Biari Youssef
email: youssefbiari@hotmail.com

Klingelhoefer Frauke

Franke Dieter

Funck Thomas

Loncke Lies

Sibuet Jean-Claude

Basile Christophe

James A Austin

Rigoti Caesar Augusto

Sahabi Mohamed

Benabdellouahed Massinissa

Roest Walter

Structure and evolution of the Atlantic passive margins: a review of existing rifting models from wide-angle seismic data and kinematic reconstruction

Deep seismic data and plate kinematic reconstructions help understand the mechanisms of rifting and opening of new oceans, basic principles of plate tectonic cycles. In this study, available deep wide-angle seismic velocity models from the Atlantic margins are reviewed and plate reconstructions used to define conjugate model pairs. The main objective was to study the question of how magma-rich and magmapoor margins develop and the role of inheritance in the break-up. We also studied the question of the mechanism of formation and the origin of transform marginal plateaus, which are typically found at the border of two ocean basins of different ages and are mostly characterized by at least one volcanic phase during their formation. The results of the study include the comparison of crustal thickness, oceanic plate thickness and the influence of volcanism along the Atlantic margins. The conjugate profiles image different degrees of asymmetry of the Atlantic Margin rifts. Marginal plateaus might form when rifting stops at barriers leading to the accumulation of heat in the mantle and increased volcanism directly before or after halting of the rifting.

Introduction 1.1 Rifting and the break-up of continents

Rifting, the break-upof continents, and opening of an oceanic basin, are subjectsof stronginterest for Earth sciences (e.g. [START_REF] Franke | Rifting, lithosphere breakup and volcanism: Comparison of magma-poor and volcanic rifted margins[END_REF][START_REF] Geoffroy | Volcanic passive margins: another way to break up continents[END_REF]Brune et al., 2017a). Passive continental margin basins around the world have good oil and gas exploration prospects. Hydrocarbons discovered in offshore passive continental margin basins especially in deep water have been increasing during the last 20 years (e.g.USA Gulf of Mexico, Angola, Brazil, Egypt, Nigeria, Guyana and Suriname). Additionally, divergent continental margins pose substantial geohazards. Submarine landslides possibly resulting in Tsunamis (e.g. [START_REF] Krastel | Large-Scale Mass Wasting on the Northwest African Continental Margin: Some General Implications for Mass Wasting on Passive Continental Margins[END_REF] andmassive CO2 degassing during rifting have been proposed as elements contributingto change climate through time [START_REF] Brune | Potential links between continental rifting, CO 2 degassing and climate change through time[END_REF]. Continental flood basalts associated withrifting have been suggested to be contributors to mass extinctions due to the release of volatiles, aerosols and dustinto the atmosphere [START_REF] Courtillot | On the ages of flood basalt events[END_REF]. The focus of our study is the Atlantic Ocean which represents a natural laboratory for investigating and testingrifting models and the formation of divergent, oblique and transform continental margins.

Geodynamic models of rifting and the genesis of rifted margins have been developed alongside the investigation techniques. In the 1970s and 1980s, two types of models of passive continental margins models were proposed: conservational model [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] where the masses are kept balanced and non-conservational models where masses are allowed to be exchanged between the crust and mantle [START_REF] Keen | Geodynamics of rifted continental margins[END_REF]. Among the first type, the pure shear model [START_REF] Mckenzie | Some remarks on the development of sedimentary basins[END_REF] suggests that extension results in the symmetric thinning of the continental crust leading to the formation of tilted blocks in the upper crust. Thinning is proposed as being directly proportional to horizontal dilatation (Figure 1). Simple shear models [START_REF] Wernicke | Uniform-sense normal simple shear of the continental lithosphere[END_REF], on the other hand, do not assume symmetrical or uniform deformation and propose the existence of a lithospheric detachment fault crossing the crust and reaching into the upper mantle along which crustal thinning and exhumation take place leading to asymmetric margin formation (Figure 1). Nonconservational models, on the contrary, include an exchange of material between the mantle and the crust and propose additional factors, such as the cause of thinning and in which the mantle has a significant role in the process of passive margin genesis [START_REF] Keen | Geodynamics of rifted continental margins[END_REF][START_REF] Aslanian | Brazilian and African passive margins of the Central Segment of the South Atlantic Ocean: Kinematic constraints[END_REF]Huismans and Beaumont, 2011 and references therein).

This simple view did change and most modern models of rifting and break-up include several stages comprising both pure shear and simple shear phases as well as interaction between the J o u r n a l P r e -p r o o f crust and the mantle. Based on geophysical and geological observations from the west Iberian margin, and geological mapping in the Alps, [START_REF] Whitmarsh | Evolution of magma-poor continental margins from rifting to seafloor spreading[END_REF] present a conceptual model of magma-poor rifted margins including a first phase of lithospheric necking and diffuse faulting, followed by a second phase of localization of rifting and the onset of seafloor spreading. Later models tried to explain the apparent discrepancy between displacement along the faults and the amount of extension through exhumation of mid-crustal and mantle material [START_REF] Lavier | A mechanism to thin the continental lithosphere at magma-poor margins[END_REF] or through a later second phase of deformation setting in after embrittlement of the crust [START_REF] Reston | Lithospheric extension from rifting to continental breakup at magma-poor margins: Rheology, serpentinisation and symmetry[END_REF]. Today, a consensus existsthat rifting is generally polyphased and results from crust-mantle interactions [START_REF] Peron-Pinvidic | Rifted Margins: State of the Art and Future Challenges[END_REF]. Depending on the rheology, rifting might accelerate abruptly at break-up due to the rapidly decreasing rift strength and slow down afterwards, when seafloor spreading sets in [START_REF] Brune | Rifted margin architecture and crustal rheology: Reviewing Iberia-Newfoundland, Central South Atlantic, and South China Sea[END_REF].

By regarding the amount of volcanism produced during rifting, two major types of divergent rifted margins can be identified: volcanic and magma-poor margins (Figure 1). Although all margins show at least some volcanic and magmatic influence, magma-poor margins show broad zones of continental thinning including faulting and the formation of tilted blocks (Manatschal, 2004;[START_REF] Reston | Lithospheric extension from rifting to continental breakup at magma-poor margins: Rheology, serpentinisation and symmetry[END_REF]Peron-Pinvindic et al., 2019). Hyper-extended margins are termed those in which the crust becomes extremely stretched and embrittled, with fluids penetrating to the mantle through faults and serpentinizing the upper mantle material [START_REF] Doré | RESEARCH FOCUS: Hyperextended continental margins-Knowns and unknowns[END_REF][START_REF] Tugend | Spatial and temporal evolution of hyperextended rift systems: Implication for the nature, kinematics, and timing of the Iberian-European plate boundary[END_REF]. For this type, conjugate margins are often asymmetric, with one margin significantly wider than its conjugate [START_REF] Lister | Detachment models for the formation of passive continental margins[END_REF][START_REF] Hopper | Continental breakup and the onset of ultraslow seafloor spreading off Flemish Cap on the Newfoundland rifted margin[END_REF]. For thesemargins, the crustal break-up often precedes the lithospheric mantle break-up leading to the exhumation of upper mantle material (Manatschal, 2004). Rifted magma poor margins are frequently associated with slow extension (e.g. [START_REF] Bown | Effect of finite extension rate on melt generation at rifted continental margins[END_REF]Perez-Gussinyé et al., 2006;[START_REF] Doré | RESEARCH FOCUS: Hyperextended continental margins-Knowns and unknowns[END_REF].

Volcanic margins are characterized by large amounts of extrusive lavas forming thick seaward dipping reflector sequences and intrusives in the form of magmatically overprinted high-velocity zones in the lower crust (e. g. [START_REF] Thybo | Moho and magmatic underplating in continental lithosphere[END_REF]. In contrast with magmapoormargins, volcanic margins show crustal thinning in a narrow zone (~20 km) and the deposition of volcanic products and magmatic additions to the lower crust [START_REF] Hinz | Evolution of North Atlantic volcanic continental margins[END_REF][START_REF] Eldholm | North Atlantic volcanic margins: Dimensions and production rates[END_REF][START_REF] Geoffroy | Volcanic passive margins: another way to break up continents[END_REF]. Here, the mantle lithosphere breaks before or during crustal break-up allowing the production of large volumes of magmatic products [START_REF] Franke | Rifting, lithosphere breakup and volcanism: Comparison of magma-poor and volcanic rifted margins[END_REF]. At the outer part of these margins, exhumed lower crust can be in direct contact with the extrusives [START_REF] Geoffroy | Volcanic passive margins: another way to break up continents[END_REF].

J o u r n a l P r e -p r o o f [START_REF] Clerc | Rifted margins: Ductile deformation, boudinage, continentward-dipping normal faults and the role of the weak lower crust[END_REF]. ( g) and (h) shows schematic representation of the architecture of a slowly extended magma-poor marginand a rapidly extended magma-rich margin (after Franke., 2013;[START_REF] Peron-Pinvidic | Structural comparison of archetypal Atlantic rifted margins: A review of observations and concepts[END_REF][START_REF] Sutra | How does the continental crust thin in a hyperextended rifted margin? Insights from the Iberia margin[END_REF][START_REF] Doré | RESEARCH FOCUS: Hyperextended continental margins-Knowns and unknowns[END_REF][START_REF] Peron-Pinvidic | Rifted Margins: State of the Art and Future Challenges[END_REF] A second group of continental margins that bounds parts of the Atlantic are transform margins, along which the movement of the plates is shear or oblique shear instead of extensional. Transform margins might be one of the main mechanisms for the break-up of continents as less force is required to break obliquely through cratonic crust [START_REF] Lundin | Non-Wilsonian break-up predisposed by transforms: examples from the North Atlantic and Arctic[END_REF][START_REF] Brune | Modeling suggests that oblique extension facilitates rifting and continental break-up[END_REF]. The kinematic evolution of a transform margin is suggested to include three stages [START_REF] Mascle | Evidence for transform margin evolution from the Ivory Coast-Ghana continental margin[END_REF]: 1) the intra-continental transform fault stage such as for example the San Andreas and Dead Sea faults; 2) the active transform margin stage, when continental lithosphere slides against oceanic lithosphere; and 3) the passive transform margin, after the spreading center has passed along the margin and the transform margin becomes inactive. The length of a transform margin depends on three parameters: the obliquity between regional trend and relative plate motion, the width of the continental rift and timing of the deformation partitioning [START_REF] Basile | Transform continental margins -part 1: Concepts and models[END_REF]. One characteristic feature of many transform margins is the existence of marginal ridges parallel to the transform margin [START_REF] Basile | Pre-cruise and site surveys: a synthesis of marine geological and geophysical data on the Côte d'Ivoire-Ghana transform margin[END_REF]. Several hypotheses have tried to explain the existence of these marginal ridges (a) crustal thickening from transpression in the intra-continental transform zone (e.g. [START_REF] Huguen | Synlithification deformation processes of the Cretaceous sediments of the Ivory Coast-Ghana transform margin: A way to detail the margin history[END_REF]; (b) thermal uplift due to heating of the continental lithosphere by the hotter oceanic lithosphere (e.g. [START_REF] Scrutton | On Sheared Passive Continental Margins[END_REF][START_REF] Reid | Effects of lithospheric flow on the formation and evolution of a transform margin[END_REF]; and (c) flexural response of the lithosphere due to unloading by erosion (e.g. Basile and

J o u r n a l P r e -p r o o f Allemand,2002). Modern numerical studies suggest that most margins do open in an oblique manner (e.g. [START_REF] Brune | Evolution of stress and fault patterns in oblique rift systems: 3 D numerical lithospheric scale experiments from rift to breakup[END_REF][START_REF] Brune | Oblique rifting: The rule, not the exception[END_REF]. Based on plate kinematic calculations, and the position of the continent-ocean transition, the authors propose that more than 70% of all rift segments exceed an obliquity of 20%.

However, some fundamental questions regarding rifting and opening of oceanic basins, remain highly debated. With this systematic review of deep seismic profiles along the Atlantic margins weaim to highlight the main open questions and put themintocontext. Three main questions that will be addressed in this contribution are.

1) What are the factors leading to the development of either volcanic or magma-poor margins and during which extension phase does this occur?

Volcanic margins have often been associated with Large Igneous Provinces and elevated potential mantle temperature [START_REF] Smallwood | Ridge-plume interaction in the North Atlantic and its influence on continental breakup and seafloor spreading[END_REF]. However, the thermal influence of a hotspot should be largest at its center, which is not the case at the US volcanic margins [START_REF] Austin | Crustal structure of the Southeast Georgia embayment-Carolina trough: Preliminary results of a composite seismic image of a continental suture(?) and a volcanic passive margin[END_REF] and at the southern South Atlantic continental margins, where the opening was directed toward the proposed hotspot [START_REF] Franke | Rifting, lithosphere breakup and volcanism: Comparison of magma-poor and volcanic rifted margins[END_REF]. It is frequently suggested that magma-poor margins result from slow extension, so it could be assumed that volcanic margins are associated with rapid extension. However, the South and Central Atlantic, which are both characterized by magma-rich zones, have been opening at ultra-slow to slow rates, and also, for example, the volcanic NE-Atlantic margin, which opened at a rate of about 25 mm/yr half spreadingrate, subsequently rapidly decreasingto half-spreading rates of 10 mm/yr (Le [START_REF] Breton | Variations in amount and direction of seafloor spreading along the northeast Atlantic Ocean and resulting deformation of the continental margin of northwest Europe[END_REF]. There are other explanations for magmatic rifting, rather than purely the mantle temperature during extension. The amount of volcanism may also be controlled by other factors such as excess decompressional melting, tectonomagmatic interactions or pre-rift rheology of the lithosphere (e.g. Koopmann et al., 2014a;Davies et al., 2017;[START_REF] Tugend | Reappraisal of the magma-rich versus magma-poor rifted margin archetypes[END_REF][START_REF] Gouiza | The Role of Inherited Lithospheric Heterogeneities in Defining the Crustal Architecture of Rifted Margins and the Magmatic Budget During Continental Breakup[END_REF].

Recent work has proposed to generalize the model developed for magma-poor rifting to a general model valid for all types of Atlantic rifted margins [START_REF] Mjelde | Lower crustal seismic velocity-anomalies; magmatic underplating or serpentinized peridotite? Evidence from the Vøring Margin, NE Atlantic[END_REF]Peron-Pinvindic et al., 2013, Tugend et al., 2018), but questions as to the existence of serpentinized upper mantle material underneath the SDR sequences on volcanic margins remain highly debated. [START_REF] Lundin | Magmatism and extension rates at rifted margins[END_REF] have also shown that some if not all volcanic margins started to evolve from a typical non-volcanic margin, changing to a typical volcanic margin sometimes during the rifting period and that the influence of a plume or hotspot is not necessary to be invoked. If rifts are associated with LIP formation, the eruption happened close to a break-up and thus was preceded by rifting, indicating that rifting was initiated by tectonic forces [START_REF] Buiter | A review of Wilson Cycle plate margins: A role for mantle plumes in continental break-up along sutures?[END_REF]. Alternate models propose a significant difference between the development of volcanic and magma poor margins, where crustal thinning leads to the exhumation of serpentinite at magma-poor margins and lithospheric pure-shear leads to hot active melting at sub-Moho levels [START_REF] Geoffroy | Volcanic passive margins: another way to break up continents[END_REF][START_REF] Zastrozhnov | Regional structure and polyphased Cretaceous-Paleocene rift and basin development of the mid-Norwegian volcanic passive margin[END_REF].

