Note the absence of salt concomitant with the structural high probably formed by volcanic activity. The zoom shows onlaps within the UU.

Figure 4

 4 Figure 4.15. A) Zoom of figure 4.7 representing the basement depth in s twt of the Hannibal Area, located between the west and the east Algerian basins. Note the basement highs, interpreted as volcanic structures by Aidi et al., (2018) and[START_REF] Mauffret | E-W opening of the Algerian Basin (western Mediterranean)[END_REF]. B) Salt thickness map (zoom of figure 4.6) shows thin/absent salt deposits in the same area.

Figure 4

 4 Figure 4.16. Gulf of Lion seismic profile showing the wide Anticlinal domain that characterize part of Gulf of Lion deep basin. Above the UU, outer arc extensional faults are often present.

Figure 4 .

 4 Figure 4.17. Profile in the east Alboran margin showing the narrow Listric domain followed by the Anticlinal domain basinward. The salt gliding in the mid slope generate salt welds. The faults involved in the basement displacement never dislocate the base of salt. Insert map: profile on the left and in fig. 4.16 location are shown.

Figure 4 .

 4 Figure 4.18. Depth map (in s twt) of the Top of the salt (MU) in the Gulf of Lion with the superposition of the salt morphologies domains interpreted in this section. Bathymetry zoom shows the seabottom active deformation. Salt structures and minibasins main direction highlight a mainly N-S axis and a secondary NW-SE axis.

Figure 4 .

 4 Figure 4.19. Zoom of seismic profile in the Gulf of Lion showing the transition between the Anticlinal and the Large Diapirs domain. Note the concordant overlying sequences in the first and discordant in the second domain, testify by onlaps on salt. mb: minibasin. Located in fig. 4.18

Figure 4

 4 Figure 4.20. Large, connected diapirs highlighted in a zoom in the WAB. Note the closer diapirs compared to the Gulf of Lion Large Diapirs domain.

  figure B shows a more intense deformation, characterized by narrow structures (length to height ratio close to 0), close, frequent and persistent. Their distribution and presence are variable but these structures commonly deform significantly the above Plio-Quaternary layers: they always deform the Pliocene layers, often the Quaternary sequence (Fig.4.21B) and sometimes they can reach the seafloor. They differ from Large Diapirs by their width and frequency. The Upper Unit is not well identified when salt deformation is too strong. In that case, the Plio-Quaternary sequence appears also immediately more deformed (Fig.4.21B).

Figure 4

 4 Figure 4.21. Seismic zooms on the same profile in the WS and EAB deep basins showing salt morphologies differences, grouped in two different domains (Regular and Irregular domains).

  4.22). Both margins show a high salt base domain with an average depth of 4.2-4.6 s twt respect to more than 5 s twt in the diapirs domains, basinward. The line-drawing in figure 4.22 shows a transect between the south Balearic and the north Balearic margin. The transect is made by the profile SPIRAL-28 from Leprêtre, (2012) and the SaltFlu09 profile crossing, with an S-NW direction, the conjugated slopes and the deep western Algerian basin. It gives a good image of both margins, showing the evolution of salt structures. From the N to the S, the area of high salt base followed the Listric domain characterized by some small listric faults in the lower slope. In the high salt base domain (green colour domain) the base of salt is sub-horizontal, as illustrated by the dashed purple line (Fig. 4.22) which represents the depth of the salt converted in meters. Here, the diapirs are close and often pierce the seafloor while southernward, the diapirs are wider, isolated and belongs to the Large diapirs domain. Approximately at the middle of the deep basin (around km 70 on Fig. 4.22), the base of salt deepens southward, towards the north Algerian margin. Profile in figure 4.23 shows an example of perpendicular transect of this domain in the north-western Sardinia margin. The boundary between the High salt base and the Connected, irregular diapir domain is underlined by a base salt step. Moreover, the boundary is delimitated by the Plio-Quaternary thickness increase in the Connected, irregular diapirs. In this profile, the green domain is affected by a basement rise that deforms the Messinian units and seems to act as a backstop to the salt deposits in the proximal part. The onlaps of the lower Pliocene reflectors on the basement and the UU thickness differences close to the structure (Zoom in fig.

Figure 4 .

 4 Figure 4.22. Top: line-drawing of S-NW seismic section crossing the WAB, from the north Algerian margin to the South Balearic. Note the shallower base of salt in the South Balearic margin and the sudden deepening towards the Algerian margin. Here, the base of salt is landward dipping, probably due to the tectonic reactivation which could landward tilted the basement. Below, the MUM (nomenclaute from Gorini et al., 2015) base (in s twt) is represented. Note contoured in dashed white lines the High salt base domain in the WS and SB margins. Map contours every 0.2 and 0.5 s twt.

Figure 4 .

 4 Figure 4.23. Seismic profile in WS margin (located in fig. 4.22) representing the High salt domain and the Irregular salt domain, basinward. Note also the syn-Messinian suggested volcanic structure.

Figure 4 .

 4 Figure 4.24. Summary of the salt morphologies interpreted in this work with the main geometrical features and a zoom framework of seismic facies (at the same scale).

  of Lion The Gulf of Lion outlined a salt structures distribution typical of salt passive margins, characterized by a lower slope raft domain (Listric domain in this work), a proximal deep basin Anticlinal domain and a distal Diapirs domain (Large Diapirs). Figures 4.26 and 4.27 present the wide-angle model and line-drawing of the Sardinia-01 and the RM01-208 (Fig. 4.27) profiles.

Figure 4 .

 4 Figure 4.25. Left: free-air gravity anomaly map representing the segmentation deriving from gravity, magnetic and wide-angle refraction interpretations (reference in the text). Dashed lines represent interpretation only constrain by gravity and magnetic data. I: East Algerian Basin (EAB); II: Hannibal Area (HA); III: Central Algerian segment and IV: Western Algerian Segment (WAB; V and VI: Thinned continental crust/intermediate domain on both sides of the Algerian Basin; 7: Mesozoic Valencia Basin (VB) and 8: Neogene Menorca Basin (MB); 9-10-11: Provençal Basin with Necking zone (11), Transitional crust (10) and (9) proto-oceanic crust. NBFZ: North Balearic Fracture Zone. CFZ: Central Fracture zone. Right map: crustal segmentation superposed on salt morphologies interpreted in the previous chapter.GoL: Gulf of Lion margin; LPB: Liguro-Provençal basin; WS: Western Sardinian margin; EAB: Eastern Algerian basin; HA: Hannibal Area; WAB: Western Algerian basin; EA: Eastern Alboran margin; SB: South Balearic margin; BP: Balearic Promontory; VB: Valencia basin; MB: Menorca basin; EBE: Emile Baudot Escarpment; ME: Mazarron Escarpment.

Figure

  Figure 4.26. Reflection and wide-angle coincident profiles crossing the Gulf of Lion (A) and the Western Sardinian margin (B). The wide-angle profiles and crustal segmentation are taken fromMoulin et al., 2015 (GoL) andAfilhado et al., 2015 (WS).

Figure 4 .

 4 Figure 4.27. A,B) Line-drawings crossing with a NW-SE direction the Gulf of Lion margin and the LPB showing the salt morphologies distribution and the crustal segmentation after gravity, magnetic and wide-angle refraction data. Note the coincidence between the salt morphologies domain and the crustal limits. C) Salt morphologies map with the profiles location; D,E) Basement depth (in s twt) representing the crustal segmentation and the salt morphologies limits (white lines) with respect the basement reflectors topography.

Figure 4 .

 4 Figure 4.28. A,B,C) Line-drawings perpendicular to the western Sardinian margin, showing the salt morphologies distribution and a focus on the High salt base domain. d) Salt morphologies map with the profiles location. e,f) Base MUM map (in s twt) showing the regional base of salt deepening with respect the crustal segmentation.

  , rather than dealing with salt tectonics. The crustal structure was investigated through a refraction survey (SPIRAL survey, fig. 4.29), composed by five wide-angle refraction lines crossing from S to N the margin and the deep Algerian basins (see chapter 1.4.2 for crustal segmentation description). Profiles in figures 4.29B and 4.30 summarize the salt morphologies in EAB, outlined by a slightly deformed diapir domain in the deep basin and a Listric and Anticlinal domain in the northern Algerian margin. Two SPIRAL refraction profiles with an N-S direction (Bouyahiaoui et al., 2015; Mihoubi et al., 2014, the latter shown in fig. 4.29D) and gravity and magnetic data give some information about the crustal structure and nature of the EAB. The first wide-angle profile is located in the Annaba sector and is the most eastward refraction profile in the Spiral survey. The second one crosses the Lesser Kabyle area in the south ending in the deep EAB, at the limit with the Hannibal Area in the west (Fig. 4.29D).

  analysing the heat flow of both margins. This area is characterized by a shallower basement (Fig.4.7), probably magmatic in nature(Aidi et al., 2018).Aidi et al. (2018) interpreted the deep domain as composed of oceanic crust (with wide-angle refraction data), with similar thin thickness as in the EAB (4-5.5 km), locally overlain by volcanic flow and volcano-clastics. The volcanic activity seems to have started in the Miocene and ended in the Pliocene (Fig.4.14), therefore well after the setting of the Great and Small Kabyle and the formation of the deep basin. The Hannibal Area appears to be a preferential zone for syn(Aidi et al., 2018) and/or post basin formation volcanism, somehow related to margin inversion. Although the northern Algerian margin in this area outlines similar salt morphologies domain than the east and west Algerian lower slope domains, the deep basin shows tabular, not deformed salt (when present) and salt absence in some areas(Fig. 4.31).

Figure 4 .

 4 Figure 4.29. Line-drawing of seismic reflection profiles in WAB (A) and EAB (B) margins, from south to north. The wide-angle seismic profiles are taken fromLeprêtre et al., 2013 (C) andMihoubi et al., 2014 (D). Location in free air anomaly map.

Figure 4 .

 4 Figure 4.30. Line-drawings of seismic profile in the EAB showing the salt morphologies distribution and the crustal segments. Insert maps (c,d) represent the localisation of the profiles on the salt morphologies and magnetic maps of the Western Mediterranean.The zoom on magnetic anomalies(f) shows the aligned anomalies testifying the oceanic crust accretion in the deep basin.

  4.29C). Likewise, the Listric salt domain is narrow and located in the lower slope (Figs. 4.29A, 4.32C). The Anticlinal domain is interpreted in profile B (Fig. 4.32), located in the eastern part of the basin. Here, the thrust faults, related to margin inversion (e.g. Domzig et al., 2006a), tilted the basement and thus the base of salt landward. The deformation, as described by Leprêtre, (2012), is post-Messinian and affected, with different impacts, all the northern Algerian margin. The Anticlinal and the Listric salt domains in the northern Algerian margin are floored by thinned continental crust and transitional crust (Fig. 4.29C).

  interpreting wide-angle refraction data), even if the velocities are higher than those of a typical oceanic crust. At the transition between the Alboran and the western Algerian basin,Medaouiri et al., (2014) interpreted an area of thinned continental crust, followed by the oceanic domain in the deep basin. The thinned continental domain corresponds well to the Anticlinal salt domain interpreted in this work (Fig.4.32D) and its termination is coincident with the boundary of the oceanic domain. Another interpretation outlined a proximal oceanic crust limit[START_REF] Booth-Rea | Crustal types and Tertiary tectonic evolution of the Alborán Sea, western Mediterranean[END_REF] interpreting seismic reflection data), at the basinward limit of the Listric salt domain (Fig.4.32D).

Figure 4 .

 4 Figure 4.31. A) Line-drawing crossing the EAB, the HA and the WAB, showing the salt morphologies distribution and variation between the deep basins. a,b,c) Salt morphologies map with the profiles localisation (also for fig. 4.32); free-air anomaly map with crustal segmentation and salt morphologies limits.

Figure 4 .

 4 Figure 4.32. (B,C,D) Line-drawings of seismic profile in the WAB (location in fig. 4.31) showing the salt morphologies distribution. To note the thrust faults in the northern Algerian margin, which can displaced the salt base and influence salt deformation.

  Figure 4.35 shows an N-S profile located offshore the Great Kabyle, in the central northern Algerian margin (from Thomas, M1 report, 2010). The margin is characterized by anticlinal salt structures of medium-low amplitude (max 0.6 s twt high) and large-scale deformed Plio-Quaternary sequences. The base of salt is sub-horizontal, gently dipping towards the continental margin (landward). The Upper Unit exhibits wide variations in thickness, especially above the anticlinal structures. As seen in the Gulf of Lion (Fig. 4.33) and in the western Sardinia (Fig. 4.34), the UU onlapping on the salt indicates an early Messinian deformation. The structures appear to be compressive, probably related to the general convergence of the margin. The base of salt is "lost" towards the margin, characterised by the presence of detrital bodies probably related to Messinian erosion.

Figure 4 .

 4 Figure 4.34. Zoom on seismic profile perpendicular to the western Sardinian margin (after DelBen et al.,in Lofi et al., 2018). The diapir deformation started early during the UU deposition, testified by the UU onlaps on the top of MU.

Figure 4 .

 4 Figure 4.35. Seismic profile perpendicular to northern Algerian margin (modified fromThomas, rapport M1, 2010). The salt started to deform during the deposition of the UU.

  today, thus deforming the seafloor, or buried and no longer active (Dos Reis, 2001). The listric faults in the Gulf of Lion are typical of thin-skinned salt tectonics, i.e. affecting only the salt and the overlying deposits. Dos Reis, (2001) extensively analysed listric faults geometries in the Gulf of Lion, finding a wide variety of structural styles mainly triggered by the sedimentary budget and salt slope. The author described margin perpendicular faults in an upslope and downslope zones. The upslope domain shows faults close to each other (1-3 km) and a base salt inclined at 2.5-5.5 ° while in the downslope area, faults are further apart, and rooted on salt base which is less inclined (around 0.5-3 °) (Dos Reis, 2001).

Figure 4 .

 4 Figure 4.36. Seismic profile in the Levant basin (East Mediterranean), after[START_REF] Gvirtzman | Intense salt deformation in the Levant Basin in the middle of the Messinian Salinity Crisis[END_REF]. The M reflector represents the end of Messinian units. The yellow reflector deformed before the end of the Messinian. Although significant differences in Messinian stratigraphy compared to the Western Mediterranean, the profile shows an early deformation, coeval to the Messinian deposits similar.

Figure 4 .

 4 Figure 4.37. Seismic profile crossing the Gulf of Lion (after Dos Reis et al., 2005) from the Listric to the Anticlinal domains showing the isopach UU in the proximal domain and well developed growth strata, mostly in the Pliocene sequence.

  (Fig. 4.37) shows growth strata mainly located in the Pliocene and Quaternary sequences. Instead, figure4.38 shows growth strata mainly from the Pliocene age, above the Messinian sequences. In all profiles (e.g. 4.37; 4.38) the UU is isopach and folded by the listric faults activity. This means that the UU were already fully deposited at the time of faults activation, whose age therefore spans from the Lower Pliocene to nowadays, as confirmed by seabed throws.

Figure 4 .

 4 Figure 4.38. Seismic section perpendicular to the Gulf of Lion, in the Listric salt domain. Note the isopach UU and the growth strata formed during the Pliocene faults dislocation.

  4.39) and shows several onlaps within it(Zoom B, fig. 4.39), suggesting deposition concomitant with fault activity. Unlike the profiles in the Gulf of Lion, where the listric faults post-UU activity is well defined, in the Sardinian margin it is difficult to understand the exact timing of the listric faults. Here, the salt gliding could have started early, just after the salt deposition.

Figure 4 .

 4 Figure 4.39 Seismic section showing the Listric salt domain in the WS. Zoom A shows small growth strata in the UU, suggesting faults activity during its deposition. Zoom B shows salt deformation activated during the deposition of the UU (lower part concordant with the salt, upper discordant). The Plio-Quaternary thickness thicken towards the deep basin.

  profiles(Figs. 4.40A,B, 4.41C) rather than the profile D (Fig.4.41D), where the UU does not show onlaps within it but displays a constant thickness parallel to the Anticlinal structures. in the Early Pliocene (5.3 Ma) and ended around 2.6 (Pliocene-Pleistocene boundary,Gibbard et al., 2010) /1.8 Ma (Figs. 4.40, 4.41). In the Listric domains it is characterised by the formation of basinward listric faults, which may be active to the present day (Fig.4.41D). After the formation of the first pillows in the deep basin (Phase 1), salt began to glide and thus forming the basinward dipped listric faults. In the NE sector of the Anticlinal domain (Figs. 4.40A,B, 4.41C), the pillows velocity of deformation seems to slow down, attested by relative constant thickness of the sequence (yellow colour) and the absence of onlaps between the reflectors. This period of quiescence is shorter in the SW sector of the Anticlinal domain (Fig.4.41D): here the constant thickness of sequence is observed only up to the pink reflector, older than the yellow reflectors marking the Pliocene-Pleistocene boundary (2.6 Ma).

Figure 4 .

 4 Figure 4.40. Seismic profiles crossing perpendicular the Gulf of Lion showing the different salt tectonics phases (1,2,3). The deformation started in the deep basin and progressed towards the proximal domain. Location in fig. 4.42.

Figure 4 .

 4 Figure 4.41. Seismic profiles crossing perpendicular the Gulf of Lion showing the different salt tectonics phases (1,2,3). Note that in profile D phase2 in the deep basin is shorter. The volcanic intrusion affected the base of salt inducing a salt thickening above it. Localisation in figure 4.42.

  4.40, 4.41). It started at the end of the Pliocene, Early Pleistocene (around 2.6-1.8 Ma) and is still active, especially in the Large Diapirs domain where most of the salt structures deform the sea-bottom. The Listric domain is characterised by active gliding of salt along its detachment surface, with the growing of basinward-dipped listric faults. These faults that are still active are located in the distal part of the Listric domain, while those buried (inactive) are localised in its proximal domain[START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF]. The most significant growth strata are located in the distal part (towards the deep basin) of the Listric domain and mainly concern Early Pleistocene units (e.g. fig. 4.40). The growing of the Anticlinal structures continues throughout the phase 3 within the entire domain, testified by the change in thickness between sequences and several onlaps. In the central sector of the Gulf of Lion Anticlinal domain, the pillows are more deformed, especially at the limit with the Large Diapirs domain (Figs. 4.40B, 4.41C).

  sedimentary inputs may have played a role in the salt deformation, and at what time. The observations made through the 2D profiles are here 3D regionalised through the thickness maps of the main Plio-Quaternary units (Fig.4.42):-Figure4.42A corresponds to the sedimentary thickness map of the Pliocene unit which age range from the end of the MSC (5.33 Ma) to the P11 reflector (2.6 Ma). In the Pliocene, the sedimentary inputs fill the canyons formed during Messinian erosion (up to 1000 m deep,[START_REF] Clauzon | Le canyon messinien du Rhone; une preuve decive du" desiccated deep-basin model[END_REF], both on land and on the shelf(Leroux, 2012) (Fig. 4.43). Sediments are then transferred into the deep basin probably with a fairly high energy[START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF]. Once the sediments supply filled the Messinian canyon, they spread in the deep basin: note that sedimentary thickness is highest in the north-eastern sector of the Anticlinal domain (profile A, B, fig. 4.40), while it decreases exponentially towards the SW (profile C,D, fig. 4.40). In the SW sector, the sedimentary input into the deep basin is weaker due to the absence of major continental inputs. The mapped sedimentary unit (MSC-P11; 5.33-2.6 Ma) corresponds to phase 2 of the salt deformation described in the previous chapter. The salt tectonics phase 2 is characterized by basinward-dipped listric faults formation in the Listric domain. Some growth strata (small depocenters) are observed concomitant with this domain, outlining a main NE-SW direction of sediments accumulation, parallel to the margin. The constant thickness in the NE sector of the Anticlinal domain confirms a period of quiescence in salt tectonics in this area while, as observed in profile D (Fig. 4.41), in the SW sector phase 2 is shorter and deformation begins already in the Pliocene. In the Large Diapirs domain, thickness variations in the present-day mini-basins suggest active deformation throughout phase 2. The significant Pliocene sedimentary fan in the deep basin of the NE sector could therefore have induced deformation only from the Large Diapirs domain. In the Anticlinal domain, despite the massive and progressive arrival of Pliocene sedimentation, the salt does not appear to have deformed as intensely and rapidly as it has in the Large Diapirs domain. This observation raises questions about the relationship between progressive sedimentary wedge towards the deep basin and salt deformation, as described by analogue models (e.g.Vendeville, 2005). -In the SW sector, characterised by a much lower sedimentary thickness, the salt deforms prematurely (Fig. 4.42A). It should be noted, however, that in the profile shown in figure 4.41D, a possible tectonic component from volcanic intrusion may have played a role in creating a more pronounced slope and thus inducing early salt sliding and deformation that began in the Pliocene.

  (Fig. 4.43).

Figure 4 .

 4 Figure 4.42. Thickness maps of the main Plio-Quaternary units in the Gulf of Lion. A) The MSC-P11 thickness (5.3-2.6 Ma) map corresponds to the salt tectonics phase 2. B and C): P11-Q10 (2.6-0.9 Ma) and Q10-SB (0.9-0 Ma) correspond to the phase 3 of salt tectonics. The profiles are shown in figures 4.40 and 4.41. The elements represented and references are marked in the legend.

  At the present day, the Gulf of Lion shows three salt morphologies domain from the lower slope to the deep basin: i) a Listric domain, ii) an Anticlinal domain and iii) a Large Diapirs domain (Fig. 4.44). The salt thickness increases from the upslope salt limit to the deep basin, characterized by vertical intense deformation (Fig. 4.44).

Figure 4 .

 4 Figure 4.43.Table representing the main reflectors interpreted by[START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF] [START_REF] Bache | Evolution Oligo Miocène des marges du micro océan Liguro-Provençal[END_REF] for the respective Plio-Quaternary and Messinian sequences. Are defined the colour, name, supposed/known ages, main features and salt tectonics phases description for each reflectors.

Figure 4 .

 4 Figure 4.44. Present-day salt thickness map on the left with a zoom on salt diapirs deforming the seafloor (bathymetry data). The profiles are shown in figures 4.39 and 4.40. On the right, salt thickness interpretation showing salt structures and minibasins directions (plots bottom right). Note a salt depocenter in the W sector of the Gulf of Lion, explained as the result of subsalt relief by Dos[START_REF] Reis | Radial gravitacional gliding indicated by subsalt relief and salt-related structures: the example of the gulf of Lions, western Mediterranean[END_REF]. Stratigraphic elements references are shown in the legend.

Figure 4 .

 4 Figure 4.45. Sketch representing the salt tectonics phases in the Gulf of Lion. The desiccation hypothesis comes from[START_REF] Bache | Messinian erosional and salinity crises: view from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF] The squares shows the main deformation area for each phase. Note the early deformation during phase 1 and the stronger and faster growth above the oceanic crust. The Hinge line is taken from[START_REF] Leroux | Post-rift evolution of the Gulf of Lion margin tested by stratigraphic modelling[END_REF] and marks the limit between a slope tilting subsidence and a deep basin purely vertical subsidence[START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF], Leroux et al., 2015).

Figure 4 .

 4 Figure 4.46. Imbalance of salt due to the difference in salt thickness. A ramp in the salt base could provoke an imbalance which in turn cause a translation and the formation of growth strata (modified after Evans and Jackson, 2020).

  with the fluid presence (red line 1 in fig. 4.47A) and around 1.9° without the fluid presence (red line 2 in fig. 4.47A). The base of salt in the Gulf of Lion has an inclination ranging from 1.02° in the Listric domain (lower slope) to a sub-horizontal in the deep basin (0.1°) (depth domain seismic profile from

Figure 4 .

 4 Figure 4.47. A) Plot representing the necessary slope of the base salt to activate the gravity gliding, considering the basin width and the sedimentary cover (km) (from Brun and Fort, 2011. B) Sketch representing the subsidence behaviour of the Gulf of Lion margin (modified from Leroux, 2012). The Hinge line marks the boundary between a tilting and a purely vertical subsidence. Note the increasing slope on the margin given by subsidence. The deep basin subsides purely vertical. C) Seismic depth profile crossing perpendicularly the Gulf of Lion (location in figure 4.49) showing the base of salt slope values in the lower slope and deep basin (modified from[START_REF] Jolivet | Continental breakup and the dynamics of rifting in back-arc basins: The Gulf of Lion margin[END_REF].

Figure 4 .

 4 Figure 4.48. Base MUM units (following Gorini et al., 2015); base salt in the deep basin, BES on the slope and MES on the shelf (following Lofi et al., 2011a) depth map. Note the high salt base domains in western Sardinian and South Balearic margin shaded in green. The Rhone fan is concomitant with a deepening of base of salt from the lower slope to the deep basin. The arrows indicate the base salt direction and the suggested are as where the implications of gravity gliding mechanism is stronger. TGS profiles is shown in figure 4.48.

  (5. fig. 4.42A). During this period (phase 2), the deformation is active only in the most distal part, concomitant with the present-day Large Diapirs domain: the sedimentary supply in this case could influence the diapirs formation but only in this domain, without inducing a movement in the Anticlinal domain (no early deformation). Nevertheless, sedimentary thicknesses are small on the slope (smaller than in the deep basin, fig.4.42A), which excludes a start of salt movement due to sediment spreading (see above). Moreover, in the SW sector the MSC-P11 thickness varies more than in the NE sector, where it is greater but relatively constant. The thickness variation depicted in 3D maps (Fig.4.42A) confirms the earliness of deformation in phase two in the SW sector. In the NE sector, on the other hand, movement is minimal during the phase 2, which would suggest that a considerable thickness of sediment does not induce salt movement. Nevertheless, the Rhone fan influence, stronger after 0.9 Ma (Fig. 4.42C), is likely to influence the direction of associated present-day diapirs and mini-basins and the strong deformation of phase 3. The massive sedimentary input along the Marti and Petit-Rhône canyons is well aligned with the present-day structure's direction (N-S and NW-SE), suggesting a strong relationship between sedimentary input and salt deformation in that case. The directions of the salt structures are lost towards the deep basin, in the Irregular connected salt domain, where the diapirs are vertically developed (salt stocks). The EAB is characterised by a relatively constant thickness in the deep basin except for a thinning area with a NW-SE direction that could suggest a structural high (also observed in base salt map depth; fig. 4.48). The entire north-Algerian margin is characterised by a considerable sedimentary thickness (more than 2 km; fig. 4.49), which would confirm the foreland basin caused by the active African compression tectonics. Minor sedimentary contributions came from the Balearic Islands, which explain the weak sedimentary thickness in the southern Balearic margin (around 1 km; fig. 4.49). These sedimentary thickness trends correlate well with the crustal domains, thus confirming the link between tectonic setting and sedimentary accumulation. As observed in the Gulf of Lion[START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF], the post break-up subsidence re-uses the initial hinge lines of the rifting phases, thus creating different contexts for sedimentary accumulation which are related to the deep segmentation. In the example of the western Sardinian margin, the deep oceanic basin (where the thickness is higher) is probably affected by both the arrival of the Rhone and a more significant subsidence than in the transitional domain, where a High Salt base domain suggests a domain with a different post break-up behaviour (Fig.4.49).

