François Bache
email: francois.bache@santos.com.

Julien Gargani

Jean-Pierre Suc

Christian Gorini

Marina Rabineau

Speranta-Maria Popescu

Estelle Leroux

Damien Do Couto

Jean-Loup Rubino

Jean-Louis Olivet

Gwenaël Jouannic

Georges Clauzon

Antonio Tadeu

Dos Reis

Daniel Aslanian

Messinian evaporite deposition during sea level rise in the Gulf of Lions (Western Mediterranean)

Keywords: Messinian, Mediterranean, Gulf of Lions, Seismic stratigraphy, Evaporites

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

The largest known sea level fall on the Earth resulted from the isolation of the Mediterranean Sea from the Atlantic Ocean at the end of the Miocene. This isolation, associated with a significant evaporation rate, led to the deposition of a series of thick evaporites in the Mediterranean basins (Hsü et al., 1973a) and intense subaerial erosion at its periphery [START_REF] Barber | Messinian subaerial erosion of the Proto-Nile delta[END_REF][START_REF] Barr | Late Tertiary channel system in Northern Lybia and its implications on Mediterranean sea level changes[END_REF][START_REF] Chumakov | Pliocene and Pleistocene deposits of the Nile Valley in Nubia and Upper Egypt[END_REF]Clauzon, 1973[START_REF] Clauzon | The Messinian Var canyon (Provence, Southern France) -Paleogeographic implications[END_REF][START_REF] Clauzon | Le canyon messinien du Rhône : une preuve décisive du "dessicated deepbasin model[END_REF][START_REF] Ryan | The nature and distribution of Messinian erosional surfaceindication of a several kilometer-deep Mediterranean in the Miocene[END_REF][START_REF] Savoye | The Messinian event on the margin of the Mediterranean Sea in the Nice area, southern France[END_REF]. The "desiccated, deep basin" model (Hsü, 1972b;[START_REF] Cita | Mediterranean evaporite: paleontological arguments for a deep-basin desiccation model[END_REF]Hsü et al., 1973a;[START_REF] Ryan | Geodynamic implications of the Messinian crisis of salinity[END_REF] explains this depositional event, known as the Messinian Salinity Crisis (MSC), by a high evaporation rate and sea-level drop of around 1500 m in a deep Mediterranean basin1 [START_REF] Cita | Mediterranean evaporite: paleontological arguments for a deep-basin desiccation model[END_REF][START_REF] Hsü | The desiccated deep-basin model for the Messinian events[END_REF]Hsü et al., 1973b;[START_REF] Hsü | Genesis of the Thethys and the Mediterranean[END_REF][START_REF] Montadert | Messinian event : seismic evidence[END_REF][START_REF] Stampfli | Messinian palaeorelief from a 3-D seismic survey in the Tarraco concession area (Spanish Mediterranean Sea)[END_REF]. Three arguments have been used to strengthen this theory: the tidal nature of the evaporites recovered in all the major basins (Hsü, 1972a, b); the pan-Mediterranean distribution of seismic reflector M that was calibrated with the abrupt contact between the evaporites and the overlying Early Pliocene marls [START_REF] Ryan | Geodynamic implications of the Messinian crisis of salinity[END_REF], and the open marine, deep bathyal nature of the pelagic sediments immediately superposed on the evaporites [START_REF] Cita | Mediterranean evaporite: paleontological arguments for a deep-basin desiccation model[END_REF]. This argument was also supported from studies on products of the marginal erosion coeval with the deep basin evaporites all around the Mediterranean [START_REF] Barr | Late Tertiary channel system in Northern Lybia and its implications on Mediterranean sea level changes[END_REF][START_REF] Chumakov | Pliocene and Pleistocene deposits of the Nile Valley in Nubia and Upper Egypt[END_REF]Clauzon, 1973[START_REF] Clauzon | L'hypothèse eustatique et le creusement prépliocène de la vallée du Rhône[END_REF]Cita and Ryan, 1978;[START_REF] Clauzon | The Messinian Var canyon (Provence, Southern France) -Paleogeographic implications[END_REF][START_REF] Rizzini | Stratigraphy and sedimentation of a Neogen-Quaternary section in the Nile delta aera (A.R.E.)[END_REF][START_REF] Ryan | The nature and distribution of Messinian erosional surfaceindication of a several kilometer-deep Mediterranean in the Miocene[END_REF][START_REF] Clauzon | Le canyon messinien de la Durance (Provence, France): Une preuve paléogéographique du bassin profond de dessiccation[END_REF][START_REF] Barber | Messinian subaerial erosion of the Proto-Nile delta[END_REF][START_REF] Clauzon | Le canyon messinien du Rhône : une preuve décisive du "dessicated deepbasin model[END_REF]. In the 1990s, the peripheral Mediterranean basins accessible to field studies were used to constrain the timing of the MSC [START_REF] Hilgen | A critical re-evaluation of the Miocene-Pliocene boundary as defined in Mediterranean[END_REF][START_REF] Gautier | Age and duration of the messinian salinity crisis[END_REF]Krijgsman et al., 1999a;[START_REF] Van Couvering | The base of the Zanclean Stage and of the Pliocene Series[END_REF][START_REF] Lourens | The Neogene Period[END_REF]. No physical link has been established between these basins and offshore Mediterranean deep basins and evaporites from the deep basins have not been fully sampled or accurately dated. Therefore the timing and the environment of evaporites deposition in the Mediterranean deep basins is still uncertain and controversial. Two groups of conceptual scenarios are usually referred to (Fig. 1): one that favours a synchronous deposition (at 5.96 Ma) of the first evaporites in all the Mediterranean basins before the huge sea level fall (Krijgsman et al., 1999a;[START_REF] Rouchy | The Messinian salinity crisis in the Mediterranean basin: A reassessment of the data and an integrated scenario[END_REF], and the second that favours a diachronous deposition of the evaporites through two phases of desiccation [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] Clauzon | Alternate interpretation of the Messinian salinity crisis: controversy resolved ?[END_REF]CIESM, 2008). According to the second scenario, peripheral basins experienced deposition of evaporites from 5.971 Ma [START_REF] Manzi | Age refinement of the Messinian salinity crisis onset in the Mediterranean[END_REF] to 5.600 Ma after an initial sea level fall (~150 m, phase 1): in this paper, we call these the "1 st step evaporites". Then, from 5.600 to 5.460 Ma [START_REF] Bache | A two-step process for the reflooding of the Mediterranean Basin after the Messinian Salinity Crisis[END_REF] the Mediterranean deep basins experienced a major sea-level fall (1500 m) and deposition of evaporites in almost completely desiccated environments. In this paper we call them the "2 nd step evaporites". During this second phase (the "peak of the MSC"), the "1 st step evaporites" were partly eroded and reworked. Interpretation of the environmental setting of some basins is also controversial. For example, the Sicilian Caltanissetta Basin has been interpreted as either a deep basin that was subsequently uplifted (Hsü et al., 1973a;Krijgsman et al., 1999a;[START_REF] Rouchy | The Messinian salinity crisis in the Mediterranean basin: A reassessment of the data and an integrated scenario[END_REF][START_REF] Roveri | The Messinian salinity crisis: Looking for a new paradigm? Palaeogeography[END_REF][START_REF] Krijgsman | Depositional environments of the Mediterranean "Lower Evaporites" of the Messinian salinity crisis: Constraints from quantitative analyses[END_REF], containing only "2 nd step evaporites", or as a peripheral basin [START_REF] Brolsma | Lithostratigraphy and foraminiferal assemblages of the Miocene-Pliocene transitional strata of Capo Rossello and Eraclea Minoa (Sicily, 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] Clauzon | Alternate interpretation of the Messinian salinity crisis: controversy resolved ?[END_REF][START_REF] Popescu | Galeacysta etrusca complex, dinoflagellate cyst marker of Paratethyan influxes into the Mediterranean Sea before and after the peak of the Messinian Salinity Crisis[END_REF] containing the "1 st step evaporites". Following the former interpretation, [START_REF] Roveri | The Messinian salinity crisis: Looking for a new paradigm? Palaeogeography[END_REF] questioned the existence of a significant (>1000 m) Messinian sea level drawdown and argued in favour of widespread tectonic movements to explain observations all around the Mediterranean. On the other hand Roveri et al. (2008a;2008b) opted for the occurrence of the two steps of evaporites in Sicily which includes peripheral basins (Calatafimi-Ciminna, Belice, Licodia) and an intermediate basin (Caltanissetta). In order to clarify the events that affected the Mediterranean basins, we describe the marginal transition from the Gulf of Lions shelf to the Provence deep Basin. Stratal relationships between the subaerial erosional surface, clastic deposits generated by this erosion and evaporites allow us to discuss the mode of deposition of the "2 nd step evaporites" and to test a refined scenario with a numerical model.