2) What is the influence of inheritance in margin break-up?

J o u r n a l P r e -p r o o f

The role of tectonic inheritance in the development of rifts and break-up is still a highly debated subject (e. g. [START_REF] Piqué | The central Atlantic rifting: Reactivation of Palaeozoic structures?[END_REF]Petersen and Schiffer, 2016). The present-day margins of the Central and North Atlantic resulted from at least two supercontinent cycles and subsequent break-upsincluding assembly of the supercontinent Rodinia, opening and closure of the Iapetus ocean, assembly and fragmentation of Gondwana and opening of the Atlantic [START_REF] Wilson | Did the Atlantic close and then re-open?[END_REF][START_REF] Thomas | Tectonic inheritance at a continental margin[END_REF]. Rifts often develop along old suture zones [START_REF] Buiter | A review of Wilson Cycle plate margins: A role for mantle plumes in continental break-up along sutures?[END_REF]. Fossil subduction zones with remnant slabs from earlier oceans might survive rifting with parts ending up on both conjugate margins [START_REF] Schiffer | A sub-crustal piercing point for North Atlantic reconstructions and tectonic implications[END_REF]. Material from fossil serpentinized subduction zone mantle wedges might be present in some ocean-continent transition zones or at the base of the thinned continental crust. However, rifts also break through existing cratons, for example the Greenland craton. [START_REF] Reuber | Control of Precambrian-to-Paleozoic orogenic trends on along-strike variations in Early Cretaceous continental rifts of the South Atlantic Ocean[END_REF] found that where orogenic fabric trends parallel to the north-south South Atlantic rift direction narrow (55-90 km) rift zones with modest continental beta factors of 2.5-3.5 develop, while basement fabric trending near-orthogonally to the northsouth South Atlantic rift direction results in wider (185-220 km) rift zones with higher beta factors of 4.3-5. These authors explain that greater amounts of stretching are needed to rupture the orthogonal, orogenic, basement fabric, while smaller amounts of rifting are needed to stretch the weaker and parallel, orogenic, basement fabric.

3) What are the origins and mechanisms of formation of Transform marginal plateaus (TMPs)?

Transform marginal plateaus (TMPs) are bathymetric highs at continental margins, situated at the limit between ocean basins of different ages. One side of the conjugate margin is associated with a transform, or, at least, it is a highly oblique margin [START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF]. The formation of TMP and its role in plate tectonics are still poorly understood. Examples in the Atlantic Ocean are the Falkland, Demerara and Guinea PLATEAUS (Schimschal and[START_REF] Schimschal | The crustal structure of the continental margin east of the Falkland Islands[END_REF][START_REF] Thomas | Tectonic inheritance at multiple scales during more than two complete Wilson cycles recorded in eastern North America[END_REF]Mercier de Lepinay, 2016) and their conjugates the Guinea and Agulhas PLATEAUS [START_REF] Parsiegla | The Agulhas Plateau: Structure and evolution of a Large Igneous Province[END_REF][START_REF] Olyphant | Evolution of the Southern Guinea Plateau: Implications on Guinea-Demerara Plateau formation using insights from seismic, subsidence, and gravity data[END_REF]. 65-90% of TMPs have seen volcanic activity during their tectonic history and only 10% are underlain by continental crust; most of these have complex crusts overprinted by volcanism [START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF]. TMPs that remained in a high position during break-up due to volcanism might have formed the last land bridges between ocean basins and have therefore probably controlled the onset and variation of ocean currents [START_REF] Friedrich | Benthic foraminiferal assemblages from Demerara Rise (ODP Leg 207, western tropical Atlantic): possible evidence for a progressive opening of the Equatorial Atlantic Gateway[END_REF]. Oceanic transforms can act as a long-lived magmatic pathway for melts in the lithosphere [START_REF] Gernigon | Geophysical insights and early spreading history in the vicinity of the Jan Mayen Fracture Zone, Norwegian-Greenland Sea. Tectonophysics, Role of magmatism in continental lithosphere extension continental lithosphere extension[END_REF] and might deform due to stresses induced by an increase in melt supplyat the neighboring mid-ocean ridge [START_REF] Maia | Extreme mantle uplift and exhumation along a transpressive transform fault[END_REF]. The systematic study of these edifices might answer questions about the link between transform margin initiation and volcanic activity [START_REF] Burke | Plume-Generated Triple Junctions: Key Indicators in Applying Plate Tectonics to Old Rocks[END_REF][START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF][START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF].

J o u r n a l P r e -p r o o f

Atlantic Ocean: Rifting, break-up and associated volcanism

The Atlantic has been an important region for plate kinematic studies because of its easily identifiable magnetic anomalies. The first kinematic reconstruction of the Atlantic was published in 1912 by Alfred Wegener, who used the shorelines and fauna on the African and South American continents to propose that Africa and South America were once joined together [START_REF] Wegener | Die Entstehung der Kontinente[END_REF]. Later, [START_REF] Bullard | The fit of the continents around the Atlantic[END_REF] was the first to propose a kinematic reconstruction of the continents around the Atlantic using computational methods based on the hinge line position. During the 1970s and 1980s other elements were incorporated into the models and kinematic reconstructions, as for example seafloor magnetic anomalies, aspects of regional geology and intra-plate deformation (e.g. Le Pichon and Fox 1971; [START_REF] Pitman | Seafloor Spreading in the North Atlantic[END_REF][START_REF] J O U R N A L P R E -P R O O F Olivet | Nouveau modèle d'évolution de l'Atlantique nord et central[END_REF][START_REF] Sibuet | Plate kinematic implications of Atlantic equatorial fracture zone trends[END_REF]Wissmann and Roeser, 1982;[START_REF] Olivet | Cinématique de l'Atlantique Nord et Central[END_REF]. Modern reconstructions use continuously closing plate circuits and include features such as crustal thinning and mountain building (e.g. [START_REF] Matthews | Global plate boundary evolution and kinematics since the late Paleozoic[END_REF]Barnett-Moore et al., 2018;[START_REF] Gurnis | New evidence for geologically instantaneous emplacement of earliest Jurassic Central Atlantic magmatic province basalts on the North American margin[END_REF][START_REF] Müller | Dynamic topography of passive continental margins and their hinterlands since the Cretaceous[END_REF] helping to calculate the position and extent of slab remnants in the mantle (e.g. [START_REF] Van Der Meer | Atlas of the underworld: Slab remnants in the mantle, their sinking history, and a new outlook on lower mantle viscosity[END_REF].

There is general agreement that rifting in the Atlantic started first in the Central Atlantic Ocean (CAO) (North America/NW-Africa) at about 195 Ma ago (Figure 2a; Table 1) with the break-up of the Gondwana continent in latest Triassic-earliest Jurassic (e. g. Olivet, 1978, Klitgord and[START_REF] Klitgord | Plate kinematics of the central Atlantic[END_REF][START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF]. Obliquity of opening in the Central Atlantic was low [START_REF] Brune | Oblique rifting: The rule, not the exception[END_REF]. The next portion of the Atlantic Ocean that opened was the South Atlantic, starting first in the southern Austral segment (Argentina/Namibia-South Africa) during the Early Cretaceous with the break-up of western Gondwana (Figure 2b) around 140 Ma (e. g., [START_REF] Granot | The Cretaceous opening of the South Atlantic Ocean[END_REF]. Extension then propagated to the north of the South Atlantic where break-up began in the late Early Cretaceous (112 Ma ago) between the Eastern Brazilian and Western African continental margins (Figure 2d). The southern North Atlantic opened in two phases (Late Triassic to Early Jurassic and Late Jurassic through Early Cretaceous) with a first phase of undistributed rifting and a second phase when rifting propagated from south to north with final break-up occurring in the Aptian-Albian around 133 Ma(Figure 2c)(e.g. Tucholke and Sibuet 2007). The Equatorial Atlantic started opening 118 Ma ago as a highly oblique margin (e.g. [START_REF] Burke | Plume-Generated Triple Junctions: Key Indicators in Applying Plate Tectonics to Old Rocks[END_REF][START_REF] Sibuet | Plate kinematic implications of Atlantic equatorial fracture zone trends[END_REF][START_REF] Unternehr | South Atlantic fits and intraplate boundaries in Africa and South America. Tectonophysics, 8th Geodynamics Symposium[END_REF]. The full oceanic connection between the Central and North Atlantic occurred during Albian-Turonian times (Figure 2e) about 106 Ma ago (e.g. [START_REF] Pletsch | Cretaceous separation of Africa and South America: the view from the West African margin (ODP Leg 159)[END_REF]. Finally, the north-eastern Atlantic started opening between East Greenland and NW Europe at 55.5 Ma [START_REF] Storey | Timing and duration of volcanism in the North Atlantic Igneous Province: Implications for geodynamics and links to the Iceland hotspot[END_REF] (Figure 2f).

J o u r n a l P r e -p r o o f J o u r n a l P r e -p r o o f (1) [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF]] (9) [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]] (2) [START_REF] Klitgord | Plate kinematics of the central Atlantic[END_REF]] (10) [Müller et al., 2008] (3) [START_REF] Tarling | Another Gondwanaland[END_REF] ( 11) [Moulin et al., 2010] (4) [START_REF] Granot | The Cretaceous opening of the South Atlantic Ocean[END_REF]] (12) [Torsvik et al., 2009] (5) [Rabinowitz and Labrecque, 1979] (13) [START_REF] Gaina | Palaeocene-Recent plate boundaries in the NE Atlantic and the formation of the Jan Mayen microcontinent[END_REF]] (6) [Tucholke and Sibuet, 2007] (14) [Brune et al., 2018] (7) [START_REF] Burke | Plume-Generated Triple Junctions: Key Indicators in Applying Plate Tectonics to Old Rocks[END_REF] (15) Mercier de Lepinay et al., 2016 (8) [START_REF] Storey | Timing and duration of volcanism in the North Atlantic Igneous Province: Implications for geodynamics and links to the Iceland hotspot[END_REF] (16) [START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF] Table 1: Summary of opening phases and their characteristics of Atlantic basins and tectonic setting of the continental margins with location map. Red and white polygons are volcanic margin parts and salt basins from [START_REF] Lundin | Magmatism and extension rates at rifted margins[END_REF] Green polygons are TMPs as defined in Mercier de [START_REF] Mercier De Lépinay | Transform continental margins -Part 2: A worldwide review[END_REF][START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF] J o u r n a l P r e -p r o o f

Observations constraining rifting and opening in the marine environment

The first observations used for the reconstruction of the opening of the Atlantic Ocean were bathymetric data (Figure 3a), allowing to constrain the basic structures of plate tectonics, such as mid-ocean ridges, transform faults and hinge lines along passive margins (e. g. [START_REF] Wegener | Die Entstehung der Kontinente[END_REF][START_REF] Bullard | The fit of the continents around the Atlantic[END_REF]. Second, magnetic anomalies were used for dating the oceanic blocks, to identify the continent-ocean transition zone, the onset of oceanic crustal accretion, as well as the velocity of seafloor spreading [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF][START_REF] Collier | New constraints on the age and style of continental breakup in the South Atlantic from magnetic anomaly data[END_REF] (Figure 3b). Over time, marine magnetic anomalies, combined with other geological information (fracture zones, marginal salt basins), provided the framework for the kinematic reconstructions of the break-up, the genesis of the Atlantic rifted margins and the geometry of seafloor spreading [START_REF] Collette | Geophysical Investigations of the Floor of the Atlantic Ocean between 10° and 38° N (Kroonvlag-project)[END_REF][START_REF] Olivet | Cinématique de l'Atlantique Nord et Central[END_REF][START_REF] Klitgord | Plate kinematics of the central Atlantic[END_REF][START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF][START_REF] J O U R N A L P R E -P R O O F Eagles | New angles on South Atlantic opening[END_REF][START_REF] Labails | An alternative early opening scenario for the Central Atlantic Ocean[END_REF]Moulin et al., 2010, Perez-Diaz and[START_REF] Pérez-Diaz | Constraining South Atlantic growth with seafloor spreading data[END_REF].

Volcanism during rifting and break-up leads to the emplacement of seaward-dipping reflector sequences (SDR) comprising up to 20km-thick layers of mainly volcanic material which often extend up to hundreds of kilometers. It typically also leads to the emplacement of highvelocity material underneath the crustal layer, as has been imaged along the US continental margin (Lase study group, 1986) or East Greenland and Norway [START_REF] Mjelde | Crustal structure of the northern part of the Voring Basin, mid-Norway margin, from wide-angle seismic and gravity data[END_REF]. The underplate layer typically shows up as a high-velocity lower crustal layer (>7.2 km/s). The continental margin of the Hatton Bank in the Northeast Atlantic is the most well-known example where this layer is thought to be caused by magmatism above a mantle thermal anomaly during continental break-up (White et al., 1987). Several studies in volcanic margins, then, interpret this high-velocity lower crustal layer as a magmatic underplate, produced by excess mantle melting (Barton andWhite, 1997, Klingelhoefer et al., 2005). For other authors, however, the high-velocity lower crustal layer represents continental crust intruded by sills [START_REF] White | Lower-crustal intrusion on the North Atlantic continental margin[END_REF]. A study in the Austral South Atlantic suggests that it can be both, heavily intruded lower crust during the early evolution of the volcanic rifted margin, and underplated bodies thereafter, during maturation of volcanic rifting after breakup [START_REF] Becker | Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup[END_REF].

These volcanic structures are one of the most characteristic features of volcanic passive margins [START_REF] Planke | Seismic volcanostratigraphy of largevolume basaltic extrusive complexes on rifted margins[END_REF][START_REF] Geoffroy | Volcanic passive margines[END_REF] and are emplaced during break-up and the initial stage of seafloor spreading (e.g [START_REF] Austin | Continental-oceanic crustal transition off Southwest Africa[END_REF][START_REF] Mutter | Origin of seaward-dipping reflectors in oceanic crustl off the Norwegian margin by subaerailseafloor spreading[END_REF][START_REF] Murillas | Structure and evolution of the Galicia Interior Basin (Atlantic western Iberian continental margin)[END_REF][START_REF] Planke | Seismic response and construction of seaward dipping wedges of flood basalts: Vøring volcanic margin[END_REF][START_REF] Gladczenko | Namibia volcanic margin[END_REF][START_REF] Geoffroy | Volcanic passive margines[END_REF].

J o u r n a l P r e -p r o o f (Müller et al., 2016).