Figure 4 .

 4 Figure 4.49. Plio-Quaternary thickness map in km. The salt morphologies domain (white dashed limits) and the crustal segmentation are represented. Note the thick PQ in the northern Algerian and Gulf of Lion margins. For the velocity conversion refer to chapter 3. Black arrows indicate the main continental sedimentary supply.

  in the western part of the Gulf of Lion (towards the Menorca basin). The recent tectonic activity is nevertheless local, buried by thick pre-salt sequence, and cannot explain the salt morphologies-crustal segmentation coincidence regionally observed. More recently, Maillard et al., (2003) claimed for the influence of basement dormant steps, below the pre-salt sediments, which can affect the overlying salt deformation. The authors carried out three physical experiments to show how the basement steps (given by not-active faults), even under km-thick pre-salt sediments, could be the cause of salt stocks/walls alignment in Gulf of Lion. The first experiment included as an initial condition a salt deposited above a basement step already present, therefore with a different thickness (Fig. 4.50). This

Figure 4 .

 4 Figure 4.50. Summary of the three experiments conditions and parameters explained in[START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF]. Note the ratio between the basement step and the initial silicone thickness (representing the salt).

  4.50). This slope is not observed, as the basement deepens more to the NW, at the boundary between lower slope and deep basin. At the boundary between the Anticlinal and Large Diapirs domain, and then further to the SE in the deep basin, the basement does not display steps or significant slope.To conclude, although the influence of basement steps leading to a different compaction of pre-salt sediments might play a role in salt deformation, in the LPB the initial conditions set in the work of[START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF] are simply not realistic and differ from our observations. We therefore consider that the basement plays only a minor (if not completely absent) role in the salt deformation of the LPB.

Figure 4 .

 4 Figure 4.51. Experiment 2 set-up and results in analogical modelling from[START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF]. The basement step height is 5 times the silicone (salt) thickness. Note the effects of a differential compaction (monoclinal flexure) above the step. This type of structure is far from being equivalent to the structures seen in the Gulf of Lion.

Figure 4 .

 4 Figure 4.52. Reconstruction representing the northern Algerian coastline at 5 Ma ago with respect the present-day position (after reconstruction ofPellen et al., submitted). The arrows indicate the NW direction of Africa movement (5mm/yr, from[START_REF] Serpelloni | Kinematics of the Western Africa-Eurasia plate boundary from focal mechanisms and GPS data[END_REF]. Below, the line-drawing crosses the Algerian basin from the South Balearic to the north Algerian margins highlighting the narrowness of the WAB. The profile zooms (in depth,from Blondel Simon, unpublished) shows the salt structure close to the Emile Baudot Escarpment. Note the squeezed diapirs suggesting contractional events.



  The salt entirely occupies the deep basin and lower slope of the Western Mediterranean, except for the Hannibal High, where the salt is almost absent. Because of purely vertical subsidence in the deep basin, we assumed a relatively constant initial salt thickness. The present-day salt thickness variation is therefore closely related to the salt tectonics.  The Western Mediterranean is a closed basin with no regional strong tectonics movement, except for the reactivation of the northern Algerian margin, since the Messinian. The pre-salt deposits are thick and filled the topography of basement.  The base of salt is sub-horizontal in the deep basin, basinward tilted in the mid-lower slope and unfaulted (except in the northern Algerian margin where the base salt is tilted landward and locally faulted). The salt layer occupied the entire deep basins and no space is available at the early phases to allow the gliding.  The Plio-Quaternary deposits are regionally thin in the lower slope and thick in the deep basin (excluding a sediment spreading origin of salt deformation), and the depocenters follow the margin segmentation. Huge sedimentation differences between the LPB and the Algerian basins are depicted, whilst no difference between the WAB and EAB are seen. The salt structures distribution highlights huge differences in the deep sub-basins composing the Western Mediterranean. In the southern part, the main difference is between the EAB, characterized by smaller salt structures, and the WAB, by discordant and piercing salt diapirs.  The thin-skinned salt tectonics is well developed only in the lower slope-proximal deep basin (Listric salt domain), as testified by the relation between margin steepness and Listric domain width. A thick-skinned salt tectonics is only observed in the north Algerian margin, due to the tectonic compression induced by the North African convergence.

  occidentale et sa relation avec la segmentation crustale. Afin d'analyser la déformation régionale du sel dans les sous-bassins, une étude des marqueurs stratigraphiques a été nécessaire pour évaluer le rôle stratigraphique et la chronologie des mouvements. Des compilations régionales des principaux marqueurs stratigraphiques de la Méditerranée occidentale sont donc présentées. Par ailleurs, une analyse des structures salifères dans toute la Méditerranée occidentale a été réalisée afin de les regrouper selon des critères géométriques. Le choix de ces morphologies a permis d'avoir une vision globale de la déformation. Les morphologies varient perpendiculairement à la pente et entre les sous-bassins, mettant en évidence de fortes différences entre les bassins du Liguro-Provençal, de l'Est et de l'Ouest algérien en particulier. Les structures décrites et classées par région sont ensuite mises en relation avec la structure crustale, mettant en avant une corrélation entre les morphologies salifères et la segmentation de la croûte dans chaque sous-domaine de la Méditerranéenne occidentale. Afin de comprendre l'importance des mécanismes et des causes de la tectonique salifère et sa relation avec la segmentation crustale, une analyse détaillée de la chronologie de la déformation a été nécessaire. Une meilleure connaissance de la chronologie peut donner des indications temporelles sur les éléments déclencheurs du mouvement, tels que l'apport sédimentaire ou les variations de l'évolution de la pente du sel. Une déformation précoce du sel profond est représentée partout, ce qui précède l'activation des failles listriques sur le talus. Dans le Golfe du Lion, le mouvement du sel s'est produit pendant deux principales phases, la première de faible amplitude au Pliocène et la seconde beaucoup plus forte, au Quaternaire. Enfin, les mécanismes régionaux qui pourraient être responsables des structures salifères ont été analysés. Chaque marge est caractérisée par une coexistence de l'influence du glissement gravitaire, de l'étalement et de la tectonique qui dépend principalement de son évolution tectonique, géomorphologique et sédimentaire. Néanmoins, ces mécanismes n'expliquent guère la correspondance observée entre la segmentation crustale et les morphologies salifères. Nous avons donc proposé d'évaluer l'hypothèse thermique, qui pourrait être liée à la segmentation crustale et ainsi avoir une influence différente selon les régions délimitées par différentes morphologies de sel. CHAPTER 5. THERMAL REGIME IN THE WESTERN MEDITERRANEAN SEA 235 CHAPTER 5. THERMAL REGIME IN THE WESTERN MEDITERRANEAN SEA CHAPTER 5. THERMAL REGIME IN THE WESTERN MEDITERRANEAN SEA 236

Figure 5 . 1 .

 51 Figure5.1. Regional setting of the Western Mediterranean Sea. The present-day segmentation is the result of plate and blocks geodynamical history. While there is a consensus about segmentation and geodynamic in the Liguro-Provençal basin[START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF], in the Algerian basin doubts about the basin opening lead to different segmentation interpretation. Wide-angle segmentation is taken from[START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF];Afhilado et al., 2015;[START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF] Aidi et al., (2018);[START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF];[START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF];[START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF]. Gravity modelling segmentation is from[START_REF] Driussi | Evidence for transform motion along the South Balearic margin and implications for the kinematics of opening of the Algerian basin[END_REF]. Gravity and magnetic segmentation is from[START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. Free-air anomaly map is from[START_REF] Smith | Global sea floor topography from satellite altimetry and ship depth soundings[END_REF]. Black squares and white circles represent the heat flow measurements acquired during WestMedFlux 1 (2016) and WestMedFlux 2 (2018), respectively. GoL: Gulf of Lion margin; LPB: Liguro-Provençal basin; WS: Western Sardinian margin; EAB: East Algerian basin; HA: Hannibal Area; SMB: South Minorca block; WAB: West Algerian basin; EA: East Alboran margin; SB: South Balearic margin; PB: Balearic Promontory; VB: Valencia basin; MB: Menorca basin. Transfer zones are from[START_REF] Pellen | The Minorca Basin: a buffer zone between the Valencia and Liguro-Provençal Basins (NW Mediterranean Sea)[END_REF].

  Figure5.1. Regional setting of the Western Mediterranean Sea. The present-day segmentation is the result of plate and blocks geodynamical history. While there is a consensus about segmentation and geodynamic in the Liguro-Provençal basin[START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF], in the Algerian basin doubts about the basin opening lead to different segmentation interpretation. Wide-angle segmentation is taken from[START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF];Afhilado et al., 2015;[START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF] Aidi et al., (2018);[START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF];[START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF];[START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF]. Gravity modelling segmentation is from[START_REF] Driussi | Evidence for transform motion along the South Balearic margin and implications for the kinematics of opening of the Algerian basin[END_REF]. Gravity and magnetic segmentation is from[START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. Free-air anomaly map is from[START_REF] Smith | Global sea floor topography from satellite altimetry and ship depth soundings[END_REF]. Black squares and white circles represent the heat flow measurements acquired during WestMedFlux 1 (2016) and WestMedFlux 2 (2018), respectively. GoL: Gulf of Lion margin; LPB: Liguro-Provençal basin; WS: Western Sardinian margin; EAB: East Algerian basin; HA: Hannibal Area; SMB: South Minorca block; WAB: West Algerian basin; EA: East Alboran margin; SB: South Balearic margin; PB: Balearic Promontory; VB: Valencia basin; MB: Menorca basin. Transfer zones are from[START_REF] Pellen | The Minorca Basin: a buffer zone between the Valencia and Liguro-Provençal Basins (NW Mediterranean Sea)[END_REF].

Figure 5

 5 Figure 5.2. A thermal conductivity-depth plot of the measurements performed on-board on the sediment cores. The cores are recovered with the Kullenberg corer.

Figure 5 . 3 .

 53 Figure 5.3. Thickness map (s twt) of complete sedimentary sequence (above basement) in Western Mediterranean Sea. Percentage correction of WMF1-2 measurements are represented. Note the higher sedimentation thickness and correction in GoL with respect the SB.

CHAPTER 5 .

 5 THERMAL REGIME IN THE WESTERN MEDITERRANEAN SEA 249 70 mW/m 2 at NE of the profile. The few HF available in the oceanic domain (Figs. 5.1, 5.4) does not exhibit higher values compared to the OCT domain. In the deep basin the values are thus constant all along the OCT and proximal oceanic domain: to note two positive (WMF1 KF25 and WMF1 KF26) and two negative (WMF1 11-07 and WMF1 11-08) HF anomalies above large salt stocks (Fig. 5.4).

Figure 5

 5 Figure 5.4. HF variation along the Sardinia-01 profile crossing from the lower slope to the oceanic deep basin the Gulf of Lion (location fig. 5.1). HF are indicated in plot above with black (measured value), blue (after refraction correction) and red (after sedimentation correction) points. The dashed lines represent the higher HF values above the two salt walls. Empty circles are projected HF from[START_REF] Burrus | Contribution to the thermal regime of the Provençal Basin based on FLUMED heat flow surveys and previous investigations[END_REF], at a maximum distance of 50 km. Thin lines above seafloor indicate the HF measurements location. Thickness in meters of Miocene pre-salt is from[START_REF] Bache | Evolution Oligo Miocène des marges du micro océan Liguro-Provençal[END_REF]. Crustal segmentation is taken from[START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. The HF measurements are from WMF1 survey.

CHAPTER 5 .

 5 THERMAL REGIME IN THE WESTERN MEDITERRANEAN SEA 250 not far away (max 25 km), other measurements were acquired during WMF1 (Fig. 5.1; fig. 5.5b

CHAPTER 5 .

 5 THERMAL REGIME IN THE WESTERN MEDITERRANEAN SEA 251 salt or whether it moved horizontally after its deposition (perhaps glided). However, regionally no differences in salt thickness are observed at the edge of the Hannibal Area suggesting a strong gliding motion: the salt therefore appears to have been deposited with smaller initial thickness. 13 HF measurements were acquired during WMF2 (2 KF and 11 HF) along the SH73-37b profile (Fig. 5.5B). The measurements in the western part of the EAB (km 200-230; fig. 5.5B) show a HF average of 72 mW/m 2 with a peak of about 87.4 mW/m 2 (HF03-07) showing a measurement error quite high for this latter. Moving south-westward, towards the WAB, the average slightly increase (about 89 mW/m 2 ), with a peak around 110 mW/m 2 (HF04-09). Above the basement, in the central sector (km 140-150; fig. 5.5B), the HF does not show anomalies.

Figure 5

 5 Figure 5.5. A) HF variation along the SH73-23A profile crossing the SMB (location fig. 5.1). Free-air gravity anomaly was acquired during WMF2 survey. B) HF variation along the SH73-37B profile, crossing from NE to SW the Hannibal Area. HF are indicated in plots above the profiles with black (measured value), and red (after sedimentation correction) points. Thin lines above seafloor indicate the HF measurements location. Crustal segmentation is taken fromDriussi et al., (2015a), Aidi et al., (2018) and[START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF]. The HF are from WMF2 survey.

Figure 5

 5 Figure 5.6. A) HF variation along the MEDS76-07D profile crossing the southern part of the South Formentera basin with a NE-SW direction (location fig. 5.1). B) HF variation along the Pre-Stack Depth Migration (PSDM) SaltFlu-03 profile, crossing from NW to SE the South Balearic margin. HF are indicated in plots above the profiles with black (measured value), blue (after refraction correction) and red (after sedimentation correction) points. Thin lines above seafloor indicate the HF measurements location. Crustal segmentation is taken fromDriussi et al., (2015a) and[START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF]. The HF are from WMF1 and WMF2 survey. Inset top right: multi-beam bathymetry acquired during WMF1-2 surveys showing the available HF measurements in the South Balearic margin. Position of Riba and Los Martines seamounts are fromRovere and Wurtz, (2015).

  two anomalously low measurements (around 40-45 mW/m 2 ; fig. 5.7) were recorded alongside the high measurement. The salt structure, well outlined in multi-beam bathymetry and seismic reflection data (Fig. 5.7), displays a vertical extension of about 2 s twt and a base width of at least 4 km. CHAPTER 5. THERMAL REGIME IN THE WESTERN MEDITERRANEAN SEA 256

Figure 5 . 7 .

 57 Figure 5.7. Zoom of salt structures interpreted in figure 5.4. In the inset above the multi-beam bathymetry acquired during WMF1 survey showing the N-S salt wall approximately 12 km long. Laterally, three low HF measurements, probably also affected by salt thermal conductivity small-scale variation.

CHAPTER 5 .

 5 THERMAL REGIME IN THE WESTERN MEDITERRANEAN SEA 258 In the sector of South Formentera intra-slope basin and Emile Baudot Escarpment, wide variations are recorded between the slope and deep basin domains (Fig. 5.6). The very low values of surface HF and the thin sedimentary cover above the basement (Fig. 5.8) suggest a recharge zone located around the Los Martines seamount, at least 40 km wide. Sub-bottom profile (Fig. 5.9) shows areas of mounded discontinuous low amplitudes seismic facies, locally chaotic, suggesting fluid circulation in the area coincident with low HF measurements.

Figure 5 . 8 .

 58 Figure 5.8. Sketch representing the HF distribution with respect the crustal segmentation in Western Mediterranean. From I to V, the Gulf of Lion, Western Sardinian, Hannibal Area, SMB and South Balearic margins are represented, respectively. The crustal segmentation is taken from[START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF],Afhilado et al., (2015),Driussi et al., (2015a),[START_REF] Leprêtre | Multiphased tectonic evolution of the Central Algerian margin from combined wide-angle and reflection seismic data off Tipaza, Algeria[END_REF]), Aidi et al., (2018). The yellow colour in the profile indicates the sedimentary thickness above basement. The plot represents the surface measured HF with respect the sedimentation thickness above basement for each profile. The dashed ellipse represents the HF variations in areas of thin sedimentary thickness, so more likely to be affected by fluid circulation. The dashed horizontal black lines represent, for each crustal segment, the average measured surface HF with the corresponding value noted. Note the very low HF values on the South Balearic associated with a low sedimentary thickness. The map in the centre represents all the available surface HF in the Western Mediterranean Sea superposed to the crustal segmentation taken from[START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. The scale is the same for all the profiles.

Figure 5

 5 Figure 5.9. A) Location of multi-beam data (zoom of figure 5.6) showing the new pockmark discovered during WMF2 survey in 2018. B) Sub-bottom profile acquired during WMF2 showing several fluid percolation seismic signatures concomitant with low surface heat flow measurements. C) Temperature profile of WMF2_05-06 measure showing the low thermal gradient (16.7 mKm-1) in the first core meters.

Figure 5 .

 5 Figure 5.10. Zoom of lower slope South Balearic margin showing high HF values probably related to a discharge zone associated to basement rise at the foot of Emile Baudot Escarpment. The fluids (red arrows) from the basement could reach the surface through salt welds and fracture/faults created by shear stress zones. Also note the polygonal faults probably associated with gypsum-anhydrite phase change.

Figure 5 .

 5 Figure 5.11. Tablesummarisingthe average HF values in the crustal segments of Liguro-Provençal and Algero-Balearic basins.Refer to regional map in figure5.8 for crustal segmentation and domains. n is the number of HF values, HF the heat flow in mW/m 2 and σ the standard deviation. In the case of the uncorrected measurements (for sedimentation), we were able to retain all available measurements, both old and newly acquired. In the case of the corrected measurements, we were forced to retain only the new measurements in which the sedimentation correction was made (refer to map in Fig.5.3).

  How do heat flow change in time and space in two different margins (Gulf of Lion and Western Algerian basin) according to a 2D divergent margin model constrained by its CHAPTER 5. THERMAL REGIME IN THE WESTERN MEDITERRANEAN SEA 267 sedimentary infill? Are there considerable differences in thermal regime linked to crustal segmentation?

Figure 5 .

 5 Figure 5.12. Location of transects used in MARGE model plotted on free-air anomaly map from[START_REF] Smith | Global sea floor topography from satellite altimetry and ship depth soundings[END_REF]. Thin black solid and dashed lines represent the crustal segmentation (from[START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF].

  4.2). The sediments heat production are calculated by the model based on the average lithological and physical properties characteristic of each stratigraphic sequence (Fig. 5.14).

Figure 5 .

 5 Figure 5.13. Seismic transects used for the models. The imaginary wells indicated the location of the temperature analysis made in chapter 5.4. A and A' are above the OCT domain while B and B' on oceanic domain for, respectively, the Gulf of Lion and South Balearic margin.

Figure 5 .

 5 Figure 5.16. Input crustal setting for the Gulf of Lion. Note the lithosphere thickness change between oceanic and continental domain, as suggested by[START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF].

Figure 5 .

 5 Figure 5.17. Final (output) crustal structure of the reference model in the Gulf of Lion. Dashed line represents top basement and Moho depth from wide-angle refraction model[START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. Note the good fitting concomitant with the thinnest crustal domain.

Fig. 5 .

 5 Fig. 5.18 shows the reference model results in which the HF trends at the basement (red lines) and at the surface (blue lines) are illustrated for different ages: -16 Ma, referring to the end of oceanisation; 5.9 Ma, to Messinian Salinity Crisis onset and 0 Ma, to the present day situation. Heat flow in the oceanic domain decrease significantly from 16 Ma (about 200 mW/m 2 ) to the present-day (about 60-70 mW/m 2 ). The difference in heat flow between the

Figure 5 .

 5 Figure5.18. Plot representing the HF timing evolution at 0, 5.9 and 16 Ma for basement and surface HF. 16 Ma is considered to be the end of oceanic crust formation, 5.9 Ma the beginning of the MSC and 0 Ma the present-day situation. The dashed horizontal black lines represent, for each crustal segment, the average measured surface HF in the whole area.

Figure 5 .

 5 Figure5.19. Above: example of stratigraphic section of the SaltFlu profile in the South Balearic margin showing the seismic stratigraphy units and, from the left to right, the density, the thermal conductivity and the heat production for each stratigraphic unit. Below: initial crustal setting showing the same parameters than above but on the crust level. See references in the text for the lithosphere structure.

  Figure 5.20.Table summarizing the lithospheric, sedimentary and opening input parameters for the reference model in the SaltFlu03 profile (South Balearic).

Figure 5 .

 5 Figure5.21 shows the HF time evolution for the reference model. Heat flow in the oceanic domain decrease significantly from 10 Ma (more than 200 mW/m 2 ) to the present-day (about 90-100 mW/m 2 ). The difference in HF between the oceanic and transitional domains is more pronounced immediately after the end of oceanic crust formation and at 5.9 Ma with respect now-days. At the Messinian epoch, HF appear to be about 20 % higher than today. This difference is more pronounced in the oceanic domain. With respect the Gulf of Lion, in the South Balearic the HF seems to be more dependent of crustal segmentation: significant differences are depicted in the model between the continental and transitional/oceanic domains.The values calculated by the model compared to the average of those measured differ significantly in the continental crust and slightly in the transitional and oceanic crust. The model confirms that the values measured in the South Formentera basin are anomalously low and can in no way be the result of deep crustal structure alone (see chapter 5.2).

Figure 5 .

 5 Figure5.21. Plot representing the HF timing evolution at 0, 5.9 and 10 Ma for basement and surface HF. 10 ma is considered to be the end of oceanic crust formation, 5.9 the onset of the MSC and 0 Ma the present-day situation. The dashed horizontal black lines represent, for each crustal segment, the average measured surface HF in the whole area.

Figure 5 .

 5 Figure 5.22. Plots showing the temperature variations with depth in the Gulf of Lion for two ages (0 and 5.9 Ma). The red line represents the well on transitional crust while the blue line the well on oceanic crust. Note the base salt temperature difference between the two domains at present-day situation. Imaginary wells location in fig. 5.13.

  MARGE model explained above takes into account the extensional rifting model devised by McKenzie, (1978). The petroleum models used in the oil field today are mainly based on this uniform stretching model (see chapter 1). MARGE has several improvements within it that move it away from McKenzie's original model. Examples are the possibility to

Figure 5 .

 5 Figure 5.23. Plots showing the temperature variations with depth in the South Balearic margin for two ages (0 and 5.9 Ma). The red line represents the well on transitional crust while the blue line the well on oceanic crust. Note the smaller base salt temperature with respect the Gulf of Lion transect. Imaginary wells location in fig. 5.13.

  campaign. In addition to depicting several high and low local anomalies of different supposed natures (e.g. fluids and salt refraction), we try to related the measured heat flow to the crustal segmentation known so far. Subsequently, in chapters 5.3 and 5.4 we used a thermo-kinematic model to try to get information on the temperature at the base of the salt in different crustal domains. I showed how the model can give us some insights into the thermal segmentation of the GoL and South

Figure 5 .

 5 Figure 5.24. Top: Sketch map representing imaginary spreading centre in the LPB, drawn approximately in the middle of the present-day oceanic crust. Below, left: HF-distance from spreading showing the HF non-corrected measurements in the different LPB (for both GoL and WS) crustal domains. A slighlty trend decrease from the oceanic to the continental crusts is depicted. Below, right: zoom on the LPB oceanic crust HF. HF are corrected for the sedimentation. The oceanic crust age is calculated according to formation age and the distance from the imaginary spreading centre. Note the lower HF values with respect the plate cooling model from[START_REF] Carlson | On modeling the thermal evolution of the oceanic upper mantle: An assessment of the cooling plate model[END_REF].

  5 explored the thermicity of the Western Mediterranean with the aim of understanding whether it can have a relationship with crustal segmentation and consequently, based on what was shown in the previous chapter, on salt deformation. In the first part the presentday surface heat flow results from the new measurements acquired in 2018 during the WMF2 campaign are represented. A detailed analysis of the thermal anomalies revealed a large variation in the measurements, probably given by local effects and basement regional heat flow. Small-wavelength surface HF anomalies, thin sedimentary cover, nearly outcropping basement, pockmarks structures, recent volcanic activity, gypsum dehydration phenomena and seismic signatures suggest an active circulation of fluids in the South Balearic margin (continental and OCT crustal domains). Some other local anomalies are clearly associated to the salt diapirism present in the Liguro-Provençal basin. On other hand, everywhere in the deep basin, fluid circulation appears to be inhibited by the thick sedimentary blanket separating the basement from the surface. Longer wavelength variation are believed to express here crustal levels processes. The attempt to decipher the crustal segmentation thermal imprint is made.In the Liguro-Provençal basin, a clearly heat flow variation is only seen between the continental and transitional crustal domain, while between transitional and oceanic domain the difference is small. Moreover, the oceanic domain shows lower HF than expected from plate cooling model. In the South Balearic margin, a well thermal segmentation is observed between the continental and the transitional-oceanic domains. The thermal regime time evolution was investigated using the thermo-kinematical model MARGE. The temperatures calculated at the base of the salt show little variation between crustal segments. Nevertheless, the model did not take into account several processes still poorly understood as exhumation and fluids interaction. The chapter shows how heat flow can be a useful tool for studying the subsurface thermal regime. However, it has shown how measurements can be easily biased from local to very local phenomena: An in-depth study of the relationship of the crustal nature with the thermal regime would require a more resolute coverage of measurements.