Data and method

The Gulf of Lions (Fig. 2) is weakly deformed by Pliocene and Quaternary tectonics and characterised by a relatively high subsidence rate which continuously created accommodation space [START_REF] Steckler | The Gulf of Lion: subsidence of a young continental margin[END_REF][START_REF] Bessis | Some remarks on the study of subsidence of sedimentary basins. Application to the Gulf of Lions margin (Western Mediterranean)[END_REF][START_REF] Burrus | Review of geodynamic models for extensional basins; the paradox of stretching in the Gulf of Lions (northwest Mediterranean)[END_REF][START_REF] Rabineau | Sedimentary sequences in the Gulf of Lion: a record of 100,000 years climatic cycles[END_REF][START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF]. This configuration, together with the availability of a large set of seismic reflection data (Fig. 2), has allowed accurate descriptions of the relationship between the Messinian halite and the sedimentary units of the Gulf of Lions margin [START_REF] Gorini | Géodynamique d'une marge passive: le Golfe du Lion (Méditerranée Occidentale)[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] Bache | Evolution Oligo-Miocène des marges du micro océan Liguro Provençal[END_REF][START_REF] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF]. In this study, conventional and high-resolution seismic reflection data are reviewed and interpreted using the principles of seismic stratigraphy [START_REF] Vail | Seismic stratigraphy and global changes of sea-level. Seismic stratigraphy-applications to hydrocarbon exploration[END_REF]. The extensive coverage of seismic data enabled an integrated seismic stratigraphy to be developed, with seismic unit identification based on the configuration of seismic reflectors, including reflector continuity and termination. Interpretation and correlation of seismic reflectors has been tied to biostratigraphic and lithostratigraphic data from eleven hydrocarbon exploration wells that sampled Miocene and younger sedimentary cover. Seismic two-way travel-time (TWT) has generally been tied to formation tops in wells using velocities from sonic logs. Data used for this study and time-depth relationships are summarised in Supplementary Figures 1 and2. We also used observations from dive 72 from the submersible Cyana (with Syledis positioning) during cruise MONICYA in 1989 on the Suroit vessel. Dive 72 was carried out along the western slope of the Cirque Marcel, where the Quaternary submarine erosion exposes a section through older rocks (Savoye and Piper, 1991: fig. 9). Here we present new complementary observations to those already published by [START_REF] Savoye | The Messinian event on the margin of the Mediterranean Sea in the Nice area, southern France[END_REF]. Finally a "water-budget" numerical model is used to test if our scenario of the MSC is reliable under realistic hydro-climatic conditions. The modelling method has been developed in several studies [START_REF] Blanc | Of sills and straits: a quantitaive assessment of the Messinian Salinity Crisis[END_REF][START_REF] Meijer | A quantitative analysis of the desiccation and re-filling of the Mediterranean during the Messinian Salinity Crisis[END_REF][START_REF] Blanc | Improved modelling of the Messinian Salinity Crisis and conceptual implications[END_REF][START_REF] Meijer | A box model of the blocked-outflow scenario for the Messinian Salinity Crisis[END_REF][START_REF] Gargani | Mediterranean Sea level variations during the Messinian salinity crisis[END_REF][START_REF] Gargani | Evaporite accumulation during the Messinian Salinity Crisis: the Suez Rift case[END_REF] and details are also reported in the "numerical model" section. Atlantic sea water inflow, river discharge and rainfall are taken into account with our observations and counterbalanced by the rate of water evaporation. The evaporation minus precipitation (E-P) value used in the model to produce results compatible with our observations and interpretations is discussed and compared with present day values.

Review of previous observations

Here, we review existing observations and interpretations related to the MSC in the Gulf of Lions. We use a new, non-interpretative, naming convention for seismic units and unconformities, which can be compared to existing nomenclature in Supplementary Figure 3. Six seismic units (named U1 to U6 in this study) bounded by unconformities (S1 to S4) can be differentiated (Fig. 3). S2, a major unconformity at the transition between synrift and postrift deposits [START_REF] Guennoc | Histoire géologique du Golfe du Lion et cartographie du rift oligo-aquitanien et de la surface messinienne[END_REF][START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF], marks the lower boundary of this study.