Methodology of this study -wide-angle seismic data help constraining rifting history

Deep sounding seismic reflection and wide-angle data provide information about the deep crustal structure of passive margins and thereby help to answer questions about rifting and the onset of seafloor spreading. Using these data, continental crust, transitional zones and oceanic domains can be better separated and characterized. The structures revealed by the seismic data are a major input for plate kinematic reconstructions and help to further describe the evolution of passive margins. In this study, published seismic reflection and refraction data along the Atlantic continental margins are reviewed. We compare profiles along each margin segment with profiles along their conjugate, in order to estimate the degree of symmetry in the original break-up as well as the influence of volcanism during break-up on the formation of a single margin or conjugate margin pair. By doing so, the geometry of the crustal structure and the degree of crustal thinning of all conjugate profiles can be compared and a model of the opening mechanism proposed. However, uncertainties in the identification of magnetic lineations as seafloor spreading features, especially in the oldest parts of oceanic basins where they could belong to continent-ocean transition (COT) zones and formed by serpentinization processes (west Iberia, [START_REF] Sibuet | Exhumed mantle forming transitional crust in the Newfoundland Iberia rift and associated magnetic anomalies[END_REF], uncertainties in paleomagnetic data of Iberia during rifting and early stages of oceanic accretion ( [START_REF] Vissers | Cretaceous slab break-off in the Pyrenees: Iberian plate kinematics in paleomagnetic and mantle reference frames[END_REF], which were later contested (Barnett- [START_REF] Moore | A reconstruction of the North Atlantic since the earliest Jurassic[END_REF], uncertainties in the identification and age of the oldest oceanic lineations (e.g. [START_REF] Eagles | Getting over continent ocean boundaries[END_REF]Causer et al., 2020 and references therein) raise new problems concerning the relationship between rifting and oceanic accretion, which can overlap through time and the nature, extent and role of COTs.

To identify conjugate margin pairs of seismicrefractionlines, we developed a set of plate kinematic reconstructions of the South, Central and North Atlantic using the GPlates Software [START_REF] Müller | Dynamic topography of passive continental margins and their hinterlands since the Cretaceous[END_REF] and including the position of published wide-angle seismic J o u r n a l P r e -p r o o f profiles. Reconstructions at complete closure as well as reconstructions at early opening stages of oceanic basins (Figure 2) were made using the rotational poles from [START_REF] Matthews | Global plate boundary evolution and kinematics since the late Paleozoic[END_REF]. However, for most regions more detailed studies exist (Eagles and Koenig, 2008;[START_REF] Moulin | A new starting point for the South and Equatorial Atlantic Ocean[END_REF][START_REF] Heine | Kinematics of the South Atlantic rift[END_REF]Barnett-Moore et al., 2018;[START_REF] J O U R N A L P R E -P R O O F Thompson | New starting point for the Indian Ocean: Second phase of breakup for Gondwana[END_REF] and they are appropriately cited in the text. The location of fracture zones [START_REF] Matthews | Geologic and kinematic constraints on Late Cretaceous to mid Eocene plate boundaries in the southwest Pacific[END_REF], magmatic provinces, hotspots [START_REF] Whittaker | Long-term interaction between mid-ocean ridges and mantle plumes[END_REF], and mid-oceanic ridges [START_REF] Müller | Ocean Basin Evolution and Global-Scale Plate Reorganization Events Since Pangea Breakup[END_REF] were used to define segment boundaries and those parts of the margins influenced by volcanism. Existing wide-angle seismic profiles were subsequently digitized and converted to a common color scheme to allow direct comparison of deep seismic profiles. However, the initial interpretations of these profiles remained unchanged as they often represent a more complete work than just modeling seismic velocities, including interpretation of additional data, such as gravity modeling, seismicreflectioninterpretations or geological constraints from the field.

One of the main difficulties of this study is the difference in the quality of the seismic data. Whileolder profiles wereoftenacquiredwith instruments sparselydeployed at 10 km intervals, modern studiesinclude dense receiverspacings of only a few kilometres. While the error of the Moho depth is typically less than a kilometer in modern studies [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], it might reach 2-3 kilometer in older work (LASE Study Group, 1986). However, all profiles selected provide sufficient detailto characterize the nature of the crust and the geometry of the crustal layers in the scope of this manuscript. A third point is the possible obliquity of rifting, which might lead to structural features imaged in an oblique angle by perpendicular profiles. The plate reconstructions themselves assume rigid plates, which probably was not the case during the opening of most of the Atlantic Margins. It is difficult to estimate the error inherent in plate kinematic reconstructions, but using different rotational poles published in the literature indicates differences of less than 15-20 km. Again, this is sufficient for the analysis and comparison presented in this study. For consistency we used the rotational poles of [START_REF] Matthews | Global plate boundary evolution and kinematics since the late Paleozoic[END_REF] throughout this work. To have exact details on error calculations and additional constraints the reader is referred to the original publications.

Central Atlantic

The Central Atlantic is defined in this study within the bounds of the Pico and Gloria fracture zones to the north and the 15°20' N, and Guinea fracture zones to the south (Figure 4). Rifting in the Atlantic started first in the central Atlantic Ocean (CAO) which encompasses the area between the conjugate northeast America (Nova Scotia and US Atlantic margin) and the northwest Africa margins (from Morocco in the north to the Guinea fracture zone in the south) (Figure 4). Rifting occurred in a single phase with the break-up of the supercontinent Gondwana in the latest Triassic-earliest Jurassic (Le Roy and Piqué, 2001;[START_REF] Michard | Continental Evolution: The Geology of Morocco: Structure, Stratigraphy, and Tectonics of the Africa-Atlantic-Mediterranean Triple Junction[END_REF][START_REF] Frizon De Lamotte | Style of rifting and the stages of Pangea breakup[END_REF] (Figure 2). Sea floor spreading and the formation of the first oceanic crust began at about 175 Ma during the Middle Jurassic [START_REF] Klitgord | Plate kinematics of the central Atlantic[END_REF] or around 195 Ma during Sinemurian times [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF].

J o u r n a l P r e -p r o o f

The opening of the Atlantic Ocean was associated with the establishment of a large igneous province known as the Central Atlantic Magmatic Province (CAMP). It is defined by tholeiitic basalts outcropping in South and North America, Africa, and Europe [START_REF] Marzoli | Extensive 200million-year-old continental flood basalts of the Central Atlantic Magmatic Province[END_REF]and 2004[START_REF] Mchone | Non-plume magmatism and rifting during the opening of the central Atlantic Ocean[END_REF]and 2003) and dated between 197 and 203 Ma (Hames et al, 2000;[START_REF] Knight | The Central Atlantic Magmatic Province at the Triassic-Jurassic boundary: paleomagnetic and 40Ar/39Ar evidence from Morocco for brief, episodic volcanism[END_REF][START_REF] Marzoli | Synchrony of the Central Atlantic magmatic province and the Triassic-Jurassic boundary climatic and biotic crisis[END_REF]. The emplacement of the CAMP volcanic products was associated with the Triassic-Jurassic extinction event, which is considered as one of Earth's major extinction events [START_REF] Courtillot | The influence of continental flood basalts on mass extinctions: Where do we stand?[END_REF][START_REF] Blackburn | Zircon U-Pb Geochronology Links the End-Triassic Extinction with the Central Atlantic Magmatic Province[END_REF]. [START_REF] Amante | ETOPO1 arc-minute global relief model: procedures, data sources and analysis[END_REF]. B) Overview of the central Atlantic Ocean located between the Pico and Gloria fracture zones to the north and the 15°20 0N, and Guinea fracture zones to the south (thick black lines), bathymetry and topography from ETOPO1 bathymetry grids [START_REF] Amante | ETOPO1 arc-minute global relief model: procedures, data sources and analysis[END_REF]. The position of the salt (light yellow) is taken from [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF], [START_REF] Davison | Central Atlantic margin basins of North West Africa: Geology and hydrocarbon potential (Morocco to Guinea)[END_REF], [START_REF] Tari | 8 -The conjugate margins of Morocco and Nova Scotia[END_REF]. Major magnetic anomalies are from [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF] and [START_REF] Labails | An alternative early opening scenario for the Central Atlantic Ocean[END_REF]. Offshore CAMP volcanism is from [START_REF] Coffin | Large igneous provinces: Crustal structure, dimensions, and external consequences[END_REF] and [START_REF] Ernst | Large Igneous Provinces[END_REF]. Going from north to south. Black lines along the North American margin represent wide-angle seismic profiles of the [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]Louden et al., 2010), LASE, EDGE-801, USGS-32, and BAa-6 (b) (LASE Study Group, 1986;[START_REF] Tréhu | Structure of the lower crust beneath the Carolina trough, U.S. Atlantic continental margin[END_REF][START_REF] Austin | Crustal structure of the Southeast Georgia embayment-Carolina trough: Preliminary results of a composite seismic image of a continental suture(?) and a volcanic passive margin[END_REF]Holbrook et al., 1994a[START_REF] Holbrook | Seismic structure of the US Mid Atlantic continental margin[END_REF][START_REF] Lizarralde | Crustal structure across the Brunswick magnetic anomaly, offshore Georgia, from coincident ocean bottom and multi-channel seismic data[END_REF][START_REF] Lizarralde | US mid-Atlantic margin structure and early thermal evolution[END_REF]. Black lines along the North African margin represent wide-angle seismic profiles of the Sismar (c), Mirror (d) and Dakhla (e) cruises (Contrucci et al., 2004b;[START_REF] Klingelhoefer | Tectonophysics Crustal structure of the SW-Moroccan margin from wide-angle and re flection seismic data (the DAKHLA experiment) Part A: Wide-angle seismic models[END_REF][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].

J o u r n a l P r e -p r o o f The northeast American and northwest African margins are characterized by the presence of four magnetic anomalies named East Coast Magnetic Anomaly (ECMA) and its conjugate West African CoastMagnetic Anomaly (WACMA), the Blake Spur Magnetic Anomaly (BSMA) and its possible conjugate the African Blake Spur Magnetic Anomaly (ABSMA) (Figure 5) (for the East Canadian margin see [START_REF] Drake | Continental margins and geosynclines: The east coast of North America north of Cape Hatteras[END_REF][START_REF] Dehler | Initial rifting and break-up between Nova Scotia and Morocco: An examination of new geophysical data and models[END_REF][START_REF] Funck | Crustal structure of the northern Nova Scotia rifted continental margin (eastern Canada)[END_REF] for the African margin see [START_REF] Hinz | The Continental Margin of Morocco: Seismic Sequences, Structural Elements and Geological Development[END_REF][START_REF] Roeser | Magnetic Anomalies in the Magnetic Quiet Zone off Morocco[END_REF][START_REF] Roeser | Structural development of the Jurassic Magnetic Quiet Zone off Morocco and identification of Middle Jurassic magnetic lineations[END_REF]Sahabi, 2004). ECMA and WACMA are thought to mark the end of rifting and onset of oceanization [START_REF] Hinz | The Continental Margin of Morocco: Seismic Sequences, Structural Elements and Geological Development[END_REF][START_REF] Roeser | Magnetic Anomalies in the Magnetic Quiet Zone off Morocco[END_REF][START_REF] Roeser | Structural development of the Jurassic Magnetic Quiet Zone off Morocco and identification of Middle Jurassic magnetic lineations[END_REF]Sahabi, 2004;[START_REF] Biari | Opening of the central Atlantic Ocean: Implications for geometric rifting and asymmetric initial seafloor spreading after continental breakup[END_REF], however the origin of the anomalies is still debated and they may originate from seawarddipping reflector sequences or magmatic underplating (Holbrook et al., 1994a;Keen and Potter 1995 a,b). The BSMA was dated by drilling at DSDP site 534 and proposed to be Callovian (165 Ma) [START_REF] Sheridan | Early history of the Atlantic Ocean and gas hydrates on the Blake Outer Ridge: Results of the Deep-Sea Drilling Project Leg 76[END_REF][START_REF] Gradstein | Geologic time scale 2004-why, how, and where next![END_REF].

J o u r n a l P r e -p r o o f

Along the eastern United States margin, thick layers of SDR and magmatic underplate were imaged (LASE Study Group, 1986;[START_REF] Tréhu | Structure of the lower crust beneath the Carolina trough, U.S. Atlantic continental margin[END_REF][START_REF] Austin | Crustal structure of the Southeast Georgia embayment-Carolina trough: Preliminary results of a composite seismic image of a continental suture(?) and a volcanic passive margin[END_REF]Holbrook et al., 1994a[START_REF] Holbrook | Seismic structure of the US Mid Atlantic continental margin[END_REF]. Volcanism decreases to the north towards the Nova Scotian margin (e. g. [START_REF] Funck | Crustal structure of the northern Nova Scotia rifted continental margin (eastern Canada)[END_REF][START_REF] Louden | Chapter 2: Plate tectonics[END_REF]. Along the conjugate African margin, only few volcanic structures interpreted as SDR and some seamounts were imaged [START_REF] Roeser | Structural development of the Jurassic Magnetic Quiet Zone off Morocco and identification of Middle Jurassic magnetic lineations[END_REF], so the northwestern African margin was defined as magma poor (Contrucci et al., 2004b;[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] 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] Benabdellouahed | Recent uplift of the Atlantic Atlas (offshore West Morocco): Tectonic arch and submarine terraces[END_REF]. During rifting four major conjugate salt basins were formed along the Central Atlantic margins: the Moroccan Atlantic salt basin and its conjugate salt basin off Nova Scotia in the northern Central Atlantic margin and the Mauritanian salt basin conjugate to the salt basin of the Carolina Trough, offshore the US margin in the southern Central Atlantic. [START_REF] Klitgord | Plate kinematics of the central Atlantic[END_REF] proposed an evolution model for the Central Atlantic considering the ECMA and WACMA as conjugates, including an eastward ridge jump south of the Canary Islands at the time of BSMA and an onset of seafloor spreading at 175 Ma. However, other authors suggest that it corresponds to a boundary between oceanic crust with a "rough" morphology in the west and a domain with a smoother morphology in the east related to an acceleration of seafloor spreading [START_REF] Markl | Stratigraphic Evolution of Blake Outer Ridge[END_REF].

Based on the identification of magnetic anomalies, salt basin location and the orientation of fracture zones, the models of [START_REF] Olivet | Cinématique de l'Atlantique Nord et Central[END_REF], [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF] and [START_REF] Labails | An alternative early opening scenario for the Central Atlantic Ocean[END_REF] describe the evolution of the North and Central Atlantic from the early stages of oceanic opening to the present. In their reconstruction both the ECMA and WACMA coincide with the limit of the salt basins. [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF] propose an age of initial opening at Sinemurian times (195 Ma), about 20 Ma earlier than proposed by [START_REF] Klitgord | Plate kinematics of the central Atlantic[END_REF].

Based on deep seismic data, [START_REF] Shuck | The role of mantle melts in the transition from rifting to seafloor spreading offshore eastern North America[END_REF] propose that full lithospheric break-up between North America and Africa did not happen during the time of volcanism that produced the ECMA, and that normal seafloor spreading started during the creation of the BSMA under a moderately high mantle potential temperature.

For comparison of the deep structure of the conjugate margins, two roughly conjugate profile pairs were selected and are presented in the following subchapters, the SMART and MIRROR profiles [START_REF] Funck | Crustal structure of the northern Nova Scotia rifted continental margin (eastern Canada)[END_REF]Biari et al., 2015, respectively) and the LASE and DAKHLA profiles (LASE Study Group, 1986 andKlingelhoefer et al., 2009, respectively).