à

  la segmentation crustale et par conséquent, sur la déformation du sel. Dans la première partie, les résultats de flux de chaleur de surface actuels issus des nouvelles mesures acquises en 2018 lors de la campagne WMF2 sont représentés. Une analyse détaillée des anomalies thermiques a révélé une grande variation dans les mesures, probablement donnée par des effets locaux régionaux influencés par la nature crustale. Des anomalies HF de surface de faible longueur d'onde, une couverture sédimentaire mince, un socle presque affleurant, des structures de type pockmarks, une activité volcanique récente, des phénomènes de déshydratation du gypse et les signatures sismiques suggèrent une circulation active de fluides dans la marge sud des Baléares (domaines crustaux continental et OCT). D'autres anomalies locales sont visiblement associées au diapirisme salifère présent dans le bassin Liguro-Provençal. D'autre part, partout dans le bassin profond, la circulation des fluides semble être inhibée par l'épaisse couverture sédimentaire qui sépare le socle de la surface. Les variations de plus grande longueur d'onde pourraient exprimer ici des processus de niveaux profond. Nous avions alors tenté de déchiffrer l'empreinte thermique de la segmentation crustale. Dans le bassin Liguro-Provençal, une nette variation du flux n'est observée qu'entre le domaine crustal continental et OCT, alors qu'entre le domaine OCT et océanique la différence est faible. De plus, le domaine océanique montre un HF plus faible que celui attendu par le modèle de refroidissement des plaques. Dans la marge sud des Baléares, une segmentation thermique est observée entre le domaine continental et OCT-océanique. L'évolution temporelle du régime thermique a été étudiée à l'aide du modèle thermo-cinématique MARGE. Les températures calculées à la base du sel montrent peu de variations entre les segments crustaux, principalement données par la profondeur de ce marqueur. Néanmoins, le modèle ne prend pas en compte plusieurs processus encore mal compris comme l'exhumation et l'interaction des fluides. Ce chapitre montre comment le flux thermique peut être un outil utile pour étudier le régime thermique de la sub-surface. Cependant, il a montré comment les mesures peuvent être facilement biaisées par des phénomènes locaux voire très locaux : une étude approfondie de la relation entre la nature de la croûte et le régime thermique nécessiterait une couverture plus résolue des mesures. CHAPTER 6. CRUSTAL SEGMENTATION AND SALT MORPHOLOGIES IN OTHER SALT-

Figure 6 . 1 .

 61 Figure 6.1. Regional world bathymetric map showing the studied areas and referred figures. For the Western Mediterranean refer to chapter 4.

Figure 6

 6 Figure 6.2. A) SANBA wide-angle refraction seismic profiles showing the crust velocity models in the Santos Basin (after[START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF][START_REF] Klingelhoefer | Imaging proto-oceanic crust off the Brazilian Continental Margin[END_REF]. The crustal limit are from[START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Reflection and refraction seismic data used in this study are referenced in chapter 3. B) Maps showing the crustal segmentation from the wide angle interpretation in the Santos Basin. Left: on the magnetic map. Center: On the gravity map. Right: with the crustal thickness. The hinge line and the Capricornio and Cruzeiro do Sul lineaments are from[START_REF] Moulin | Kinematic keys of the Santos-Namibe basins[END_REF].

CHAPTER 6 . 292 -

 6292 CRUSTAL SEGMENTATION AND SALT MORPHOLOGIES IN OTHER SALT-BEARING PASSIVE MARGINS CC: corresponds to the unthinned continental crust, 30-35 km thick (based on gravity data) -N: refers to the 50 km-wide necking zone, with an abrupt thinning of crust of about 20 km.

CHAPTER 6 .

 6 CRUSTAL SEGMENTATION AND SALT MORPHOLOGIES IN OTHER SALT-BEARING PASSIVE MARGINS

Figure 6 . 3 .

 63 Figure 6.3. From top to bottom: map showing the crustal segmentation in the Angolan margin. The crustal limits are fromContrucci et al., (2004a) and[START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]. Reflection and refraction seismic data used in this study are represented (references in chapter 3). Bottom: wide-angle refraction seismic profile showing the crust velocity model in Zaiango03 (Z03) profile (afterContrucci et al., 2004a). Dashed black lines represent the lower and upper limit of the crust.

CHAPTER 6 .

 6 CRUSTAL SEGMENTATION AND SALT MORPHOLOGIES IN OTHER SALT-BEARING PASSIVE MARGINS 295

Figure 6 . 4 .

 64 Figure 6.4. Map showing crustal structure and wide-angle refraction survey in Gulf of Mexico on free-air gravity anomaly(from Sandwell and Smith, 1997). Four ocean-continent boundaries interpretation are represented (references in the figure legend). The greatest uncertainty is in the north GoM deep basin, where salt is more deformed and masks deep imaging. Black lines represent seismic profile used in this study (references in chapter 3). Bottom: Gumbo1 wide-angle seismic profile showing velocity model in the NW GoM margin. Crustal segmentation in black is from this study and discussion in[START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF]. Dashed black lines represent the lower and upper limit of the crust.

  6.5). The Moroccan margin segmentation is divided into three crustal domains (Fig.6.5, Biari CHAPTER 6. CRUSTAL SEGMENTATION AND SALT MORPHOLOGIES IN OTHER SALT-BEARING PASSIVE MARGINS 297 et al., 2015): unthinned continental crust of 36 km thick, a thinning continental crust domain

Figure 6 . 5 .

 65 Figure 6.5. Map showing crustal segmentation and wide-angle refraction surveys in Morocco-Nova Scotia conjugated margins. Crustal segmentation is taken from SMART, SISMAR and MIRROR refraction studies (references in the chapter 3). Bottom: Smart1 and Mirror1 profiles are from[START_REF] Funck | Crustal structure of the northern Nova Scotia rifted continental margin (eastern Canada)[END_REF] and[START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF], respectively. Black lines represent seismic profile used in this study (references in chapter 3). ECMA and WACMA are from[START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF].

  domain, -Diapirs domain and -Massive-Canopy domain. The Raft domain is so-called for the typical extensional thin-skinned structures as salt rollers, turtlebacks and base salt-rooted normal faults. The counterpart in the Western Mediterranean Sea is the Listric domain (Chapter 4), which characterized all the mid-lower slope margins. The Diapirs domain includes salt stocks and walls characterized by discordant overburden, autochthonous connected or disconnected structures. To note that in Gulf of Mexico the Diapirs domain can exhibits coalescence sheets and allochthonous salt as well as basinward listric faults[START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF][START_REF] Fort | Kinematics of regional salt flow in the northern Gulf of Mexico[END_REF] and roller structures. Its counterpart in the Western Mediterranean Sea are the Large, Regular and Irregular Diapirs domains, mainly present in the deep basins. The density of seismic data at our disposal in the Western Mediterranean allows further categorisation of the diapiric domain, which is not possible in the other analysed passive margins. The Massive-Canopy domain is located in the downdip part of the salt basins and is

  In domain B the wide-angle profile shows an irregular top of the crust (Fig.6.7; dashed black line), with a deepening of basement. Nevertheless, the basement and the top of salt is separated by a thick pre-salt sequence (e.g.[START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF], which is supposed to smooth the topography of base of salt, even if[START_REF] Pichel | Base-salt relief controls salt-tectonic structural style, São Paulo Plateau, Santos Basin, Brazil[END_REF] described several basal salt reliefs in the Santos basin, which can influenced the evolution of the salt tectonics.

Figure 6 . 6 .

 66 Figure 6.6. Map showing the salt morphologies in the Santos and Campos basins. With black square are represented the isopach maps, from[START_REF] Mohriak | Salt: geology and tectonics of selected Brazilian basins in their global context[END_REF] and[START_REF] Guerra | Role of halokinesis in controlling structural styles and sediment dispersal in the Santos Basin, offshore Brazil[END_REF]. References of structural elements in figure6.2. Below: seismic reflection Sanba01 profile showing the basinward evolution of salt morphologies with a NW-SE direction, crossing all the Santos basin. Blue area represents the Raft salt domain distribution; pink area the Large and Narrow Diapirs domains; yellow area the Canopy-Massive salt domain.

Figure 6

 6 Figure 6.7 (A) Map showing the salt morphologies and crust segmentation in the Santos and Campos basins. On the left it is shown only the crustal segmentation while on the right we added the salt morphologies domains. Blue area represents the Raft salt domain distribution; pink area the Large and Narrow Diapirs domains; yellow area the Canopy-Massive salt domain. Wide-angle profile location and crust segmentation are from[START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Volcanic structures are from[START_REF] Mohriak | Salt tectonics, volcanic centers, fracture zones and their relationship with the origin and evolution of the South Atlantic Ocean: geophysical evidence in the Brazilian and West African margins[END_REF]. The hinge line and the Capricornio and Cruzeiro do Sul Lineaments are from[START_REF] Moulin | Kinematic keys of the Santos-Namibe basins[END_REF]. Black lines represent seismic profile interpreted (references in the chapter 3). (B)From top to bottom, Sanba01 (SB01) time-migrated reflection seismic line uninterpreted and interpreted (location in the maps above). The interpreted salt morphologies are represented, showing their evolution from the lower slope to the deep basin. Sanba01 wide-angle profile (SB01), coincident with the reflection seismic line showing crust segmentation along SSPS (from[START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Dashed black lines represent the lower and upper limit of the crust.

Figure 6 . 8 .

 68 Figure 6.8. Maps showing salt distribution in the Angolan margin. Salt isopach maps is from[START_REF] Baudino | Modelling Petroleum Systems of Hyperextended Margins: the Angola Case Study[END_REF], red is thin and blue is thick salt. The inferred location in dashed black lines. Black lines indicate seismic profiles used in this work. Below: reflection seismic profile showing the salt morphologies along the African margin (modified from[START_REF] Unternehr | Hyper-extended crust in the South Atlantic: in search of a model[END_REF].

  Whatever the crustal nature of the different segments in the transitional domain, there is a strong coincidence between: 1) crustal domain T1 and the overlaying Large Diapir Domain, 2) crustal domain T2 and the Canopy-Massive Salt domain (Fig.6.9). The basinward limit of the Large Diapirs domain corresponds to the disappearance of the high velocity layer located at the base of the crust (T1 domain). Moreover, as observed in the Santos CHAPTER 6. CRUSTAL SEGMENTATION AND SALT MORPHOLOGIES IN OTHER SALT-BEARING PASSIVE MARGINS 307 basin (C domain), the Moho underlying the Massive-Canopy salt domain is shallower and the crustal thickness thinner (up to 5 km).

Figure 6

 6 Figure 6.9. (A) Map showing the salt morphologies and crust segmentation in Angolan margin. On the left it is shown only the crustal segmentation while on the right we added the salt morphologies. Blue area represents the Raft salt domain distribution; pink area the Large Diapir domain; yellow area the Canopy-Massive salt domain. Wide-angle profile location and crust segmentation are fromContrucci et al. (2004a) and[START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]. Black lines represent seismic profile interpreted in this study (references in the text). (B) From top to bottom, time migrated reflection profile (Z-03) and line-drawing interpretation (modified after[START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]; location on maps above) showing salt morphologies domains. Z-03 wide-angle coincident profile showing crust segmentation byContrucci et al., (2004a). Dashed black lines represent the lower and upper limit of the crust.

Figure 6 . 10 .

 610 Figure 6.10. Map showing salt morphologies distribution along the northern Gulf of Mexico. Salt structures outline are from[START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF]. Fault trends are from[START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF] [START_REF] Stephens | Basement controls on subsurface geologic patterns and near-surface geology across the northern Gulf of Mexico: a deeper perspective on coastal Louisiana[END_REF]. The salt morphologies boundaries are modified from previous interpretation of[START_REF] Seni | Evolution of salt structures during burial of salt sheets on the slope, northern Gulf of Mexico[END_REF]. Salt structural domains map is from P. Bourges (personal communication); original salt distribution is from[START_REF] Karlo | Classifications of syndepositional Systems and Tectonic Provinces of the Northern Gulf of Mexico[END_REF]; the profiles are modified from[START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF] [START_REF] Schuster | Deformation of allochthonous salt and evolution of related salt-structural systems, eastern Louisiana Gulf Coast[END_REF].

Figure 6 .

 6 Figure 6.11. (A) Map showing crustal segmentation and salt morphologies in Gulf of Mexico. On the left it is shown only the crustal segmentation while on the right the superposed salt morphologies. Outlined in red the salt structures from[START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF]. Salt morphologies boundary are redrawnfrom Seni, (1992). The oceanic domain boundaries fromHudec et al., (2013a);[START_REF] Sawyer | The crust under the Gulf of Mexico Basin. The Gulf of Mexico Basin: Geological Society of America[END_REF],[START_REF] Christeson | Deep crustal structure in the eastern Gulf of Mexico[END_REF] and[START_REF] Curry | Extensional models for the development of passive-margin salt basins, with application to the Gulf of Mexico[END_REF] are represented. Black lines represent Gumbo wide-angle survey profiles (references in chapter 3). Fault trends are from[START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF] [START_REF] Stephens | Basement controls on subsurface geologic patterns and near-surface geology across the northern Gulf of Mexico: a deeper perspective on coastal Louisiana[END_REF]. Black lines represent seismic profile, interpreted in this study (references in the text). (B) PSDM ION GulfSPAN 2450 profile from[START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF] Dickinson, (2017) approximately in the location of GUMBO 1 profile (location in (A) maps). The salt morphologies are from this study. Below, the GUMBO1 wide-angle profile. Crustal segmentation in black is from this study and discussion in[START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF]. Dashed black lines represent the lower and upper limit of the crust.

Figure 6 .

 6 Figure 6.12. Map showing salt morphologies of Nova Scotia-Morocco conjugated margins. Salt structures arefrom Shimeld, (2004);[START_REF] Sahabi | Evolution cinématique triasico-jurassique de l'Atlantique central: Implications sur l'évolution géodynamique des marges homologues nord ouest africaine et américaine[END_REF] and[START_REF] Tari | Salt tectonics in the Atlantic margin of Morocco[END_REF]. Black lines represent the seismic profiles used in this study (references in chapter 3). Canopy (allochthonous) salt in Nova Scotia isfrom Sahabi, (2004) interpretation. Tafelney canopy area is from interpretation of[START_REF] Tari | Salt tectonics along the Atlantic margin of Morocco[END_REF]. Nova Scotia seismic profile is modified fromLouden et al., (2012). Mirror01 profile is takenfrom Biari, (2015) (salt structures interpretation is taken from his work).

Figure 6 .

 6 Figure 6.13. (A) Maps showing salt morphologies and crustal segmentation in Nova Scotia and Morocco conjugated margins. Crust segmentation is taken from SMART, SISMAR and MIRROR refraction studies (references in the chapter 3). WACMA and ECMA are from[START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF]. (B) Mirror01 reflection and wide-angle associated profiles (location in map above (A)). Modified after[START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF].

  6.14). A crustal thinning, a rise of the Moho and a change in crustal CHAPTER 6. CRUSTAL SEGMENTATION AND SALT MORPHOLOGIES IN OTHER SALT-BEARING PASSIVE MARGINS 316 nature seem to be associated with an increase in the intensity of salt deformation, both in the South Atlantic -Gulf of Mexico and in the Western Mediterranean Sea (Fig. 6.14).

Figure 6 .

 6 Figure 6.14. Classification and comparison of salt-bearing margins studied in this work, including the Western Mediterranean margins. The margins are divided into pre/syn and post-oceanic spreading salt depositions and based on the "sag" basin presence. The colours describe the nature of the crust, after authors interpretation; solid lines are iso-velocity curves and dashed lines divide upper and lower layers in crust, where interpreted in literature. The profiles are at the same scale, vertical exaggeration 1:7. In the western Algerian margin the crustal nature in the deep basin is uncertain. Note the coincidence between the crustal segmentation and the salt morphologies domain variations, particularly clear in Angolan, Santos and Mediterranean basins. The WACMA and ECMA in the Nova Scotia-Morocco margins define the initial salt deposition distal limit: here, the basinward salt is interpreted as allochthonous.

Figure 6 .

 6 Figure 6.15. Salt deposits features and morpho-structure margins relationship. Modified after Rowan, (2014).

Figure 6 .

 6 Figure 6.16. The main crustal and geophysical features of each margins are related to the salt morphologies interpreted in this work. As in figure 6.14, the margins are divided into pre/syn and post-oceanic spreading salt depositions and based on the "sag" basin presence.

CHAPTER 6 .

 6 CRUSTAL SEGMENTATION AND SALT MORPHOLOGIES IN OTHER SALT-BEARING PASSIVE MARGINS 320

Figure 1 . 2 .Figure 1 . 3 .Figure 1 . 4 .Figure 1 . 5 .Figure 1 . 6 .

 1213141516 Figure 1.2. Schematic section of a volcanic passive margin. To note the presence of SDR's all along the relatively narrow transitional domain. Sketch from the Austral segment of the South Atlantic conjugate(From Chauvet et al., 2021). 23

Figure 1 . 10 .

 110 Figure 1.10. Plate cooling model from[START_REF] Stein | A model for the global variation in oceanic depth and heat flow with lithospheric age[END_REF] andParson and Sclater, (1977). Points are

Figure 1 . 15 .Figure 1 . 16 .Figure 1 . 17 .

 115116117 Figure 1.15. Sketch showing the two main scenario proposed in literature illustrating the effects in subduction zone configurations. A) N-S extension with roll back of the slab that goes from Gibraltar to Corsica, B) E-W extension in the Algerian basin with roll back confined to the Balearic-Corso-Sardinian segments (after Van Hinsbergen et al., 2014). 41 Figure 1.16. Kinematic reconstructions of the Western Mediterranean Sea from Pellen and Aslanian, (personal communication). The sketches represent three different models of Algerian basin opening and show the situations at 20 and 16 Ma. 20 Ma is the onset of oceanisation in the Liguro-Provençal basin while 16 Ma represents the end of Corso-Sardinian and Kabyle blocks movement. The three scenarios are closely related to the initial position of the AlKaPeCa blocks. 44

Figure 1 .

 1 Figure 1.18. The SARDINIA wide-angle profiles are represented as well as their position in the Liguro-Provençal basin. A) Gulf of Lion profile and refraction segmentation from[START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. The first profile on the top

Figure 1 .

 1 Figure 1.19. The SPIRAL wide-angle refraction profiles are represented as well as their position in the Algerian basin, from east (A) to west (E). The profiles A and B cross the East Algerian basin (segment I), the profile C crosses the north-western part of the Hannibal Area (segment II), the profile D crosses the Central Algerian basin (segment III) and the profile E crosses the West Algerian basin (segment IV). All the profile have a N-S direction

Figure 2 . 1 .Figure 2 . 2 .Figure 2 . 3 .Figure 2 . 4 .

 21222324 Figure 2.1. Sketch representing the percentage of evaporites formed by evaporating 1 km of seawater column[START_REF] Warren | Evaporites: sediments, resources and hydrocarbons[END_REF] 55Figure2.2. Nonmarine and marine evaporites comparisonfrom Warren, (2006). 57 Figure 2.3. Sketch representing the Quaternary continental lacustrine deposits in relation to their Koeppen climate zone and latitude during the deposition. The brown shade indicates "horse latitude" (Oliver, 2008), characterized by light winds and fine, clear weather. 58 Figure 2.4. Latitudinal distribution of evaporites from Permian to now-days. Shaded belts indicated "horse latitudes". The sketch plots latitude occurrence and not the evaporite volume. Note the dominance of northern

Figure 2 . 14 .

 214 Figure 2.14. Seismic profiles zoom of Messinian seismic records: C) sketch from Gulf of Lion,[START_REF] Lofi | Erosional processes and paleo-environmental changes in the Western Gulf of Lions (SW France) during the Messinian Salinity Crisis[END_REF]

Figure 2 . 15 .

 215 Figure 2.15. Density versus depth plot. The density of salt is compared to other rocks. The salt, incompressible,

Figure 2 . 18 .

 218 Figure 2.18. Temperature influence on thermal conductivity of several specimen byf different authors (references in the text). Note the higher thermal conductivity with lower temperatures. 77 Figure 2.19. The general creep trend shows three stages. In the salt rock, the primary elastic creep is negligible compared with the permanent creep deformation (secondary-steady creep) (after Jackson and Hudec, 2017).

Figure 2 . 22 .

 222 Figure 2.22. Differential stress -strain rate diagram summarising low temperature laboratory data for a wide range of rock salts. Broken line is extrapolation of the dislocation creep law, for temperature of 30 and 50 °C. Solid line is the room temperature (20 °C) solution-precipitation creep law for different grain sizes (0.1, 0.6, 3, 10 mm). It can be seen that for a grain size of 3 mm the two mechanisms contribute equally to the deformation at a strain rate of 10 -10 to 10 -11 s -1

Figure 2 . 25 .

 225 Figure 2.25. Effective viscosity derived from the two mechanisms creep (pressure solution and dislocation creep). The three plots (a,b,c) indicate three different grain sizes specimens. Bold lines indicate viscosity behaviour at 160 °C; normal lines at 20 °C. Dashed and solid lines indicate specimens deriving from different areas. Note that the behaviour of the two mechanisms depends on the strain rate(after Van Keken et al., 1993). 86

Figure 2 . 28 .

 228 Figure 2.28. Log equivalent viscosity versus temperature plot of variations in viscosity at 1 MPa differential stress by three different equations. Viscosities for solid curves and dashed curves are stress-dependent while for dotted curves are not(after Carter et al., 1993). 88

Figure 2 . 29 . 90 Figure 2 . 30 .Figure 2 . 31 .

 22990230231 Figure 2.29. Comparison between strain rate of Halite, Gypsum and Anhydrite (Williams-Stroud and Paul, 1997). 90 Figure 2.30. Gravity-driven deformation: (a) gravity gliding, in which a rigid block slides down a detachment; (b) gravity spreading, in which a rock mass distorts under its own weight by vertical collapse and lateral spreading; and (c) mixed mode deformation. Shaded areas are the final stages and arrows show material movement vectors (after[START_REF] Rowan | Gravity-driven fold belts on passive margins[END_REF]. 91 Figure 2.31. Diagram showing the minimum margin tilt angle necessary to activate the dominant gliding of a salt basin with different width. The two sets of curves have been calculated for thicknesses of the initial sedimentary cover in km and for a normal frictional angle (red) and a reduced frictional angle (blue) of the sediments (after Brun and Fort, 2011). 92 Figure 2.32. Sketch showing the displacement loading mechanism acting on pre-existing salt structures. (a) During shortening, the horizontal displacement load forces salt to rise. Salt, in this case, would flow out, going to cover the sediments. (b) In extension, the salt subsides because of lateral movement of one or both sidewalls (after

94Figure 2 . 34 .Figure 2 . 35 .

 234235 Figure 2.34. Interpreted section from Warsitzka et al., (2018) showing a salt diapir overlying a large-offset normal faults (thick-skinned tectonics). Zechstein salt deposits, south Permian basin. The basement tectonic has a major control on salt deformation. 95 Figure 2.35. Sketch showing examples of salt structures depicted in nature. It is shown the evolution of structures according to their maturity and sources: a) structures growth from line source; b) structures growth from point sources (after[START_REF] Jackson | A glossary of salt tectonics[END_REF]. 96

Figure 2 . 38 .

 238 Figure 2.38. Geometries and characteristics of the two typical halokinetic sequences (A) Hook and (B) Wedge. To note the red line dip, which indicates the angular discordance separating each halokinetic sequence. (C) the vertical stacking of hook type halokinetic sequences will form a tabular type composite sequence (D) the vertical stacking of wedge type halokinetic sequences will form a tapered composite sequence (after Giles and Rowan, 2012). 99 Figure 2.39. Sketch representing the three end-member used to describe the timing of salt deposition with respect the rifting stages. A) Pre-rift salt basins; note the present-day uneven salt distribution along the margin and the absence of a thick pre-salt sedimentary sequence. B) Syn-rift salt basin: uneven initial salt thickness which deposited in structural highs and lows. C) Post-rift salt basins; the salt is highly continuous and is deposited above a thick sag pre-salt sedimentary sequence (from[START_REF] Rowan | Passive-margin salt basins: hyperextension, evaporite deposition, and salt tectonics[END_REF][START_REF] Jackson | Salt tectonics: Principles and practice[END_REF]. 101

Figure 2 . 40 .

 240 Figure 2.40. Sketch illustrating the dominant gliding (a,b) and pure spreading (c) end-members(Brun and Fort,

Figure 2 . 43 .Figure 2 . 45 .Figure 2 . 46 .

 243245246 Figure 2.43. Sketch of the three structural domains resulting from thin-skinned tectonics in passive margins (after Vendeville, 2005). 106 Figure 2.44. Tectono-stratigraphic provinces of the Gulf of Lions basin, showing first-order salt sub-systems alongthe extensional province[START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF]. In each of these salt-structural domains, overburden extension evolved under variable influence of progradational sediments and residual relief in the base salt. 107

Figure 3 . 1 .Figure 3 . 2 .Figure 3 . 3 .Figure 3 . 4 .Figure 3 . 5 .Figure 3 . 6 .Figure 3 . 7 .Figure 3 . 8 .

 3132333435363738 Figure 3.1. Seismic dataset used in this study for salt structures interpretation. In the legend are represented the available surveys and the resolutions: very low (VL), low (L), high (H) and very high (VH). 115 Figure 3.2. Zooms of seismic available dataset. A) Gulf of Lion margin and Provençal deep basin. B) West-Sardinian margin and deep Provençal basin. C) Algerian basin. 116 Figure 3.3. Global dataset used for the construction of isobath and isopach maps. The dataset includes seismic lines used in Leroux, (2012) and Pellen, (2016). The difference with respect the figure 3.1 is the higher coverage in the Valencia basin and in the Gulf of Lion shelf and upper slope. 118 Figure 3.4. Wide-angle refraction profiles available in the Western Mediterranean Sea. We only considered the refraction surveys crossing salt deposits. See references in the text for the surveys description. 119

Figure 3 . 9 .Figure 3 . 11 . 128 Figure 3 . 12 .Figure 3 . 13 133 Figure 3 . 14 .Figure 3 . 15 .Figure 3 . 16 .