Seismic unit U3 overlies S2 and is characterised by parallel and continuous reflectors that prograde with an offlap break located approximately below the present-day slope (Figs. 3 and4). U3 is commonly considered as a wide Aquitanian to Tortonian prograding shelf based on seismic interpretations [START_REF] Guennoc | Histoire géologique du Golfe du Lion et cartographie du rift oligo-aquitanien et de la surface messinienne[END_REF][START_REF] Bache | Evolution of rifted continental margins: the case of the Gulf of Lions (Western Mediterranean Basin)[END_REF] and benthic and planktonic foraminifers found at wells (Fig. 5) [START_REF] Cravatte | Les sondages du Golfe du Lion: Stratigraphie, Sédimentologie, Notes et Mémoires n°11[END_REF][START_REF] Guennoc | Histoire géologique du Golfe du Lion et cartographie du rift oligo-aquitanien et de la surface messinienne[END_REF]. U3 is locally deformed in the western part of the Gulf of Lions where faults and roll-over tilting are observed [START_REF] Mauffret | Structural geometry in the eastern Pyrenees and western Gulf of Lion (Western Mediterranean)[END_REF][START_REF] Gorini | The Late Messinian salinity crisis and Late Miocene tectonism : interaction and consequences on the physiography and post-rift evolution of the Gulf of Lions margin[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]. U3 is regionally truncated by two distinct unconformities, S3 and S4 (Figs. 3 and4). Unconformity S3 is inclined (~2.5°) toward the basin and has been mapped in detail with high resolution and conventional seismic reflection data [START_REF] Lofi | Evidence for pre-messinian submarine canyons on the Gulf of Lions slope (Western Mediterranean)[END_REF][START_REF] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF]. The surface truncates the prograding reflectors of U3 and is made of two major incisions (up to 1500 m) filled by seismic unit U4 (Figs. 2, 6 and7). Seismic unit U4 is composed of 3 sub-units separated by minor unconformities (see [START_REF] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF]Lofi and[START_REF] Lofi | Evidence for pre-messinian submarine canyons on the Gulf of Lions slope (Western Mediterranean)[END_REF]. U4a and U4b are characterised by clinoforms that dip steeply basinward and extend beneath U5 (Figs. 8 and9). U4a is between 2424 and 2997 m in Autan 1 and described as undetermined Middle to Upper Miocene calcareous shale (Fig. 5; [START_REF] Cravatte | Les sondages du Golfe du Lion: Stratigraphie, Sédimentologie, Notes et Mémoires n°11[END_REF]. U4b is between 3703 and 4650 m in well GLP 2 and described as Middle to Upper? Miocene (Langhian to Tortonian) calcareous shale (Figs.5 and 10;[START_REF] Brun | Sondage Golfe du Lion profond n°2 GLP2, France, études de laboratoire[END_REF]. U4c is characterised by a chaotic high-amplitude seismic facies passing laterally to the upper part of U5 [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] Lofi | Seismic atlas of the Messinian salinity crisis markers in the offshore Mediterranean domain[END_REF] and has never been drilled. Despite the sampling of U4a and U4b by Autan 1 and GLP 2 wells (Figs. 5,6,10 and 11), two conflicting interpretations for their age and for the age of their basal unconformity S3 have been proposed. One interpretation gives an age between 16.4 Ma and 5.6 Ma for the deposition of U4a and U4b, i.e. before the peak of the MSC [START_REF] Lofi | Evidence for pre-messinian submarine canyons on the Gulf of Lions slope (Western Mediterranean)[END_REF]. The other interpretation links S3, U4a and U4b with the main MSC sea level fall at 5.6 Ma [START_REF] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF]. U4c is classically interpreted as resulting from margin erosion during the peak of the MSC [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] Lofi | Evidence for pre-messinian submarine canyons on the Gulf of Lions slope (Western Mediterranean)[END_REF][START_REF] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF]. Interpretations of S3, U4a and U4b and consequences for the MSC will be developed in the "Refining our scenario for the peak of the MSC" section. S4 is characterised by two distinct morphologies. S4rough is a rough surface that truncates U3 on the shelf [START_REF] Ryan | The nature and distribution of Messinian erosional surfaceindication of a several kilometer-deep Mediterranean in the Miocene[END_REF][START_REF] Gennesseaux | Le Golfe du Lion et le Paléo-Rhône messinien[END_REF][START_REF] Lefebvre | Evolution morphologique et structurale du Golfe du Lion. Essai de traitement statistique des données[END_REF][START_REF] Gorini | Géodynamique d'une marge passive: le Golfe du Lion (Méditerranée Occidentale)[END_REF][START_REF] Guennoc | Histoire géologique du Golfe du Lion et cartographie du rift oligo-aquitanien et de la surface messinienne[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] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF]. Mapping reveals a pattern of up to 5 th order dendritic drainage with two main systems (Fig. 2) [START_REF] Gennesseaux | Le Golfe du Lion et le Paléo-Rhône messinien[END_REF][START_REF] Guennoc | Histoire géologique du Golfe du Lion et cartographie du rift oligo-aquitanien et de la surface messinienne[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] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF]. The two systems have been mapped upstream in the Languedoc-Roussillon region and in the Rhône Valley where erosion is observed up to at least 350 km from the present coast [START_REF] Clauzon | The Messinian Var canyon (Provence, Southern France) -Paleogeographic implications[END_REF][START_REF] Clauzon | Le canyon messinien de la Durance (Provence, France): Une preuve paléogéographique du bassin profond de dessiccation[END_REF](Clauzon, , 1982a)). Boreholes Tramontane 1, Calmar 1 and Mistral 1 show that S4rough truncates Upper Miocene sediments (U3) and is covered by sediments of the earliest stage of the Pliocene (U6) (Fig. 5) [START_REF] Cravatte | Les sondages du Golfe du Lion: Stratigraphie, Sédimentologie, Notes et Mémoires n°11[END_REF][START_REF] Guennoc | Histoire géologique du Golfe du Lion et cartographie du rift oligo-aquitanien et de la surface messinienne[END_REF]. S4rough is commonly interpreted as a subaerial erosional surface (the Messinian Erosional Surface or Margin Erosion Surface, MES) sculpted during the main MSC sea level fall [START_REF] Ryan | The nature and distribution of Messinian erosional surfaceindication of a several kilometer-deep Mediterranean in the Miocene[END_REF][START_REF] Guennoc | Histoire géologique du Golfe du Lion et cartographie du rift oligo-aquitanien et de la surface messinienne[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] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF]. S4rough gives way basinward to a planar and smooth morphology (S4smooth) that is locally conformable with U3 but that is also locally erosional as it truncates U4 (Figs. 3 and 6 to 8). The transition between S4rough and S4smooth lies at a constant two-way traveltime depth of 1.6 seconds over most of the shelf [START_REF] Bache | The 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 Basin after the Messinian Salinity Crisis[END_REF]. This difference of morphology has been explained either by retrogressive erosion during a MSC relative sea level fall [START_REF] Lofi | Erosional processes and paleo-environmental changes in the Western Gulf of Lions (SW France) during the Messinian Salinity Crisis[END_REF] or by a two-step reflooding process ending the MSC [START_REF] Bache | A two-step process for the reflooding of the Mediterranean Basin after the Messinian Salinity Crisis[END_REF]. In this later interpretation, S4smooth represents a transgressive ravinement surface created during a first step of reflooding and S4rough represents a subaerial surface (i.e. the MES) preserved from wave erosion after a sudden acceleration of the reflooding (rapid enough to prevent wave abrasion). The preserved shoreline at the point where S4smooth (wave cut surface) meets the S4rough (subaerial erosion) is thought to represent the shoreline or a zero sea level marker just before the final rapid reflooding [START_REF] Bache | A two-step process for the reflooding of the Mediterranean Basin after the Messinian Salinity Crisis[END_REF]. Seismic unit U5 is composed of 3 sub-units (U5a, U5b and U5c). U5a is a 1500 m thick unit characterised by continuous parallel high-amplitude reflectors (Figs. 3,8 and 12) [START_REF] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF]. The lower part of U5a shows onlap terminations on U4b (Figs. 3,8 and 12, see also Supplementary Figure 6). Its upper part has been described as a lateral equivalent of the chaotic sub-unit U4c [START_REF] Lofi | Erosional processes and paleo-environmental changes in the Western Gulf of Lions (SW France) during the Messinian Salinity Crisis[END_REF]. U5b is a transparent seismic facies characterised by domes structures and U5c is made of a group of parallel and relatively continuous reflectors that onlap landward onto the top of U4 (Figs. 3 and8). U5a (or its upper part), U5b and U5c have classically been interpreted as the three components of the "2 nd step Evaporites" (Lower Evaporites, Salt, Upper Evaporites) of the MSC in the Mediterranean deep basins [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] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF]. The "massive salt" (U5b) is the most common facies of the Messinian in the Gulf of Lions deep basin. Domes were formed after the Early Pliocene and during the deposition of the Pliocene and Quaternary turbidites (Dos [START_REF] Reis | Implications of salt-sediment interactions for the architecture of the Gulf of Lions deep-water sedimentary systems, western Mediterranean[END_REF]. The "Upper Evaporites" (U5c) is the only member of the trilogy that has been drilled (Hsü et al., 1973b). It is made-up of intercalated beds of anhydrite and clay [START_REF] Ryan | Initial Reports of the Deep Sea Drilling Project[END_REF] and has been deformed by creeping and sliding of the underlying salt and by listric faulting [START_REF] Reis | Implications of salt-sediment interactions for the architecture of the Gulf of Lions deep-water sedimentary systems, western Mediterranean[END_REF]. Either the upper part of U5a [START_REF] Montadert | Messinian event : seismic evidence[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] or the entire sub-unit [START_REF] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF] have been interpreted as the "Lower Evaporites" (probably intercalated with detritus from the margin erosion) but have never been drilled so that their lithology is still unknown. Seismic unit U6 is observed in the entire region and lies above U3, U4 or U5 (Figs. 3 and8). This unit, running from Lower Pliocene to Quaternary (Fig. 5, [START_REF] Cravatte | Les sondages du Golfe du Lion: Stratigraphie, Sédimentologie, Notes et Mémoires n°11[END_REF], shows prograding sediments downlapping directly onto S4rough is interpreted as an overall regressive sequence characterised by the reconstruction of shelf-slope geometries [START_REF] Lofi | Plio-Quaternary prograding clinoform wedges of the western Gulf of Lion continental margin (NW Mediterranean) after the Messinian salinity crisis[END_REF][START_REF] Rabineau | Sedimentary sequences in the Gulf of Lion: a record of 100,000 years climatic cycles[END_REF]. The basal geometric configuration of U6 (downlaps on S4rough and absence of transgressive deposits) has been interpreted as the consequence of a very rapid reflooding at the end of the MSC [START_REF] Lofi | Plio-Quaternary prograding clinoform wedges of the western Gulf of Lion continental margin (NW Mediterranean) after the Messinian salinity crisis[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]. This rapid reflooding is also suggested by a sharp contact between the Messinian "2 nd step evaporites" and Zanclean mudrocks drilled in the Western Mediterranean Basin during DSDP expeditions (Cita et al., 1978). Onshore, this contact corresponds to the prograding sedimentary filling of widely distributed Gilbert-type fan deltas within the Zanclean rias without any onlapping transgressive parasequence [START_REF] Clauzon | Restitution de l'évolution géodynamique néogène du bassin du Roussillon et de l'unité adjacente des Corbières d'après les données écostratigraphiques et paléogéographiques[END_REF].

New observations

We provide new key observations and detail stratal relationship between U3, U4 and U5, together with a critical review of well data information. These observations are critical for interpreting the mode of deposition of the Messinian evaporites.

Transition between U3 and U4 (S3)

Previous analyses of borehole data concluded an Aquitanian to Tortonian age for U3 (Tramontane 1, Mistral 1, Calmar 1) and a Langhian to Tortonian age for U4 (GLP 2, Autan 1), suggesting that part of these units may have been deposited contemporaneously (Fig. 5). However, the presence of a major unconformity between the two seismic units (S3) indicates that U4 is younger than U3 (Figs. 6 and7). U3 is made of parallel and continuous strata easy to follow and correlate on seismic data, all wells give a general agreement on its Miocene age and marine depositional environment. No major hiatuses or erosion can be observed on the seismic data and strata show a general agradationnal stacking pattern with no evidence of reworking (Figs. 3 and4). Seismic horizons within U3 therefore provide characteristic age markers that can be used to constrain the age of U4. We have interpreted five horizons within U3 (H1 to H5 on figures) that are tied to boreholes (Figs. 3 to 6). All these horizons can be followed towards the basin below S4; H1 to H5 are therefore older than U4. We can then assume that the age of the shallowest horizon (H5) also corresponds to the maximum age for U4 deposition. H5 intersects three wells at the exact position of a clear change in depositional environment corresponding to a regression (from slope or shelf to littoral facies in Mistral 1) or just above it (in Tramontane 1 and Calmar 1 boreholes) (Fig. 5). In Tramontane 1 and Mistral 1 boreholes the change, respectively located at 1540 and 1675 m depth, also corresponds to a clear regression with a transition from marine to littoral conditions (Fig. 5; [START_REF] Cravatte | Les sondages du Golfe du Lion: Stratigraphie, Sédimentologie, Notes et Mémoires n°11[END_REF]. The littoral sediments are dated from Middle (Langhian-Serravallian) to Upper Miocene (Tortonian-Messinien) (Fig. 5, [START_REF] Cravatte | Les sondages du Golfe du Lion: Stratigraphie, Sédimentologie, Notes et Mémoires n°11[END_REF]. In Calmar 1, the contact is located at 1420 m and has been ascribed to the Serravallian/Tortonian transition, i.e. around 11 Ma (Fig. 5; [START_REF] Guennoc | Histoire géologique du Golfe du Lion et cartographie du rift oligo-aquitanien et de la surface messinienne[END_REF]. This age (which is the most precise) therefore suggests that deposition of U4 occurred after 11 Ma. As U4 is also overlain by U6 (earliest Pliocene to Quaternary), we conclude that this unit has been deposited later than 11 Ma and before the end of the MSC, usually placed at 5.332 Ma [START_REF] Hilgen | A critical re-evaluation of the Miocene-Pliocene boundary as defined in Mediterranean[END_REF][START_REF] Van Couvering | The base of the Zanclean Stage and of the Pliocene Series[END_REF][START_REF] Lourens | The Neogene Period[END_REF] but recently revised at 5.460 Ma [START_REF] Bache | A two-step process for the reflooding of the Mediterranean Basin after the Messinian Salinity Crisis[END_REF]. Note also that erosion reaching more than 1000 m was observed on the shelf above this H5 horizon [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] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF]. Age inconsistency for U4 in GLP 2 and Autan 1 boreholes may be explained by reworking. The seismic facies observed in U4 clearly show evidences of reworking with strong erosion observed at its base and internal truncation and erosional surfaces. Some indications of reworking were also found within U4 in GLP 2 [START_REF] Brun | Sondage Golfe du Lion profond n°2 GLP2, France, études de laboratoire[END_REF] suggesting that U3 fauna may have been reworked within U4 during a significant sea level fall [START_REF] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF]. Micropaleontologic assemblages are also generally poor in stratigraphic markers in GLP 2 [START_REF] Brun | Sondage Golfe du Lion profond n°2 GLP2, France, études de laboratoire[END_REF].