The Nova Scotia and Moroccan conjugate margin pair

Both margins have been sampled by wide-angle seismic cruises, the 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] and OETR [START_REF] Lau | Continent-Ocean Transition Across the Northeastern Nova Scotian Margin from a Dense Wide-Angle Seismic Profile[END_REF] cruises on the North American side and the SISMAR [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] and 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] cruises on the Africanside (Figure 5). The three SMART profiles were acquired in regions were the ECMA shows different amplitudes to study the origin of this magnetic anomaly and the transition J o u r n a l P r e -p r o o f from volcanic to magma-poor rifting. While the SMART 1 profile in the north shows a 150 km broad region with serpentinized upper mantle material exhumed to the seafloor and very thin oceanic crust, the central profile, SMART 2, is characterized by high lower crustal velocities, probably due to a mixture of serpentinized upper mantle material with gabbroic layer 3 [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]. The southernmost profile, SMART 3, images a 100km-wide region of thin crust underlain by a 5 to 10km-thick body interpreted to be magmatic underplate neighboring normal oceanic crust of 7 km thickness [START_REF] Louden | Chapter 2: Plate tectonics[END_REF]. The OETR profile is located about 100 km north of the northernmost SMART profile and shows structures similar to the SMART 1 profile, including a zone of partially serpentinized upper mantle and a thin oceanic crust [START_REF] Lau | Continent-Ocean Transition Across the Northeastern Nova Scotian Margin from a Dense Wide-Angle Seismic Profile[END_REF] indicating that rifting was magma-poor in this region. Seismic profiles from the MIRROR cruise on the NW-African margin and located conjugate to the SMART 1 profile show no indications for the existence of serpentinized upper mantle material [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 image an oceanic crust of 7-8 km thickness, typical of oceanic crust. The crustal structure of unthinned continental crust is similar along both profiles, including three distinct layers and a thickness of 35-38 km, thinning over a distance between 150-200 km. Therefore, a symmetric rifting phase followed by asymmetric oceanic crustal accretion with accretion of mainly serpentinized mantle material towards the Canadian side and magmatic crust towards the African side has been proposed [START_REF] Biari | Opening of the central Atlantic Ocean: Implications for geometric rifting and asymmetric initial seafloor spreading after continental breakup[END_REF] (Figure 6). The difference in oceanic crustal thickness may be explained by the passage of the Canary Hotspot in the region around 60 Ma [START_REF] J O U R N A L P R E -P R O O F Holik | Effects of Canary hotspot volcanism on structure of oceanic crust off Morocco[END_REF]. Alternatively, a 16 km eastward mid-oceanic rift jump has been proposed to explain this asymmetry [START_REF] Lau | Continent-Ocean Transition Across the Northeastern Nova Scotian Margin from a Dense Wide-Angle Seismic Profile[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]. Abbreviations are HSM, highly serpentinised mantle; PSM, serpentinised mantle.

J o u r n a l P r e -p r o o f

(a) After initial extension, (b) asymmetric seafloor spreading, with exhumation to the west and magmatic accretion to the east, and (c) accretion of thin magmatic oceanic crust (after

The US and NW-African margin pair

A second conjugate seismic profile pair is located offshore NW-Africa [START_REF] Klingelhoefer | Tectonophysics Crustal structure of the SW-Moroccan margin from wide-angle and re flection seismic data (the DAKHLA experiment) Part A: Wide-angle seismic models[END_REF] and the US continental coast (LASE Study Group, 1986) (Figure 7). Here, the American margin is highly magmatic, with a thick layer of SDR and other volcanic products. Along its conjugate no SDR were identified, which might explain the lower magnitude of the magnetic anomalies in this region. Some volcanic intrusions are emplaced into the lower crust along the Dakhla profile [START_REF] Klingelhoefer | Tectonophysics Crustal structure of the SW-Moroccan margin from wide-angle and re flection seismic data (the DAKHLA experiment) Part A: Wide-angle seismic models[END_REF]. One major difference is the location of the first identifiable magnetic anomaly, located at thinned continental crust on the African margin and in the oceanic domain at its conjugate. A second difference is the thickness of the pre-rift continental crust, which is 27 km at the African side compared to 40 km along the US continental margin. The fact that the crustal thickness is less along the DAKHLA profiles when compared to those to the north and on the conjugate margin can be explained by the presence of the ReguibatRidge,a large basement high which forms an uplifted part of the West African Craton, [START_REF] Klingelhoefer | Tectonophysics Crustal structure of the SW-Moroccan margin from wide-angle and re flection seismic data (the DAKHLA experiment) Part A: Wide-angle seismic models[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] Benabdellouahed | Recent uplift of the Atlantic Atlas (offshore West Morocco): Tectonic arch and submarine terraces[END_REF]. This Ridge remained stable during the Hercynian orogeny and the Central Atlantic opening and led to the formation of several NE-SW oriented basins (Tarfaya-Laayoune and Mauritanian-Senegal BASINS). Therefore, its crustal thickness is not a direct result of rifting only. The oceanic part of both profiles images a 7 to 10km-thick crust with velocities typical for oceanic crust. [START_REF] Biari | Opening of the central Atlantic Ocean: Implications for geometric rifting and asymmetric initial seafloor spreading after continental breakup[END_REF].

J o u r n a l P r e -p r o o f

(a) After initial extension, (b) accretion of highly intruded and underplated oceanic crust and seaward dipping reflector sequences on the western margin and slightly intruded oceanic crust on the eastern margin, and (c) accretion of thin normal oceanic crust

Southern Atlantic

Several studies have been published to improve the [START_REF] Bullard | The fit of the continents around the Atlantic[END_REF] original opening model of the South Atlantic, by using other geological, geophysical, magnetic and gravity data, but until now the opening mechanism of the South Atlantic Ocean has remained a matter of debate [START_REF] Le Pichon | Marginal Offsets, Fracture Zones, and the Early Opening of the South Atlantic[END_REF]1971;[START_REF] Dietz | Geophysical Illusions of Continental Drift: A DISCUSSION[END_REF][START_REF] Mascle | New pole for early opening of South Atlantic[END_REF][START_REF] Smith | Paleocontinental maps for the Mesozoic and Cenozoic 50[END_REF][START_REF] Sibuet | Plate kinematic implications of Atlantic equatorial fracture zone trends[END_REF][START_REF] Curie | Ouverture de l'Atlantique Sud et discontinuités intra-plaques : une nouvelle analyse[END_REF][START_REF] Unternehr | South Atlantic fits and intraplate boundaries in Africa and South America. Tectonophysics, 8th Geodynamics Symposium[END_REF][START_REF] J O U R N A L P R E -P R O O F Eagles | New angles on South Atlantic opening[END_REF][START_REF] Moulin | A new starting point for the South and Equatorial Atlantic Ocean[END_REF]. During the opening of the South Atlantic, several conjugate pairs of rift basins were formed, Argentina -NamibiaBASINS, Santos, Campos -Espirito Santo -Angola basins and Bahia-Sergipe-Gabon BASINS. However, even if they show almost the same tectono-sedimentary evolution, they display differences from very wide marginal basins with the presence of a thick layer of Aptian salt to very narrow basins with no Aptian salt [START_REF] Davison | Wide and narrow margins of the Brazilian South Atlantic[END_REF][START_REF] Mohriak | South Atlantic divergent margin evolution: rift-border uplift and salt tectonics in the basins of SE Brazil[END_REF]. From analyses of an extensive magnetic dataset it was proposed that a significant portion of the SDR was produced subaerially [START_REF] Collier | New constraints on the age and style of continental breakup in the South Atlantic from magnetic anomaly data[END_REF].

Relative plate motions between the South American and African plates are still debated due to the lack of identifiable magnetic anomalies during most of the continental break-up period. The Cretaceous Magnetic Quiet Zone (CMQZ) is related to a period during which there were no geomagnetic reversals [START_REF] Rabinowitz | The Mesozoic South AtlanticOcean and evolution of its continental margins[END_REF][START_REF] Malinverno | M-sequence geomagnetic polarity time scale (MHTC12) that steadies global spreading rates and incorporates astrochronology constraints[END_REF][START_REF] Granot | The Cretaceous opening of the South Atlantic Ocean[END_REF][START_REF] Collier | New constraints on the age and style of continental breakup in the South Atlantic from magnetic anomaly data[END_REF]. Due to the lack of magnetic data, weak magnetic anomalies close to the equator and a lack of magnetic reversals, several kinematic J o u r n a l P r e -p r o o f reconstructions for the Equatorial segment have been suggested based on fracture zone positions (e.g [START_REF] Olivet | Cinématique de l'Atlantique Nord et Central[END_REF][START_REF] Campan | Analyse cinematique de l'atlantique equatorial : implications sur l'evolution de l'atlantique sud et sur la frontiere de plaques amerique du nord/amerique du sud (These de doctorat)[END_REF][START_REF] Fidalgo González | La cinématique de l'Atlantique Nord : la question de la déformation intraplaque[END_REF]. Along the Central and Austral segments, the thickness of sedimentary layers along the continental domain mask and complicate the gravity response, and only a few gravimetric anomalies identified in the deep ocean can be extended towards the continents [START_REF] Moulin | A new starting point for the South and Equatorial Atlantic Ocean[END_REF].

After the first work of [START_REF] Rabinowitz | The Mesozoic South AtlanticOcean and evolution of its continental margins[END_REF], identifying magnetic signatures back to M11 on the African side off South Africa and back to M4 on the conjugate South American plate off Argentina, the authors identified a high amplitude magnetic anomaly, named the G Anomaly interpreted to mark the ocean-continent transition. As it coincides with thick wedges of seaward-dipping reflectors (SDR) [START_REF] Gladczenko | South Atlantic volcanic margins[END_REF][START_REF] Bray | Geology, Age, and Tectonic Setting of the Cretaceous Sliderock Mountain Volcano[END_REF] these reflectors have been suggested to be its cause [START_REF] Bauer | Deep structure of the Namibia continental margin as derived from integrated geophysical studies[END_REF][START_REF] Corner | Volcanic passive margin of Namibia: A potential fields perspective[END_REF]. Later, Moulin et al.;2010 proposed that the M11 and M9 anomalies do not exist on the South American side and interpret a part of the G anomaly in the PelotasBASIN as M4 anomaly, suggesting to merge them into a single anomaly called Large Marginal Anomaly (LMA) (Moulin et al.;2010).

By constructinga modern evolution model of the South Atlantic Ocean taking into account the direction and timing of the opening as well as the best continental fits, [START_REF] Moulin | A new starting point for the South and Equatorial Atlantic Ocean[END_REF] proposes 4 phases of opening : (1) Opening of the Austral Segment between LMA (~133 Ma) and M4 (130 Ma) (2) Movement of the Santos Block westward and start of extensional movement in the Central Segment (3) Opening of the Central Segment between Late Aptian/Early Albian accompanied by an eastward ridge jump, very close to the African coast, allowing the formation of a first continuous mid-ocean ridge (4) Opening of the Equatorial Atlantic Ocean during Albian times, and definitive water connection between the Central and South Atlantic Oceans. Opening of the Falkland segment preceded these phases. However, it is linked closely to the movement of the Antarctican plate and therefore partly disconnected from the other segments [START_REF] Moulin | A new starting point for the South and Equatorial Atlantic Ocean[END_REF].

In the following figures we present deep seismic transects from theFalkland, Austral, and Central South Atlantic segments (Figure 8 and9). [START_REF] Amante | ETOPO1 arc-minute global relief model: procedures, data sources and analysis[END_REF]. (B) Overview of the South Atlantic Ocean divided into four segments from the north to the south, the Equatorial segment, the Central segment, the South Segment and the Falkland Segment (e. g Popoff, 1988[START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]. Bathymetry and topography from ETOPO1 bathymetry grids [START_REF] Amante | ETOPO1 arc-minute global relief model: procedures, data sources and analysis[END_REF]. The Aptian salt as well as SDR structures are from [START_REF] Torsvik | A new scheme for the opening of the South Atlantic Ocean and the dissection of an Aptian salt basin[END_REF]. The large igneous province volcanics are from [START_REF] Coffin | Large igneous provinces: Crustal structure, dimensions, and external consequences[END_REF]. Magnetic anomalies are from [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 along the South American margin represent wide-angle seismic profiles of the Amazon Cone Experiment and the MARGATS cruise (a) (Greenroyd et al., 2008[START_REF] Lizarralde | Crustal structure across the Brunswick magnetic anomaly, offshore Georgia, from coincident ocean bottom and multi-channel seismic data[END_REF]; SalSa experiment (b) [START_REF] Loureiro | Imaging exhumed lower continental crust in the distal Jequitinhonha basin, Brazil[END_REF]SanBa experiment (c) [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]; BGR04-REFR01(d) and BGR98-REFR2 (e) are from [START_REF] Becker | Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup[END_REF] The AWI-20130010 (f) wide-angle seismic profile running from East Falkland to the Georgia BASIN is after [START_REF] Schimschal | The Falkland Plateau in the context of Gondwana breakup[END_REF] On the African conjugate margin (g) represents wide-angle seismic profiles of the ZaïAngo cruise [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]; (h) P2 profile along the Walvis Ridge after [START_REF] Fromm | Interaction between a hotspot and a fracture zone: The crustal structure of Walvis Ridge at 6° E[END_REF](i) Profile 2 from the MAMBA experiments after Bauer et al., 2000 and (j) Springbok line after Schinkel et al., 2007. J o u r n a l P r e -p r o o f

Falkland Segment

Opening of the South Atlantic started in the south during theEarly Cretaceous (Figure 10) [START_REF] Smith | The fit of the southern continents[END_REF][START_REF] Tarling | Another Gondwanaland[END_REF]. There may be a link to the earlier break-up of the southwestern Weddel Sea that probably started around 160 Ma and was preceded by the emplacement of the Karoo/Ferrar mafic Large Igneous Province (LIP) [START_REF] Lawver | Evolution of the Antarctic continental margins[END_REF][START_REF] Jourdan | Karoo large igneous province: Brevity, origin, and relation to mass extinction questioned by new 40Ar/39Ar age data[END_REF]. Break-up of East Gondwana and the initiation of seafloor spreading in the Riiser-Larsen Sea and MozambiqueBASINand West SomaliBASINS took place at similar times by 160 Ma [START_REF] Roeser | The development of the crust off Dronning Maud Land, East Antarctica[END_REF]Eagles and Koenig, 2008;[START_REF] Leinweber | The Jurassic history of the Africa-Antarctica corridor -new constraints from magnetic data on the conjugate continental margins[END_REF]. [START_REF] Torsvik | Gondwana from top to base in space and time[END_REF] link the break-up of Gondwana to its location over hot mantle over the large African low shear-wave velocity province. The exact motions during break-up are still debated and many detailed studies taking into account plate motions and overlaps, paleo J o u r n a l P r e -p r o o f stress, sedimentary basins and seismic studies have recently been published [START_REF] Leinweber | The Jurassic history of the Africa-Antarctica corridor -new constraints from magnetic data on the conjugate continental margins[END_REF][START_REF] Gaina | The African plate: A history of oceanic crust accretion and subduction since the Jurassic[END_REF][START_REF] Schimschal | The Falkland Plateau in the context of Gondwana breakup[END_REF][START_REF] J O U R N A L P R E -P R O O F Thompson | New starting point for the Indian Ocean: Second phase of breakup for Gondwana[END_REF]. In the southern South Atlantic, the Falkland/Malvinas TMP and its conjugate, the Agulhas TMP, are two of the most prominent morphological features (Figure 10). They are located south and north of the Agulhas-Falkland/Malvinas Fracture zone (AFFZ), respectively. First studies of the Scotia Sea and Falkland PLATEAUS using sonobuoy data led to the suggestion J o u r n a l P r e -p r o o f of a continental nature of the Falkland PLATEAU [START_REF] Ewing | Structure of the Scotia Sea and Falkland Plateau report the final analysis of these data (Table1), South Orkney Islands and South Georgia by km / sec was measured. The overlying crustal layer has a velocity of about 6. 0 km / sec, more Islands and G[END_REF]. Later analysis of magnetic anomalies and seismic data led to the hypothesis that the eastern boundary of the plateau corresponds to a volcanic margin [START_REF] Barker | Evidence for a volcanic rifted margin and oceanic crustal structure for the Falkland Plateau Basin[END_REF]. Recent studies show that it comprises three regions: the Falkland/Malvinas islands, underlain by a 35 km crust of continental origin; the Falkland PLATEAU BASIN, underlain by thick oceanic crust; and the Maurice Ewing Bank, a 28 km thick continental fragment which is heavily overprinted by magmatic intrusions [START_REF] Schimschal | The crustal structure of the continental margin east of the Falkland Islands[END_REF][START_REF] Schimschal | The Falkland Plateau in the context of Gondwana breakup[END_REF] (Figure 11).