 39311128312313133314315316 Figure 3.9. Seismic section showing in time (a) and in depth (b) the presence of salt deposits. It is shown the pullup effect and its correction. A correct input velocity model removes pull-ups in depth. The section is from offshore Brazil (Santos basin), after Herron, (2011). 126 Figure 3.10. Example of GMT grid calculation for the basement reflector with an interpolation of 500 m. It is shown the less dense coverage in the Algerian basin and the points add from works of Arab et al., (2016) and Do Couto, (2014) (located to the East Algerian basin and Alboran domain, respectively). The visualisation allows to define uncertainities and more resolute areas. 127 Figure 3.11. Example of seismic velocities for the Plio-Quaternary sequence used for the map depth conversion. 128 Figure 3.12. Example of refraction correction in the SaltFlu03 profile. The plot represents the result given by MARGE model in percentage of correction to apply to the surface heat flow. The greater values correspond to a higher lateral variation of thermal conductivity. The model calculates it from interpretation of seismic section given by the operator as input. The y-axis represents the percentage of correction to add (if > 0) or to subtract (if < 0). In the x-axis the distance of the profile in km. 132 Figure 3.13 Example of velocity analysis on CMP-supergather via coherence spectra. In the left and centralside, it is shown real data (un-corrected hyperbole and NMO-corrected reflectors). On the right it is shown the picking of maximum of coherence to get a velocity function. We performed the first velocity analysis every 500 CDP. 133 Figure 3.14. Flowchart applied for the horizon-based tomography. To note the iterative process between the quality control and the refining of residual move-out analysis. 135 Figure 3.15. Example of zoom in SaltFlu03 velocity field. The green colour represented the velocity set for the salt deposits (4.2 km/s). These velocities gave the best flattening in the CIGs within the salt. 136 Figure 3.16. Comparison between zoom of SaltFlu03 profile in time (left) and depth (right) domain. 138

Figure 4 . 1 .

 41 Figure 4.1. Schematic cross section representing the present day distribution of the MSC markers following the nomenclature ofLofi et al., (2011a[START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF] Note also the differences between the West and the East Mediterranean

Figure 4 . 4 .Figure 4 . 5 .Figure 4 . 6 .

 444546 Figure 4.4. Salt diapir structure in Gulf of Lion deep basin. Three possible interpretations are represented. Note also the pull-up effect on the base of salt and pre-salt reflectors. 148 Figure 4.5. Isopach map of evaporites and Messinian related sediment in the Western Mediterranean (After Haq et al., 2020). Note the thick deposits in the LPB and the thinner between the EAB and the WAB. Although the map gives a good framework of Messinian deposits distribution, the low resolution does not provide valuable information about the salt structures distribution. 149 Figure 4.6. Thickness maps of salt in the Western Mediterranean. A) Salt thickness map in time (s twt). B) Salt thickness in km, with an average velocity of 4.5 km/s. The interpolation step is 4km and the contour every 0.2 and 0.8 s twt (A) and 0.4 and 1 km (B). Note the greater thickness in the deep Gulf of Lion and in the WAB. In the EAB,

Figure

  Figure 4.7.Basement depth map (in s twt). The salt limit is from[START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF],Driussi et al., (2015a),

Figure 4 . 11 .Figure 4 . 12 .Figure 4 . 13 .Figure 4 . 14 .

 411412413414 Figure 4.11. High resolution seismic sections in the Gulf of Lion lower slope margin. The profile shows the Listric salt domain characterized by basinward-dipping normal faults, salt rollers and rollover structures. Vertical

Figure 4 . 16 .Figure 4 . 17 . 170 Figure 4 . 18 .Figure 4 . 19 .Figure 4 . 20 .Figure 4 . 21 .Figure 4 . 22 .

 416417170418419420421422 Figure 4.16. Gulf of Lion seismic profile showing the wide Anticlinal domain that characterize part of Gulf of Lion deep basin. Above the UU, outer arc extensional faults are often present. 169

Figure 4 . 188 Figure 4 . 29 .

 4188429 Figure 4.27. A,B) Line-drawings crossing with a NW-SE direction the Gulf of Lion margin and the LPB showing the salt morphologies distribution and the crustal segmentation after gravity, magnetic and wide-angle refraction data. Note the coincidence between the salt morphologies domain and the crustal limits. C) Salt morphologies map with the profiles location; D,E) Basement depth (in s twt) representing the crustal segmentation and the salt morphologies limits (white lines) with respect the basement reflectors topography. 187 Figure 4.28. A,B,C) Line-drawings perpendicular to the western Sardinian margin, showing the salt morphologies distribution and a focus on the High salt base domain. d) Salt morphologies map with the profiles location. e,f) Base MUM map (in s twt) showing the regional base of salt deepening with respect the crustal segmentation. 188 Figure 4.29. Line-drawing of seismic reflection profiles in WAB (A) and EAB (B) margins, from south to north.

Figure 4 .

 4 Figure 4.30. Line-drawings of seismic profile in the EAB showing the salt morphologies distribution and the crustal segments. Insert maps (c,d) represent the localisation of the profiles on the salt morphologies and magnetic maps of the Western Mediterranean. The zoom on magnetic anomalies (f) shows the aligned anomalies testifying the oceanic crust accretion in the deep basin. 193 Figure 4.31. A) Line-drawing crossing the EAB, the HA and the WAB, showing the salt morphologies distribution and variation between the deep basins. a,b,c) Salt morphologies map with the profiles localisation (also for fig. 4.32); free-air anomaly map with crustal segmentation and salt morphologies limits. 196

Figure 4 .Figure 4 . 33 .Figure 4 . 34 .Figure 4 . 35 .Figure 4 . 37 . 203 Figure 4 . 38 .Figure 4 . 39 .Figure 4 . 40 .Figure 4 . 41 .Figure 4 . 42 .Figure

 4433434435437203438439440441442 Figure 4.32. (B, C, D) Line-drawings of seismic profile in the WAB (location in fig. 4.31) showing the salt morphologies distribution. To note the thrust faults in the northern Algerian margin, which can displaced the salt base and influence salt deformation. 197

Figure 4 . 46 .Figure 4 . 49 .Figure 4 . 50 .

 446449450 Figure 4.46. Imbalance of salt due to the difference in salt thickness. A ramp in the salt base could provoke an imbalance which in turn cause a translation and the formation of growth strata (modified after Evans and Jackson, 2020). 219 Figure 4.47. A) Plot representing the necessary slope of the base salt to activate the gravity gliding, considering the basin width and the sedimentary cover (km) (from Brun and Fort, 2011. B) Sketch representing the subsidence behaviour of the Gulf of Lion margin (modified from Leroux, 2012). The Hinge line marks the boundary between a tilting and a purely vertical subsidence. Note the increasing slope on the margin given by subsidence. The deep basin subsides purely vertical. C) Seismic depth profile crossing perpendicularly the Gulf of Lion (location in figure 4.49) showing the base of salt slope values in the lower slope and deep basin (modified from[START_REF] Jolivet | Continental breakup and the dynamics of rifting in back-arc basins: The Gulf of Lion margin[END_REF]. 224

Figure 4 . 51 . 230 Figure 4 . 52 .

 451230452 Figure 4.51. Experiment 2 set-up and results in analogical modelling from[START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF]. The basement step height is 5 times the silicone (salt) thickness. Note the effects of a differential compaction (monoclinal flexure) above the step. This type of structure is far from being equivalent to the structures seen in the Gulf of Lion. 230 Figure 4.52. Reconstruction representing the northern Algerian coastline at 5 Ma ago with respect the presentday position (after reconstruction of Pellen et al., submitted). The arrows indicate the NW direction of Africa

Figure 5 .Figure 5 . 3 .Figure 5 . 4 .

 55354 Figure 5.2. A thermal conductivity-depth plot of the measurements performed on-board on the sediment cores. The cores are recovered with the Kullenberg corer. 248 Figure 5.3. Thickness map (s twt) of complete sedimentary sequence (above basement) in Western Mediterranean Sea. Percentage correction of WMF1-2 measurements are represented. Note the higher sedimentation thickness and correction in GoL with respect the SB. 251

Figure 5 .

 5 Figure 5.5. A) HF variation along the SH73-23A profile crossing the SMB (location fig. 5.1). Free-air gravity anomaly was acquired during WMF2 survey. B) HF variation along the SH73-37B profile, crossing from NE to SW the Hannibal Area. HF are indicated in plots above the profiles with black (measured value), and red (after sedimentation correction) points. Thin lines above seafloor indicate the HF measurements location. Crustal

Figure 5 .

 5 Figure 5.6. A) HF variation along the MEDS76-07D profile crossing the southern part of the South Formentera basin with a NE-SW direction (location fig. 5.1). B) HF variation along the Pre-Stack Depth Migration (PSDM)SaltFlu-03 profile, crossing from NW to SE the South Balearic margin. HF are indicated in plots above the profiles with black (measured value), blue (after refraction correction) and red (after sedimentation correction) points.

Figure 5 . 7 .Figure 5 . 8 .

 5758 Figure 5.7. Zoom of salt structures interpreted in figure 5.4. In the inset above the multi-beam bathymetry acquired during WMF1 survey showing the N-S salt wall approximately 12 km long. Laterally, three low HF measurements, probably also affected by salt thermal conductivity small-scale variation. 260 Figure 5.8. Sketch representing the HF distribution with respect the crustal segmentation in Western

Figure 5 .Figure 5 . 10 .Figure

 5510 Figure 5.9. A) Location of multi-beam data (zoom of figure 5.6) showing the new pockmark discovered during WMF2 survey in 2018. B) Sub-bottom profile acquired during WMF2 showing several fluid percolation seismic signatures concomitant with low surface heat flow measurements. C) Temperature profile of WMF2_05-06 measure showing the low thermal gradient (16.7 mKm-1) in the first core meters. 265 Figure 5.10. Zoom of lower slope South Balearic margin showing high HF values probably related to a discharge zone associated to basement rise at the foot of Emile Baudot Escarpment. The fluids (red arrows) from the basement could reach the surface through salt welds and fracture/faults created by shear stress zones. Also note the polygonal faults probably associated with gypsum-anhydrite phase change. 266 Figure 5.11.Table summarising the average HF values in the crustal segments of Liguro-Provençal and Algero-

Figure 5 . 13 .Figure 5 . 14 .

 513514 Figure 5.13. Seismic transects used for the models. The imaginary wells indicated the location of the temperature analysis made in chapter 5.4. A and A' are above the OCT domain while B and B' on oceanic domain for, respectively, the Gulf of Lion and South Balearic margin. 272 Figure 5.14. Above: example of stratigraphic section of the Gulf of Lion showing the seismic stratigraphy units and, from the left to right, the density, the thermal conductivity and the heat production for each stratigraphic unit.

Figure 5 .

 5 Figure 5.15.Table summarizing the lithospheric, sedimentary and opening input parameters for the reference

Figure 5 . 16 .

 516 Figure 5.16. Input crustal setting for the Gulf of Lion. Note the lithosphere thickness change between oceanic and continental domain, as suggested by[START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF]. 275

Figure 5 . 18 .Figure 5 . 19 .Figure 5 . 22 .Figure 5 . 23 .Figure 5

 5185195225235 Figure 5.18. Plot representing the HF timing evolution at 0, 5.9 and 16 Ma for basement and surface HF. 16 Ma is considered to be the end of oceanic crust formation, 5.9 Ma the beginning of the MSC and 0 Ma the presentday situation. The dashed horizontal black lines represent, for each crustal segment, the average measured surface HF in the whole area. 276 Figure 5.19. Above: example of stratigraphic section of the SaltFlu profile in the South Balearic margin showing the seismic stratigraphy units and, from the left to right, the density, the thermal conductivity and the heat production for each stratigraphic unit. Below: initial crustal setting showing the same parameters than above but on the crust level. See references in the text for the lithosphere structure. 278 Figure 5.20. Table summarizing the lithospheric, sedimentary and opening input parameters for the reference model in the SaltFlu03 profile (South Balearic). 279 Figure 5.21. Plot representing the HF timing evolution at 0, 5.9 and 10 Ma for basement and surface HF. 10 ma is considered to be the end of oceanic crust formation, 5.9 the onset of the MSC and 0 Ma the present-day situation. The dashed horizontal black lines represent, for each crustal segment, the average measured surface HF in the whole area. 280 Figure 5.22. Plots showing the temperature variations with depth in the Gulf of Lion for two ages (0 and 5.9 Ma). The red line represents the well on transitional crust while the blue line the well on oceanic crust. Note the base salt temperature difference between the two domains at present-day situation. Imaginary wells location in fig. 5.13. 281 Figure 5.23. Plots showing the temperature variations with depth in the South Balearic margin for two ages (0 and 5.9 Ma). The red line represents the well on transitional crust while the blue line the well on oceanic crust. Note the smaller base salt temperature with respect the Gulf of Lion transect. Imaginary wells location in fig. 5.13. 282 Figure 5.24. Top: Sketch map representing imaginary spreading centre in the LPB, drawn approximately in the middle of the present-day oceanic crust. Below, left: HF-distance from spreading showing the HF non-corrected measurements in the different LPB (for both GoL and WS) crustal domains. A slighlty trend decrease from the oceanic to the continental crusts is depicted. Below, right: zoom on the LPB oceanic crust HF. HF are corrected for the sedimentation. The oceanic crust age is calculated according to formation age (20.4-16 Ma) and the distance from the imaginary spreading centre. Note the lower HF values with respect the plate cooling model from

Figure 6 . 1 .

 61 Figure 6.1. Regional world bathymetric map showing the studied areas and referred figures. For the Western Mediterranean refer to chapter 4. 291 Figure 6.2. A) SANBA wide-angle refraction seismic profiles showing the crust velocity models in the Santos Basin

Figure 6 . 6 .Figure 6

 666 Figure 6.6. Map showing the salt morphologies in the Santos and Campos basins. With black square are represented the isopach maps, from[START_REF] Mohriak | Salt: geology and tectonics of selected Brazilian basins in their global context[END_REF] and[START_REF] Guerra | Role of halokinesis in controlling structural styles and sediment dispersal in the Santos Basin, offshore Brazil[END_REF]. References of structural elements in figure6.2. Below: seismic reflection Sanba01 profile showing the basinward evolution of salt morphologies with a NW-SE direction, crossing all the Santos basin. Blue area represents the Raft salt domain distribution; pink area the Large and Narrow Diapirs domains; yellow area the Canopy-Massive salt domain.307

Figure 6 . 8 .

 68 Figure 6.8. Maps showing salt distribution in the Angolan margin. Salt isopach maps is from Baudino et al., (2018), red is thin and blue is thick salt. The inferred location in dashed black lines. Black lines indicate seismic

Figure 6 .

 6 Figure 6.11. (A) Map showing crustal segmentation and salt morphologies in Gulf of Mexico. On the left it is

  Regional thermal anomalies and/or fluid escapes, associated with the exhumation phase, or the mantle heat segmentation, could therefore play a role in adding a further component on the already known salt tectonics mechanisms. The compilation of crustal segmentation and salt morphologies in different salt-bearing margins, such as the Santos, Angolan, Gulf of Mexico and Morocco-Nova Scotia margins, seems to depict the same coincidence. In view of what observed in Western Mediterranean Sea, the heat segmentation influence in the passive margins should not overlooked and deserves further investigation.

  , D, E) and Figure 7 (F, G, H, I) present nine seismic transects across the different subbasins.. The profiles provide a regional view of salt morphologies following the nomenclature described in fig. 4 and, respectively, highlight: (1) the Liguro-Provençal basin (LPB): the Gulf of Lion margin and the western Sardinia margin (Figs. 6A; 7F,G); (2) the east Algerian Basin (EAB) and the southern part of Liguro-Provençal Basin by crossing the North Balearic Fracture Zone (NBFZ, e.g. Olivet, 1996) (Figs. 6B,C; 7H ); (3) the western Algerian Basin (WAB) and the EAB by crossing the Hannibal Area (Fig. 6C); (4) the eastern and western part of the WAB (Figs. 6D,E; 7I). These long transects show the relationship between salt morphologies and crustal segmentation all along the Western Mediterranean Sea and the regional salt structures variations, here summarized: • The Listric domain is characterized by salt rollers and rollover anticlines and basinwarddipping normal faults involving the displacement of the Upper Unit and Plio-Quaternary deposits (e.g. Figs. 6A; 7I). The faults can be still active or buried (e.g. Gulf of Lion, Dos Reis,

  horizontal pre-salt deposits. It is not present in the western Sardinia, south Balearic and northwestern Algerian margins, where basinward the Listric domain the deep basins are dominated by diapirs structures characterized by discordant overburden (Figs.6C,D,E; 7F,G,H). As shown in Gulf of Lion (Fig.2b), the anticlinal began to grow early, just after their deposition, during the deposition of the Upper Unit still belonging to the Messinian Salinity Crisis time. The evolution is then characterized by period of quiescence during the Pliocene and strong deformation in the Quaternary.

  the southern North Sea,[START_REF] Underhill | Role of intrusion-induced salt mobility in controlling the formation of the enigmatic 'Silverpit Crater', UK Southern North Sea[END_REF] suggested a heating induced by Paleogene dikes as main trigger for the salt movement. Recently, Magee et al. (2020) suggested a salt flow enhanced by the hot magma emplacement in the Santos basin. Moreover, the salt morphologies

  different temperature distribution at the base of salt related to fluids and/or heat segmentation resulting from different crustal natures could play a role, affecting the salt rheology and thus adding a further component on the well-known mechanisms. The same coincidence is observed in some world salt-bearing passive margins. Although the discussion on the salt tectonics main mechanisms in the passive margins is still open, the heat segmentation hypothesis should not be overlooked and deserves further investigation, especially in view of what has been observed in Western Mediterranean Sea.

Figure 1 :

 1 Figure 1: A) Location of the study area marked by the black outlined rectangle. Note the structural threshold separating the Western Mediterranean Sea to the Atlantic Ocean and the Tyrrhenian basin, making it a present-day closed system. B) Dataset and bathymetry of the Western Mediterranean Sea. Bathymetric contours every 200 m. MCS and wide-angle seismic lines are represented. Red circles represent the OBS and the land stations deployed for the wideangle acquisition. References profiles are from work of Leprêtre et al., (2013); Badji, (2014); Arab et al., (2016). Labels: Gulf of Lion (GoL), LPB (Liguro-Provençal basin), WS (west Sardinian margin), MB (Minorca basin), VB (Valencia basin), EAB (east Algerian basin), HA (Hannibal area), WAB (western Algerian basin), EA (east Alboran margin), SMB (south Minorca Block), SB (south Balearic margin), BP (Balearic promontory).

Figure 2 :

 2 Figure 2: (A) Zoom on high-resolution seismic profile of Gulf of Lion lower slope (location Fig. 1) showing salt rollers and rollover structures from the Early Pliocene deposits.

Figure 3 :

 3 Figure 3: From top to bottom: NW-SE Sardinia 01 time-migrated seismic profile,uninterpreted and interpreted (location in Fig.1). At the bottom, Sardinia 01 wide-angle refraction profile showing crust segmentation along Gulf of Lion margin (modified from[START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF]. Dashed black lines represent the lower and upper limit of the crust.

Figure 4 :

 4 Figure 4: Salt morphologies nomenclature and description used in the Western Mediterranean Sea. Seismic zooms are all presented at the same scale to enable comparison. Vertical exaggeration 1:4.

Figure 5 :

 5 Figure 5: Map showing the distribution of salt morphologies and crust segmentation in

Figure 6 :

 6 Figure 6: Regional line drawings of seismic sections from the Gulf of Lion to the West Algerian margin (location in Fig.5). Are represented the main salt morphologies domains in Western Mediterranean Sea. The crustal segmentation is from literature (references are shown below the segments). Position of the Transfer Zone is from[START_REF] Pellen | The Minorca Basin: a buffer zone between the Valencia and Liguro-Provençal Basins (NW Mediterranean Sea)[END_REF]. Note the horizontally pre-salt and base salt reflectors and the salt morphology differences between east (B-C profiles) and west (C-D-E) Algerian sub-basins. Vertical exaggeration 1:6.

Figure 7 :

 7 Figure 7: Additional regional line drawings in Western Sardinian and West Algerian margins (location in Fig. 5), (same colour-code as previous Figures).Vertical exaggeration 1:6.

Figure 8 :

 8 Figure 8: Regional bathymetric map showing location of the world passive margins study areas.

Figure 9 :

 9 Figure 9: (A) Map showing the salt morphologies and crust segmentation in the Santos and Campos basins. On the left it is shown only the crustal segmentation while on the right also the salt morphologies domains. Blue area represents the Raft salt domain distribution; pink area the Large and Narrow Diapirs domains; yellow area the Canopy-Massive salt domain. Wideangle profile location and crust segmentation are from[START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Volcanic structures are from[START_REF] Mohriak | Salt tectonics, volcanic centers, fracture zones and their relationship with the origin and evolution of the South Atlantic Ocean: geophysical evidence in the Brazilian and West African margins[END_REF]. The hinge line and the Capricornio and Cruzeiro do Sul Lineaments are from[START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF]. Black lines represent seismic profile interpreted (references in the text). (B) From top to bottom, Sanba01 time-migrated reflection seismic line uninterpreted and interpreted (location in Fig.9a). The interpreted salt morphologies are represented, showing

Figure 10 :

 10 Figure 10: (A) Map showing the salt morphologies and crust segmentation in Angolan margin. On the left it is shown only the crustal segmentation while on the right we have superposed the salt morphologies. Blue area represents the Raft salt domain distribution; pink area the Large Diapir domain; yellow area the Canopy-Massive salt domain. Wide-angle profile location and crust segmentation are from Contrucci et al. (2004) and[START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF].

Figure 11 :

 11 Figure 11: (A) Map showing crustal segmentation and salt morphologies in Gulf of Mexico. On the left it is shown only the crustal segmentation while on the right the superposed salt morphologies. Outlined in red the salt structures from[START_REF] Diegel | Cenozoic structural evolution and tectono-stratigraphic framework of the northern Gulf Coast continental margin[END_REF]. Salt

Figure 12 :

 12 Figure 12: Map showing salt morphologies and crustal segmentation in Nova Scotia and Morocco conjugated margins. Crust segmentation is taken from SMART, SISMAR and MIRROR refraction studies (references in the text). Salt structures are from Shimeld, (2004);

Figure 1 ANNEXE

 1 Figure 1

Figure 1 .

 1 Figure 1. Extension map of the MSC evaporites in the Western Mediterranean Sea (modified afterRabineau et al., 2015 and[START_REF] Pellen | The Messinian Ebro River incision[END_REF]. LB: Ligurian basin; GoL: Gulf of Lion margin; PB: Provençal basin; WS: western Sardinian margin; EAB: eastern Algerian basin; WAB: western Algerian basin; AB: Alboran basin; SB: south Balearic margin; BP: Balearic Promontory; VB: Valencia basin; MB: Menorca basin. Black line indicates the approximate position of the profile showed in figure 2.

Figure 2 .

 2 Figure 2. A) Synthesis of offshore stratigraphic markers on a profile crossing the Gulf of Lion margin (location figure 1). PQ: Plio-Quaternary sequence; MSC: Messinian Salinity Crisis. LU: Lower Unit; MU: Mobile Unit; UU: Upper Unit;MES: Margin Erosion Surface; TES/TS: Top (Erosion) Surface; BES/BS: Bottom (Erosion) Surface; CU: Complex Unit. MLM: Messinian Lower Megasequence; MUM: Messinian Upper Megasequence; LU0: erosion on the shelf and detrital deposits in the basin. The base of the PQ sequence corresponds to the MES on the shelf, to the top of MSC detrital units on the slope and to the top of UU in the basin (modified after Leroux et al., 2019). B) Seismic zoom representing seismic units facies and reflectors provided in this work.

Figure 3 .

 3 Figure 3. Acoustic basement isobath map. The NE Algerian margin interpretation comes from Arab, (2016).

Figure 4 .

 4 Figure 4. Base salt (Base MU) isobath map. The NE Algerian margin interpretation comes from Arab, (2016). Upslope salt (MU) limit is fromBellucci et al., (submitted).

Figure 5 .

 5 Figure 5. Top salt (Top MU) isobath map. The NE Algerian margin interpretation comes from[START_REF] Arab | Analyse des systèmes pétroliers de l'offshore algérien oriental: Quantification, modélisation stratigraphique et thermique[END_REF]. Upslope salt (MU) limit is fromBellucci et al., (submitted).

Figure 6 .

 6 Figure 6. Base Plio-Quaternary isobath map. The NE Algerian margin interpretation comes from Arab, (2016).

Figure 7 .

 7 Figure 7. Seafloor isobath map.

Figure 2 . 1 .

 21 Figure 2.1. Plot representing the surface HF variations for 4 tests considered at 0 and 5.9 Ma. Refer to table 2.5 for input parameters.

Figure 2 . 2 .

 22 Figure 2.2. Plot representing the surface HF variations for 4 tests considered at 0 Ma. The zoom is taken in the OCT domain. Refer to table 2.6 for the input parameters.

Figure 2 . 3 .

 23 Figure 2.3. The lines indicate the temperature variation with depth while the colour the overpressure in the sedimentary column (see colour bar). The stratigraphy as set in the input conditions is represented. On the left the 0 Ma situation and on the right the 5 Ma situation are represented. Note the present-day overpressure above the salt layer, as also described in Dave et al., (2021).

Figure 2 . 4 .

 24 Figure 2.4. Percentage of shortening (raccoursissement) versus time in seconds (temps).The difference between the high temperature trend curve and the low temperature curve is clearly visible (M2,Ziane R.)

  conceived and thought by Véronique Gardien and Philippe Grandjean of the Laboratoire de Géologie de Lyon Terre, Planète, Environnement (Lyon). The instrumentation is characterized by an oven (temperature range: 0-150 °C) and a sensor that measures the variation of length (sensitivity of ±0.002 mm) (Fig.2.5). The sample is placed in the oven and a weight (it varies from 1.5 Kg to 2.4 Kg based on our choice) is loaded to simulate a constant pressure (Fig.2.5).

  Figure 2.7 shows the experiments with the first phase of heating and the second of cooling. The heating phase simply starts with the oven ignition. The oven reaches the established temperature after a few minutes and maintains it with extreme precision. The cooling phase starts when the oven is turned off and opened, to quickly reach the room temperature.

Figure 2 . 6 .

 26 Figure 2.6. Plot of halite tests with the description of each experiment.

Figure 2 . 7 .