Transition between U4 and U5

In GLP2, a heterogenous evaporitic body (166 m thick) has been sampled between 3437 and 3603 m depth that comprises alternate layers of halite, clays and anhydrite (Figs. 10 and11). Fifty two metres of sandstones (between 3385 m and 3437 m) overlie the evaporites and contain a clay layer at 3426.70 m depth with a calcareous nannoflora containing Amaurolithus primus and A. tricorniculatus (Fig. 11, [START_REF] Brun | Sondage Golfe du Lion profond n°2 GLP2, France, études de laboratoire[END_REF] that in the absence of Discoaster quinqueramus and Ceratolithus acutus can be dated between 5.54 and 5.35 Ma [START_REF] Raffi | A review of calcareous nannofossil astrobiochronology encompassing the past 25 million years[END_REF][START_REF] Di Stefano | Refinements of calcareous nannofossil biostratigraphy at the Miocene/Pliocene Boundary on the Mediterranean region[END_REF]. This indicates a late Messinian age for the evaporitic body, which is also supported by the presence of Globigerina nepenthes at 3508.70 m depth [START_REF] Brun | Sondage Golfe du Lion profond n°2 GLP2, France, études de laboratoire[END_REF]. The evaporitic unit sampled in GLP 2 extends toward the basin within the upper part of U5a (Fig. 9). U5a is characterised by a general retrogradational pattern with onlap terminations on U4 and S4smooth (Figs.8, 9 and 12, see also Supplementary Figure 6). It means that a significant part of U5 (upper part of U5a, U5b and U5c) has been deposited during or after the formation of S4smooth. This observation contrasts with previous interpretations assuming that only the "Upper Evaporites" (U5c) and the 52 m of sandstones drilled in GLP 2 were deposited during a transgressive phase that shaped S4smooth [START_REF] Bache | The 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 Basin after the Messinian Salinity Crisis[END_REF].

Complementary dive observations

The region offshore the French Riviera is suitable for dive observations because of the Quaternary cutting of sub-marine canyons that exposes deposits along a large present-day bathymetric range. In this area, a detritic fan and "2 nd step evaporites" have been mapped by [START_REF] Savoye | The Messinian event on the margin of the Mediterranean Sea in the Nice area, southern France[END_REF] according to seismic profiles (Fig. 13A) but these authors did not clearly show the relationship between the detrital deposits and these evaporites. The detritic fan is exposed in the Cirque Marcel (Fig. 13A) where cross bedded sandstones at 2152 m below sea level (bsl) (Fig. 13B) have been described below conglomerates (from ca. 2100 to ca. 2000 m bsl) (Fig. 13C) and marls (above 1950 m bsl) (Fig. 13D) (see also Savoye and Piper, 1991: fig. 13). An unpublished photograph of the conglomerates show that they comprise rounded pebbles cemented by a reddish matrix (Fig. 13B). Rocks with similar colour are not known in the drainage basin landward of the Nice -Monaco area and suggests that these conglomerates may have been exposed to weathering processes. As these deposits are immediately overlain by bedded silty turbidites (Fig. 13D) dated from the early Zanclean [START_REF] Savoye | The Messinian event on the margin of the Mediterranean Sea in the Nice area, southern France[END_REF], we propose to ascribe the conglomerates to the Messinian lowstand detritic fan. However, alternative age interpretations may exist. Similar land-deposited conglomerates characterize in the region the beginning of the continental syn-rift Oligocene deposits, forced by intensive tectonics and erosion, such as the Vazzio and Ussana formations in southwestern Corsica [START_REF] Ferrandini | La formation conglomératique du Vazzio près d'Ajaccio (Corse-du-Sud), un témoin des dépôts du Chattien supérieur continental synrift en Méditerranée occidentale[END_REF] and southern Sardinia [START_REF] Cherchi | The stratigraphic response to the Oligo-Miocene extension in the western Mediterranean from observations on the Sardinia graben system (Italy)[END_REF], respectively. There, alluvial fans are narrowly linked to proximity of a high relief. Such a Corsican important relief is considered to have provided the pollen grains of altitudinal trees recorded in the early Aquitanian clays of the Vence Basin near Nice [START_REF] Suc | Neogene and Lower Pleistocene in Southern France and Northeastern Spain. Mediterranean environments and climate[END_REF]Fauquette et al., accepted), consistently with palaeogeographic reconstructions (Meulenlamp and Sissingh, 2003;[START_REF] Cherchi | The stratigraphic response to the Oligo-Miocene extension in the western Mediterranean from observations on the Sardinia graben system (Italy)[END_REF]. But [START_REF] Savoye | The Messinian event on the margin of the Mediterranean Sea in the Nice area, southern France[END_REF] have undoubtedly shown the north origin of the conglomerates evidenced by the dives whereas the absence of important relief northward the Nice area is established at the earliest Miocene (Fauquette et al., accepted, and references herein). In a subsidence -uplift reconstruction, [START_REF] Savoye | The Messinian event on the margin of the Mediterranean Sea in the Nice area, southern France[END_REF] evidenced that this subaerial detritic fan deposited at an altitude of about 1100-1300 m below the present-day sea level, a value inconsistent with the Oligocene sea level fall [START_REF] Haq | Chronology of Fluctuating Sea Levels Since the Triassic[END_REF]Miller et al., 2001) but consistent with the Messinian sea level drop of the Mediterranean. For the abovementioned reasons, an Oligocene age cannot be considered for the palaeo-Var conglomerates. According to [START_REF] Savoye | The Messinian event on the margin of the Mediterranean Sea in the Nice area, southern France[END_REF], this detritic fan is "restricted to channels on the Messinian surface". Taking also into account the early Zanclean age of the overlying turbiditic marls indicated by foraminifers, they suggested that deposition of these conglomerates followed the post-MSC marine reflooding. However, it has been recently established that this detritic fan was stopped inland at that time of high sea level, being illustrated by the Carros breccia [START_REF] Bache | A two-step process for the reflooding of the Mediterranean Basin after the Messinian Salinity Crisis[END_REF]. We thus conclude that deposition of this detritic fan just before the 2 nd step Messinian evaporites remains the most suitable hypothesis. At last, according to J.-P. Réhault (in litteris, 2012), such fluvial conglomerates with a matrix suggesting rubefaction have been commonly observed in several dives in the area, asserting that the major detritic fans are, in the basin, re-covered by the Messinian halite (2 nd step evaporites) despite some lateral shifts.

Refining our scenario for the peak of the MSC

Deposition of U4 during the main Messinian sea-level fall

We have constrained the age of deposition of U4 between 11 Ma and the end of the MSC.

Existing interpretations for the age of deposition of U4a and U4b, i.e. before or during the MSC, can thus be discussed with respect to this time interval. [START_REF] Lofi | Evidence for pre-messinian submarine canyons on the Gulf of Lions slope (Western Mediterranean)[END_REF] interpreted erosion of S3 at the base of U4a and U4b to one, or the combination of several factors among which (1) the occurrence of fluctuations in sea level after 16.4 Ma (especially the pronounced sea-level fall that occurred at the Serravallian/Tortonian transition) and ( 2) a local tectonic event on the western platform of the Gulf of Lions. These authors disregard the deposition of U4a and U4b during the MSC because (1) the identification of five successive generations of submarine canyons at the base and within U4a and U4b and (2) aggradational geometry of the topsets beds observed within one of the interpreted canyons that seems incompatible with a major MSC lowering phase. However, our observations from seismic and wells show that the Serravallian/Tortonian transition (reflector H5) extends below S3 (Fig. 6). The corresponding pronounced sea-level fall cannot therefore be responsible for S3 erosion and the deposition of U4a and U4b.