J o u r n a l P r e -p r o o f

The southern margin of the African margin, including the conjugate Agulhas PLATEAU were studied in the scope of the Inkabaye Africa project. The plateau underwent two major stretching phases during the Early Jurassic with the initial Gondwana break-up and during the Early Cretaceous due to shear tension along the AFFZ [START_REF] Parsiegla | Deep crustal structure of the sheared South African continental margin: first results of the Agulhas-Karoo Geoscience Transect[END_REF]2009). Along the profile FRA the Moho rises from 40 km inland to 30 km at the coast and then the crust is further thinning toward the AFFZ, where the ocean-continent transition is located [START_REF] Stankiewicz | Crustal structure of the southern margin of the African continent: Results from geophysical experiments[END_REF]. On the subparallel profile GRA, lava flows are identified from seismicreflectiondata. The middle crust is found to be thickened by intrusions and a lower crustal body with velocities between 7.0 km/s and 7.6 km/s makes up about half of the total crustal thickness [START_REF] Parsiegla | The Agulhas Plateau: Structure and evolution of a Large Igneous Province[END_REF] (Figure 12).

Austral Segment

From the Falkland segment, rifting propagated to the north into the Austral segment (Figure 13) about 133 Ma ago [START_REF] Becker | The crustal structure of the southern Argentine margin[END_REF]. The South Atlantic opened in the Early Cretaceous with suggested opening ages between 126 Ma and 137 Ma [START_REF] Rabinowitz | The Mesozoic South AtlanticOcean and evolution of its continental margins[END_REF][START_REF] Unternehr | South Atlantic fits and intraplate boundaries in Africa and South America. Tectonophysics, 8th Geodynamics Symposium[END_REF][START_REF] Nürnberg | A new model for the Paleogene motion of Greenland relative to North America: Plate reconstructions of the Davis Strait and Nares Strait regions between Canada and Greenland[END_REF][START_REF] Gladczenko | South Atlantic volcanic margins[END_REF][START_REF] Jokat | Timing and geometry of early Gondwana breakup[END_REF], and it is commonly proposed that this process progressed from south to north (Rabinowitz &LaBrecque1979;[START_REF] Austin | Continental-oceanic crustal transition off Southwest Africa[END_REF][START_REF] Uchupi | The tectonic style of the Atlantic Mesozoic rift system[END_REF][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]. The opening of this segment of the Atlantic Ocean may thus be described as a northward unzipping of the continent.

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Due to volcanism during rifting, the Austral segment is characterized by volcanic products in the form of layered volcanic sequences and mafic intrusions/underplate at the base of the crust [START_REF] Bauer | Deep structure of the Namibia continental margin as derived from integrated geophysical studies[END_REF][START_REF] Schnabel | The structure of the lower crust at the Argentine continental margin, South Atlantic at 44°S[END_REF][START_REF] Blaich | Crustal breakup and continent-ocean transition at South Atlantic conjugate margins[END_REF][START_REF] Becker | Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup[END_REF]. However, the rifted margins are not continuously of the volcanic type since the southernmost 200 to 300 kilometers are magma-poor (Koopmann et al., 2014b;[START_REF] Koopmann | The late rifting phase and continental break-up of the southern South Atlantic: the mode and timing of volcanic rifting J o u r n a l P r e -p r o o f and formation of earliest oceanic crust[END_REF][START_REF] Franke | Birth of a volcanic margin off Argentina[END_REF]. The change from a non-volcanic to volcanic margin occurs abruptly at both conjugate margins.

The deep structure of the conjugate margins has been imaged over several surveys, across the Colorado BASIN offshore Argentina [START_REF] Franke | Crustal structure across the Colorado Basin, offshore Argentina[END_REF], at the north Falkland BASIN [START_REF] Becker | The crustal structure of the southern Argentine margin[END_REF], the Namibian margin [START_REF] Bauer | Deep structure of the Namibia continental margin as derived from integrated geophysical studies[END_REF], and the southern margin of the African continent [START_REF] Stankiewicz | Crustal structure of the southern margin of the African continent: Results from geophysical experiments[END_REF]. In addition, toseismic wide-angle studies, seismic reflection data and gravity data have been used [START_REF] Franke | Margin segmentation and volcano-tectonic architecture along the volcanic margin off Argentina/Uruguay, South Atlantic[END_REF][START_REF] Blaich | Crustal-scale architecture and segmentation of the Argentine margin and its conjugate off South Africa[END_REF][START_REF] Franke | Birth of a volcanic margin off Argentina[END_REF]. The relationship betweenSDR and the COB (continent ocean boundary) is not homogeneous along the South Atlantic margins and most likely variable on either conjugate section [START_REF] Koopmann | The late rifting phase and continental break-up of the southern South Atlantic: the mode and timing of volcanic rifting J o u r n a l P r e -p r o o f and formation of earliest oceanic crust[END_REF]. According to [START_REF] Koopmann | The late rifting phase and continental break-up of the southern South Atlantic: the mode and timing of volcanic rifting J o u r n a l P r e -p r o o f and formation of earliest oceanic crust[END_REF] , there is no reason to doubt the existence of mainly mafic (oceanic) crust seaward of the outer SDR due to magnetic lineations and seismic character, and there is little doubt that thinned continental crust underlies the feather edge of the SDR.

Paton et al; 2017a; 2017b identified that the Colorado-Orange BASIN rift phase formed a tripartite system with the Namibian Gariep Belt (for location see Figure 33), which they called the Garies Triple Junction. All three rift branches were active during the break-up of Gondwana, but during the Atlantic rift phase the Colorado BASIN failed while the other branches continued to rift, defining the present-day location of the South Atlantic. This clearly contradicts the suggestion that rifting follows zones of crustal heterogeneity (Paton et al;2017a and b).

Two wide-angle seismic profiles acquired perpendicular to the Namibian continental margin cross two wedges of seaward dipping reflectors (inner and outer SDR) at 100-150 km and 300 km offshore [START_REF] Bauer | Deep structure of the Namibia continental margin as derived from integrated geophysical studies[END_REF] (Figure 14). Normal oceanic crust is imaged oceanward of the western SDR wedge, while the continent-ocean transition zone is located at the landward end of the eastern inner SDRs [START_REF] Bauer | Deep structure of the Namibia continental margin as derived from integrated geophysical studies[END_REF]. For the northern Namibian margin, [START_REF] Bauer | Deep structure of the Namibia continental margin as derived from integrated geophysical studies[END_REF] show that the landward-most SDR complex overlies continental crust of about 30 km thickness, and the seaward SDR overlies a high-velocity lower crustal body (HVLC) of 15-20 km thickness with seismic velocities exceeding 7.0 km/s. On the conjugate South American margin, [START_REF] Schnabel | The structure of the lower crust at the Argentine continental margin, South Atlantic at 44°S[END_REF] propose values of 20-25 km for the thickness of the (partly thinned) continental crust underlain by a first high velocity lower crustal body up to 7.3 km/s below the SDR and a further thinning crust seaward of the SDR. The entire transition zone is underlain by up to 20 km of high velocity material, which the authors interpret to be exclusively igneous material and not intruded continental crust. [START_REF] Koopmann | The late rifting phase and continental break-up of the southern South Atlantic: the mode and timing of volcanic rifting J o u r n a l P r e -p r o o f and formation of earliest oceanic crust[END_REF] conclude that the SDR occur at the very end of the rifting process prior to continental break-up of crust of varying thickness that thins quite dramatically towards the 'seaward-most' SDR.

J o u r n a l P r e -p r o o f

Further south, several wide-angle seismic profiles were acquired offshore South Africa (Schinkel et al., 2006;[START_REF] Becker | Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup[END_REF]. The profiles show a single thick SDR complex and up to 10 km thick underplate layers at the transition zone. On the conjugate Argentinian and Uruguay margin three wide-angle seismic transects were acquired [START_REF] Becker | Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup[END_REF]. Although this margin also shows SDR packages and underplate layers, the amount of volcanic products is much lower here, only about 25% of that on the conjugate African margin. According to the authors, the difference in the amount of volcanic products can be explained by asymmetrical rifting in simple shear mode, similar to structures observed in the conjugate East Greenland/Hatton Bank margins. The results also question a simple causal relationship between SDR and high velocity lower layers [START_REF] Becker | Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup[END_REF]. In addition, the location of the underplate with respect to the SDR sequences varies from south to north along the margins of the Austral South Atlantic. In the south, close to the Falkland-Agulhas Fracture Zone, a thin high velocity layer is present, without volcanic extrusiveslike SDR. In the center of the margin segment, the underplate layer is located beneath the inner wedges of the SDR packages and in the north close to the Rio Grande Rise-Walvis Ridge this layer reaches seaward of the SDR domain [START_REF] Becker | Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup[END_REF].

The only timing information on the SDR in the South Atlantic is from the Kudu wells at the border between Namibia and South Africa. Sediments directly overlying the drilled basalts are dated as Late Barremian (in the time-scale used here c. 122-123 Ma [START_REF] Gradstein | Geologic time scale 2004-why, how, and where next![END_REF]. Sparse microfauna in the lowermost interval interbedded with volcanics may indicate an age no older than Valanginian [START_REF] Erlank | Preliminary note on the geochemistry of basalt samples from the Kudu boreholes[END_REF]). From the successive disappearance of magnetic anomalies in the region of SDR, Koopmann et al,. 2016 derive a minimum age estimate for the seaward-most volcanic flows and suggest that the volcanism related to the formation of the South Atlantic propagated from south to north along with the opening of the oceanic basin itself [START_REF] Koopmann | The late rifting phase and continental break-up of the southern South Atlantic: the mode and timing of volcanic rifting J o u r n a l P r e -p r o o f and formation of earliest oceanic crust[END_REF]). (after Schinkel et al., 2007 and[START_REF] Becker | Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup[END_REF]. (a) reconstruction for break-up (COB), (b) accretion of oceanic crust.

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Central segment

The extension propagatedfurther to the North and break-up in the central segment took place in the late Early Cretaceous between theEastern Brazilian/Western African continental margins [START_REF] Rabinowitz | The Mesozoic South AtlanticOcean and evolution of its continental margins[END_REF]Changet al., 1992;[START_REF] Heilbron | From collision to extension: the roots of the southeastern continental margin of Brazil[END_REF][START_REF] Mohriak | South Atlantic divergent margin evolution: rift-border uplift and salt tectonics in the basins of SE Brazil[END_REF][START_REF] Blaich | Crustal breakup and continent-ocean transition at South Atlantic conjugate margins[END_REF] (Figure 16). J o u r n a l P r e -p r o o f

Brazilian-Zaïre Angolan Margin pair

The north of the central segment of the South Atlantic was imaged by two wide-angle seismic surveys, the SALSA survey in 2014 [START_REF] Loureiro | Imaging exhumed lower continental crust in the distal Jequitinhonha basin, Brazil[END_REF][START_REF] Pinheiro | Lithospheric structuration onshore-offshore of the Sergipe-Alagoas passive margin, NE Brazil, based J o u r n a l P r e -p r o o f on wide-angle seismic data[END_REF] on the Brazilian margin at the Sergipe-Alagoas and Jequitinhonha BASINS and the ZAIANGO survey in 2000 in the Congo BASIN [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]. In the reconstruction (Figure 17), the Zaiango 14 profile is located about 150 km south of the Salsa 11 profile, during opening times.

Spanning the Angola-Zaïremargin, Profile 14 is 270 km long (Figure 17b), from the coast to the abyssal plain and crosses the Zaïre canyon [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]. It is located nearly conjugate to the SALSA 11 profile acquired across the Brazilian Campos margin (Loureiro et al., 2018). The Zaïre-Angolan margin is characterized by the presence of a deep subsalt basin which is underlain by an intermediary or transitional type crust neither purely oceanic nor continental [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]. This transitional zone is bounded by a basement ridge with high seismic velocities (6.6 km/s to 6.8 km/s). A relatively thin (2-3 km) high velocity layer at the base of the crust has been suggested to consist of either serpentinizedmantle material or lower crustal material [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]) (Figure 17). The neighboring oceanic crust, despite having a typical thickness of oceanic crust, is unusual in that the upper layer is 5 km thick with laterally highly variable velocities. It has been proposed to consist of an alternation of gabbros, basalt and serpentine, overlying a lower layer of only 2 km thickness with a seismic velocity of 7.5 km/s possibly consisting of serpentinite. The up-to-6 km-thick layer of evaporites can be explained by either an elevated position of the basin at opening [START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF] or a pre-existing depression, repetitively refilled and closed off [START_REF] Crosby | Evolution of deep-water rifted margins: Testing depth-dependent extensional models[END_REF]. Loureiro et al., 2018 and[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].

Along the Jequitinhonha BASIN the SALSA 11 profile images a continental crust of about 20 km thickness thinning to less than 5 km in the distal basin. Here, it is characterized by high seismic velocities and gradients and therefore cannot, according to the authors, beclassified as typicaloceaniccrust, suchthattypicaloceaniccrustwasneverobservedalong the profile. Although the authors suggest that the crust consists of exhumed lower continental crust which has crept towards the basin [START_REF] Loureiro | Imaging exhumed lower continental crust in the distal Jequitinhonha basin, Brazil[END_REF]) (Figure 17), the seismic velocities (> 7.6 km/s) of this layer are significantly higher than those measured in typical lower continental crust elsewhere. In fact, the velocities are much closer to those of the high velocity layer above the Moho identified for example at the Nova Scotia margin, where it is proposed to consist of serpentinized mantle material from seawater descending through thin oceanic crust into the upper mantle [START_REF] Wu | Crustal structure of the central Nova Scotia margin off Eastern Canada[END_REF].

Santos BASIN -Namibia BASIN pair

South of these profiles, another near conjugate wide-angle seismic profile pair consists of the SanBa experiment in the Santos BASIN offshore Brazil and an experiment in the Walvis ridge area. However, the two experiments are not located in the same segment as the SanBa profiles are situated north and the Walvis ridge profiles south of the Florianopolis fracture zone, so a direct comparison is not possible. The nature of the conjugate margins changes across the fracture zone from moderate to low magmatic in the north to heavily magmatic in the south.