 27 Figure 2.7. Particular of the experiment's trends.

Titre:

  Relation entre la segmentation de la croûte terrestre, la nature, la thermicité et la tectonique du sel dans la mer Méditerranée occidentale. Mots clés : Méditerranée Occidentale, tectonique salifère, segmentation crustale, marge passive, flux de chaleur. Résumé : Certains des systèmes pétroliers les plus prolifiques du monde sont situés dans des marges passives salifères. En raison de ses caractéristiques rhéologiques, le sel affecte largement les bassins sédimentaires. En mer Méditerranée occidentale, le sel s'est déposé pendant la Crise de Salinité Messinienne (CSM, 5,96-5.32 Ma), principalement dans les sous-bassins profonds et la pente inférieure. A l'aide d'un vaste ensemble de données sismiques, une description régionale et une catégorisation des structures salifères sont présentées. Les structures changent de morphologie en fonction des différentes natures crustales. La compilation de la segmentation crustale et des morphologies du sel dans différentes marges salifères telles que les marges de Santos (Brésil), d'Angola, du Golfe du Mexique, du Maroc et de Nouvelle-Ecosse, semble confirmer cette correspondance. En Méditerranée occidentale, l'épaisseur initiale constante du sel, la base du sel horizontale dans le bassin profond, l'épaisseur pré-Messinienne homogène de plusieurs kilomètres, la déformation précoce au-dessus de la croûte transitionnelle et océanique et une faible couverture sédimentaire sur la pente (sauf pour le Golfe du Lion) semblent remettre en question les mécanismes classiques de la tectonique salifère, qui expliquent difficilement la correspondance segmentation crustalemorphologies salifères. L'hypothèse d'une influence thermique sur la déformation est donc prise en considération. Le régime thermique a été étudié en analysant et interprétant les données de flux de chaleur (HF) de surface récemment acquises lors des campagnes WestMedFlux1-2 (2016-2018) avec pour complément un modèle thermo-cinématique. Parmi les HF de petite longueur d'onde influencés par des phénomènes locaux, une segmentation thermique régionale est observée. Le rôle de la température sur la déformation du sel reste la seule hypothèse plausible pour expliquer la correspondance observée et mérite d'être approfondie. Title : Relationship between crustal segmentation, nature, thermicity and salt tectonics in the Western Mediterranean Sea. Keywords : Western Mediterranean Sea, salt tectonics, crustal segmentation, passive margin, heat flow.

  . The high-resolution lines (H) display Messinian sequences with a very good resolution, allowing trustful interpretation of the base of the Mobile Unit (e.g. Lofi

	et al., 2011a) (when the salt structures are not too developed) and of the top of the Upper Unit.
	Nonetheless, the basement is interpretable only on the slope, where it is shallow. The industrial
	MEDS76 lines are a high-resolution example, acquired by the Western Geophysical in the
	Balearic area. Finally, the very high resolution lines (VH) well image the Plio-Quaternary
	sequence, the top of salt but, more difficultly, the base of salt. In the Liguro-Provençal basin,
	the PROGRES survey (DOI: 10.17600/3020080) is acquired in 2003 with the objectives to

  Table representing the main reflectors interpreted by

  Le sel de la Méditerranée occidentale a été déposé pendant la Crise de Salinité Messinienne, vers 5,6 Ma. Cela en fait le géant salin le plus jeune de la planète. Contrairement aux autres marges passives salifères, en Méditerranée occidentale certaines caractéristiques en font une zone d'étude privilégiée pour l'analyse de la tectonique salifère et de sa relation avec la croûte profonde:  Le dépôt de sel a lieu vers ~5,6 Ma dans le bassin profond, montrant un pinch-out sur les dépôts marins pré-sel de la pente dans un contexte d'abaissement régional du niveau de la mer (le débat est toujours en cours) qui a créé une forte érosion dans les chenaux à la fois sur terre et au large. Compte tenu de la subsidence purement verticale dans le Une corrélation existe entre les morphologies du sel, la segmentation structurelle et la nature de chaque sous-domaine. Dans le bassin Liguro-Provençal, le domaine Listric est situé sur les bords des marges, où les en literature est interprétée une croûte transitoire et/ou amincie, ainsi que tout le long de la marge nord algérienne et à la transition entre le WAB et le bassin d'Alboran. Dans la marge occidentale de la Sardaigne, les limites du domaine High Salt Base correspondent bien à la croûte transitionelle. Dans le bassin profond du Liguro-Provençal, la morphologie du sel connectée et irrégulière correspond à une croûte proto-océanique et/ou océanique selon l'interprétation des données de réfraction. Au contraire, un domaine Connected, Regular est interprété dans l'EAB, qui semble être constitué d'une croûte océanique mince comme le montrent les données de réfraction et les anomalies magmatiques visiblement alignées. Le WAB, dont la structure crustale fait encore l'objet de débats, est caractérisé par des structures salifères généralement plus déformées, avec des différences dans les secteurs est et nord-ouest : dans le sud-ouest du bloc de Minorque sud, les structures sont connectées et la base du sel est moins profonde, tandis que le bassin profond est caractérisé par l'approfondissement du sel et des morphologies plus larges. La transition entre le domaine continental et le domaine océanique dans la limite Alboran-WAB correspond à un changement de morphologie du sel, entre un domaine Anticlinal et un domaine Large/Connected. La transition brusque et rapide entre une croûte continentale amincie à une croûte océanique mince (ou atypique) le long de la marge nord algérienne est associée à une transition soudaine des morphologies du sel.  Étant donné les différents mécanismes impliqués dans le modelage des structures salifères, une relation directe entre la nature de la croûte et les morphologies spécifiques n'a pas été trouvée. Cependant, il est clair qu'un changement de la nature crustale (segmentation) coïncide avec un changement de géométrie des structures. La conséquence naturelle de ces considérations était d'essayer de comprendre pourquoi cette correspondance se produisait. Nous avons donc analysé en détail les aspects impliqués dans la déformation du sel tels que décrits par les modèles précédents. Pour ce faire, nous avons analysé les éléments et les mécanismes impliqués et défini leur rôle et leur dominance dans le système. La tectonique salifère thin-skinned n'est bien développée que dans le bassin profond proche de la pente inférieure (Listric Salt domain). La largeur de ce domaine est indirectement proportionnelle à l'inclinaison de la marge. Le principal mécanisme impliqué dans ce domaine serait le glissement gravitaire, entraîné par la pente de la base du sel.  La marge nord-algérienne subit une tectonique salifère thick-skinned due à la compression tectonique induite par la convergence nord-africaine, comme déjà montré par certains auteurs. Le bassin nord-algérien présente localement une base du sel inclinée vers le continent qui exclut un glissement gravitaire régional.  Le socle et l'influence tectonique ne jouent qu'un rôle mineur (voire complètement absent) dans la déformation du sel en LPB. Au contraire, la compression qui affecte et a affecté le dépôt du sel dans la marge nord algérienne peut avoir une influence sur les morphologies observées, en particulier dans la partie la plus proche de la marge.  Le sel a commencé à se déformer dans le bassin profond pendant le dépôt de l'unité supérieure du Messinien. Les failles listriques situées dans la partie inférieure de la pente se sont activées qu'à partir du Pliocène inférieur jusqu'à aujourd'hui. Cela signifie que le mécanisme de glissement gravitaire n'est pas la cause du déclenchement de la déformation initiale du sel dans le bassin profond, sauf localement. Le glissement du sel est donc une conséquence de l'espace créé par le mouvement initial du sel dans le bassin profond et alimente les structures, en particulier près de la marge. Son rôle est amplifié au fil du temps par la subsidence thermique. Anticlinal proximal. Dans le domaine profond, caractérisé par une base horizontale du sel, on considère son effet secondaire. L'influence de la tectonique est inexistante. Néanmoins, le taux de déformation au-dessus de la croûte océanique est beaucoup plus élevé qu'au-dessus de la croûte de transition. Les modèles classiques de la tectonique salifère (glissement gravitaire, étalement et influence de la tectonique) expliquent difficilement la correspondance entre la segmentation crustale et les morphologies observées. La seule hypothèse qui reste à évaluer est une influence thermique des différentes natures crustales qui aurait pu affecter la déformation des sels. Golfe du Lion et dans la marge sud des Baléares. Dans le cadre de cette thèse, les mesures de flux de chaleur de la campagne WMF2 sont présentées pour la première fois et mises en relation avec les mesures antérieures. Les principaux résultats montrent à la fois des variations à courte longueur d'onde -de l'ordre de 10-20 km -et des variations à l'échelle régionale. Les variations locales les plus significatives ont été observées dans la marge sud des Baléares. Ici, la fine couverture sédimentaire, les hauts du socle et les anomalies du flux de chaleur fortement positives et négatives indiquent une importante circulation de fluides. Dans sections modélisées et la structure crustale actuelle, ce qui a donc permis de définir une gamme de température plausible dans le dépôt du sel. Néanmoins, le modèle est basé sur des hypothèses non fondées concernant le régime thermique de la phase d'ouverture de l'océan. En outre, le modèle ne peut pas prédire des phénomènes tels que l'exhumation et la remontée de fluides du socle dans le domaine transitionnel, qui sont encore mal compris mais pourraient pourtant jouer un rôle clé dans la déformation. L'analyse de la corrélation entre les morphologies du sel et les domaines crustaux dans les principales marges passives du monde confirme la correspondance observée en Méditerranée occidentale. Les principales différences se situent au niveau des marges passives caracterisés par un bassin sag (marges du Brésil, de l'Afrique de l'Ouest et du Golfe du Mexique) par rapport aux marges plus abruptes où le sel a été déposé irrégulièrement pendant l'ouverture continentale (marges du Maroc et Nouvelle-Écosse). Bien que les causes de la tectonique salifère soient ici multiples et n'aient été analysées de la même manière qu'en Méditerranée occidentale, nous avons montré que la correspondance entre la segmentation crustale et les morphologies du sel ne doit pas être négligée. En conclusion, cette étude a pour la première fois décrit régionalement les structures et les causes de la tectonique salifère en Méditerranée occidentale. La correspondance avec la segmentation crustale semble être expliquée uniquement par une influence indirecte, comme la température, et non par les modèles classiques existants. Plus de questions que de réponses émergent de cette thèse. La plus importante concerne le rôle du régime thermique dans l'évolution des marges passives et donc son influence sur la tectonique salifère. La perspective directe de ce travail est d'étudier plus en détail le régime thermique régional afin d'identifier les éventuelles différences entre les différents segments crustaux. Une première approche pourrait être l'acquisition de plus de données de flux de chaleur dans ces régions.Un autre domaine de recherche qui doit être exploré directement est la relation entre la tectonique salifère, la température et les fluides. Bien que certaines études rhéologiques proposent une relation directe, une application géologique est une approche qui n'a jamais été abordée. Quel est l'impact de la diminution de la viscosité du sel en fonction de la température sur les structures ? Le taux de déformation augmente-t-il avec l'élévation de la température ?Ce ne sont là que quelques-unes des questions soulevées après cette étude. Là encore, deux approches complémentaires seraient nécessaires : La modélisation analogique : les processus de la tectonique salifère sont souvent modélisés à l'aide de modèles analogiques où le sel est remplacé par ls silicone et les sédiments par des sables plus ou moins fins. Pour comprendre la relation entre la déformation et la température dans un système dynamique, il faudrait connaître les propriétés rhéologiques du silicone et sa réaction face à l'augmentation de la température.Modélisation numérique: plusieurs études de modélisation numérique des processus de la tectonique salifère sont disponibles dans la littérature (par exemple,[START_REF] Ings | Numerical modeling of salt tectonics on passive continental margins: Preliminary assessment of the effects of sediment loading, buoyancy, margin tilt, and isostasy[END_REF][START_REF] Pichel | The impact of pre-salt rift topography on salt tectonics: A discrete-element modeling approach[END_REF]. Dans la phase finale de cette thèse, un principe de collaboration avec l'Université de Mainz a vu le jour (Tobias Baumann), dans lequel l'objectif sera de tester avec un modèle numérique réalisé dans le Golfe du Lion (profil SARDINIA) l'influence de la variation de température dans le système. Le modèle tient compte de la rhéologie du sel et de ses propriétés thermiques. Bien que pour l'instant ce travail ne soit qu'un projet, il pourrait donner un aperçu du rôle de la température, qui est encore négligé dans la littérature.

	bassin profond, mise en évidence par des études antérieures, et d'une horizontalité globale des dépôts du Plio-Quaternaire, nous pouvons suggérer que le sel s'est déposé uniformément dans l'espace et avec une épaisseur constante. Au bord du bassin, dans les pentes, où la subsidence se présente sous la forme d'un basculement, le sel peut présenter des épaisseurs plus faibles.  Entre le socle et le sel, une épaisse couverture de sédiments principalement miocènes est répandue dans les escarpements et les bassins profonds. Cette couverture de sédiments marins, d'environ 1 km d'épaisseur, remplit les aspérités du socle et n'est pas faillée.  Les mouvements horizontaux dus au mouvement des plaques sont presque inexistants depuis le Messinien. La seule zone active depuis au moins le Tortonien, est la marge nord algérienne, caractérisée par une inversion tectonique en compression. Les autres bassins ne montrent pas de mouvements tectoniques depuis 16 Ma (8 Ma pour la partie occidentale du bassin algérien). En gardant à l'esprit les spécificités de la Méditerranée occidentale, le premier objectif était de décrire et de cartographier les structures salifères en utilisant des critères exclusivement géométriques. De cette première partie du travail, deux ordres de segmentation des morphologies ont été observés: 1) Le premier est perpendiculaire aux marges, de la pente inférieure au bassin profond et concerne principalement l'amplitude et la distribution des domaines Listric et Anticlinal Salt ainsi que les limites des domaines Diapirs. Lorsque les marges sont plus abruptes, ces domaines sont plus étroits alors que lorsque la marge présente une pente faible, les domaines sont plus étendus. 2) Le deuxième ordre de segmentation concerne les différences observées au sein des sous-bassins profonds de la Méditerranée occidentale qui présentent une morphologie distincte pour chacun d'entre eux. De fortes différences sont décelées entre les bassins Liguro-Provençal, de l'ouest et de l'est de l'Algérie. Dans le bassin algérien, le domaine oriental est caractérisé par une déformation du sel moins intense (moins perçant) par rapport au domaine occidental. Par la suite, les différents domaines salifères ont été mis en relation avec la segmentation crustale définie sur la base des interprétations de la sismique réfraction grand-angle et des anomalies gravimétriques et magnétiques. L'objectif principal était d'étudier la relation entre la distribution des morphologies de sel et la segmentation crustale. Certains résultats ont été obtenus:  Une analyse détaillée de la chronologie de la déformation a été réalisée principalement dans le Golfe du Lion, où le large jeu de données disponible, une calibration chronologique des réflecteurs et les connaissances sédimentaires antérieures ont permis de discuter plus en détail des principaux mécanismes dans cette zone. Concernant les principales causes et les mécanismes impliqués dans la tectonique salifères, plusieurs points sont décrits :  Les dépôts du Plio-Quaternaire sont régionalement peu épais dans la partie inférieure de la pente et épais dans le bassin profond. Les dépocentres suivent la segmentation de la marge. Cela exclut donc un étalement régional de la sédimentation comme par exemple ce qui a été décrit par Vendeville, (2005) ou observé dans le bassin de Santos (par exemple Guerra et Underhill, 2012), à l'exclusion du Golfe du Lion. Les différences de sédimentation entre le LPB et les bassins algériens sont confirmées, alors qu'aucune différence entre le WAB et l'EAB n'est observée. Toute la marge nord-algérienne est caractérisée par une épaisseur sédimentaire considérable, ce qui confirme la presence d'un bassin d'avant-pays causé par la tectonique de compression africaine active.   Dans le Golfe du Lion, nous avons proposé une évolution de la tectonique salifère en trois phases principales, depuis son dépôt (~5.6 Ma) jusqu'à aujourd'hui : Phase 1) une déformation précoce s'est produite uniquement dans le bassin profond; Phase 2) l'activation de failles listriques inclinées vers le bassin, quiescence dans le domaine de croûte transitionnelle et forte déformation par diapirisme passif dans le domaine océanique ; Phase 3) forte déformation à la fois au-dessus de la croûte transitionnelle et de la croûte océanique.  Dans le Golfe du Lion, les causes majeures sont dues à l'évolution de l'apport du Rhône. Le glissement agit en bordure de marge, là où la pente peut être supérieure à un degré techniques consistant en l'observation des mesures actuelles du flux thermique de surface -la seule mesure directe de la thermicité de la sub-surface -et la modélisation thermo-cinématique. Grâce à l'acquisition de nouvelles mesures de flux de chaleur lors des campagnes WestMedFlux1-2 (WMF1-2) en 2016 et 2018, la densité des mesures a été augmentée, notamment dans le le Golfe du Lion les diapirs du sel agissent comme une pompe à chaleur, augmentant significativement le flux mesuré à la surface. Nos observations confirment que la marge sud des Baléares est une zone affectée par une importante circulation de fluide, probablement aussi liée à des processus volcaniques récents. Le domaine de la croûte transitionnelle et océanique est souvent caractérisé par une épaisse couverture de sédiments de plusieurs kilomètres, y compris une épaisse couverture de sel. Les sédiments ont ainsi scellé les remontées de fluides à la surface, qui sont uniquement visibles localement. La production de chaleur qui est supposée se produire pendant la phase Divers essais de modélisation (numériques et analogiques) pourraient alors être réalisés. Un exemple serait d'effectuer deux tests du même système salifère régional, comme le classique extension-translation-contraction à des températures différentes. Un autre test pourrait consister à faire varier la température au niveau du socle en fonction du domaine crustal auquel il et dans le domaine Pour tester l'hypothèse de l'influence thermique, nous avons utilisé deux principales d'exhumation (manteau et/ou croûte inférieure) ne semble pas affecter la surface, où de grandes différences de flux de chaleur entre les domaines transitionnels et océaniques n'ont pas été observées. La modélisation par des modèles thermo-cinématiques a permis de trouver un bon (par exemple les fluides, le sel...) et que seule une grande densité de points peut nous donner des informations fiables sur l'état thermique profond. Une deuxième approche pourrait être la modélisation numérique. Des étapes importantes ont été franchies depuis les premiers modèles de McKenzie sur l'étirement de la lithosphère. Néanmoins, la diatribe est plus ouverte que appartient : continental, transitionnel, proto-océanique et/ou océanique. De cette manière, il serait possible de comprendre si la température joue réellement un rôle dans la déformation ou si elle est un paramètre secondaire par rapport aux modèles classiques. Outre la modélisation, d'autres perspectives d'avenir pourraient permettre d'étendre l'observation de la relation entre la segmentation crustale et les morphologies salifère à d'autres ajustement entre les Nous avons vu que les mesures de flux sont facilement influencées par les processus de surface jamais, notamment sur le domaine transitionnel où différentes hypothèses coexistent. marges mondiales, comme la Mer Rouge, une marge jeune et chaude

  . Yellow colour represents sediment thickness. To note the high heat flow in the OCT domain, similar to

	those measured in the oceanic domain.	37
	Figure 1.14. Map of Mediterranean area outlining the major structural features. The map plots the different
	formation ages of Mediterranean sub-basins, highlighting fundamental differences between the East
	Mediterranean (Mesozoic age) and the Western Mediterranean (Cenozoic age) (modified from

  . The plot shows in which temperature/pressure fields act the dislocation creep (glide and climb) and the solution precipitation creep.

	81
	Figure 2.21. Optical micrograph showing truncation (t) and overgrowth (o) structures typical of pressure solution
	in a wet synthetic salt aggregate. After

  base (in s twt) is represented. Note contoured in dashed white lines the High salt base domain in the WS and SB margins. Map Seismic profile in WS margin (located in fig. 4.22) representing the High salt domain and the Irregular salt domain, basinward. Note also the syn-Messinian suggested volcanic structure. Reflection and wide-angle coincident profiles crossing the Gulf of Lion (A) and the Western Sardinian margin (B). The wide-angle profiles and crustal segmentation are taken from

	contours every 0.2 and 0.5 s twt.	178
	Figure 4.23. 179
	Figure 4.24. Summary of the salt morphologies interpreted in this work with the main geometrical features and a
	zoom framework of seismic facies (at the same scale).	180
	Figure 4.25. Left: free-air gravity anomaly map representing the segmentation deriving from gravity, magnetic
	and wide-angle refraction interpretations (reference in the text). Dashed lines represent interpretation only
	constrain by gravity and magnetic data. I: East Algerian Basin (EAB); II: Hannibal Area (HA); III: Central
	Algerian segment and IV: Western Algerian Segment (WAB; V and VI: Thinned continental crust/intermediate
	domain on both sides of the Algerian Basin; 7: Mesozoic Valencia Basin (VB) and 8: Neogene Menorca Basin
	(MB); 9-10-11: Provençal Basin with Necking zone (11), Transitional crust (10) and (9) proto-oceanic crust.
	NBFZ: North Balearic Fracture Zone. CFZ: Central Fracture zone. Right map: crustal segmentation superposed
	on salt morphologies interpreted in the previous chapter.GoL: Gulf of Lion margin; LPB: Liguro-Provençal basin;
	WS: Western Sardinian margin; EAB: Eastern Algerian basin; HA: Hannibal Area; WAB: Western Algerian
	basin; EA: Eastern Alboran margin; SB: South Balearic margin; BP: Balearic Promontory; VB: Valencia basin;
	MB: Menorca basin; EBE: Emile Baudot Escarpment; ME: Mazarron Escarpment.	183
	Figure 4.26.

Table representing

 representing Present-day salt thickness map on the left with a zoom on salt diapirs deforming the seafloor (bathymetry data). The profiles are shown in figures 4.39 and 4.40. On the right, salt thickness interpretation showing salt structures and minibasins directions (plots bottom right). Note a salt depocenter in the W sector of the Gulf of Lion, explained as the result of subsalt relief by Dos[START_REF] Reis | Radial gravitacional gliding indicated by subsalt relief and salt-related structures: the example of the gulf of Lions, western Mediterranean[END_REF]. Sketch representing the salt tectonics phases in the Gulf of Lion. The desiccation hypothesis comes from

	the main reflectors interpreted by Leroux, (2012) and Bache, (2008) for the respective Plio-Quaternary and Messinian sequences. Are defined the colour, name, supposed/known ages, main features and salt tectonics phases description for each reflectors. 214 references are shown in the legend. 216 Figure 4.44. Stratigraphic elements Figure 4.45.

  . The yellow colour in the profile indicates the sedimentary thickness above basement. The plot represents the surface measured HF with respect the sedimentation thickness above basement for each profile. The dashed ellipse represents the HF variations in areas of thin sedimentary thickness, so more likely to be affected by fluid circulation. The dashed horizontal black lines represent, for each crustal segment, the average measured surface HF with the corresponding value noted. Note the very low HF values on the South Balearic associated with a low sedimentary thickness. The map in the centre represents all the available surface HF in the Western Mediterranean Sea superposed to the crustal segmentation taken from

  LIST OF FIGURES398from the wide angle interpretation in the Santos Basin. Left: on the magnetic map. Center: On the gravity map.

Reflection and refraction seismic data used in this study are referenced in chapter 3. B) Maps showing the crustal segmentation

  LIST OF FIGURES 400 lines are iso-velocity curves and dashed lines divide upper and lower layers in crust, where interpreted in literature. The profiles are at the same scale, vertical exaggeration 1:7. In the western Algerian margin the crustal nature in the deep basin is uncertain. Note the coincidence between the crustal segmentation and the salt morphologies domain variations, particularly clear in Angolan, Santos and Mediterranean basins. The WACMA The main crustal and geophysical features of each margins are related to the salt morphologies interpreted in this work. As in figure6.14, the margins are divided into pre/syn and post-oceanic spreading salt depositions and based on the "sag" basin presence.

	and ECMA in the Nova Scotia-Morocco margins define the initial salt deposition distal limit: here, the basinward
	salt is interpreted as allochthonous.	320
	Figure 6.15. Salt deposits features and morpho-structure margins relationship. Modified after Rowan, (2014).
		321
	Figure 6.16.

318 Figure 6.14. Classification and comparison of salt-bearing margins studied in this work, including the Western Mediterranean margins. The margins are divided into pre/syn and post-oceanic spreading salt depositions and based on the "sag" basin presence. The colours describe the nature of the crust, after authors interpretation; solid

  2008). The 3 domains are so-defined based to their main geometric characteristics and associated structures, as done in the Western Mediterranean Sea, in order to give a global and homogenous view, and are named: -Raft domain, -Diapirs domain and -Massive-Canopy domain. The Raft domain is so-called for the typical extensional thin-skinned structures as salt rollers, turtlebacks and base salt-rooted normal faults. The Diapirs domain includes salt stocks and walls characterized by discordant overburden, autochthonous connected or disconnected structures. To note that in Gulf of Mexico the Diapirs domain can exhibits coalescence sheets

[START_REF] Kukla | South Atlantic salt basins-witnesses of complex passive margin evolution[END_REF]

; Mohriak et ANNEXE-1. SCIENTIFIC PRODUCTION 422 al.,

  Table 2.1. Table of heat measurements acquired during the WMF2 survey.The columns, from left to right, are: the site name where HF are POGO-type measurements while KF means core measurements, longitude, latitude, depth is the bathymetry from echosounding (meters), PenD is the penetration of the instrument in meters (POGO type or core), Wat.T is the water temperature (°C), Th is the number of thermistors, Grad is the temperature gradient (°C), SigG is the standard error for gradient, K is the thermal conductivity (Wm-K -1 ), SigK is the standard error for the thermal conductivity, HF the heat flow (mW/m 2 ) and SigHF the standard error for HF. Table 2.2. Table of WMF1 heat flow measurements corrected for sedimentation. HF are POGO-type measurements while KF means core measurements. The columns, from left to right are: measurement name, surface HF measures value (mW/m 2 ), total sedimentation thickness above basement (meters), Cor is the percentage correction, HF+Cor is HF corrected for sedimentation (mW/m 2 ) and HF_sedcor the HF added to surface measure (mW/m 2 ). Table 2.3. Table of WMF2 and MedSalt heat flow measurements corrected for sedimentation. HF are POGO-type measurements while KF means core measurements The columns, from left to right are: measurement name, surface HF measures value (mW/m 2 ), total sedimentation thickness above basement (meters), Cor is the percentage correction, HF+Cor is HF corrected for sedimentation (mW/m 2 ) and HF_sedcor the HF added to surface measure (mW/m 2 ).