The western part of the Gulf of Lions is characterised by the presence of normal faults that have affected U3 before the S4rough event (Fig. 3). This configuration highlights the existence of a local Upper Miocene tectonic event [START_REF] Mauffret | Structural geometry in the eastern Pyrenees and western Gulf of Lion (Western Mediterranean)[END_REF][START_REF] Gorini | The Late Messinian salinity crisis and Late Miocene tectonism : interaction and consequences on the physiography and post-rift evolution of the Gulf of Lions margin[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] Lofi | Evidence for pre-messinian submarine canyons on the Gulf of Lions slope (Western Mediterranean)[END_REF] suggested that this episode, probably accompanied by an increase of clastic sediment supply, is a possible origin for the formation of S3 and subsequent filling with U4a and U4b. In order to decipher the tectonic and eustatic origin of theses canyons, the same authors suggest looking for the existence of sub-marine canyons in the eastern Gulf of Lions, an area where the Upper Miocene tectonics has not been observed.

The recent identification of U4a and U4b prisms and their basal major incision (S3) in the eastern part of the Gulf of Lions (Figs. 2 and4; see also [START_REF] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF] therefore suggests that the tectonic hypothesis alone cannot explain the sedimentary geometries in the Gulf of Lions. [START_REF] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF] interpreted U4a and U4b prisms as the detrital sediments reworked by S4rough erosion. This interpretation is supported by the quantitative assessment of eroded and deposited volumes [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] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF] which shows that the volume of the entire U4 unit (9400 km 3 ) is similar to the estimated volume of eroded material (more than 10000 km 3 ). [START_REF] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF] also argued that the most prominent erosional event (i.e. erosion of the margin during the peak of the MSC) must have been recorded seaward by the most prominent geological features, i.e. S3 and U4a/U4b prisms.

Our observations show that a direct correlation between S4rough (Messinian erosion) and the entire U4 unit is the only hypothesis that is consistent with our time-window for the deposition of U4. The existence of sub-marine canyons at the base and within U4 [START_REF] Lofi | Evidence for pre-messinian submarine canyons on the Gulf of Lions slope (Western Mediterranean)[END_REF] is not inconsistent with a MSC sea-level drop. These canyons could have been formed at the beginning of the MSC sea-level fall, when the shelf was already exposed to subaerial erosion, but before the end of the regressive phase. We therefore do not exclude the influence of subaqueous processes for the formation of the S3 unconformity, which could correspond to a "basal surface of forced regression" sensu [START_REF] Hunt | Stranded parasequences and the forced regressive wedge systems tract: deposition during base-level fall[END_REF]. In fact, this is exactly what is observed on the shelf of the Gulf of Lions during Quaternary lowstands with a regressive surface of marine erosion at the base of forced regressive prisms [START_REF] Rabineau | Sedimentary sequences in the Gulf of Lion: a record of 100,000 years climatic cycles[END_REF].

Transgressive evaporites (U5)

Drawdown and shrinkage of pre-concentrated brine bodies [START_REF] Hardie | Criteria for recognition of ephemeral salt-pan facies in halite evaporites[END_REF] have been argued to explain the distribution of salt across much of the sea floor beyond the shelf edge but inversely proportional in thicknesses to elevation above the basin floor [START_REF] Ryan | Decoding the Mediterranean salinity crisis[END_REF]. Halite deposits would therefore be thin on slopes, thicker on deep-sea fan aprons and thickest on the abyssal plains [START_REF] Ryan | Decoding the Mediterranean salinity crisis[END_REF]. Such distribution is true for the Gulf of Lions. However, our observations also show that a significant part of U5 (upper part of U5a, U5b and U5c) is deposited with an onlap configuration against S4smooth, which truncates older deposits (U4). Interpretation of S4smooth as a wave ravinement surface is argued based on its smooth morphology and its geometric relationship with underlying and overlying units [START_REF] Bache | The 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 Basin after the Messinian Salinity Crisis[END_REF]. One of the most compelling observations that supports this interpretation is the landward transition of S4smooth with S4rough, which can be observed at a constant depth (1.6 s TWT) in the whole Gulf of Lions margin [START_REF] Bache | The 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 Basin after the Messinian Salinity Crisis[END_REF]. Such a transition, between a deeply incised, typical subaerial surface (S4rough, MES) and a smooth surface (S4smooth) with erosional truncations below and onlaps above, is likely to represent the paleoshoreline at the end of the wave abrasion. Erosional truncation implies the deposition of strata and their subsequent removal [START_REF] Mitchum | Seismic stratigraphy and global changes of sea level, part 6: Stratigraphic Interpretation of Seismic Reflection Patterns in Depositional Sequences[END_REF]. Onlap is a relation in which seismic reflections are interpreted as initially horizontal strata terminating progressively against an initially inclined surface, or as initially inclined strata terminating progressively updip against a surface of greater inclination [START_REF] Mitchum | Seismic stratigraphy and global changes of sea level, part 6: Stratigraphic Interpretation of Seismic Reflection Patterns in Depositional Sequences[END_REF]. This stratal relationship between U4 and U5a together with the presence of a wave-ravinement surface (S4smooth) between the two units suggest that a significant part of the "2 nd step evaporites" (upper part of U5a, U5b and U5c) was deposited during a landward migration of the shoreline (transgressive trend) that also reshaped previous topography to form S4smooth. This interpretation is also supported by the presence of clays within U5 (sampled in GLP 2) characterised by 80% planktonic foraminifers (at 3508.70 m from a side well core; Fig. 11; [START_REF] Brun | Sondage Golfe du Lion profond n°2 GLP2, France, études de laboratoire[END_REF], suggesting the occurrence of fully marine conditions in the basin and thus compatible with deposition of U5 during sea-level rise. Landward migration of the shoreline implies an increase in accommodation that can be caused by (i) subsidence, (ii) a rise of the Mediterranean sea level or (iii) a combination of both. Transport of sediment from the eroded margins to the basin, accompanied by a high precipitation rate of evaporites, can generate subsidence in the deep basins by loading. However observation of a smooth surface comparable to S4 smooth almost exactly at the same depth (1.4-1.7 s TWT) in the Valencia Trough [START_REF] García | The Catalan margin during the Messinian Salinity Crisis: Physiography, morphology and sedimentary record[END_REF] suggests the influence of a Mediterranean sea-level rise. Submarine terraces have also been described in the Alboran margin [START_REF] Estrada | Impact of pulsed Atlantic water inflow into the Alboran Basin at the time of the Zanclean flooding[END_REF] and SW Mallorca Island and Bay of Oran [START_REF] Just | Erosion of continental margins in the Western Mediterranean due to sea-level stagnancy during the Messinian Salinity Crisis[END_REF], and could be a consequence of this potential sea-level rise. This transgressive context coupled with a high evaporation rate provided favourable conditions for the precipitation of thick "2 nd step evaporites". The large amount of salt precipitated during the MSC requires the evaporation of about 8 times the volume of the present-day Mediterranean and thus implies continuous seawater input to the Mediterranean during the precipitation stage [START_REF] Hsü | History of the Mediterranean salinity crisis[END_REF][START_REF] Benson | An important current reversal (influx) in the Rifian Corridor (Morocco) at the Tortonian-Messinian boundary: The end of the Tethys Ocean[END_REF][START_REF] Blanc | Improved modelling of the Messinian Salinity Crisis and conceptual implications[END_REF][START_REF] Gargani | Evaporite accumulation during the Messinian Salinity Crisis: the Suez Rift case[END_REF][START_REF] Ryan | Decoding the Mediterranean salinity crisis[END_REF]. Recent numerical models suggest that such input is insufficient or unlikely to occur after the closure of the Rifian Corridor [START_REF] Blanc | The opening of the Plio-Quaternary Gilbraltar Strait : assessing the size of a cataclysm[END_REF][START_REF] Garcia-Castellanos | Catastrophic flood of the Mediterranean after the Messinian salinity crisis[END_REF][START_REF] Govers | Choking the Mediterranean to dehydration: The Messinian salinity crisis[END_REF][START_REF] Govers | Regional isostatic response to Messinian Salinity Crisis events[END_REF], the age of which is well-constrained at 5.60 Ma at its Mediterranean and Atlantic exits (Krijgsman et al., 1999b;[START_REF] Warny | Timing and progression of climatic, tectonic and glacioeustatic influences on the Messinian Salinity Crisis[END_REF]. Precipitation in all the basins before any significant Messinian sea-level fall and before the total isolation of the Mediterranean (Krijgsman et al., 1999a) has been reproduced with numerical models [START_REF] Meijer | A quantitative analysis of the desiccation and re-filling of the Mediterranean during the Messinian Salinity Crisis[END_REF][START_REF] Blanc | Improved modelling of the Messinian Salinity Crisis and conceptual implications[END_REF][START_REF] Ryan | Modelling the magnitude and timing of evaporative drawdown during the Messinian salinity Crisis[END_REF][START_REF] Garcia-Castellanos | Messinian Salinity Crisis regulated by competing tectonics and erosion at the Gibraltar arc[END_REF]. However sedimentary geometries in the Gulf of Lions do not support this hypothesis, which would imply major erosion and detritic deposition after the deposition of thick "2 nd step evaporites". Our observations rather show major erosion (S3 and S4rough) and detrital sediment deposition (U4) before evaporite precipitation (U5). [START_REF] Loget | How did the Messinian Salinity Crisis end?[END_REF] have shown that intense regressive erosion developed in the Gibraltar area after the Messinian sea-level drawdown. This process could result from a continuous input of ocean water to precipitate enough evaporites in an almost completely desiccated Mediterranean Basin. [START_REF] Hardie | Did the Mediterranean sea dry out during the Miocene? A reassessment of the evaporite evidence from DSDP legs 13 and 42A cores[END_REF] re-interpreted cores from DSDP Legs 13 and 42A and suggest that (upper) evaporites of the Mediterranean deep basins were deposited under "relatively deep-water (below wave base) conditions". Considering that only a small part of the upper stratigraphic units of the evaporitic body have been sampled (tens of metres), these authors noted that "Until we have deep cores that penetrate the entire evaporite section we cannot hope to unravel more from existing DSDP cores than the depositional history of the very last phase of the Messinian evaporite body that lies beneath the floor of the Mediterranean Sea".