The profiles, located in the vicinity of the Walvis ridge and a proposed hotspot trail (Duncan, 1984, Perez-Diaz and[START_REF] Pérez-Diaz | Constraining South Atlantic growth with seafloor spreading data[END_REF], show high lower crustal velocities of up to 7.5 km/s. In contrast to the neighboring profiles at the southwestern African margin where these high velocities do not extend underneath the continent [START_REF] Bauer | Deep structure of the Namibia continental margin as derived from integrated geophysical studies[END_REF]Schinkel, 2007;[START_REF] Hirsch | Deep structure of the western South African passive margin -Results of a combined approach of seismic, gravity and isostatic investigations[END_REF], here, they extend several tens of kilometers underneath the African continent, and might therefore be connected to a mantle thermal anomaly or hot spot [START_REF] Fromm | Interaction between a hotspot and a fracture zone: The crustal structure of Walvis Ridge at 6° E[END_REF][START_REF] Fromm | Interaction between a hotspot and a fracture zone: The crustal structure of Walvis Ridge at 6° E[END_REF]. However, the authors find it unlikely that this thermal anomaly triggered the initial opening of the South Atlantic Ocean due to the missing large-scale intrusions within the continental crust in the region.

During one of the first deep seismic studies along the Santos BASIN, a combined reflection and expanding-spread-profiles (ESP) study was conducted (Figure 18) to roughly image the COBin the Santos BASIN [START_REF] Leyden R | Structure of continental margin off Punta del Este, Uruguay, and Rio de Janeiro, Brazil[END_REF]. The interpretation of 12 000 km of deep sounding seismicreflectiondata, coupled with gravimetric and magnetic modelling, provided a first 3-D view of the deep structure of the Santos, Campos and Espirito Santo BASINS [START_REF] Zalán | An Entirely New 3D-View of the Crustal and Mantle Structure of a South Atlantic Passive Margin -Santos, Campos and Espírito Santo Basins, Brazil[END_REF]. The authors interpreted a large area of proposed exhumed and serpentinized upper mantle material. Based on gravity modelling, serpentinization was deduced to occur down to several kilometers depth.

J o u r n a l P r e -p r o o f

The SanBa profiles [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF] along the Brazilian continental margin spanning the Santos BASIN-São Paulo PLATEAUSystem, show a very abrupt thinning from a 40 km thick continental crust to less than 15 km. Adjacent is a 350 km-wide basin underlain mostly by thinned continental crust [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. Parts of this basin show anomalous velocities for thinned continental crust and they are proposedto be either atypical oceanic crust or, exhumed lower crust overlying altered mantle, or, alternatively, upper continental crust intruded by mafic material, overlying intruded lower continental crust [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF]. A triangular -shaped region in the SE of the Santos BASIN-São Paulo PLATEAUSystem is proposed to consist of either serpentinizedexhumed upper mantle material or proto oceanic crust including basaltic flows on top of a layer of serpentinized upper mantle material [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][START_REF] Fromm | Interaction between a hotspot and a fracture zone: The crustal structure of Walvis Ridge at 6° E[END_REF]. (a) Reconstruction at 86 Ma, (b) Reconstruction at 112 Ma, (c) reconstruction for break-up (COB), (d) accretion of oceanic crust. Red polygons mark volcanism [START_REF] Whittaker | Long-term interaction between mid-ocean ridges and mantle plumes[END_REF] and green polygons mark transform marginal plateaus [START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF].

J o u r n a l P r e -p r o o f

Two transform marginal plateaus (TMP) are located along this segment, the Sao Paulo PLATEAU north of the Florianopolis Fracture Zone and the Walvis PLATEAU south of it. The Walvis PLATEAU consists of a 26 to 35 km-thick heavily intruded crust, probably of continental origin with a more-than-300 km-wide HVLC and the western part is proposed to consist of "Icelandic" type crust [START_REF] Fromm | Interaction between a hotspot and a fracture zone: The crustal structure of Walvis Ridge at 6° E[END_REF][START_REF] Planert | The wide-angle seismic image of a complex rifted margin, offshore North Namibia: Implications for the tectonics of continental breakup[END_REF]. The Sao Paulo PLATEAUwas found to consist of thinned continental crust; however, small scale volcanic activity also took place during its construction [START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF], Klingelhoefer et al., 2015).

Equatorial Segment

The last and northernmost segment of the Southern Atlantic between South America and Africa started rifting in a predominantly transform mode in the Early Cretaceous [START_REF] Burke | Plume-Generated Triple Junctions: Key Indicators in Applying Plate Tectonics to Old Rocks[END_REF][START_REF] Sibuet | Plate kinematic implications of Atlantic equatorial fracture zone trends[END_REF][START_REF] Unternehr | South Atlantic fits and intraplate boundaries in Africa and South America. Tectonophysics, 8th Geodynamics Symposium[END_REF]) (Figure 19). Rifting here was strike-slip or highly oblique in nature and controlled by large-scale transform faults, (from south to north the Chain, Romanche and Saint Paul fracture zones) with intermittent short segments of divergent margins [START_REF] Nürnberg | A new model for the Paleogene motion of Greenland relative to North America: Plate reconstructions of the Davis Strait and Nares Strait regions between Canada and Greenland[END_REF]Edwards et al, 1997;[START_REF] Basile | Phanerozoic geological evolution of the Equatorial Atlantic domain[END_REF][START_REF] Heine | Kinematics of the South Atlantic rift[END_REF]. A transtensional shear corridor with a dextral sense of displacement developed at the northern continental margin of Brazil (Azevedo, 2011) (Figure 19). From numeric modeling, a break-up age of 118 Ma is predicted [START_REF] Heine | Kinematics of the South Atlantic rift[END_REF] which is in good agreement with other studies [START_REF] Karner | Tectonic significance of syn-rift sediment packages across the Gabon-Cabinda continental margin[END_REF][START_REF] Dupré | Structure of the Gabon Margin from integrated seismic reflection and gravity data[END_REF]. Numerical modeling also shows that oblique rifting facilitates the rifting process [START_REF] Brune | Modeling suggests that oblique extension facilitates rifting and continental break-up[END_REF], the obliqueness of a rift can accelerate its evolution and final opening as compared to orthogonal rifts, thereby explaining the failing of the central and western African rifts [START_REF] Heine | Oblique rifting of the Equatorial Atlantic: why there is no Saharan Atlantic Ocean[END_REF] around 110 Ma. Linked to this failure is the onset of transpression along the Côte d'Ivoire-Ghana Ridge leading to a regional uplift event and theformation of a regional unconformity in mid-Albian times [START_REF] Pletsch | Cretaceous separation of Africa and South America: the view from the West African margin (ODP Leg 159)[END_REF][START_REF] Basile | Phanerozoic geological evolution of the Equatorial Atlantic domain[END_REF]. The break-up between the African and South American continental lithospheres occurred at 104 Ma with the oceanic spreading center passing the Côte d'Ivoire/Ghana Marginal Ridge by 100-99 Ma [START_REF] Clift | Transform tectonics and thermal rejuvenation on the Côte d'Ivoire-Ghana margin, west Africa[END_REF][START_REF] Pletsch | Cretaceous separation of Africa and South America: the view from the West African margin (ODP Leg 159)[END_REF][START_REF] Basile | Phanerozoic geological evolution of the Equatorial Atlantic domain[END_REF][START_REF] Antobreh | Rift-shear architecture and tectonic development of the Ghana margin deduced from multichannel seismic reflection and potential field data[END_REF]. The riftBASINSentered a phase of thermal subsidence with a minor reactivation in post-Early Cretaceous times (e.g. [START_REF] Janssen | Temporal and spatial correlations between changes in plate motions and the evolution of rifted basins in Africa[END_REF]. The first deepwater connection between the Central and South Atlantic became established in the late Albian to middle Conician [START_REF] Pletsch | Cretaceous separation of Africa and South America: the view from the West African margin (ODP Leg 159)[END_REF]. This separation had far-reaching implications for the definitive separation of African and South American fauna and flora, oceanic currents and the sedimentary and geochemical evolution in the neighboring ocean basins (e.g. [START_REF] J O U R N A L P R E -P R O O F Wegener | Two notes concerning my theory of continental drift[END_REF][START_REF] Pletsch | Cretaceous separation of Africa and South America: the view from the West African margin (ODP Leg 159)[END_REF].

While the Central Atlantic creates margins with long rifted segments separated by a few transform faults which offset the mid-ocean ridge, the rifted margins along the Equatorial Atlantic are generally short and associated with complex transform fault tectonics [START_REF] Azevedo | Interpretation of a Deep Seismic Reflection Profile in the Pará Maranhăo Basin[END_REF].

The African side of this margin was studied during the Charles Darwin Cruise 55 [START_REF] Peirce | Cote d'Ivoire-Ghana margin: seismic imaging of passive rifted crust adjacent[END_REF] as well as part of the Equasis programs of 1983 and 1990 (Edwards et al., 1997a and b) on a NW-SE profile offshore Ghana, spanning the complete transform margin. It is J o u r n a l P r e -p r o o f extremely narrow here thinning the crust from 23 km to 10 km over a distance of only 15 km. The neighboring oceanic crust is thin (~4-5 km) and the transition zone includes crust of highvelocities but no sign of volcanic underplating [START_REF] Peirce | Cote d'Ivoire-Ghana margin: seismic imaging of passive rifted crust adjacent[END_REF]Edwards et al., 1997a and b). Along the Suriname and French Guyana margin and the Brazilian margin, seismic data were acquired in the scope of the ACE study (Amazon Cone Experiment) [START_REF] Greenroyd | Crustal structure of the French Guiana margin, West Equatorial Atlantic[END_REF](Greenroyd et al., , 2008a(Greenroyd et al., and 2008b) ) and offshore French Guiana and Suriname during the MARGATS deep seismic cruise [START_REF] Lizarralde | Crustal structure across the Brunswick magnetic anomaly, offshore Georgia, from coincident ocean bottom and multi-channel seismic data[END_REF] (Figure 8 and 19). Profile A (Figure 20) images a 38 km-thick crust interpreted to be of continental origin at the margin of French Guiana [START_REF] Greenroyd | Crustal structure of the French Guiana margin, West Equatorial Atlantic[END_REF]. The zone of crustal thinning is only 50 km wide, narrower than normal rifted margins, but wider than most transform margins. The continent-ocean transition is about 30 km wide and oceanwards, a 4-5 km thin oceanic crust was modeled, comparable to that on the African side, despite the fact that these profiles are not conjugate(Figure 19). The profile is interpreted to reflect a "leaky" transform margin formed through transtensional extension (Greenroyd et al., 2008b) or a hyper-oblique margin [START_REF] Sapin | Post-rift subsidence of the French Guiana hyper-oblique margin: From rift-inherited subsidence to Amazon deposition effect[END_REF]. [START_REF] Greenroyd | Crustal structure of the French Guiana margin, West Equatorial Atlantic[END_REF]2008). Orange transparent polygons represent the location of volcanic provinces [START_REF] Whittaker | Long-term interaction between mid-ocean ridges and mantle plumes[END_REF] and green transparent areas TMP [START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF].

J o u r n a l P r e -p r o o f

J o u r n a l P r e -p r o o f

Four TMPs are located along this segment: the conjugate Demerara and Guinea PLATEAUS, the Liberia PLATEAU, and the Côte d'Ivoire-Ghana PLATEAU. Based on a tight network of industrial deep seismic reflection profiles, [START_REF] Reuber | Demerara Rise, offshore Suriname: Magma-rich segment of the Central Atlantic Ocean, and conjugate to the Bahamas hot spot[END_REF] propose the presence of thick SDR sequences possibly related to the Bahamas hotspot constituting a large part of the DemeraraPLATEAU. These SDR could originate from the presence of the Bahamas HotSpot in the region during the initial opening of the Central Atlantic [START_REF] Reuber | Demerara Rise, offshore Suriname: Magma-rich segment of the Central Atlantic Ocean, and conjugate to the Bahamas hot spot[END_REF]. These SDR were confirmed later by two wide-angle seismic velocity models from the MARGATS cruise seismic experiment [START_REF] Lizarralde | Crustal structure across the Brunswick magnetic anomaly, offshore Georgia, from coincident ocean bottom and multi-channel seismic data[END_REF] (Figure 20). Results of [START_REF] Lizarralde | Crustal structure across the Brunswick magnetic anomaly, offshore Georgia, from coincident ocean bottom and multi-channel seismic data[END_REF], show a 30 km-thick crust, with an upper SDR crust and a middle crust, where velocities vary from 4.50 km/s to 7.00 km/s; the deepest layer was modeled by high velocities between 7.20 km/s and 7.60 km/s, and are interpreted as intruded magmatic material. For the authors, the DemeraraPLATEAU would, therefore, be an inherited Jurassic volcanic margin boarding the Central Atlantic [START_REF] Lizarralde | Crustal structure across the Brunswick magnetic anomaly, offshore Georgia, from coincident ocean bottom and multi-channel seismic data[END_REF]. The presence of SDR sequences and HVLC at the DemeraraPLATEAU led to suggesting a polyphased origin of the Plateau including a first phase creating the volcanic western margin and, during the Cretaceous, a second phase creating its northern (transform or highly oblique) and eastern (divergent) margins [START_REF] Basile | Structure and evolution of the demerara plateau, offshore frenchguiana: Rifting, tectonic inversion and post-rift tilting at transform-divergent margins intersection[END_REF][START_REF] Reuber | Demerara Rise, offshore Suriname: Magma-rich segment of the Central Atlantic Ocean, and conjugate to the Bahamas hot spot[END_REF][START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF][START_REF] Lizarralde | Crustal structure across the Brunswick magnetic anomaly, offshore Georgia, from coincident ocean bottom and multi-channel seismic data[END_REF]. Although much-less explored, thick SDR sequences were also identified along the conjugate Guinea PLATEAU (Mercier de Lepinay et al., 2016). In a later phase (Aptian-Albian), the Guinea PLATEAU was overprinted by volcanic extrusions [START_REF] Olyphant | Evolution of the Southern Guinea Plateau: Implications on Guinea-Demerara Plateau formation using insights from seismic, subsidence, and gravity data[END_REF]. At the neighboring Sierra Leone Rise, magma feeder dikes for these volcanics are proposed to have been guided by transform-related lithospheric discontinuities [START_REF] Jones | Lamprophyric volcanism of Cenozoic age on the Sierra Leone Rise: Implications for regional tectonics and the stratigraphic time scale[END_REF]. While little data exist on the Liberia TMP, the Côte d'Ivoire Ghana PLATEAUhas been extensively studied and consists of stretched continental crust at the intersection between a divergent and a transform margin [START_REF] Sage | Crustal structure of the continent-ocean transition off the Cote d'Ivoire-Ghana transform margin: Implications for thermal exchanges across the palaeotransform boundary[END_REF]. [START_REF] Greenroyd | Crustal structure of the French Guiana margin, West Equatorial Atlantic[END_REF]Greenroyd et al., 2008;[START_REF] Lizarralde | Crustal structure across the Brunswick magnetic anomaly, offshore Georgia, from coincident ocean bottom and multi-channel seismic data[END_REF]. [START_REF] Amante | ETOPO1 arc-minute global relief model: procedures, data sources and analysis[END_REF]