	ANNEXE-2. HEAT FLOW MEASUREMENTS, MODELS AND RHEOLOGY EXPERIMENT ANNEXE-2. HEAT FLOW MEASUREMENTS, MODELS AND RHEOLOGY EXPERIMENT ANNEXE-2. HEAT FLOW MEASUREMENTS, MODELS AND RHEOLOGY EXPERIMENT ANNEXE-2. HEAT FLOW MEASUREMENTS, MODELS AND RHEOLOGY EXPERIMENT ANNEXE-2. HEAT FLOW MEASUREMENTS, MODELS AND RHEOLOGY EXPERIMENT ANNEXE-2. HEAT FLOW MEASUREMENTS, MODELS AND RHEOLOGY EXPERIMENT
	WMF2_HF-04-06 WMF2_KF-09 WMF1-HF-07-05 WMF1-HF-09-10 WMF-KF-24 WMF2-HF-05-08		3,9833 1,9548 83,9 79,2 52,9 4,4	38,0817 2787 5,0 38,2186 1545 5,6 753,35 3811,55 7213,3 483,85 7% 5,40% 3,78 12,90 0,00 2,63 13,15 0,00 88,4306 12,10% 88,7832 18,70% 62,7923 4,708	4,53 9,58 9,89	4 5 0,3	83,6 7,4 28,8 1,0	4 32	0,97 0,16 81,1 1,08 0,09 30,9	15,0 2,5
	WMF2_HF-04-07 WMF2_KF-10 WMF1-HF-07-06 WMF1-HF-09-11 WMF-KF-25 WMF2-HF-05-09		3,9067 5,8851 100,9 43,7 153,4 0,8	38,0583 2794 4,7 39,2802 2857 1,1 535,75 3432 8149,55 814,65 6% 3,90% 19,96 12,90 0,00 61,81 13,34 0,00 104,8351 11% 48,507 21,20% 185,9208 0,848	4 3 32,52 3,94 4,81 0,0	85,2 7,8 135,3 36,5	4 0	1,11 0,17 94,4 1,08 0,09 145,848 11,6 16,8
	WMF2_HF-04-08 WMF2_KF-11 WMF1-HF-07-07 WMF1-HF-09-12 WMF-KF-26 WMF2-HF-05-10		3,7283 6,1601 87 61,1 129,6 6,1	38,0017 2803 5,0 39,6195 2848 6,6 629,7 2490,3 5958,075 1009,55 6% 4,10% 6,85 12,90 0,01 4,06 13,34 0,02 90,567 9,40% 66,8434 15,90% 150,2064 6,466	4 5 20,61 3,57 5,74 0,4	97,2 2,0 71,1 3,0	4 30	1,03 0,08 100,6 0,98 0,17 69,7	7,6 12,3
	WMF2_HF-04-09 WMF1-HF-07-08 WMF1-HF-09-13 WMF-KF-27 WMF2-HF-05-11		3,6617 89,4 43,1 50 47,5	37,9800 2803 5,0 1205,4 3687,2 6199,35 836,45 4,80% 7,39 12,90 0,02 6,40% 95,1216 10,90% 47,7979 16,60% 58,3 49,78	5,72 4,70 8,30	4 2,3	91,8 4,0	4	1,24 0,19 113,3	17,8
	WMF2_HF-04-10 Measure WMF1-HF-07-09 WMF1-HF-09-14 WMF-KF-28 WMF2-HF-05-12		3,6083 HF 91,1 80,3 53,7 34,4	37,9650 2805 5,0 Total thickness 1546,5 5463,425 6378,125 450 1,30% 7,14 12,91 0,03 Cor HF+Cor 7,70% 98,1147 15,70% 92,9071 17,20% 62,9364 34,8472	4 HF_sedcor 83,1 11,5 7,01 12,61 9,24 0,4	4	1,12 0,16 92,9	18,2
	Station WMF2_HF-05-01 WMF1-HF-01-01 WMF1-HF-07-10 WMF1-HF-10-01 WMF2-HF-05-13 WMF2_HF-01-01 WMF2_HF-05-02 WMF1-HF-01-02 WMF1-HF-07-11 WMF1-HF-10-02 WMF2-HF-05-14 WMF2_HF-01-02 WMF2_HF-05-03 WMF1-HF-01-03 WMF1-HF-07-12 WMF1-HF-10-03 WMF2-HF-05-15 WMF2_HF-01-03 WMF2_HF-05-04 WMF1-HF-01-04 WMF1-HF-07-13 WMF1-HF-10-04 WMF2-HF-05-16 WMF2_HF-01-04 WMF2_HF-05-05 WMF1-HF-02-01 WMF1-HF-07-14 WMF1-HF-10-05 WMF2-HF-05-17 WMF2_HF-01-05 WMF2_HF-05-06 WMF1-HF-03-01 WMF1-HF-07-15 WMF1-HF-10-06 WMF2-HF-05-18 WMF2_HF-01-06 WMF2_HF-02-01 WMF2_HF-02-02 WMF2_HF-02-03 WMF2_HF-02-04 WMF2_HF-02-05 WMF2_HF-03-01 WMF2_HF-03-02 WMF2_HF-03-03 WMF2_HF-03-04 WMF2_HF-03-05 WMF2_HF-03-06 WMF2_HF-03-07 WMF2_HF-04-01 WMF2_HF-04-02 WMF2_HF-04-03 WMF2_HF-04-04 WMF2_HF-04-05 WMF2_HF-05-07 WMF2_HF-05-08 WMF2_HF-05-09 WMF2_HF-05-10 WMF2_HF-05-11 WMF2_HF-05-12 WMF2_HF-05-13 WMF2_HF-05-14 WMF2_HF-05-15 WMF2_HF-05-16 WMF2_HF-05-17 WMF2_HF-05-18 WMF2_KF-01 WMF2_KF-02 WMF2_KF-03 WMF2_KF-04 WMF2_KF-05 WMF2_KF-06 WMF2_KF-07 WMF1-HF-03-02 WMF1-HF-03-03 WMF1-HF-03-05 WMF1-HF-03-06 WMF1-HF-03-07 WMF1-HF-03-08 WMF1-HF-03-09 WMF1-HF-03-10 WMF1-HF-03-12 WMF1-HF-07-16 WMF1-HF-07-17 WMF1-HF-07-18 WMF1-HF-07-19 WMF1-HF-07-20 WMF1-HF-07-21 WMF1-HF-07-22 WMF1-HF-07-23 WMF1-HF-10-07 WMF1-HF-10-08 WMF1-HF-10-09 WMF1-HF-10-10 WMF1-HF-10-11 WMF1-HF-10-12 WMF1-HF-10-13 WMF1-HF-10-14 Measure MedSalt_GC-01 WMF2-HF-01-01 MedSalt_GC-02 WMF2-HF-01-02 MedSalt_GC-03 WMF2-HF-01-03 MedSalt_GC-06 WMF2-HF-01-04 MedSalt_GC-07 WMF2-HF-01-05 MedSalt_GC-09 WMF2-HF-01-06 MedSalt_GC-10 WMF2-HF-02-01 MedSalt_GC-11 WMF1-HF-04-01 WMF1-HF-07-24 WMF1-HF-10-15 WMF2-HF-02-02 WMF2-KF-03 WMF1-HF-04-02 WMF1-HF-07-25 WMF1-HF-10-17 WMF2-HF-02-03 WMF2-KF-04 WMF1-HF-04-03 WMF1-HF-08-01 WMF1-HF-10-18 WMF2-HF-02-04 WMF2-KF-01 WMF1-HF-04-04 WMF1-HF-08-02 WMF1-HF-10-19 WMF2-HF-02-05 WMF2-KF-11 WMF1-HF-04-05 WMF1-HF-08-03 WMF-KF-01 WMF2-HF-03-01 WMF2-KF-02 WMF1-HF-05-01 WMF1-HF-08-04 WMF-KF-02 WMF2-HF-03-02 WMF2-KF-05 WMF1-HF-05-02 WMF1-HF-08-05 WMF-KF-03 WMF2-HF-03-03 WMF2-KF-06 WMF1-HF-05-03 WMF1-HF-08-06 WMF-KF-04 WMF2-HF-03-04 WMF2-KF-07 WMF1-HF-05-04 WMF1-HF-08-07 WMF-KF-05 WMF2-HF-03-05 WMF1-HF-05-05 WMF1-HF-05-06 WMF1-HF-08-08 WMF1-HF-08-09 WMF-KF-06 WMF-KF-07 WMF2-HF-03-07 Margin WMF2-HF-04-01 Sea bottom WMF1-HF-05-07 WMF1-HF-05-08 WMF1-HF-05-09 WMF1-HF-08-10 WMF1-HF-08-11 WMF1-HF-08-12 WMF-KF-08 WMF-KF-09 WMF-KF-10 WMF2-HF-04-02 1 WMF2-HF-04-03 Q5 (450ka) 2 WMF2-HF-04-04 Q10 (0,9ka) WMF1-HF-05-10 WMF1-HF-06-01 WMF1-HF-06-02 WMF1-HF-08-13 WMF1-HF-08-14 WMF1-HF-08-15 WMF-KF-11 WMF-KF-12 WMF-KF-13 WMF2-HF-04-05 3 WMF2-HF-04-06 P11 (2,6Ma) 4 WMF2-HF-04-07 Top UU WMF1-HF-06-03 WMF1-HF-06-06 WMF1-HF-08-16 WMF1-HF-08-17 WMF-KF-14 WMF-KF-15 WMF2-HF-04-08 5 WMF2-HF-04-09 Top Salt 6 WMF1-HF-06-07 WMF1-HF-06-08 WMF1-HF-06-09 WMF1-HF-07-01 WMF1-HF-07-02 WMF1-HF-07-03 WMF1-HF-07-04 WMF1-HF-09-09 WMF-KF-23 WMF2-HF-05-07 WMF1-HF-09-08 WMF-KF-22 WMF2-HF-05-06 WMF1-HF-09-06 WMF-KF-21 WMF2-HF-05-05 WMF1-HF-09-05 WMF-KF-20 WMF2-HF-05-04 WMF1-HF-09-04 WMF-GF-19 WMF2-HF-05-03 Basement WMF1-HF-08-18 WMF1-HF-09-01 WMF1-HF-09-02 WMF-KF-16 WMF-KF-17 WMF-KF-18 WMF2-HF-05-02 8 WMF2-HF-04-10 Top LU WMF2-HF-05-01 Base MSC 7	1900 2100 2400 3000	longitude latitude Depth PenD Tilt 1,7800 38,1400 1740 4,8 3,61 12,84 0,00 Wat.T SigWat Th Grad SigG 6 68,8 1,1 54,50 7304,5 19,60% 65,182 10,68 100,2 1396,75 7,10% 107,3142 7,11 51,5 2866,9 8,90% 56,0835 4,58 57,3 604,8 1,80% 58,3314 1,0 4,6833 39,1683 2218 5,0 2,10 12,89 0,02 7 88,3 3,5 1,8200 38,1633 1693 4,8 4,70 12,84 0,01 6 45,7 1,4 60,80 7127,9 18,70% 72,1696 11,37 93,8 1250,55 6,50% 99,897 6,10 62,4 3059,1 9,40% 68,2656 5,87 35,1 745,1 4,30% 36,6093 1,5 4,6917 39,1267 2355 5,0 5,18 12,92 0,01 7 74,3 1,6 1,8450 38,1817 1652 4,4 6,56 12,83 0,00 6 31,8 1,2 57,40 7635,55 20,20% 68,9948 11,59 85,4 934,4 5,10% 89,7554 4,36 51,7 3576 11,40% 57,5938 5,89 125,7 1010,85 6,20% 133,4934 7,8 4,7036 39,0883 2405 5,0 3,52 12,93 0,00 7 78,7 3,1 1,8733 38,1933 1613 4,8 6,63 12,81 0,00 6 21,0 1,8 60,40 7362,15 19% 71,876 11,48 126,8 1163,45 6,30% 134,7884 7,99 54,5 3991,35 12,80% 61,476 6,98 142,6 679,85 3,50% 147,591 5,0 4,7150 39,0550 2570 5,0 2,84 12,96 0,01 7 94,6 1,9 1,9050 38,2067 1571 4,8 6,66 12,82 0,00 6 24,8 0,7 61,50 6724,225 18,10% 72,6315 11,13 103,6 1650,3 8,40% 112,3024 8,70 54,2 3802,25 12,30% 60,8666 6,67 103,2 957,75 5,70% 109,0824 5,9 4,7200 39,0217 2662 5,0 3,09 12,98 0,01 7 87,8 2,0 1,9333 38,2133 1512 4,2 2,34 12,84 0,01 6 16,7 2,0 71,40 3469,85 13,80% 81,2532 9,85 86,8 1939,3 9,30% 94,8724 8,07 48,6 4594,5 14,30% 55,5498 6,95 110,7 2796,8 13,40% 125,5338 14,8 4,7317 38,9883 2668 4,8 19,13 12,98 0,00 7 56,0 0,9 4,7450 38,9550 2625 5,0 3,05 12,97 0,00 7 65,3 2,8 4,7617 38,8750 2628 4,7 20,75 12,97 0,01 7 105,1 2,7 4,7683 38,8417 2684 5,0 2,59 12,98 0,01 7 97,2 1,1 4,7800 38,8000 2677 5,0 2,87 12,98 0,01 7 84,5 1,5 4,7933 38,7600 2677 4,8 17,84 12,99 0,01 7 88,0 2,3 4,8033 38,7250 2694 5,0 5,39 12,88 0,01 6 89,8 2,9 4,8100 38,6933 2678 5,0 6,18 12,87 0,01 5 80,2 0,6 4,8167 38,6500 2684 5,0 7,08 12,88 0,01 6 81,2 2,1 4,8350 38,8077 2709 4,5 26,49 12,88 0,01 5 79,6 2,3 4,8433 38,5417 2718 4,9 11,83 12,89 0,00 5 75,2 0,8 4,8633 38,4700 2769 0,8 78,50 12,89 0,00 6 252,7 406,1 0 Th 6 7 6 7 6 7 6 7 6 7 6 0 0 0 0 7 7 5 5 5 4 4 4,8967 38,3567 2801 5,0 7,12 13,07 0,09 4 59,8 24,3 3 4,8267 38,3383 2797 5,0 5,53 12,89 0,01 5 69,7 6,2 4 4,7450 38,3117 2772 5,0 5,90 12,89 0,00 5 74,5 5,4 4 4,3850 38,2017 2745 5,0 6,82 12,88 0,01 5 79,7 2,1 4 4,2817 38,1667 2765 5,0 7,14 12,88 0,01 5 86,6 2,4 4 4,1400 38,1317 2763 5,0 7,28 12,89 0,01 4 96,2 3,1 4 1,9583 38,2200 1447 4,0 2,20 12,84 0,01 6 10,8 0,8 6 1,9700 38,2333 1422 4,2 14,48 12,81 0,02 6 4,4 1,5 6 1,9850 38,2450 1415 5,0 2,78 12,82 0,03 6 0,8 0,9 6 2,0067 38,2600 1440 4,3 19,57 12,82 0,01 6 6,1 1,4 6 2,0433 38,3367 1312 4,4 2,47 12,84 0,01 6 36,9 1,6 6 2,0667 38,3800 1302 4,4 1,29 12,84 0,00 6 51,5 2,6 6 2,0917 38,3283 1502 4,1 36,31 12,83 0,02 6 35,4 1,9 6 2,1100 38,3100 1642 3,8 40,23 12,83 0,01 6 59,0 3,6 6 2,0567 38,3050 1417 3,5 40,15 12,83 0,01 6 47,4 3,2 6 2,1117 37,9750 2437 5,0 3,27 12,94 0,00 6 127,2 2,4 6 2,1450 37,9300 2805 2,6 59,43 13,01 0,01 6 143,7 16,2 6 2,1533 37,9200 2804 5,0 7,38 13,01 0,01 6 98,4 2,5 6 4,9934 39,8629 2708 10,0 2,22 13,31 0,01 7 94,7 0,6 25 5,5408 38,9461 2848 9,0 2,16 13,33 0,01 7 72,2 2,8 21 5,0268 38,4051 2808 10,0 2,61 13,47 0,00 7 57,7 0,8 24 3,5253 37,9390 2806 10,0 0,54 13,53 0,00 7 74,9 1,3 73 2,8871 38,6261 2618 10,0 0,92 13,47 0,00 7 76,7 1,8 37 2,8019 38,6851 2658 10,0 0,89 13,43 0,00 7 84,4 2,4 39 2,4513 38,2968 2745 9,6 2,28 13,38 0,00 7 77,7 1,2 34 71,90 3486 13,80% 81,8222 9,92 81,30 2149,6 8,50% 88,2105 6,91 105,40 1777,7 8,90% 114,7806 9,38 107,40 1167,85 6,50% 114,381 6,98 74,80 952,95 5,60% 78,9888 4,19 67,40 1874,1 9,80% 74,0052 6,61 86,90 962,15 5,70% 91,8533 4,95 86,70 1063,6 6% 91,902 5,20 106,40 2347,05 10,50% 117,572 62,9 2535,85 11,60% 70,1964 7,30 78,5 2529,4 10,60% 86,821 8,32 89,7 2720,2 11% 99,567 9,87 97,5 2860,35 11,40% 108,615 11,12 91,3 3274,65 13,70% 103,8081 12,51 116,8 3025,6 12,30% 131,1664 14,37 105,7 3008,35 12,50% 118,9125 13,21 99,7 3222,5 12,90% 112,5613 12,86 60,3 4938,95 15% 69,345 9,05 50,4 4841,1 14,70% 57,8088 7,41 59,9 4912,1 15,10% 68,9449 9,04 57,1 6161,65 17,20% 66,9212 9,82 62,7 6535,175 18,20% 74,1114 11,41 60,6 6135,675 16,40% 70,5384 9,94 54,1 6437,2 17,30% 63,4593 9,36 55,9 6467,475 17,20% 65,5148 9,61 HF Total Thickness Cor HF+Cor 86 2230,15 11,50% 95,89 9,9 HF_sedcor 92,2 1247,45 6,50% 98,193 85,3 1537 9,30% 93,2329 7,9 6,0 75,7 775,8 4,20% 78,8794 29,6 1460,4 8,30% 32,0568 2,5 3,2 78,7 568,9 2,90% 80,9823 91,1 677,6 3,80% 94,5618 3,5 2,3 87,4 583,75 3,10% 90,1094 60,6 1126,75 5,50% 63,933 3,3 2,7 84,4 462,15 2,70% 86,6788 72,3 2065,95 9,40% 79,0962 6,8 2,3 56,0 574 4,10% 58,296 67,3 949,15 6,60% 71,7418 4,4 2,3 65,3 1438,5 8% 70,524 61,0 3663,1 14% 69,56166 8,5 5,2 11,17 78,4 860 5,30% 82,5552 95 3186,85 12,80% 107,16 12,16 55,8 5917,65 15,80% 64,6164 8,82 105,1 1824,8 9,50% 115,0845 71,3 3234,5 12,10% 79,9034227 8,6 10,0 4,16 56,5 574,7 3,50% 58,4775 91,2 3035,05 12% 102,144 10,94 53,8 6052,55 16% 62,408 8,61 97,2 1118,25 6,20% 103,2264 95,0 1777,8 7,70% 102,315 7,3 6,0 1,98 49,2 1631,35 8,50% 53,382 103,8 1991,05 9,50% 113,661 9,86 40,1 7031,2 18,10% 47,3581 7,26 88,8 1227,4 7,60% 95,5488 69,7 4251,35 15,40% 80,4338 10,7 6,7 4,18 69,1 2175,45 10,70% 76,4937 104 1989,3 9,70% 114,088 10,09 45,4 6395,45 17,30% 53,2542 7,85 126,3 1336,7 7% 135,141 74,9 4069,45 16% 86,884 12,0 8,8 7,39 68,7 1996,55 10% 75,57 127,4 1749,8 8,60% 138,3564 10,96 58,3 7830,525 20,40% 70,1932 11,89 103,4 2051 9,10% 112,8094 75,7 3244,2 13,10% 85,5996219 9,9 9,4 6,87 95,3 4507,3 13,30% 107,9749 105,5 745 4% 109,72 4,22 73,5 6028,875 16,20% 85,407 11,91 87,2 1940,05 8,30% 94,4376 85,3 1714 7,70% 91,8417135 6,6 7,2 12,67 71,8 4450,25 13,30% 81,3494 114,3 816,9 4,20% 119,1006 4,80 94,3 1121,35 4,90% 98,9207 4,62 81,7 2609,25 10,70% 90,4419 77,1 4505,95 16,80% 90,0906432 13,0 8,7 9,55 94,3 3653,45 10,90% 104,5787 111,5 730,4 4,10% 116,0715 4,57 68,3 4304,9 12,80% 77,0424 8,74 80,0 418,9 2,50% 82 30,9 484,75 11,50% 34,4535 3,6 2,0 10,28 86,6 3944,7 11,70% 96,7322 98,2 1179,5 6,10% 104,1902 5,99 61,9 2738,9 10,40% 68,3376 6,44 77,0 3421,35 13,30% 87,241 10,2 10,13 72,5 4213,4 13,10% 81,9975 9,50 69,7 4058,15 12,90% 78,6913 103,1 1488,1 7,70% 111,0387 7,94 106,6 1199,65 7% 114,062 7,46 105,3 996,2 5,30% 110,8809 5,58 89,4 731,6 4,30% 93,2442 87,4 4953,95 19,20% 104,1808 16,8 Basin 3,84 68,1 2411,45 9% 74,229 6,1 Sea bottom 8,99 88,4 4096,875 14,60% 101,3064 12,91 76,5 499,45 3% 78,795 2,30 71,1 2460,7 8,60% 77,2146 116 765,05 5,10% 121,916 5,92 100,6 1290,9 7,30% 107,9438 7,34 94,6 1212,2 7% 101,222 6,62 92,7 2523,2 9,60% 101,5992 8,90 100,8 2535 9,80% 110,6784 9,88 95,4 2860,35 11,40% 106,2756 74,9 3925,95 14,90% 86,0601 1 1950 11,2 74,7 3636,65 14,10% 85,2327 Q5 (450ka) 10,5 2 2100 2200 2300 10,88 81,5 3346,1 13% 92,095 Q10 (0,9ka) 2600 2400 10,6 6,11 66,5 2030,45 8,20% 71,953 5,45 84,7 1343,75 5,50% 89,3585 4,66 59,1 2388,05 9,60% 64,7736 159,6 93 2,20% 163,1112 3,51 136,2 1250,55 6,50% 145,053 8,85 6,8 637,9 4,10% 7,0788 0,28 88,3 3186,85 12,80% 99,6024 11,30 83,3 2028,2 32% 109,956 26,66 82 3066,7 11,50% 91,43 94,6 1991,75 7,80% 101,9788 3 2600 7,4 81,1 3091,6 11,90% 90,7509 P11 (2,6Ma) 9,7 4 3000 9,43 94,4 3228,7 12,40% 106,1056 Top UU 11,7 5,67 91,2 3504,075 12,40% 102,5088 11,31 72,4 4945,875 15,80% 83,8392 32,5 1140,05 6,70% 34,6775 2,18 163,2 858,9 5,10% 171,5232 8,32 130,3 3066,7 11,50% 145,2845 14,98 123,9 3274,65 13,70% 140,8743 16,97 100,6 3009,35 11,70% 112,3702 5 3700 11,8 113,3 3021,4 11,20% 125,9896 Top Salt 12,7 6 4500 11,44 71,9 5151,175 15,90% 83,3321 11,43 71,5 4350,6 13,70% 81,2955 9,80 71,9 5012,15 15,40% 82,9726 57,6 621,6 3,80% 59,7888 13,1 859,05 5,20% 13,7812 38,6 637,9 4,10% 40,1826 50,2 965,9 6,10% 53,2622 62,6 3969,4 12,40% 70,3624 7,76 44,6 3736,1 12,60% 50,2196 5,62 10,1 488,25 7,60% 10,8676 0,8 3,06 67,9 3432,35 10,60% 75,0974 7,20 52,5 6507,525 17,30% 61,5825 9,08 15,6 287,95 5,80% 16,5048 0,9 1,58 17,2 3064,2 10,70% 19,0404 1,84 57,3 6434,95 17,30% 67,2129 9,91 21,7 386,9 10,50% 23,9785 2,3 0,68 43 1812,35 6,10% 45,623 2,62 2,3 1608,1 7,10% 2,4633 0,16 20,7 775,2 4,60% 21,6522 1,0 2,19 15,6 1987,15 6,80% 16,6608 1,06 79,9 3292,3 12,50% 89,8875 9,99 29,9 557 4,60% 31,2754 1,4 Basement 11,07 52,7 848,7 5,20% 55,4404 2,74 98,8 1221,65 4,80% 103,5424 4,74 61,3 1272 4,90% 64,3037 3,00 21,3 859,05 5,20% 22,4076 1,11 146,7 858,9 5,10% 154,1817 7,48 163,1 1111,4 5% 171,255 40,7 1595,55 6,30% 43,2641 2,6 8 5100 8,16 92,9 3004,35 11,10% 103,2119 Top LU 3500 10,3 63,9 591 5,30% 67,2867 Base MSC 4800 3,4 7 4600 4000 (only Upper Unit)	K 0,93 0,01 63,9 SigK HF 1,04 0,03 92,2 0,89 0,02 40,7 1,02 0,02 75,7 0,94 0,02 29,9 1,00 0,04 78,7 0,99 0,03 20,7 0,92 0,07 87,4 0,88 0,01 21,7 0,96 0,04 84,4 0,93 0,04 15,6 1,00 0,30 56,0 1,00 0,30 65,3 1,00 0,30 105,1 1,00 0,30 97,2 1,05 0,07 88,8 1,44 0,23 126,3 1,15 0,14 103,4 1,09 0,05 87,2 1,01 0,04 81,7 1,01 0,16 80,0 1,02 0,06 77,0 1,00 0,30 252,7 1,46 0,14 87,4 0,98 0,05 68,1 1,01 0,09 74,9 0,94 0,03 74,7 0,94 0,02 81,5 0,98 0,05 94,6 0,94 0,04 10,1 1,01 0,05 4,4 0,99 0,03 0,8 0,99 0,03 6,1 0,95 0,05 35,1 0,95 0,03 48,7 0,97 0,03 34,4 0,97 0,05 57,3 1,00 0,03 47,5 0,99 0,04 125,7 0,99 0,05 142,6 1,05 0,03 103,2 1,00 0,07 95,0 1,04 0,09 74,9 1,06 0,15 61,0 0,95 0,12 71,3 0,99 0,10 75,7 1,01 0,12 85,3 0,99 0,12 77,1	1,4 SigHF 1,6 4,5 1,3 2,5 1,9 4,2 0,7 6,5 1,9 3,8 16,8 19,8 31,6 29,2 6,3 20,1 12,6 4,1 4,1 12,6 4,4 413,1 36,4 7,0 8,7 3,0 2,6 5,5 0,9 1,5 0,9 1,4 2,4 2,8 2,1 4,4 3,5 5,3 17,7 4,2 6,7 6,6 8,1 9,7 7,4 9,8 9,4	455 456
							458 459 460 461

  -2. HEAT FLOW MEASUREMENTS, MODELS AND RHEOLOGY EXPERIMENT

		SARD_MB1 SARD_MB2 SARD_MB3 SARD_MB4 SARD_MB6 SARD_MB7	SARD_MB8	SARD_MB9
	Astenosphere temperature	1333	1333	1333	1333	1333	1333	1333	1333
	isostasy model	Airy	Airy	Airy	Airy	Airy	Airy	Airy	450 °C/10DON
	Upper crust thickness (initial) (km)	16	16	16	16	16	16	16	16
	Lower crust thickness (initial) (km)	17	17	17	17	17	17	17	17
	Oceanic crust thickness (final) (km)	6	6	6	6	6	6	6	6
	Continental lithospheric thickness (initial) (km)
									465

Table 2 .