Deep-water (below wave base) conditions for the top of the evaporite unit are in agreement with deposition during sea-level rise.

A three-step scenario for the peak of the MSC

The largely accepted diachronous scenario of Messinian evaporites [START_REF] Clauzon | Alternate interpretation of the Messinian salinity crisis: controversy resolved ?[END_REF]CIESM, 2008) involves the isolation of "peripheral" basins and "1 st step evaporites" deposition with an initial sea-level fall followed by deposition of "2 nd step evaporites" in the deepest parts of the Mediterranean after a major drawdown. A relative fall and rise of the Mediterranean sea level at the end of the Miocene is commonly proposed to explain observations in the Gulf of Lions [START_REF] Guennoc | Histoire géologique du Golfe du Lion et cartographie du rift oligo-aquitanien et de la surface messinienne[END_REF][START_REF] Gorini | The Late Messinian salinity crisis and Late Miocene tectonism : interaction and consequences on the physiography and post-rift evolution of the Gulf of Lions margin[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] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF]. This interpretation is supported by the observation of conglomerates with reddish matrix resulting from oxidation in the Cirque Marcel. Indeed, the present depth of this Messinian fluvial conglomerates at more than 2000 m bsl (a depth somewhat increased by Pliocene subsidence) is consistent with a significant sea level fall during the Messinian.

Our new observations in the Gulf of Lions also support this scenario. Seismic unit U4 has been deposited during the desiccation phase (2-I) and a significant part of U5 ("2 nd step evaporites") has been deposited during a relatively slow transgressive phase (2-II), just before the final rapid re-flooding (2-III) (Figs. 14 to 16). This three-step scenario for the peak of the MSC is a simplification of the four-step scenario of [START_REF] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF] where the deposition of the "2 nd step evaporites" and the relatively slow transgressive phase were separated into two different steps. This new scenario should provide a solution to the controversy about water depth over the "2 nd step evaporites" during their deposition. Similarities of seismic records between the Western and Eastern Mediterranean basins have been shown and discussed by [START_REF] Bache | A two-step process for the reflooding of the Mediterranean Basin after the Messinian Salinity Crisis[END_REF]. Indeed, in the Eastern Mediterranean, the "2 nd step evaporites" are sandwiched between thick clastic deposits [START_REF] Bertoni | Clastic depositional systems at the base of the late Miocene evaporites of the Levant region, eastern Mediterranean[END_REF][START_REF] Montadert | Petroleum systems offshore Cyprus[END_REF] and an abrasion surface located just below the earliest Pliocene sediments [START_REF] Bertoni | Clastic depositional systems at the base of the late Miocene evaporites of the Levant region, eastern Mediterranean[END_REF]. These observations, comparable to observations in the Western Mediterranean, could be explained by similar sea level variations in the two Mediterranean basins assuming a relatively low sill between Sicily and Tunisia. On the contrary, a marine water input from the Red Sea is to be foreseen.

Numerical model 7.1. Model setup

To obtain the interpreted sea level variation and to predict the observed evaporite thickness in the Western Mediterranean Basin, it is necessary to calculate the water budget and to take into account the geometry of the basin. Instead of using a semi-empirical equation to simulate the erosion of the Gibraltar sill and the theoretical increase of the Atlantic flux Q ocean (t), we estimate the best set of Atlantic flux Q ocean (t) and E-P that allow the model to fit our observations (sea-level variation, timing and evaporite thickness). This approach allow us to verify the global coherency of the proposed scenario and to estimate a first order quantitative value for several parameters (E-P and Q ocean (t)) that permit to obtain a realistic simulation. The water budget of the Western Mediterranean Basin is estimated by summing the discharge from rivers Q river (t), the precipitation P(t) and the Atlantic Ocean flux Q ocean (t). The fresh water loss by evaporation E(t) is also taken into account. For simplification, Q river (t), P(t) and E(t) are considered constant during the simulation. Q ocean (t) is not constant and increase with time. This increase is calibrated to allow the model to fit the sea level variations and the evaporate thickness observed. Starting from an initial volume of sea water V 0 of the Western Mediterranean Basin a new volume V(t+1) is calculated at the time t. The water budget is given by:

ΔV(t+1) = V 0 -V(t+1) = V 0 + (Q river (t) + P(t) + Q ocean (

t) -E) . S(t) . t

Using the water budget calculated ΔV(t+1), we estimate the Mediterranean Sea surface at the next step using the equation S 2 (t+1) = S 2 (t) -2ΔV(t+1)/a. The sea level of the Mediterranean Z(t+1) is calculated from the area of the Mediterranean Sea S(t+1) using the equation Z(t+1)=a.S(t+1)+Z 0 , where a and Z 0 are parameters that depend on the geometry of the Western Mediterranean Basin at the Messinian time. For the Western Mediterranean Basin a and Z 0 are assumed to be equal to 4461.5 x 10

-12 m -1
and to -3123 m respectively. During the MSC in the Mediterranean area, the evaporation E was higher than the sum of the water influx triggering a drawdown of the Mediterranean sea level Z(t+1) during part of the crisis until the increase of the Atlantic flux Q ocean (t) allowed the progressive reflooding of the Mediterranean.

To calculate the evaporite thickness, it is necessary to know the water volume V(t) and the salt concentration C(t). The salinity of the Mediterranean Sea at the beginning of the crisis C 0 is considered to be 35 g/l, equal to the salinity of the Atlantic Ocean C ocean . The salinity of rivers C river is assumed to be of 1 g/l. The salt concentration of the Western Mediterranean Basin at time t is therefore given by:

C(t) = [M 0 + M river (t) + M ocean (t)] / V(t)
where V(t) is the volume of the sea water at the time t and M 0 = C 0 .V 0 is the mass of evaporites when all the water in the Western Mediterranean is evaporated. M river (t) = Q river (t) . C river . t is the mass of evaporites which come from river discharge Q river , M ocean (t)=Q ocean (t) . C ocean . t is the mass of evaporites which come from the Atlantic Ocean through an oceanic inflow Q ocean (t) when Atlantic Ocean waters flooded over the Gibraltar sill. The salt precipitates when C(t) >130 g/l. This precipitation allows the formation of evaporite minerals. The salt density used to calculate the volume of evaporites is 2170 kg/m 3 .