J o u r n a l P r e -p r o o f

. (B) and (C) Overview of the North Atlantic

Ocean. SDR, extrusive lavas and sills are from [START_REF] Horni | Offshore volcanic facies[END_REF][START_REF] Horni | Regional distribution of volcanism within the North Atlantic Igneous Province[END_REF]. Magnetic anomalies are from [START_REF] Bronner | Magmatic breakup as an explanation for magnetic anomalies at magma-poor rifted margins[END_REF] and [START_REF] Nirrengarten | Kinematic Evolution of the Southern North Atlantic: Implications for the Formation of Hyperextended Rift Systems[END_REF]. Sedimentary basins from [START_REF] Funck | Crustal structure[END_REF], [START_REF] Alves | Diachronous evolution of Late Jurassic-Cretaceous continental rifting in the northeast Atlantic (west Iberian margin)[END_REF], Lundin and[START_REF] Lundin | Hyperextension, serpentinization, and weakening: A new paradigm for rifted margin compressional deformation[END_REF][START_REF] J O U R N A L P R E -P R O O F Tugend | Formation and deformation of hyperextended rift systems: Insights from rift domain mapping in the Bay of Biscay-Pyrenees[END_REF] [START_REF] Voss | Variations in magmatic processes along the East Greenland volcanic margin[END_REF]; (c) LVMT (after Tsikalas et al., 2005);(d) ARK 1988-3 (after Weigel et al. 1995); (e) JMKR 95-3 (after Kodaira et al., 1998a); (f) OBS2000-8 (after [START_REF] Mjelde | Crustal transect across the North Atlantic[END_REF]; (g) KRISE 7 (after [START_REF] Brandsdottir | Evolution of a Divergent Plate Boundary; From the Active Kolbeinsey Ridge, N-Iceland to the Exinct Aegir Ridge, Norway Basin[END_REF](h) OBS 2000-1 (after Breivik et al., 2006); (i) Vøring 96 Line 8A (after Raum, 2002); (j) Vøring 96 Line 8B (after J o u r n a l P r e -p r o o f [START_REF] Raum | Crustal structure of the southern part of the Vöring Basin, mid-Norway margin, from wide-angle seismic and gravity data[END_REF]; (k) SIGMA 1 (after Holbrook et al. 2001); (l) ICEMELT Line (after [START_REF] Darbyshire | Crustal structure above the Iceland mantle plume imaged by the ICEMELT refraction profile[END_REF](m) FIRE offshore (after Richardson et al. 1998) ;(n) iSIMM Faroe line (after [START_REF] Roberts | Imaging igneous rocks on the North Atlantic rifted continental margin[END_REF]); (o) SIGMA 2 [START_REF] Korenaga | Crustal structure of the southeast Greenland margin from joint refraction and reflection seismic tomography[END_REF]; (p) AMP Line E (after [START_REF] Klingelhofer | Crustal structure of the NE Rockall Trough from wide-angle seismic data modeling[END_REF]. Black lines along offshore West Iberia margin, represent wideangle seismic profiles of the ISE1, CAM144, and IAM9 [START_REF] Bullock | From continental extension to seafloor spreading: Crustal structure of the Goban Spur rifted margin, southwest of the UK[END_REF][START_REF] Zelt | Assessment of crustal velocity models using seismic refraction and reflection tomography[END_REF][START_REF] Chian | Deep structure of the oceancontinent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: Ocean Drilling Program (Legs 149 and 173) transect[END_REF][START_REF] Dean | Deep structure of the oceancontinent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: The IAM-9 transect at 40°20′N[END_REF] and wide-angle seismic profiles Screech1,2 and 3 along the Newfoundland margin [START_REF] Funck | Crustal structure of the ocean-continent transition at Flemish Cap: Seismic refraction results[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] Lau | Crustal structure across the Grand Banks -Newfoundland Basin Continental Margin -I. Results from a seismic refraction profile[END_REF].

: HB (Hatton BASIN); RT (Rockall Trough); PB (Porcupine BASIN); CS (Celtic Sea); WAB (Western Approach BASIN); OK (Orphan Knoll); OB (OrphinBASIN); FPB (Flemish Pass BASIN); JAB (Jeanne d 'Arc BASIN); WB (Whale BASIN); HoB (Horseshoe BASIN); SWB (South Whale BASIN); HoB (Horseshoe BASIN); CB (Carson BASIN); DB (Le DanoisBASIN); PoB (Porto BASIN); PeB (PenicheBASIN); LB (Lusitanian BASIN); AB (AlentejoBASIN); AlB (Algarve BASIN). Black lines along the NE Atlantic margin represent wide-angle seismic profiles of the (a) Barents 98 line 3E (after Breivik et al. 2003) (b) AWI 20030200 (after

Southern North Atlantic

Some studies consider the North Atlantic Ocean to be completely closed at Early Jurassic (e.g. [START_REF] Schettino | Tectonic history of the western Tethys since the Late Triassic[END_REF][START_REF] Vissers | Mesozoic rotation of Iberia: Subduction in the Pyrenees?[END_REF]Barnett-Moore et al., 2016), while other studies indicate that rifting started already in the Late Triassic to Early Jurassic south of Iberia due to the north-westward propagation of CAO extension (e.g. [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]. During this time, rifting is accompanied by only minor crustal thinning [START_REF] Pérez-Gussinyé | The rift to drift transition at nonvolcanic margins: Insights from numerical modelling[END_REF]Tucholke and Sibuet, 2007;Mohn et al., 2015 and references therein). Break-up started first in Late Jurassic-Early Cretaceous along the southern Iberia margin and then propagated northward to the Galicia Margin. During this phase, the extension led to the formation of a series of rift basins with typically asymmetric half grabens (e.g. Orphan and Rockall BASINS, Bay of Biscay, Jeanne d'Arc and Whale BASINS) filled by Triassic evaporites and Jurassic carbonates [START_REF] Murillas | Structure and evolution of the Galicia Interior Basin (Atlantic western Iberian continental margin)[END_REF][START_REF] Enachescu | Structural setting and petroleum potential of the Orphan Basin, offshore Newfoundland and Labrador[END_REF]Tucholke et al., 2007;Tucholke and Sibuet, 2007;[START_REF] Pereira | Post-rift compression on the SW Iberian margin (eastern North Atlantic): a case for prolonged inversion in the ocean-continent transition zone[END_REF]. Seafloor spreading started during the mid-Cretaceous (Aptian-Albian) (Tucholke and Sibuet, 2007). The full oceanic connection between the Central and North Atlantic occurred during Albian-Turonian times [START_REF] Koutsoukos | Paleobathymetry of the continental margin of Brazil during the Albian[END_REF][START_REF] Koutsoukos | Micropalaeontological and geochemical evidence of mid-Cretaceous dysoxic-anoxic palaeoenvironments in the Sergipe Basin, northeastern Brazil[END_REF]).

In the southern North Atlantic, the conjugate Iberian and Newfoundland margins are magmapoor rifted margins, with no SDRs or other volcanic structures observed [START_REF] Manatschal | Rifting and early evolution of ancient ocean basins: the record of the Mesozoic Tethys and of the Galicia-Newfoundland 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]) (Figures 21 and22).

To the south, theJ anomaly was imaged over exhumed mantle and thinned continental crust. It is a large and high amplitude magnetic anomaly (> 800 nT) that characterizes the Iberia-Newfoundland conjugate margin pair [START_REF] Srivastava | Magnetic evidence for slow seafloor spreading during the formation of the Newfoundland and Iberian margins[END_REF][START_REF] Russell | Magmatism at the west Iberia non-volcanic rifted continental margin: evidence from analyses of magnetic anomalies[END_REF][START_REF] Funck | Crustal structure of the ocean-continent transition at Flemish Cap: Seismic refraction results[END_REF]. These conjugate anomalies were used to identify the OCT zone. For [START_REF] Srivastava | Magnetic evidence for slow seafloor spreading during the formation of the Newfoundland and Iberian margins[END_REF], the J anomaly represents the beginning of the M sequence of seafloor-spreading magnetic anomalies (M0-M3). The nature of the J-magnetic anomaly is debated.Many authors propose magmatic activity as the cause, including magmatic intrusions [START_REF] Russell | Magmatism at the west Iberia non-volcanic rifted continental margin: evidence from analyses of magnetic anomalies[END_REF] or a pulse of magmatism that accompanied the finalbreak-up of the Iberian-Newfoundland rift systems [START_REF] Bronner | Magmatic breakup as an explanation for magnetic anomalies at magma-poor rifted margins[END_REF]. However, [START_REF] Sibuet | Exhumed mantle forming transitional crust in the Newfoundland Iberia rift and associated magnetic anomalies[END_REF] propose that here, exhumed and serpentinized subcontinental mantle material might form weak magnetic anomalies similar to oceanic anomalies, withan alignment of magnetite grains during theserpentinization process. Furthermore, it has been argued that the Janomaly might be polygenetic, i.e. originating from several magmatic events and not suitable for reconstructing J o u r n a l P r e -p r o o f the opening and seafloor spreading [START_REF] Bronner | Magmatic breakup as an explanation for magnetic anomalies at magma-poor rifted margins[END_REF][START_REF] Nirrengarten | Kinematic Evolution of the Southern North Atlantic: Implications for the Formation of Hyperextended Rift Systems[END_REF], an hypothesis which was contested by [START_REF] Tucholke | Problematic plate reconstruction[END_REF].

Figure 22: Reconstruction of the Southern North Atlantic at 105 Ma with rotational poles from [START_REF] Matthews | Global plate boundary evolution and kinematics since the late Paleozoic[END_REF]. The fixed plate is North America. Locations of wide-angle seismic profiles are marked by solid lines.

The southern North Atlantic margins are among the best-studied margins on Earth with a wealth of marine geophysical surveys including reflection and wide-angle seismic data. In the scope of the IODP and ODP drilling program, several wells have been drilled [START_REF] Boillot | The north and north-west Spanish continental margin: a review[END_REF][START_REF] Sawyer | Proceedings of the Ocean Drilling Program,Initial Reports[END_REF]Whitmarsh and Wallace, 2001;ODP Leg 173 Shipboard Scientific Party, 1998;Tucholke and Sibuet, 2007;[START_REF] Bayrakci | Fault-controlled hydration of the upper mantle during continental rifting[END_REF]. However, magnetic anomalies that are key for kinematic reconstructions are unclear in this region and do not necessarily have a conjugate or a precise age [START_REF] Gillard | Tectonomagmatic evolution of the final stages of rifting along the deep conjugate Australian-Antarctic magma-poor rifted margins: Constraints from seismic observations[END_REF]Causer et al., 2020). Based on a compilation of seismic and geochronological data, [START_REF] Nirrengarten | Nature and origin of the J-magnetic anomaly offshore Iberia-Newfoundland: implications for plate reconstructions[END_REF] showed that the J anomaly, which was used for many kinematic models, does not correspond to an oceanic magnetic anomaly and therefore should not be used as such for kinematic restorations. As a result, the rift and early seafloor spreading evolution as well as the rotation poles remain still highly debated (Le Pichon and [START_REF] J O U R N A L P R E -P R O O F Le Pichon | Western extension of boundary between European and Iberian plates during the Pyrenean orogeny[END_REF][START_REF] Olivet | La cinématique de la plaque ibérique[END_REF][START_REF] Rosenbaum | Reconstruction of the tectonic evolution of the western Mediterranean since the Oligocene[END_REF][START_REF] Sibuet | Pyrenean orogeny and plate kinematics[END_REF][START_REF] Vissers | Mesozoic rotation of Iberia: Subduction in the Pyrenees?[END_REF]Barnett-Moore et al., 2016). Taking these factors into account, the opening of the southern North Atlantic most likely started with an extension phase leading to the formation of half-graben type basins (Peron-Pinvidic and Manatschal, 2009), followed by increased thinning in Tithonian to Barremian times [START_REF] Boillot | Ocean-continent boundary off the Iberian margin: A serpentinite diapir west of the Galicia Bank[END_REF]. Numerous interpretations have been made for the break-up age. Based on structural and stratigraphic data, [START_REF] Wilson | Rifting along non-volcanic passive margins: stratigraphic and seismic evidence from the Mesozoic successions of the Alps and western Iberia[END_REF] propose an early Valanginian age (138 Ma). In contrast, [START_REF] Whitmarsh | Models of the development of the West Iberia rifted continental margin at 40°30′N deduced from surface and deep-tow magnetic anomalies[END_REF] and [START_REF] Russell | Magmatism at the west Iberia non-volcanic rifted continental margin: evidence from analyses of magnetic anomalies[END_REF] from the fact that serpentinized upper mantle material with magmatic additions can form regions characterized by a magnetic anomaly pattern similar to the pattern over true oceanic crust [START_REF] Bronner | Magmatic breakup as an explanation for magnetic anomalies at magma-poor rifted margins[END_REF]Causer et al., 2020).

In terms of deep crustal structure, the Newfoundland margin was studied as part of the SCREECH seismic experiment. Three wide-angle seismicrefractionprofiles were acquired across the margins of the Grand Banks of Newfoundland and Flemish Cap in the direction of extension, with the objective to image the deep structure of the margin from the continental platform onto the abyssal plain. The conjugate Iberian margin was studied by lines ISE 1 [START_REF] Zelt | Assessment of crustal velocity models using seismic refraction and reflection tomography[END_REF]2003), CAM 144 [START_REF] Chian | Deep structure of the oceancontinent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: Ocean Drilling Program (Legs 149 and 173) transect[END_REF], and IAM9 [START_REF] Dean | Deep structure of the oceancontinent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: The IAM-9 transect at 40°20′N[END_REF], Davy et al., 2016). We divide the Iberian -Newfoundland conjugate rifted margins into northern, central and southern segments.

Northern segment

SCREECH Line 1 is a 320-km-long profile acquired on the southeastern Flemish Cap continental margin (Figure 23). Along this line, [START_REF] Funck | Crustal structure of the ocean-continent transition at Flemish Cap: Seismic refraction results[END_REF] found a 30-km-thick continental crust, with velocities ranging from 6.0 km/s to6.7 km/s. This continental crust thins to just 1.5 km, over a distance of 90 km. A 3km-thick oceanic crust that thins locally to 1 km is imaged with velocities of 4.7 km/s and 6.9 km/s. Over an 80-km-wide zone, a layer with velocities of 7.6 km/s and8.0 km/s underlying both the thinned continental crust and the thin oceanic crust is imaged and interpreted as partially serpentinized mantle with velocities between 7.6 km/sand 8.0 km/s (Figure 20). Adjacent to the zone with serpentinized mantle, a 6-km-thick oceanic crust is encountered.

The western margin of Galicia Bank was imaged along the ISE 1 line [START_REF] Whitmarsh | The ocean/continent transition beneath the Iberia Abyssal Plain and continental-rifting to seafloor-spreading processes[END_REF]. The continental crust at Galicia Bank is divided into only two layers with velocities between 5.2 km/sand 6.9 km/s. The velocity model shows a 60km-wide zone of serpentinized mantle with velocities between 7.2 km/sand 7.6 km/s underlying both thin continental and thin oceanic crust. A peridotite ridge exposed at the seafloor was interpreted as the border of the margin that separates continental from oceanic crust. It has been modeled with velocities of 3.5 km/s. A 7km-thick oceanic crust displays velocities from 4.6 km/s to 4.8 km/s at the top of layer 2 and 7.0 km/s in layer 3. Where the oceanic crust overlies serpentinized mantle, the thickness is reduced from 2.5 to 3.5 km (Figure 23).