 2 5. Table showing the tests carried out with MARGE thermo-kinematic model for the transect in theGulf of Lion. The blue-coloured tests are shown in figure 2.1. The bold text represents the parameter changed.ANNEXE-2. HEAT FLOW MEASUREMENTS, MODELS AND RHEOLOGY EXPERIMENT

	466

Heat production Miocene sequence (µW m -3 )

			16-12-8	16-12-8	16-12-8	16-12-8	30-20.4-16	16-12-8	16-12-8	16-12-8
	Heat production Plioquaternary sequence (µW m	-3 ) 0.915	0.915	0.915	0.915	0.915	0.915	0.915	0.915
	Hea production salt (µW m	-3 )	0.05	0.05	0.05	0.05	0.05	0.05	0.05	0.05
			0.9575	0.9575	0.9575	0.9575	0.9575	0.9575	0.9575	0.9575

Density of underplating magma (Kg m -3 ) OCT Limit Medium Medium Medium Far Far Far Far Driussi et al., 2015 Colours in graphs

	Blue	Yellow	Red	Purple

Table 2 .

 2 6. Table showing the tests carried out with MARGE thermo-kinematic model for the transect in theSouth Balearic margin. The blue-coloured tests are shown in figure 2.2. The bold text represents the parameter changed.

CHAPTER 3. DATA AND METHOD

Figure 3.16. Comparison between zoom of SaltFlu03 profile in time (left) and depth (right) domain.

Figure 4.33. Zooms of seismic profiles located in the Gulf of Lion showing the early salt deformation in the deep basin (Anticlinal salt domain). The onlaps and the variations in thicknesses highlighted a first, early deformation syn-deposition of UU, still belonging to the Messinian age.

(2015a). NBFZ: North Balearic Fracture Zone. CFZ: Central Fracture Zone. Gravity map from[START_REF] Smith | Global sea floor topography from satellite altimetry and ship depth soundings[END_REF]; magnetic map from[START_REF] Galdeano | Assemblage à altitude constante des cartes d'anomalies magnétiques couvrant l'ensemble du bassin occidental de la Méditerranée[END_REF].

Acknowledgements

The authors acknowledge the fruitful and constructive English editing advice and corrections by Alison Chalm. This work was supported by Labex MER (ANR10-LABX-19) and the ISblue project, Interdisciplinary graduate school for the blue planet (ANR-17-EURE-0015) co-funded by a grant from the French government under the program "Investissements d'Avenir" and by a PHD grant awarded to M. Bellucci by the Regional Council of Brittany and IFREMER and prepared at the EDSML doctoral School at UBO (University of Brest) and the University of Trieste. It was further supported by COST-CA15103-MEDSALT program and "Université Franco-Italienne, Programme VINCI 2019".

We thank the captains, crew and science parties of campaigns WESTMEDFLUX (R/V ANNEXE-1. SCIENTIFIC PRODUCTION

Balearic Promontory and South Balearic margin: refer to Driussi, (2014), Dal Cin et al., (2016) ;Pellen, (2016) and Raad et al., (2020). Additional data by SIGEOF Spanish site and Schlumberger.

Gulf of Lion: refer to Gorini, (1993), Maillard, (1993), Rabineau, (2001), Lofi, (2002), Bache, (2008) and Leroux, (2012).

Liguro-Provençal basin: refer to Gorini, (1993), Maillard, (1993), Rabineau, (2001), Bache, (2008), Leroux, (2012), Geletti et al., (2014), Bellucci, (M2, 2017).

North-East Algerian margin: refer to Arab, ( 2016) and Leroux et al., (2019).

Valencia and Menorca basins: refer to Maillard, (1993), Garcia et al., (2011), Driussi, (2014) and Pellen, (2016). Additional data by SIGEOF Spanish site and Schlumberger.

Western Sardinian margin: refer to Geletti et al., (2014), Dal Cin et al., (2016) and Bellucci, (M2, 2017). Additional data by VIDEPI Italian site.

Figure 12

ANNEXE-1. SCIENTIFIC PRODUCTION

LIST OF FIGURES

LIST OF FIGURES

385

(Northern; Gulf coast); 50. Gulf of Mexico (Southern;51. Haltenbanken;53. Holbrook Basin;54. Horseshoe Basin (Grand Banks);55. Hudson Bay;56. Ionian;57. Jeanne d'Arc Basin (Grand Banks);58. Jianghan Basin;59. Jura/Rhodanian;60. Katangan;61. Khorat Basin;62. Kuqa Foreland (Tarim Basin);63. La Popa (Monterrey) Basin;64. Lusitanian;65. Mackenzie Basin;66. Maestrat;67. Majunga Basin;68. Mandawa Basin;70. Maritimes Basin;80. Michigan Basin;81. Moesian;82. Moose River Basin;83. Neuquen Basin;84. Nordkapp Basin;85. Officer Basin;86. Olduvai depression;87. Oman (Fahud Salt Basin);88. Oman (Ghaba Salt Basin). 89. Oman (Ghudun Salt Basin); 90. Oman (South Oman Salt Basin); 91. Oriente-Ucayali (Pucara) Basin;92. Orpheus Graben;93. Palmyra;94. Paradox Basin;95. Parry Islands Fold Belt;96. Pricaspian Basin;97. Pripyat Basin;98. Qaidam Basin;100. Red Sea (North);101. Red Sea (South);102. Rot Salt Basin;103. Ruvuma Basin;104. Sabinas Basin;105. Sachun Basin;106. Salar Basin 118 (Grand Banks); 107. Salt Range (Hormuz-Punjab region); 108. Salt Range (Kohat Plateau); 109. Saltville 119 (Appalachian);110. Scotian Basin;111. Siberia,East;112. Sirjan Trough;113. Solimoes;114. SomaliaKenya;115. South Whale Basin (Grand Banks);117. Sverdrup Basin (Melville Is);118. Tabriz Salt Basin;119. Tadjik Basin;120. Takutu Salt Basin;121. Transylvanian;122. Tromso Basin;123. USA Midcontinent;; 125. West Africa ; 127. West Africa (Morocco-S. Spain); 128.

Western Canada (Alberta Basin);129. Whale Basin (Grand Banks);130. Williston Basin;131. Zagros (Mesopotamian Basin);132. Zagros (Mesopotamian Basin); 133. Zechstein (NW Europe); 134. Zechstein (onshore UK) ;and 135. Zipaquira Basin (after Warren, 2010). Different colours are referred in the text. 62 Figure 2.7. Sketch showing plate reconstruction at 600 Ma from [START_REF] Li | Assembly, configuration, and break-up history of Rodinia: a synthesis[END_REF]. 64

Figure 2.8. Chrono-stratigraphic scale of the Permian and Triassic periods. The main salt deposition events are represented (modified after Soto et al., 2017). 65

Figure 2.9. Summary map of the Zechstein Basin in Central Europe showing salt distribution, diapirs and pillows location (after Soto et al., 2017 and references therein). 66

Figure 2.10. Segmentation of Central Atlantic from [START_REF] Labails | La marge sud-marocaine et les premières phases d'ouverture de l'océan Atlantique Central[END_REF] showing the salt deposits distribution all along both margins before the oceanic break-up (reconstruction at 195 Ma after [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF]. 67

Figure 2.11. Salt basins in the Gulf of Mexico region showing locations of salt structures and the oceaniccontinental crust limit interpreted from reflection seismic data (Hudec et al., 2013a). 69

Figure 2.12. Present-day evaporites distribution in the deep and intermediate Mediterranean Sea. The outline of main deep-sea fans are indicated by dotted lined: 1) Rhone, 2)Ebro, 3)Nile. In the Western Mediterranean Sea a thick evaporites deposit (more than 500 m) occupies all the present-day deep basins (after [START_REF] Gorini | New imaging of the salinity crisis: Dual Messinian lowstand megasequences recorded in the deep basin of both the eastern and western Mediterranean[END_REF]. References are given in the reference chapter of this thesis.

71

keywords: salt tectonics; passive margin; Western Mediterranean Sea; thermicity; Messinian Salinity Crisis

Introduction

The study of salt tectonics is a widely discussed topic, especially since 1990 and mainly due to its importance in oil exploration. Under geological strain rate and due to its rheological properties, salt or halite, flows like a fluid causing spectacular geometries. Triggering can be induced by several mechanisms, including gravity, tectonic force, salt buoyancy or differential loading [START_REF] Ge | Kinematics and dynamics of salt tectonics driven by progradation[END_REF][START_REF] Hudec | Terra infirma: Understanding salt tectonics[END_REF]. On passive margins, salt tectonics is distributed into three domains [START_REF] Jackson | Structural dynamics of salt systems[END_REF][START_REF] Letouzey | Evolution of salt-related structures in compressional settings[END_REF][START_REF] Ings | A new conceptual model for the structural evolution of a regional salt detachment on the northeast Scotian margin, offshore eastern Canada[END_REF][START_REF] Hudec | Terra infirma: Understanding salt tectonics[END_REF]: an extensional zone on the slope dominated by basementinvolved or basement-detached reactive diapirism [START_REF] Duval | Raft tectonics in the Kwanza basin, Angola[END_REF][START_REF] Jackson | Structural dynamics of salt systems[END_REF][START_REF] Vendeville | Scale models of salt tectonics during basementinvolved extension[END_REF], a mid-slope more or less deformed transitional domain [START_REF] Cramez | Superposed deformation straddling the continental-oceanic transition in deep-water Angola[END_REF][START_REF] Dooley | Coeval extension and shortening above and below salt canopies on an uplifted, continental margin: Application to the northern Gulf of Mexico[END_REF][START_REF] Ge | Progressive tilting of salt-bearing continental margins controls thin-skinned deformation[END_REF] and an area of contraction characterized by salt thickening, thrust faults and folding [START_REF] Hudec | Advance of allochthonous salt sheets in passive margins and orogens[END_REF]. Regional differential loading induced by detachment surface slope and/or sedimentary loading are often summarized as the cause of gravity gliding and gravity spreading end-member models. The discussion of which of the two models prevails is still debated [START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF]2012;[START_REF] Rowan | Salt tectonics at passive margins: Geology versus models-Discussion[END_REF][START_REF] Schultz-Ela | Excursus on gravity gliding and gravity spreading[END_REF][START_REF] Peel | How do salt withdrawal minibasins form? Insights from forward modelling, and implications for hydrocarbon migration[END_REF]. During gravity spreading, salt moves by sedimentary differential loading [START_REF] Ge | Kinematics and dynamics of salt tectonics driven by progradation[END_REF][START_REF] Jackson | External shapes, strain rates, and dynamics of salt structures[END_REF][START_REF] Vendeville | Salt tectonics driven by sediment progradation: Part I-Mechanics and kinematics[END_REF][START_REF] Hudec | Terra infirma: Understanding salt tectonics[END_REF] whilst during gravity gliding, the salt and its overburden slide towards the deep basin [START_REF] Cobbold | Some experiments on interacting sedimentation and deformation above salt horizons[END_REF][START_REF] Demercian | Style and pattern of salt diapirs due to thin-skinned gravitational gliding, Campos and Santos basins, offshore Brazil[END_REF][START_REF] Fort | Salt tectonics on the Angolan margin, synsedimentary deformation processes[END_REF] triggered by the inclination of the margin occurring during thermal subsidence. During the well-known Messinian Salinity Crisis (MSC) in the Mediterranean Sea, evaporite deposition (up to 3 km thick, [START_REF] Haq | Deep Mediterranean's Messinian evaporite giant: How much salt?[END_REF] was triggered by a combination of global tectonic events, which led to the closure of the Strait of Gibraltar (e.g. [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF] and climatic evolution (e.g. , 2008). Salt tectonics in the Liguro-Provençal basin has been studied since the works of [START_REF] Le Cann | Le diapirisme dans le bassin Liguro-Provençal (Méditerranée occidentale)[END_REF][START_REF] Gaullier | Diapirisme salifère et dynamique sédimentaire dans le bassin Liguro-Provençal. Données sismiques et modèles analogiques[END_REF]) and Gorini,(1993) and, along with recent studies, is outlined as the combination of several parameters: (i) differential loading and gliding of the brittle-ductile series during gravity spreading [START_REF] O Obone-Zue-Obame | The sedimentary markers of the Messinian salinity crisis and their relation with salt tectonics on the Provençal margin (western Mediterranean): results from the "MAURESC" cruise[END_REF], (ii) initial conditions and morpho-structure evolution of the basin [START_REF] Gaullier | Salt tectonics in the deep Mediterranean: indirect clues for understanding the Messinian Salinity Crisis. The Messinian salinity crisis from mega-deposits to microbiology-A consensus report[END_REF], (iii) local geodynamic setting that could induce thick-skinned tectonics [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF][START_REF] Déverchère | Active thrust faulting offshore Boumerdes, Algeria, and its relations to the 2003 Mw 6.9 earthquake[END_REF]. The application of the two salt tectonic end-member models highlights problems when we take into account the differences in salt morphologies in the Western Mediterranean Sea. In the Western Mediterranean Sea, salt was deposited in a closed basin, already formed, above a thick marine sequence deposited during the Late Oligocene and Miocene intervals.

CIESM

Moreover, the purely vertical subsidence in the deep basin implies small difference in initial salt thickness that could have controlled salt supply variations.

We present here a compilation of the relationships between salt morphologies and crustal nature in well-studied salt-bearing basins throughout the world. We first focus on the Western Mediterranean Sea, for which we present a new detailed map of salt morphologies. We categorized regional salt morphologies in order to superimpose them onto the crustal segmentation, constrained by wide-angle seismic studies, magnetic and gravity maps. We then discussed the possible causes for this relationship, taking into account the Western Mediterranean Sea peculiarities. We then applied the same method to South-Atlantic margins (Angolan and Santos Basins), Gulf of Mexico, Morocco and Nova Scotia margins in order to observe if this coincidence is also confirmed in different salt tectonics systems.

Particularity of Western Mediterranean salt-bearing basin: a divergent closed and fossil system

The Cenozoic opening of the Western Mediterranean in an overall convergence context between Africa and Eurasia is closely linked to the creation of the Alpine chains, which surround it (e.g. [START_REF] Carminati | Geodynamic evolution of the central and western Mediterranean: Tectonics vs. igneous petrology constraints[END_REF]. The Algero-Provençal basin opened during the Late Oligocene-Early Miocene times in the Tethyan subduction zone context. Since Late Oligocene, the slab retreat is predominant in the formation of back-arc basins, such as the Alboran, the Liguro-Provençal, the Tyrrhenian, the Aegean basins [START_REF] Jolivet | Mediterranean extension and the Africa-Eurasia collision[END_REF]. The Liguro-Provençal basin was created by the counter-clockwise rotation of the Corso-Sardinian block (e.g. [START_REF] Auzende | The origin of the western Mediterranean basin[END_REF][START_REF] Olivet | La cinématique de la plaque ibérique[END_REF], dated from Late Eocene (~Priabonian: 33.7 Ma) ranging between 23 to 19 Ma according to authors [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF]. The reconstruction of initial conditions of the Liguro-Provençal rifting [START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF] shows similarities with those of Central [START_REF] Labails | Crustal structure of the SW Moroccan margin from wide-angle and reflection seismic data (the Dakhla experiment). Part B-The tectonic heritage[END_REF] and South Atlantic margins [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF][START_REF] Aslanian | Palaeogeographic consequences of conservational models in the South Atlantic Ocean[END_REF], such as the high structural position before the breakup and the strong subsidence that followed.

While there is a general consensus on the geodynamics of the Liguro-Provençal basin, the opening direction of the Algerian basin is still a matter of debate, as well as the initial position of the AlKaPeCa (Alboran, Kabylies, Peloritan and Calabria) blocks. There are several hypotheses regarding the opening direction and the nature of the margins [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF].

The first group of authors claim a dominant N-S opening (e.g. [START_REF] Gueguen | On the post-25 Ma geodynamic evolution of the western Mediterranean[END_REF]Frizon de Lamotte et al., 2000;Rosenbaum et al., 2002;[START_REF] Schettino | Plate kinematics of the Western Mediterranean region during the Oligocene and Early Miocene[END_REF] with no significant displacement of the Alboran block [START_REF] Faccenna | Lateral slab deformation and the origin of the western Mediterranean arcs[END_REF]. The second hypothesis claims an E-W opening with an important westward migration of the Alboran block (e.g. [START_REF] Malinverno | Extension in the Tyrrhenian Sea and shortening in the Apennines as result of arc migration driven by sinking of the lithosphere[END_REF][START_REF] Royden | Evolution of retreating subduction boundaries formed during continental collision[END_REF]. The third hypothesis proposes a two-step opening scenario, with a first N-S movement which led to the opening of the East Algerian basin and a second E-W, with the opening of the West Algerian basin [START_REF] Etheve | Extensional vs contractional Cenozoic deformation in Ibiza (Balearic Promontory, Spain): Integration in the West Mediterranean back-arc setting[END_REF]Lepretre et al., 2018). Another model claimed by [START_REF] Vergés | Tethys-Atlantic interaction along the Iberia-Africa plate boundary: The Betic-Rif orogenic system[END_REF] proposes an initial SE-dipping subduction that shifted to a faster E-dipping subduction which could explain some observations made in the Betic-Rif orogenic system, including the Alboran back-arc basin opening.

Other authors do not agree with the rollback process and propose a collapse of the thickened continental crust (Dewey, 1989) or a lithospheric delamination [START_REF] Roure | Alpine inversion of the North African margin and delamination of its continental lithosphere[END_REF].

In the Algerian basin, the Plio-Quaternary period is affected by tectonic inversion caused by the NW-SE convergence between the African and European plates with a slow rate of shortening (0.5 to ~1 cm/yr) (Kherroubi et al., 2009). This still present-day shortening causes deformation and tectonic inversion offshore Algeria and even in the SE Iberian margin (Maillard and Mauffret, 2013). The Algerian tectonic inversion is the only remarkable post-salt deposition tectonic activity which has an impact on the present-day salt structures.

About 6 million years ago (~5.96-5.32 Ma, Krijgsman et al., 1999a), when the Algerian and Liguro-Provençal basins were already formed, the Mediterranean underwent a rapid and extreme paleo-environmental event known as Messinian Salinity Crisis. The closure of the Strait of Gibraltar (Hsu et al., 1973), or deeper lithospheric processes (Garcia-Castellanos and Villasenor, 2011), caused a significant sea-level fall and the deposition of evaporites associated to considerable erosion mostly located in the upper parts of the margin (e.g. [START_REF] Clauzon | Alternate interpretation of the Messinian salinity crisis: controversy resolved?[END_REF][START_REF] Rouchy | The Messinian salinity crisis in the Mediterranean basin: a reassessment of the data and an integrated scenario[END_REF]. In the Western Mediterranean Sea, the Messinian deposits have been described as a trilogy, composed of lower evaporites, salt and upper evaporites [START_REF] Montadert | De l'âge tertiaire de la série salifère responsable des structures diapiriques en méditerranée occidentales (nord-est des baléares)[END_REF]Réhault et al., 1985). The salt layer is considered to be composed of pure halite, while the evaporites can be interpreted as intercalations of gypsum/anhydrite and clastics deposits. The uppermost part of Upper Evaporites (also called Upper Unit, [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF][START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF] has been sampled during DSDP Leg XIII [START_REF] Hsü | Late Miocene desiccation of the Mediterranean[END_REF] revealing dolomitic marls and anhydrite layers. Nevertheless, the vertical and lateral facies variability suggest that the lithology of the Upper Unit can vary at the basin scale [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF]. The Upper and [START_REF] Medaouri | The transition from Alboran to Algerian basins (Western Mediterranean Sea): chronostratigraphy, deep crustal structure and tectonic evolution at the rear of a narrow slab rollback system[END_REF][START_REF] Mihoubi | Seismic imaging of the eastern Algerian margin off Jijel: integrating wide-angle seismic modelling and multichannel seismic pre-stack depth migration[END_REF][START_REF] Badji | Geophysical evidence for a transform margin offshore Western Algeria: a witness of a subduction-transform edge propagator?[END_REF][START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF][START_REF] Hamai | Flexural behaviour of the north Algerian margin and tectonic implications[END_REF], Arab et al., 2016a[START_REF] Arab | Coupling stratigraphic and petroleum system modeling tools in complex tectonic domains: case study in the North Algerian Offshore[END_REF][START_REF] Aïdi | Deep structure of the continental margin and basin off Greater Kabylia, Algeria-New insights from wide-angle seismic data modeling and multichannel seismic interpretation[END_REF] in the Algerian Basin. The lack of wide-angle surveys in the South Balearic basin compels us to use the segmentation of this margin derived from gravity and magnetic data interpretations [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF].

In the Santos and Campos basins, we used the crustal interpretation from the SanBa Project [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF] and from the Zaiango Project [START_REF] Contrucci | Deep structure of the West African continental margin (Congo, Zaïre, Angola), between 5 S and 8 S, from reflection/refraction seismics and gravity data[END_REF][START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF] in the Angolan margin. In Gulf of Mexico, the segmentation is from the refraction seismic project GUMBO [START_REF] Eddy | Deep crustal structure of the northeastern Gulf of Mexico: Implications for rift evolution and seafloor spreading[END_REF][START_REF] Eddy | Structure and origin of the rifted margin of the northern Gulf of Mexico[END_REF][START_REF] Christeson | Deep crustal structure in the eastern Gulf of Mexico[END_REF][START_REF] Van Avendonk | Continental rifting and sediment infill in the northwestern Gulf of Mexico[END_REF] and interpretation from (Hudec et al., 2013a;[START_REF] Sawyer | The crust under the Gulf of Mexico Basin. The Gulf of Mexico Basin: Geological Society of America[END_REF][START_REF] Curry | Extensional models for the development of passive-margin salt basins, with application to the Gulf of Mexico[END_REF]. In Morocco-Nova Scotia conjugated margins the crustal segmentation is taken from [START_REF] Biari | Deep crustal structure of the north-west African margin from combined wide-angle and reflection seismic data (MIRROR seismic survey)[END_REF]; [START_REF] Contrucci | Deep structure of the West African continental margin (Congo, Zaïre, Angola), between 5 S and 8 S, from reflection/refraction seismics and gravity data[END_REF]; [START_REF] Funck | Crustal structure of the northern Nova Scotia rifted continental margin (eastern Canada)[END_REF]; [START_REF] Wu | Crustal structure of the central Nova Scotia margin off Eastern Canada[END_REF].

Western Mediterranean salt deformation

Salt tectonics mechanisms

Given its rheological properties, salt can acts as a level of décollement and can flow driven by sedimentary loading and margin tilting (e.g. [START_REF] Ge | Kinematics and dynamics of salt tectonics driven by progradation[END_REF][START_REF] Vendeville | Salt tectonics driven by sediment progradation: Part I-Mechanics and kinematics[END_REF][START_REF] Hudec | Terra infirma: Understanding salt tectonics[END_REF][START_REF] Gaullier | Role of thick-skinned tectonics on thin-skinned salt tectonics in the Western Mediterranean: A comparison between the Algerian and North-Balearic basins[END_REF][START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF][START_REF] Rowan | Salt tectonics at passive margins: Geology versus models-Discussion[END_REF].

In the Western Mediterranean, salt tectonics was previously locally described by some authors, as in the Gulf of Lion [START_REF] Le Cann | Le diapirisme dans le bassin Liguro-Provençal (Méditerranée occidentale)[END_REF][START_REF] Pautot | Morphology and extension of the evaporitic structures of the Liguro-Provençal Basin: New Sea-Beam data[END_REF][START_REF] Gaullier | Diapirisme salifère et dynamique sédimentaire dans le bassin Liguro-Provençal. Données sismiques et modèles analogiques[END_REF][START_REF] Gorini | Géodynamique d'une marge passive: le Golfe du Lion (Méditerranée occidentale[END_REF][START_REF] Reis Dos | La Tectonique Salifère et son Influence sur l'Architecture Sédimentaire Quaternaire de la Marge du Golfe du Lion-Méditérranée Occidentale[END_REF]Dos Reis, 2005, 2008;[START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF][START_REF] Granado | Geodynamical framework and hydrocarbon plays of a salt giant: the NW Mediterranean Basin[END_REF], in the Provence margin (Obone-Zue-Obame et al., 2011), in west Sardinian margin [START_REF] Geletti | The Messinian Salinity Crisis: new seismic evidence in the West-Sardinian Margin and Eastern Sardo-Provençal Basin (West Mediterranean Sea)[END_REF][START_REF] Dal Cin | Seismic imaging of Late Miocene (Messinian) evaporites from Western Mediterranean back-arc basins[END_REF], in South Balearic basin [START_REF] Camerlenghi | Morphogenesis of the SW Balearic continental slope and adjacent abyssal plain, Western Mediterranean Sea[END_REF][START_REF] Dal Cin | Seismic imaging of Late Miocene (Messinian) evaporites from Western Mediterranean back-arc basins[END_REF][START_REF] Blondel | Image improvement of Late Miocene (Messinian) to Plio-Quaternary units in the Algero-Balearic basin[END_REF] or in the north Algerian margin (e.g. [START_REF] Déverchère | Active thrust faulting offshore Boumerdes, Algeria, and its relations to the 2003 Mw 6.9 earthquake[END_REF][START_REF] Domzig | Searching for the Africa-Eurasia Miocene boundary offshore western Algeria (MARADJA'03 cruise)[END_REF]Arab et al., 2016a). Following these works, the salt structures in the Western Mediterranean Sea are mainly the result of: i) multi-directional thin-skinned tectonics driven by the seaward dipping base of salt and the sedimentary loading given by thickness differences in the overburden, ii) the local geodynamic context which, via differences in subsalt setting, could influence the salt deformation, as shown by several authors in several other passive margins (e.g. [START_REF] Haddou | Subsalt exploration potential of the Moroccan salt basin[END_REF][START_REF] Evans | Base-salt relief controls salt-related deformation in the Outer Kwanza Basin, offshore Angola[END_REF][START_REF] Pichel | Base-salt relief controls salt-tectonic structural style, São Paulo Plateau, Santos Basin, Brazil[END_REF].