Model implications

Input variables (precipitation, evaporation, river discharge, Atlantic sea water inflow) were chosen in order to honour our geological observations and interpretations (Fig. 16) and thus determine if their values are realistic. Model inputs include a 1500 m sea-level drawdown at 5.60 Ma; deposition of the thick "2 nd step evaporites" body starting after the sea-level fall and during a slow sea-level rise from -1500 m to -900/-600 m depth [START_REF] Bache | A two-step process for the reflooding of the Mediterranean Basin after the Messinian Salinity Crisis[END_REF], followed by an instantaneous re-flooding. Our numerical simulation (Fig. 17) shows that (1) the sea level in the deep basins and the thickness of the evaporites are strongly dependent on evaporation/precipitation rates and Atlantic Ocean water inflow; (2) a value of E-P of >1.75 m 3 /m 2 /yr is required to reproduce a precipitation of thick "2 nd step evaporites" (>2000 m) in the deep basins after the major sea-level drawdown, assuming a river discharge of about 7500 m 3 /s, comparable to that of the present-day [START_REF] Struglia | River discharge into the Mediterranean Sea: climatology and aspects of observed variability[END_REF][START_REF] Meijer | A quantitative analysis of the desiccation and re-filling of the Mediterranean during the Messinian Salinity Crisis[END_REF][START_REF] Gargani | Mediterranean Sea level variations during the Messinian salinity crisis[END_REF]. In the absence of any alternative, previous studies of the water and salt budget have used present-day hydrological fluxes with E-P ranging between 0.5 and 1 m 3 /m 2 /yr [START_REF] Meijer | A quantitative analysis of the desiccation and re-filling of the Mediterranean during the Messinian Salinity Crisis[END_REF]). E-P value of 0.9-1 m 3 /m 2 /yr during the peak of the MES is also suggested from recent climate modelling [START_REF] Murphy | A numerical study of the climate response to lowered Mediterranean Sea level during the Messinian Salinity Crisis[END_REF]. The higher value of E-P (1.75 m 3 /m 2 /yr) required in our model is consistent with the reconstructed climatic parameters at the time of the MSC indicating lower annual precipitations and higher mean annual temperature than today in the southwest Mediterranean lands [START_REF] Fauquette | How much did climate force the Messinian salinity crisis? Quantified climatic conditions from pollen records in the Mediterranean region[END_REF][START_REF] Van Dam | Geographic and temporal patterns in the late Neogene (12-3 Ma) aridification of Europe: The use of small mammal as paleoprecipitation proxies[END_REF]. A higher E-P value than today is also supported by the momentary migration of the subdesertic plants 3° northward of their habitat at the onset of the MSC [START_REF] Fauquette | How much did climate force the Messinian salinity crisis? Quantified climatic conditions from pollen records in the Mediterranean region[END_REF][START_REF] Popescu | Earliest Zanclean age for the Colombacci and uppermost Di tetto formations of the "latest Messinian" northern Apennines: New palaeoenvironmental data from the Maccarone section (Marche Province, Italy)[END_REF]. In the present Dead Sea the rate of evaporation has been measured between 1.25 m 3 /m 2 /yr and 1.7 m 3 /m 2 /yr today and in 1944 respectively [START_REF] Yechieli | Will the Dead Sea die?[END_REF]. With regard to the low precipitation rate (about 0.1 m 3 /m 2 /yr) at the shore of the Dead Sea [START_REF] Neumann | Vegetation history and climate fluctuations on a transect along the Dead Sea west shore and their impact on past societies over the last 3500 years[END_REF], an average E-P value of 1.5 m 3 /m 2 /yr can be considered. Moreover, evaporation rates >2 m 3 /m 2 /yr have been recorded in various lakes in arid regions [START_REF] Kotwicki | Hydrology of Lake Eyre, Australia: El Nino link[END_REF][START_REF] Abd Ellah | Evaporation rate at Wadi El-Rayan Lake, Egypt[END_REF]. Therefore 1.75 m 3 /m 2 /yr is a plausible value for the time of the MSC.

Conclusion

Using seismic lines and data from wells in the Gulf of Lions, we showed that detrital prisms started to be deposited in the Provence-Algiers Basin before the deposition of the "2 nd step evaporites" and then partly during their deposition. The upper part of these evaporites has been deposited contemporaneously with the formation of a transgressive ravinement surface, during the landward migration of the shoreline. Three successive steps subdividing the peak of the MSC (5.60-5.46 Ma) are defined to characterise the sedimentary pattern observed in seismic reflection and borehole data: step 2-I (5.60-? Ma) corresponds to the deposition of detrital sediment in relation with intensive subaerial erosion immediately after the onset of the fast and major Messinian sea-level drawdown; step 2-II (?-5.46 Ma) is characterised by deposition of evaporites (up to 3 kilometres in thickness) during a slow sea-level rise and associated landward migration of the shoreline; step 2-III is the geologically instantaneous reflooding of the Mediterranean at 5.46 Ma. This scenario, which details the peak of the MSC, has been numerically modelled for the Western Mediterranean and the expected thickness of evaporites implies that E-P was higher than today in the central basins when they were dried up. Because of similar observations in the Eastern Mediterranean, this scenario might be applicable for the whole Mediterranean. The key pieces of information required for continuing to improve understanding of the peak of the MSC at the scale of the whole Mediterranean are ground-truth observations of the "2 nd step evaporites" and the pre-evaporite lithologies with accurate dating for the corresponding sediments. Recognition of the critical stratigraphic markers identified in the Gulf of Lions and in other Mediterranean basins should allow: 1. more detailed chronostratigraphy of the MSC, leading to comparisons between different basins. In particular, the understanding of the connections between Western and Eastern Mediterranean basins and the role of sills that probably separated these basins is necessary to model the MSC for the whole Mediterranean [START_REF] Gargani | Mediterranean Sea level variations during the Messinian salinity crisis[END_REF][START_REF] Gargani | Evaporite accumulation during the Messinian Salinity Crisis: the Suez Rift case[END_REF][START_REF] Leever | Messinian sea level fall in the Dacic Basin (Eastern Paratethys): palaeogeographical implications from seismic sequence stratigraphy[END_REF][START_REF] Leever | The evolution of the Danube gateway between Central and Eastern Paratethys (SE Europe): insight from numerical modelling of the causes and effects of connectivity between basins and its expression in the sedimentary record[END_REF][START_REF] Bache | A two-step process for the reflooding of the Mediterranean Basin after the Messinian Salinity Crisis[END_REF]; 2. quantification of vertical movements across the whole Mediterranean that will lead to a better understanding of the behaviour of the lithosphere, its rigidity and response to rapid load variations during the MSC (sedimentary transfers, sea-level variations). 3. new constraints for hydrocarbon generation models for which age and lithology of sedimentary units are critical to assess the petroleum potential of sedimentary basins. [START_REF] Brun | Sondage Golfe du Lion profond n°2 GLP2, France, études de laboratoire[END_REF] and [START_REF] Guennoc | Histoire géologique du Golfe du Lion et cartographie du rift oligo-aquitanien et de la surface messinienne[END_REF]. The bold line corresponds to a clear change in depositional environment. Position of the seismic units and unconformities identified in this study is deduced from two-way time -depth relationships (Supplementary Figure 2). Depths are measured depths in meters below Kelly Bushing (mMDKB). [START_REF] Brun | Sondage Golfe du Lion profond n°2 GLP2, France, études de laboratoire[END_REF]. We interpret this interval as a possible product of the erosion that occurred on the slope during the peak of the MSC. Stratigraphic boundaries come from [START_REF] Brun | Sondage Golfe du Lion profond n°2 GLP2, France, études de laboratoire[END_REF]. Depths are measured depths in meters below Kelly Bushing (mMDKB). [START_REF] Bache | A two-step process for the reflooding of the Mediterranean Basin after the Messinian Salinity Crisis[END_REF] and from seismic interpretation in the Gulf of Lions [START_REF] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF]this study). Subdivisions of the MSC: 1, First phase leading to evaporite deposition in the peripheral basins ("1 st step evaporites") after a limited sea level fall; 2, Second phase (i.e. the peak of the MSC) characterised by a significant sea level drop, evaporite deposition in the deep basins ("2 nd step evaporites"), and subaerial erosion of the margins. Subdivisions of the peak of the MSC: step 2-I, detrital deposition in the deep basins during the significant sea level drop; step 2-II, deep evaporites deposited and S4smooth created during the landward migration of the shoreline; step 2-III, rapid reflooding. [START_REF] Bache | A two-step process for the reflooding of the Mediterranean Basin after the Messinian Salinity Crisis[END_REF]. Subdivisions of the MSC: 1, First phase leading to evaporite deposition in the peripheral basins ("1 st step evaporites") after a limited sea-level fall; 2, Second phase (i.e. the peak of the MSC) characterised by a significant sea level drop, evaporite deposition in the deep basins ("2 nd step evaporites"), and subaerial erosion of the margins. Subdivisions of the peak of the MSC: step 2-I, detrital deposition in the deep basins during the significant sea-level drop; step 2-II, central evaporites deposited and S4smooth created during the landward migration of the shoreline; step 2-III, rapid reflooding.

Figure 1 .

 1 Figure1. The synchronous and diachronous scenarios for the deposition of the Messinian evaporites in the Mediterranean Sea. In the synchronous scenario phase 1 corresponds to a series of limited sea-level fall and rise leading to evaporite deposition in both the central and peripheral basins; i.e. at variable sea levels. Phase 2 (i.e. the peak of the MSC) is characterized by a large sea level drop, evaporite deposition in the central basins, and subaerial erosion of the margins. In the diachronous scenarios evaporites were only deposited in the peripheral basins during phase 1 and in the central basins during phase 2.

Figure 2 .

 2 Figure 2. Map showing the data used for this study and the location of Messinian seismic markers in the Gulf of Lions. Landward limit of U5 (evaporites) is deduced from the landward limit of the listric faults. Boreholes: Ca1, Calmar1; Ci1, Cicindelle1; Am1, Agde Maritime1; Si1, Sirocco1; Mi1, Mistral1; Tra1, Tramontane1; Ra1, Rascasse1; Au1, Autan1; Au2, Autan2; GLP1, Golfe du Lion Profond 1; GLP2, Golfe du Lion Profond 2.

Figure 3 .

 3 Figure 3. Sedimentary and morphological evolution of the Gulf of Lions from the margin to basin. (a) Line drawing of seismic cross-sections highlighting the markers of the MSC (location on Fig. 1). (b) Chronostratigraphic chart based on seismic interpretations assuming the deposition of a significant part of evaporites after the major sea-level fall and during a landward migration of the shoreline. Subdivisions of the MSC: 1, First phase leading to evaporite deposition in the peripheral basins ("1 st step evaporites") after a limited sea level fall; 2, Second phase (i.e. the peak of the MSC) characterised by a significant sea level drop, evaporite deposition in the deep basins ("2 nd step evaporites"), and subaerial erosion of the margins. Subdivisions of the peak of the MSC: step 2-I, detrital deposition in the central

Figure 4 .