The flowing of salt along a detachment surface in passive margin is a well-known process [START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF][START_REF] Hudec | Regional restoration across the Kwanza Basin, Angola: Salt tectonics triggered by repeated uplift of a metastable passive margin[END_REF][START_REF] Jackson | Structural dynamics of salt systems[END_REF][START_REF] Schultz-Ela | Excursus on gravity gliding and gravity spreading[END_REF]) and causes three kinematically linked zone: i) an updip area of extension, ii) a mid-slope transition and a iii) downdip contraction areas, as also observed in the Gulf of Lion (Le Cann, 1987; Gorini,

1993; [START_REF] Gaullier | Diapirisme salifère et dynamique sédimentaire dans le bassin Liguro-Provençal. Données sismiques et modèles analogiques[END_REF]Dos Reis et al., 2005). The updip extension area is characterized by normal basinward-dipped faults, salt rollers and rollover strata and is considered to be coeval with the thrusting and buckling in the distal contraction domain [START_REF] Cobbold | Radial gravitational gliding on passive margins[END_REF]Marton et al., 2000, Cramez andJohnson, 2000;Tari et al., 2001;Brun andFort, 2004, 2011;[START_REF] Rowan | Gravity-driven fold belts on passive margins[END_REF]. Nevertheless, in the Gulf of Lion, the listric faults were activated only in the Early Pliocene, as evidenced by growth strata and rollover structures clearly visible above the Messinian deposits (Fig. 2a): the basinward-dipping normal faults in that proximal domain were activated only after the complete deposition of the UU, as highlighted by the constant thickness of this unit involved in the displacement. Conversely, in the deep basin, the difference of thicknesses and the onlaps in the Upper Unit (UU) (Fig. 2b) suggest a salt deformation that began with the deposition of this unit, still belonging to the Messinian Salinity Crisis [START_REF] Rowan | Salt tectonics at passive margins: Geology versus models-Discussion[END_REF]: the sliding postdates the deep deformation. It seems that early deformation in the deep basin has induced a space that allowed the salt to glide from the lower slope, leading to the listric fault formation. The Early Pliocene thin-skinned extension tectonics therefore appears here to be a consequence of the space created by the distal diapir formation.

Several authors [START_REF] Le Cann | Le diapirisme dans le bassin Liguro-Provençal (Méditerranée occidentale)[END_REF][START_REF] Pautot | Morphology and extension of the evaporitic structures of the Liguro-Provençal Basin: New Sea-Beam data[END_REF] observed a striking correlation between the OCT (Ocean-Continent Transition) limit and a variation in salt structures in Gulf of Lion, as shown in figure 3. [START_REF] Pautot | Morphology and extension of the evaporitic structures of the Liguro-Provençal Basin: New Sea-Beam data[END_REF][START_REF] Le Cann | Le diapirisme dans le bassin Liguro-Provençal (Méditerranée occidentale)[END_REF] claimed for the reactivation of rifting-involved faults which could influence the salt deformation and [START_REF] Maillard | Influence of differential compaction above basement steps on salt tectonics in the Ligurian-Provençal Basin, northwest Mediterranean[END_REF] for an influence of differential compaction of subsalt sediments given by basement steps filled by pre-Messinian sediments.

The Messinian salt system peculiarity and the coincidence observed in Gulf of Lion (Fig.

3) led us to extend the salt structures-crustal segmentation analysis on the global Western Mediterranean (Fig. 4).

We interpreted salt structures in Liguro-Provençal and Algerian basins, leaving aside the Alboran Sea due to the absence of Messinian halite (e.g. [START_REF] Couto | Lago Mare and the Messinian salinity crisis: evidence from the Alboran Sea (S. Spain)[END_REF] and the Ligurian basin due to lack of data (Fig. 1). We defined a nomenclature for regional salt morphologies (Fig. 4) in order to classify them in 5 groups sharing the same geometrical features. The classification allowed to directly compare the salt morphologies to the crustal segmentation and nature and then to regionally discuss the salt structures genesis and evolution. The classification (Fig. 4) is mainly based on geometric criteria, such as: shape, base diapir width, geometrical relationship with the overlying layers and associated dominant features, such as faults, minibasins [START_REF] Jackson | A glossary of salt tectonics[END_REF] or welds [START_REF] Jackson | Seismic recognition of salt welds in salt tectonics regimes. In Gulf of Mexico salt tectonics, associated processes and exploration potential[END_REF]. Although every salt and oceanic spreading. The salt is therefore not involved in any rifting-extension movement, as some authors claimed for instance in Gulf of Mexico (Hudec et al. 2013b). Therefore, in the Mediterranean Sea, the salt was deposited everywhere in the deep, already formed oceanic basins and lower slopes, onlapping the pre-salt sedimentary sequences. The lower slope (concomitant with the Listric salt domain) is characterized by a margin basinward tilting while the deep basin by a purely vertical subsidence, started just after the oceanic break-up [START_REF] Rabineau | Quantifying subsidence and isostatic readjustment using sedimentary paleomarkers, example from the Gulf of Lion[END_REF][START_REF] Leroux | Post-rift evolution of the Gulf of Lion margin tested by stratigraphic modelling[END_REF][START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF]. The vertical subsidence suggests an approximately constant initial salt thickness in all the deep basins, without regional differences given by variations in accommodation space during the deposition. Salt initial thickness is thus envisioned constant in all the deep basin, above a thick pre-salt sedimentary layer that cover all initial topographic variations, except for the margin edges, in the lower slope, where probably was thinner. The tilting in the slopes actually induced a well-developed thin-skinned tectonics, as previously described by different authors [START_REF] Gaullier | Diapirisme salifère et dynamique sédimentaire dans le bassin Liguro-Provençal. Données sismiques et modèles analogiques[END_REF]Dos Reis et al., 2005;[START_REF] Brun | Salt tectonics at passive margins: Geology versus models[END_REF]. Nevertheless, we have shown as the salt has started to deform during the Messinian while the listric faults in the margin were activated only in the Lower Pliocene, as a direct consequence of the deep basin deformation. Thin-skinned extension tectonics therefore appears to be an effect of the initial deep basin deformation, not the cause. The infra-Messinian deformation was active in all the deep basin, as also observed in the north Algerian [START_REF] Bouyahiaoui | Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean[END_REF] and western Sardinian margins and was already observed in the Levant basin [START_REF] Gvirtzman | Intense salt deformation in the Levant Basin in the middle of the Messinian Salinity Crisis[END_REF]. If, as we said, we envisioned a constant salt initial thickness and no salt translation at time, an imbalance of salt flux [START_REF] Pichel | Base-salt relief controls salt-tectonic structural style, São Paulo Plateau, Santos Basin, Brazil[END_REF][START_REF] Evans | Base-salt relief controls salt-related deformation in the Outer Kwanza Basin, offshore Angola[END_REF] which could have created accommodation for growth sedimentation and so early differential loading is to exclude. Another possible interpretation is an erosional phase infra-UU which could have created differential load in the early overburden, inducing an early salt deformation. An infra-UU unconformity named IES (Intermediate Erosion Surface) is observed in western Sardinian and south Balearic margin [START_REF] Lofi | Seismic Atlas of the Messinian Salinity Crisis markers in the Mediterranean Sea[END_REF][START_REF] Geletti | The Messinian Salinity Crisis: new seismic evidence in the West-Sardinian Margin and Eastern Sardo-Provençal Basin (West Mediterranean Sea)[END_REF] and in the intermediate-depth basins, such as Valencia and east Corsica basins [START_REF] Lofi | Seismic atlas of the "messinian salinity crisis[END_REF]. The IES has an erosional truncation character and divides the UU into two sub-units. It is tricky to understand if the erosional surface could be the cause or if it marks the end of the infra-Messinian deformation. In figure 2 the IES is not observed (probably due to the low resolution of the line) and the deeper sub-unit of the UU seems to go in onlap on the salt. The relation between the IES surface with respect the infra-UU salt deformation is therefore still doubtful.

Annexe 1.2

The aim of the work presented below is to make available and public the interpretation of seismic stratigraphic markers in the Western Mediterranean Sea. The work is designed by Daniel Aslanian and the interpretations are largely derived from the work of this thesis.

Significant help was given by Romain Pellen.

Abstract

The Western Mediterranean Sea is a natural laboratory to address questions about the formation and evolution of continental margins and the relationship between surface and deep processes. The evaporites deposited during the late Miocene's Messinian Salinity Crisis (MSC) strongly impact its sedimentological and geomorphological evolution. Hereafter, we present a

Brief dataset history

Since the 1960s the Western Mediterranean Sea has been exploited by reflection seismic surveys, both with academic and industrial objectives. Although some surveys are relatively old, new processing techniques have allowed a good improvement of quality. The results gave a great variability of available data, with strong differences in resolution and quality. In the Western Mediterranean area (Fig. 1), a first industrial and academic reflection seismic compilation was made by [START_REF] Mauffret | Étude géodynamique de la marge des îles Baléares[END_REF][START_REF] Gorini | Géodynamique d'une marge passive: le Golfe du Lion (Méditerranée occidentale[END_REF]) and Maillard, (1993), complemented by Bache, ( 2008), [START_REF] Garcia | The Catalan margin during the Messinian Salinity Crisis: Physiography, morphology and sedimentary record[END_REF][START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF][START_REF] Driussi | Evolution de la région Baléares (Méditerranée ocidentale) du Néogène à l'actuel: aspects géodynamiques et paléoenvironnementaux[END_REF] and [START_REF] Pellen | Géodynamique et impact de la crise d'érosion et de salinité Messinienne sur les transferts sédimentaires (bassins de Valence et Adriatique)[END_REF]. The last three aforementioned authors digitalized a dense seismic grid in the Valencia and Menorca basins as well as the Balearic Promontory. Over the years the dataset has grown, thanks to collaborations between several French and foreign institutes and industry, such as the GDR "Margins" (Groupement de Recherches 'Marges') followed by Action Marges, which had the objectives to better understand the processes that control the formation and evolution of continental margins (e.g. [START_REF] Berne | The Gulf of Lions: An overview of recent studies within the French'Margins' programme[END_REF].

Within this framework, we could undertake multidisciplinary studies through a collaboration between the University of Brest, Ifremer, Sorbonne University, University of Montpellier, University of Toulouse, University of Barcelona, Consejo Superior de Investigaciones Cientificas (CSIC), TOTAL, IFP Energies Nouvelles and Bureau de

Recherches Gélogiques et Minières (BRGM).

More recently, we added some new lines to the dataset coming from the Italian institutions thanks to the close collaboration with OGS (National Institute of Oceanography and Applied Geophysics) and the University of Trieste. To this date, this work provides the largest and most comprehensive stratigraphic markers compilation available to the scientific community across the Mediterranean Sea.

Stratigraphic markers presentation

This work provides the interpretation of several stratigraphic markers, below briefly described and referred (Fig. 2). We provide xyz files, where x is the longitude, y the latitude and z the depth in second twt. The coordinates are not projected and the datum/ellipsoid is the WGS84 (EPSG 4326).

The Top acoustic Basement is interpreted in all the geomorphological domains, from the shelf to the deep basin (Fig. 3). It coincides with the deepest continuous, high amplitude and

Authors' contribution:

This project was designed by DA and realised by MB with active participation of RP. The data organisation and setting up was made by JP. Gulf of Lion: the interpretation was made by MR, FB and EL during their PhD [START_REF] Rabineau | Un modèle géométrique et stratigraphique des séquences de dépôts quaternaires sur la marge du Golfe du Lion: enregistrement des cycles climatiques de 100 000 ans[END_REF][START_REF] Bache | Evolution Oligo Miocène des marges du micro océan Liguro-Provençal[END_REF][START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF] with the supervision and collaboration of MR, CG and DA.

Seismic interpretation for this data compilation

Liguro-Provençal basin: the interpretation was made by MB, EL, FB and RP during their PhD [START_REF] Bache | Evolution Oligo Miocène des marges du micro océan Liguro-Provençal[END_REF][START_REF] Leroux | Quantification des flux sédimentaires et de la subsidence du bassin Provençal[END_REF][START_REF] Pellen | Géodynamique et impact de la crise d'érosion et de salinité Messinienne sur les transferts sédimentaires (bassins de Valence et Adriatique)[END_REF] with the collaboration of MR, CG, DA and MM.

North-East Algerian margin: the interpretation was made by MB and RP during their PhD and Post-Doc, respectively, with the supervision and collaboration of MR, DA, MM and EL. The interpretation was complemented by digitalisation from the thesis of [START_REF] Arab | Analyse des systèmes pétroliers de l'offshore algérien oriental: Quantification, modélisation stratigraphique et thermique[END_REF].

Valencia and Menorca basins: the interpretation was made by RP during his thesis [START_REF] Pellen | Géodynamique et impact de la crise d'érosion et de salinité Messinienne sur les transferts sédimentaires (bassins de Valence et Adriatique)[END_REF] under the supervision of MR and DA. The Catalan margin was interpreted by MG Post-Doc [START_REF] Garcia | The Catalan margin during the Messinian Salinity Crisis: Physiography, morphology and sedimentary record[END_REF] with the collaboration of DA, MB and AM.

Western Sardinian margin: the interpretation was made by MB during his PhD with the collaboration and supervision of ADB, EL, MR, RP, MM and DA. The north Sardinian margin was supplemented by interpretation of AM.

Data organisation and supply

Alboran basin: refer to [START_REF] Couto | Lago Mare and the Messinian salinity crisis: evidence from the Alboran Sea (S. Spain)[END_REF] for the data source.

Algerian deep basin: AC provided part of the dataset. Refer to [START_REF] Leroux | Atlas of the stratigraphic markers in the western mediterranean with focus on the Messinian, Pliocene and Pleistocene of the Gulf of Lion[END_REF] for other data source.

ANNEXE 2. HEAT FLOW MEASUREMENTS, MODELS AND RHEOLOGY EXPERIMENT Annexe 2.1 -Surface heat flow measurements and sedimentary correction

In this first part of the Annexe-2 I show the details of the surface HF measurements acquired during the WMF2 survey. The sedimentary correction values and the velocity used for the timedepth conversion are also shown.

ANNEXE-2. HEAT FLOW MEASUREMENTS, MODELS AND RHEOLOGY EXPERIMENT

Annexe 2.2 -MARGE Annexe 2.2.1 -Principle of the thermo-kinematical model

Here, I explain in more detail the principles of the model, as referred in chapter 3. The model allows to investigate with a 2D finite elements model the basin and lithosphere evolution (Latil-Brun and Lucazeau, 1988;[START_REF] Lucazeau | Dynamic interactions between the Gulf of Guinea passive margin and the Congo River drainage basin: 2. Isostasy and uplift[END_REF][START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF][START_REF] Gernigon | A moderate melting model for the Vøring margin (Norway) based on structural observations and a thermo-kinematical modelling: Implication for the meaning of the lower crustal bodies[END_REF]. The mathematical approach can be find in [START_REF] Gernigon | A moderate melting model for the Vøring margin (Norway) based on structural observations and a thermo-kinematical modelling: Implication for the meaning of the lower crustal bodies[END_REF] and supplementary material of [START_REF] Lucazeau | Persistent thermal activity at the Eastern Gulf of Aden after continental break-up[END_REF]. As mentioned in chapter 3, it takes into account several second-order phenomena and lines of importance in the basin thermal evolution:

The continental lithosphere is divided into four layers with intrinsic properties, which are the upper, middle, lower crust and the upper mantle. Each layer has different properties (density, thermal conductivity, heat production, thickness, etc.) which can be modified by the operator.

The thermal conductivity generally decreases when temperature increases [START_REF] Birch | The thermal conductivity of rocks and its dependence upon temperature and composition[END_REF] but it may change for different rock types. In the model the relationship between thermal conductivity and temperature comes from Wells (1980). The sediments thermal conductivities are lower than that of the basement, because of water or air that can fill the pore and by matrix intrinsic conductivity, and they are predicted by mineralogy (Brigaud and Vasseur, 1989;Brigaud et al., 1990). Likewise, the radiogenic heat production depends on radioelement concentrations and is calculated from the lithology chosen by the operator.

Although the heat production in upper mantle is still debated (e.g. Pollack and Chapman, 1977;van Den Berg et al., 2001;Mareschal and Jaupart, 2013;Korenaga, 2017), the model take into account the [START_REF] Schatz | Thermal conductivity of earth materials at high temperatures[END_REF] work, which provide a relatively higher uppermost mantle radiative contribution. Thermal expansion or contraction is also included in the model and is related on temperature variation with a fixed coefficient of thermal expansion.

The mesh can include five to fifteen layers in the sediments and in the crust and 50 to 200 columns (Fig. 3.15). The mesh and the nodes change during the evolution of the rift, according to the kinematical field of deformation. During the oceanic accretion, new elements are added and the temperature evolution will depend to the original plate model of [START_REF] Parsons | An analysis of the variation of ocean floor bathymetry and heat flow with age[END_REF].

As previously described, sediments represent an insulating blanket on the lithosphere and affect the thermal cooling and the subsidence of lithosphere. The model takes into account the sediment properties, as the compaction increasing with depth (Sclater and Christie, 1980).

ANNEXE-2. HEAT FLOW MEASUREMENTS, MODELS AND RHEOLOGY EXPERIMENT

463

The model also allows to choose between local and regional isostasy. In the case of local isostasy (Airy), the lithostatic pressure at a certain depth below the lithosphere bottom is same as that of the initial lithosphere. When the system undergoes density variations, subsidence or uplift accommodates the differences. In the case of regional isostasy, the system depends to a thin plate elastic model and its deflection is influenced by its flexural rigidity. The model allows to change the flexural rigidity values, in order to change the EET (equivalent elastic thickness).

The operator can manually change the rigidity of the plate or change the temperature to which the value is driven (for instance 450 °C after Reemst and Cloething, 2000). The final surface topography undergoes to internal load which are recover by plastic necking (Kooi et al., 1992).

The restoring forces, in order to reach the regional isostatic equilibrium, are driven by the depth of necking, a virtual equilibrium level in the lithosphere. The restoring force is proportional with the subsidence related to necking and the subsidence related to Airy model. The depth of necking, which is possible to modify in the model, controls the subsidence and the thinning of the lithosphere. Generally, for a deeper depth of necking the crustal lithosphere will be thicker while for a shallower depth of necking the thinning will be greater.

The deformation in the lithosphere corresponds to pure shear stretching model as defined by [START_REF] Mckenzie | Some remarks on the development of sedimentary basins[END_REF]. It is obtained by an iterative process fitting the present-day bathymetry with an RMS error in the order of 100 meters and is the stretching parameter defined for each column (β). The model allows to modify the (β) factor along the profile and between crust and mantle, in order to impose stretching differences in the two domains. The present-day bathymetry constrains the determination of the (β) distribution.

Some authors claimed a mantle partial melting if the stretching and upwelling are rapid enough [START_REF] Mckenzie | The volume and composition of melt generated by extension of the lithosphere[END_REF][START_REF] Wilson | Magmatism and the geodynamics of basin formation[END_REF]. The pressure in the lithosphere can then fall below the melt solidus and induce the formation of melt, which will rise up and settle under the Moho because of lower crustal density. The mesh geometry will change, according to how much magma is produced, by adding layers at the base of the crust into which the melt will settle. Since the model cannot predict the age of underplating, it assumes that there are no erupted magmatic parts in pre-rifting. The heat input from the magma is then calculated (Lachenbruch et al., 1985) related to the advection of heat from mantle and from the release of latent heat when the magma is cooling below the solidus.

Annexe 2.3 -PetroMod model

We used PetroMod 1D (free version available online) to look at the temperature difference with the previously proposed models (MARGE) and to get a range of pressures below the salt deposit, which might have an influence, although not yet known (e.g. [START_REF] Dale | The Messinian Salinity Crisis as a trigger for high pore pressure development in the Western Mediterranean[END_REF], on the deformation.

The PetroMod ® software package fully integrates seismic, stratigraphic and geological interpretations into multi-dimensional simulations of thermal, fluid-flow and petroleum migration history in sedimentary basins. PetroMod ® is primarily used in hydrocarbon exploration, but several authors used it for research purpose (e.g. [START_REF] Grassmann | pT-effects of Pleistocene glacial periods on permafrost, gas hydrate stability zones and reservoir of the Mittelplate oil field, northern Germany[END_REF][START_REF] Schenk | Petroleum system modeling of northern Alaska[END_REF][START_REF] He | A basin modeling and organic geochemistry study in the Vallecitos syncline, San Joaquin Basin, California[END_REF]. Without going into the mathematical details behind the model (a full summary can be found in [START_REF] Hantschel | Fundamentals of basin and petroleum systems modeling[END_REF], the model is similar to MARGE but allows less control over the choice of input parameters. PetroMod main focus is the prediction of timing and location of petroleum generation, expulsion and migration processes (e.g. [START_REF] Pinero | 3-D numerical modelling of methane hydrate accumulations using PetroMod[END_REF]Kroeger et al., 2015). Regarding heat flow, PetroMod uses the model of [START_REF] Mckenzie | Some remarks on the development of sedimentary basins[END_REF] to predict and reconstruct the thermal regime of a passive margin. The HF will therefore be higher with higher crustal stretching (Beta factor) and subsequently tend to decrease as a result of post break-up lithospheric cooling. Multiple stretching factors were introduced in PetroMod, following [START_REF] Hellinger | Some comments on two-layer extensional models for the evolution of sedimentary basins[END_REF] and [START_REF] Royden | Rifting process and thermal evolution of the continental margin of eastern Canada determined from subsidence curves[END_REF] proposed lithology to be entered, corresponding to certain values of thermal conductivity, porosity, heat production etc that the model calculates itself. The point on which the analysis was carried out corresponds to the Anticlinal salt domain, where the salt is little deformed and the sedimentary sequence is complete (Fig. 5.13). The crust in this zone is transitional, interpreted as exhumed lower continental crust or exhumed mantle [START_REF] Moulin | Deep crustal structure across a young passive margin from wide-angle and reflection seismic data (The SARDINIA Experiment)-I. Gulf of Lion's margin[END_REF][START_REF] Jolivet | Continental breakup and the dynamics of rifting in back-arc basins: The Gulf of Lion margin[END_REF]. Paleo-water depth, seafloor temperature and present-day surface heat flow are the required boundary conditions. The heat flow is 52.5 mW/m2, measured during the WMF1 survey [START_REF] Poort | Heat flow in the Western Mediterranean: Thermal anomalies on the margins, the seafloor and the transfer zones[END_REF].

PetroMod offers a good visualisation of outputs, with the possibility to change visualisation parameters including ages and a number of characteristics for each sedimentary layer, such as sedimentation rate, overpressures and temperature.

The two plots below (Fig. 2.3) show the variation of temperature with depth at two age steps: 0 Ma (on the left) and 5 Ma (on the right). At the present-day situation the salt has a temperature of around 90-100 °C and at 5.9 Ma around 30 °C. The halite high thermal conductivity is the cause to the lower temperature increase within the salt deposits. The colours in the plots show overpressures in the sedimentary column. The salt seals the fluids below and thus increasing the pressure (also according to Dan et al., 2021). Note how the overpressures are stronger at 0 Ma than at 5 Ma. The temperatures obtained with PetroMod are very similar to those obtained with MARGE, shown in the previous paragraph. As the case of MARGE The samples used for the tests belong to the Messinian Salinity Crisis deposits (from Véronique Gardien collection). They come from inland outcrops (Realmonte Mine, Sicily)

wherein the record of the crisis is preserved. The Messinian Realmonte salt is part of the Caltanissetta Basin salt deposits. Some of these contain potash layers mainly represented by kainite; in a few, carnallite, bishofite, and sylvite are present, whereas only one contains kieserite and langbeinite (Decima and Wezel, 1971;[START_REF] Lugli | Giant polygons in the Realmonte Mine (Agrigento, Sicily); evidence for the desiccation of a Messinian halite basin[END_REF]. The samples used for the tests come from unit C, described as white halite layers separated by grey mud laminae [START_REF] Lugli | Giant polygons in the Realmonte Mine (Agrigento, Sicily); evidence for the desiccation of a Messinian halite basin[END_REF] Annexe 2.4.

-Description of experiments

The first experiment was conducted with clay, in order to understand the sensibility of the sensor. The clay specimen came from the petrography laboratory. Initially, we had problems with the software (DitelCapture) that recorded the experience, so we took the measures every 5 minutes. The weight on the sample was of 1.4 Kg and the temperature fixed at 100°C. We observed a constant extension since the start of the experience which has stopped with a maximum deformation of 0.3%. When the oven is turned off, the sample length returned to the initial condition. We interpret the behaviour just described as elastic comportment due to the thermal expansion. For the halite, even if we calculated the extension in only one direction, we expect an isotropic deformation, involving a change in volume in all directions. Moreover, it is clearly showed that the differential stress necessary to reach a plastic behaviour is, at least, about 7

MPa, too high for our experimental apparatus. Other authors (see chapter 2) claim that beyond a pressure value (over than 5 MPa) the thermal expansion is countered by stress, which avoids the extension of the halite. [START_REF] Peach | Effect of confining pressure on dilatation, recrystallization, and flow of rock salt at 150 C[END_REF] found the transition from net dilatation at 3 MPa pressure to increasing compaction at pressures of 6.5 MPa and above. Therefore, it is deductible that the Messinian halite, deposited under hundreds of meters of sediments, is not affected by the phenomenon of thermal expansion.