 4 Figure 4. Uninterpreted and interpreted seismic profile across the Gulf of Lions shelf (LRM 28) showing the position of seismic reflectors H1 to H5 beneath U4. A Serravallian/Tortonian age for H5 leads to a younger age for the deposition of U4. Location of seismic profiles on Fig. 2.

Figure 5 .

 5 Figure 5. Stratigraphic correlation between wells Tramontane 1, Calmar 1, Mistral 1 (shelf) and Autan 1 and GLP 2 (slope) in the Gulf of Lions (Location on Fig. 2). Stratigraphic boundaries and interpretation of depositional environments come from Cravatte et al. (1974),[START_REF] Brun | Sondage Golfe du Lion profond n°2 GLP2, France, études de laboratoire[END_REF] and[START_REF] Guennoc | Histoire géologique du Golfe du Lion et cartographie du rift oligo-aquitanien et de la surface messinienne[END_REF]. The bold line corresponds to a clear change in depositional environment. Position of the seismic units and unconformities identified in this study is deduced from two-way time -depth relationships (Supplementary Figure2). Depths are measured depths in meters below Kelly Bushing (mMDKB).

Figure 6 .

 6 Figure 6. Zoom of Figure4showing the stratal relationship between U3 and U4 and the unconformity S3 that separates these units. Seismic reflectors H1 to H5 are older than U4. A Serravallian/Tortonian age for H5 leads to a younger age for the deposition of U4.

Figure 7 .

 7 Figure 7. Seismic profiles showing the stratal relationship between U3 and U4 and the unconformity S3 that separates these units. U3 is truncated by S3 and U4 is clearly younger than U3.

Figure 8 .

 8 Figure 8. Uninterpreted and interpreted seismic profile across the Gulf of Lions showing the transition from the Miocene shelf (U3) to the evaporite layers (U5). U4 is represented in yellow. S4smooth is characterised by underlying erosional truncations and overlying onlap terminations. Location of seismic profiles on Fig. 2.

Figure 9 .

 9 Figure 9. Zoom of Figure 8 showing the transition between U4b and U5a. The evaporitic unit drilled in GLP2 can be correlated with the upper part of U5a.

Figure 10 .

 10 Figure 10. Stratigraphic log of GLP 2 showing the evaporites interval between 3437 and 3703 m and the interval corresponding to seismic unit U4b between 3703 m and 4650 m. Micropaleontologic assemblages are generally poor and non-characteristics between 3703 m and 4650 m[START_REF] Brun | Sondage Golfe du Lion profond n°2 GLP2, France, études de laboratoire[END_REF]. We interpret this interval as a possible product of the erosion that occurred on the slope during the peak of the MSC. Stratigraphic boundaries come from[START_REF] Brun | Sondage Golfe du Lion profond n°2 GLP2, France, études de laboratoire[END_REF]. Depths are measured depths in meters below Kelly Bushing (mMDKB).

Figure 11 .

 11 Figure 11. Zoom of Figure 8 showing onlap configuration of the strata that overlies S4smooth. These strata correspond with the evaporitic unit drilled by well GLP2 (3703 -3437 m depth). The (52 m thick) overlying sandstones and clays (3437 -3385 m depth) are indistinct on the seismic profile. Depths are measured depths in meters below Kelly Bushing (mMDKB).

Figure 12 .

 12 Figure 12. Seismic profile Ligo20 used in Figure 3 showing the onlap configuration of U5a on U4b.

Figure 13 .

 13 Figure 13. Observations and photographs made by one of us (J.-L.R.) during a dive using the Cyana submersible (cruise MONICYA in 1989, dive 72) in the sub-marine Cirque Marcel (western slope) offshore Nice (Southeastern France) corresponding to the proximal part of the Messinian lowstand detritic fan. The vertical scale (10 cm) is valid for the photographs B, C and D. A, Location map of the dive (within the box). Bathymetry is from Pautot et al. (1984). Map of Messinian evaporites and detritic fan is from Savoye and Piper (1991). 1, Messinian evaporites; 2, Messinian lowstand detritic fan in extension of the Messinian valley drawn onshore. B, Cross bedded sandstones described by Savoye and Piper (1991) at 2150 m bsl, underlying fluvial conglomerates. C, Fluvial conglomerates at 2020 m bsl with imbricated clasts of the proximal part of the lowstand detritic cone with a rubefacted matrix. D, Thinly bedded silty turbidites of the distal bottomset beds of the Var Zanclean Gilbert-type fan delta observed at 1940 m bsl.

Figure 14 .

 14 Figure14. Proposed scenario of the MSC interpreted from the available onshore data for the peripheral basins (see[START_REF] Bache | A two-step process for the reflooding of the Mediterranean Basin after the Messinian Salinity Crisis[END_REF] and from seismic interpretation in the Gulf of Lions[START_REF] Bache | The Messinian Erosional and Salinity Crises: View from the Provence Basin (Gulf of Lions, Western Mediterranean)[END_REF] this study). Subdivisions of the MSC: 1, First phase leading to evaporite deposition in the peripheral basins ("1 st step evaporites") after a limited sea level fall; 2, Second phase (i.e. the peak of the MSC) characterised by a significant sea level drop, evaporite deposition in the deep basins ("2 nd step evaporites"), and subaerial erosion of the margins. Subdivisions of the peak of the MSC: step 2-I, detrital deposition in the deep basins during the significant sea level drop; step 2-II, deep evaporites deposited and S4smooth created during the landward migration of the shoreline; step 2-III, rapid reflooding.

Figure 15 .

 15 Figure15. Chronology of events which affected the Mediterranean peripheral (including the Sicilian Caltanissetta Basin and the Apennine Foredeep) and deep basins with respect to sealevel changes (modified from[START_REF] Bache | A two-step process for the reflooding of the Mediterranean Basin after the Messinian Salinity Crisis[END_REF]. Subdivisions of the MSC: 1, First phase leading to evaporite deposition in the peripheral basins ("1 st step evaporites") after a limited sea-level fall; 2, Second phase (i.e. the peak of the MSC) characterised by a significant sea level drop, evaporite deposition in the deep basins ("2 nd step evaporites"), and subaerial erosion of the margins. Subdivisions of the peak of the MSC: step 2-I, detrital deposition in the deep basins during the significant sea-level drop; step 2-II, central evaporites deposited and S4smooth created during the landward migration of the shoreline; step 2-III, rapid reflooding.

Figure 16 .

 16 Figure 16. Variation of the Mediterranean Sea level in the Gulf of Lions between 6 and 5.30 Ma encompassing the MSC (augmented from Bache et al. (2012)). Successive major changes are estimated with respect to present-day sea level (0 m). The initial position of the paleoshoreline just before the rapid reflooding (step 2-III) has been estimated between 600 and 900 m below the present day sea level by Bache et al. (2012). The rapid increase in water depth during step 2-III was thus between 600 and 900 m. Solid and dashed black lines are constrained by an increase of 600 m and 900 m respectively. Subdivisions of the MSC shown on Fig. 14.

According to their geographic respective location, we distinguish (1) peripheral basins characterised by continuous shallow-water conditions in the Messinian and Zanclean (most of them being onshore today), and (2) deep basins where deep marine conditions prevailed except during the peak of the MSC.

Acknowledgments

The authors acknowledge Petroceltic and Total for allowing use of the seismic data. Vaughan Stagpoole (GNS Science) is acknowledged for critical discussions and editing the English.

Figure 17. Numerical simulations that predict precipitation of central basin evaporites after the main Messinian sea level fall. Variation of sea level is in blue and that of water budget in black. The resulting simulation of evaporite thickness is in purple. Solid and dashed lines are constrained by the initial position of the paleoshoreline just before step 2-III, respectively at 600 m and 900 m below the present sea level [START_REF] Bache | A two-step process for the reflooding of the Mediterranean Basin after the Messinian Salinity Crisis[END_REF]. The geometry of the basins is identical to that previously modelled by [START_REF] Meijer | A quantitative analysis of the desiccation and re-filling of the Mediterranean during the Messinian Salinity Crisis[END_REF]. Evaporites begin to precipitate when water salinity reaches 130g/l [START_REF] Meijer | A quantitative analysis of the desiccation and re-filling of the Mediterranean during the Messinian Salinity Crisis[END_REF][START_REF] Gargani | Evaporite accumulation during the Messinian Salinity Crisis: the Suez Rift case[END_REF]. The water budget is calculated using river and Atlantic Ocean flow as well as precipitation and evaporation [START_REF] Gargani | Mediterranean Sea level variations during the Messinian salinity crisis[END_REF]. The evaporation -precipitation (E-P) value that is the most compatible with our observations is 1.75 m 3 /m 2 /yr.

Supplementary