Comparison between the two conjugate profiles suggests symmetric oceanic crustal accretion as both profiles show the same velocities and thickness for the oceanic part overlying the serpentinized mantle. However, the continental crust at Galicia Bank is divided into only two layers with velocities between 5.2 km/s and 6.9 km/s, whereas the Flemish Cap crust exhibits three layers with velocities ranging from 6.0 km/s to 6.7 km/s. [START_REF] Funck | Crustal structure of the ocean-continent transition at Flemish Cap: Seismic refraction results[END_REF] relate this to differences in the internal structure or composition. In addition, the crustal thinning at Galicia Bank extends over a wider zone compared to the conjugate margin surveyed with SCREECH line 1. Some basement highs imaged along the West Iberia margin were, by comparison with the drilled peridotite ridge, proposed to also consist mainly of exhumed J o u r n a l P r e -p r o o f continental serpentinite [START_REF] Dean | Galicia Bank ocean-continent transition zone: new seismic reflection constraints[END_REF]. These ridges are similar to oceanic core complexes consisting of exhumed mantle material sampled at the Mid-Atlantic Ridge, implying the existence of a gradual transition between continental extension, accretion of amagmatic seafloor and magmatic spreading (Jagoutz et al., 2007;[START_REF] Dean | Galicia Bank ocean-continent transition zone: new seismic reflection constraints[END_REF]. The first magmatically accreted oceanic crust located 20 km from the peridotite ridge, has a thickness of only 0.5 km [START_REF] Davy | Continental hyperextension, mantle exhumation, and thin oceanic crust at the continent-ocean transition, West Iberia: New insights from wide-angle seismic[END_REF]. (after Funck et al., 2003 and[START_REF] Whitmarsh | The ocean/continent transition beneath the Iberia Abyssal Plain and continental-rifting to seafloor-spreading processes[END_REF]. (a) Reconstruction of the Southern North Atlantic at 125 Ma (b) reconstructed for the initiation of seafloor spreading and (c)at the time of magnetic anomaly M0 (118 Ma).

Central segment

The 368-km-long seismicrefractionline SCREECH 2 (Van Avendonk et al., 2006;2009) extends from the eastern Grand Banks into the NewfoundlandBASIN (Figure 24). The tomographic inversion indicates that the continental crust has a maximum thickness of 27 km, with velocities varying from 5.5 km/s to 6.5 km/s.The crustal thickness thins to 6 km beneath thecontinental slope of Grand Banks and coincides with anomalously-high seismic velocities (7.0-7.2 km•s-1) in the lower crust of the shelf edge. Further seaward, a 25-km-wide zone isinterpreted to consist of exhumed and serpentinized continental mantle with velocities from 6.3 km/s to 7.7 km/s. Unroofed mantle and very thin oceanic crustwereimaged seaward, with J o u r n a l P r e -p r o o f seismic velocities ranging from 5.0 km/s to 7.0 km/s. The mantle layer was modeled with velocities between 7.8 km/s and 8.2 km/s (Figure 24). At the conjugate Iberia Abyssal Plain south of Galicia Bank, the seismic velocity structure along line CAM 144 shows 2-5 km thick upper continental crust with several fault blocks and velocities of 5.0 km/s to6.6 km/s. This crust is underlain by a high-velocity layer (7.3 km/s to7.9 km/s) of poorly serpentinized peridotite (0-25%). There was no evidence for the existence of a basement with characteristics of oceanic crust along this profile [START_REF] Chian | Deep structure of the oceancontinent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: Ocean Drilling Program (Legs 149 and 173) transect[END_REF].

Thick continental crust is not modeled on either conjugate profiles, however, thin continental crust is imaged on both sides of the rift with a different observed nature [START_REF] Van Avendonk | Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada[END_REF]2009). Exhumed mantle that was serpentinized to a great depth is exposed on both margins. No prerift sediments were imaged within on the transition zone along, the SCREECH line 2, which lead [START_REF] Van Avendonk | Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada[END_REF] to suggest that the Newfoundland BASINwas formed by exhumation of midcrustal or lower crustal rocks. However, on the conjugate margin along Cam144, continental crust blocks appear to be cut by seawarddipping normal faults. Therefore, compared to the transition zone of SCREECH line 2, the basement relief along Cam144 is higher and the continental crust is thinner [START_REF] Chian | Deep structure of the oceancontinent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: Ocean Drilling Program (Legs 149 and 173) transect[END_REF][START_REF] Van Avendonk | Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada[END_REF] J o u r n a l P r e -p r o o f [START_REF] Van Avendonk | Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada[END_REF]2009 and[START_REF] Chian | Deep structure of the oceancontinent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: Ocean Drilling Program (Legs 149 and 173) transect[END_REF].

Southern segment

SCREECH line 3 is 565 km long and is the southernmost profile acquired across the Grand Banks-Newfoundland BASIN [START_REF] Lau | Crustal structure across the Grand Banks -Newfoundland Basin Continental Margin -I. Results from a seismic refraction profile[END_REF] (Figure 25). The velocity model of this part of the margin shows a 36km-thick continental crust with P wave velocities of 5.8 km/s to 6.9 km/s. Crustal thinning occurs over a 170km-wide zone and is characterized by the presence of several large tilted blocks with a width of ~20 km that decreases oceanward. An 80kmwide zone of transitional crust is imaged, with a thickness of 5 to 6 km and velocities ranging from 4.4 to 7.8 km/s and interpreted as exhumed serpentinized mantle. A 200-km-wide zone with reduced mantle velocities (7.6 km/s to 7.9 km/s) is observed under the transitional zone and thin continental crust and interpreted as partially (<10 percent) serpentinized mantle. Oceanwards, a 2 to 6km-thick oceanic crust is imaged and interpreted as a result of slow seafloor spreading [START_REF] Lau | Crustal structure across the Grand Banks -Newfoundland Basin Continental Margin -I. Results from a seismic refraction profile[END_REF] (Figure 25).

The conjugate line IAM 9 is 320 km long and was acquired in the southern Iberian Abyssal Plain [START_REF] Dean | Deep structure of the oceancontinent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: The IAM-9 transect at 40°20′N[END_REF]. The velocity model shows a 28km-thick continental crust that thins to 7 km over an 80-km-wide zone and is characterized by the presence of several large tilted blocks. A 170-km-wide zone of transitional crust is imaged with a thickness of 4.5 km and velocities ranging from 7.3 km/s to 7.9 km/s.This zone is interpreted as a peridotite ridge and has been directly sampled [START_REF] Dean | Deep structure of the oceancontinent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: The IAM-9 transect at 40°20′N[END_REF].

Even if mantle exhumation and serpentinization appears to have occurred on both margins before oceanic crust was formed, comparison between the two conjugate profiles suggests asymmetrical margins. This strong asymmetry shows that continental break-up was concentrated on the Iberian side and a wider zone of extended continental crust has been left on the Newfoundland side. [START_REF] Lau | Crustal structure across the Grand Banks -Newfoundland Basin Continental Margin -I. Results from a seismic refraction profile[END_REF] suggest that such significant asymmetry may be related to the large width (270 km) of thSe rift. Moreover, the S reflector, a reflector J o u r n a l P r e -p r o o f whichslopes slightly towards the continent, is not observed on the Newfoundland margin, which contradicts Wernicke's simple shear model [START_REF] Wernicke | Uniform-sense normal simple shear of the continental lithosphere[END_REF]. [START_REF] Lau | Crustal structure across the Grand Banks -Newfoundland Basin Continental Margin -I. Results from a seismic refraction profile[END_REF][START_REF] Dean | Deep structure of the oceancontinent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: The IAM-9 transect at 40°20′N[END_REF]. (a) Reconstruction of the Southern North Atlantic at 125 Ma (b) reconstructed for the initiation of seafloor spreading and (c)at accretion of oceanic crust.

Northeast Atlantic

During the Cretaceous, EW extension between the North American and Eurasian plates led to rifting and break-up in the Labrador Sea and Baffin Bay. The start of seafloor spreading is disputed but lies between magnetic Chron C31 (69 Ma, e.g. [START_REF] J O U R N A L P R E -P R O O F Roest | Sea-floor spreading in the Labrador Sea: A new reconstruction[END_REF][START_REF] Keen | Structural characteristics of the ocean-continent transition along the rifted continental margin, o ff shore central Labrador[END_REF] and C27 (62 Ma, e.g. [START_REF] Nürnberg | A new model for the Paleogene motion of Greenland relative to North America: Plate reconstructions of the Davis Strait and Nares Strait regions between Canada and Greenland[END_REF][START_REF] Hosseinpour | Full-fit reconstruction of the Labrador Sea and Baffin Bay[END_REF] and J o u r n a l P r e -p r o o f ceased before Chron C13 (33 Ma, [START_REF] Chalmers | Development of the continental margins of the Labrador Sea: a[END_REF][START_REF] Delescluse | The oceanic crustal structure at the extinct, slow to ultraslow Labrador Sea spreading center[END_REF][START_REF] Peace | An evaluation of Mesozoic rift-related magmatism on the margins of the Labrador Sea: Implications for rifting and passive margin asymmetry[END_REF]. East of Greenland, break-up occurred at 55.5 Ma in the Early Eocene (e.g. [START_REF] Storey | Timing and duration of volcanism in the North Atlantic Igneous Province: Implications for geodynamics and links to the Iceland hotspot[END_REF][START_REF] Seton | Global continental and ocean basin reconstructions since 200Ma[END_REF][START_REF] Gaina | Break-up and seafloor spreading domains in the NE Atlantic[END_REF] resulting in simultaneous oceanic crustal accretion east and west of Greenland until the spreading ceased in the Labrador Sea and Baffin Bay.

The NE Atlantic is bounded by the Senja Fracture Zone in the north and the Charlie Gibbs Fracture Zone in the south. It opened after several rifting phases spanning more than 300 Ma, from the Late Palaeozoic to the Mesozoic/Early Cenozoic (e.g. Fossen, 2010 and references therein). However, it is important to note that in the NE Atlantic there were multiple phases of rifting in contrast to e.g. the Newfoundland-Iberia margin that saw multiphase rifting [START_REF] Reston | Lithospheric extension from rifting to continental breakup at magma-poor margins: Rheology, serpentinisation and symmetry[END_REF]Peron-Pinvindic et al., 2013).

The North Atlantic Igneous Province (NAIP) formed prior to, during and after breakup [START_REF] Coffin | Large igneous provinces: Crustal structure, dimensions, and external consequences[END_REF][START_REF] Saunders | The north Atlantic igneous province[END_REF][START_REF] Horni | Regional distribution of volcanism within the North Atlantic Igneous Province[END_REF]. Basaltic rocks of this large igneous province extend over a surface area of at least 1.3×106 km2 [START_REF] Eldholm | North Atlantic volcanic margins: Dimensions and production rates[END_REF]. Two main periods of magmatism have been proposed.Thefirst at 62-57 Ma and a second major pulse of magmatism at c. 56-54 Ma [START_REF] Saunders | The north Atlantic igneous province[END_REF][START_REF] Storey | Timing and duration of volcanism in the North Atlantic Igneous Province: Implications for geodynamics and links to the Iceland hotspot[END_REF].However, [START_REF] Wilkinson | Compilation and appraisal of geochronological data from the North Atlantic Igneous Province (NAIP)[END_REF] propose that there was no time gap in volcanism.

The associated volcanic activity was extensive and produced thick seaward dipping reflector (SDR) sequences along the continental margins [START_REF] Parkin | Influence of the Iceland mantle plume on oceanic crust generation in the North Atlantic[END_REF]. The highest amount of volcanic/magmatic products is recorded in the vicinity of the Greenland-Iceland-Faroe Ridge (GIFR) [START_REF] Holbrook | Mantle thermal structure and active upwelling during continental breakup in the North Atlantic[END_REF]. The transform margin in the north between Svalbard/SW Barent Sea and NE Greenland (Ritzman and Jokat, 2003;[START_REF] Ritzmann | Crustal structure between the Knipovich Ridge and the Van Mijenfjorden (Svalbard)[END_REF], is unaffected by the magmatism. After break-up east of Greenland, the Aegir Ridge spreading center and the proto-Reykjanes Ridge propagated through the North Atlantic Craton (Figure 21). Several models have been proposed to explain the shape of the NAIP, the volcanic YermakPLATEAU and Morris Jesup Rise (e.g. [START_REF] White | Magmatism at rift zones: The generation of volcanic continental margins and flood basalts[END_REF][START_REF] Jones | Lamprophyric volcanism of Cenozoic age on the Sierra Leone Rise: Implications for regional tectonics and the stratigraphic time scale[END_REF]. Some continental fragments, such as the Jan Mayen Microplate north of Iceland were left behind after rifting and break-up [START_REF] Gernigon | The Norway Basin revisited: From continental breakup to spreading ridge extinction[END_REF]. This continental fragment was the result of the separation of a part of Greenland through the Kolbeinsey Ridge after spreading ceased at the Aegir Ridge [START_REF] Gaina | Palaeocene-Recent plate boundaries in the NE Atlantic and the formation of the Jan Mayen microcontinent[END_REF]. Many studies associate the 35 to 40-km-thick igneous crust along the Greenland-Iceland-Faroe Ridge (GIFR) with the magmatic activity of an Iceland hotspot or plume [START_REF] Staples | Faroe-Iceland Ridge Experiment 1. Crustal structure of northeastern Iceland[END_REF][START_REF] Darbyshire | Crustal structure above the Iceland mantle plume imaged by the ICEMELT refraction profile[END_REF]. In a study involving receiver functions and numerical modeling, [START_REF] Foulger | The Iceland Microcontinent and a continental Greenland-Iceland-Faroe Ridge[END_REF] propose that part of the lower crust of Iceland and the GIFR may contain heavily intruded continental crust [START_REF] Foulger | The Iceland Microcontinent and a continental Greenland-Iceland-Faroe Ridge[END_REF]. Similarly, Torsvik et al. (2015) suggested the J o u r n a l P r e -p r o o f existence of an up to 70 km wide zone of continental crust beneath southeastern Iceland based on isotope data.

Between Greenland and NW Europe, the NE Atlantic Ocean contains patches of ocean crust with a series of symmetric magnetic anomalies parallel to the oceanic ridges. Chron 24 (52.9

Ma) is the oldest magnetic anomaly identified in the NE Atlantic Ocean. However, the origin of some of these magnetic anomalies remains disputed. For example, anomalies between the Jan Mayen Ridge and the Vøring Marginal High originally thought to be part of the 24 chron system [START_REF] Skogseid | Early Cenozoic crust at the Norwegian continental margin and the conjugate Jan Mayen Ridge[END_REF] were later interpreted to result from recent magmatic activity on Jan Mayen Island rather than by seafloor spreading, as indicated by aeromagnetic data and geological sampling [START_REF] Gernigon | Geophysical insights and early spreading history in the vicinity of the Jan Mayen Fracture Zone, Norwegian-Greenland Sea. Tectonophysics, Role of magmatism in continental lithosphere extension continental lithosphere extension[END_REF]Torsvik et al., 2015). J o u r n a l P r e -p r o o f

Svalbard transform segment

Based on wide-angle seismic data of [START_REF] Breivik | Crustal structure and transform margin development south of Svalbard based on ocean bottom seismometer data[END_REF], the northern transform margin west of Svalbard has a narrow continent-ocean transition zone typical of transform margins, thinning from 25 km to 10 km thickness over a distance of only 50 km (Figure 27). Two transform marginal plateaus are located along this margin, the Morris Jesup Rise and the YermakPLATEAUat the border between the NE Atlantic and Arctic Ocean [START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF]. However, the crustal nature of both plateaus is still debated to be either continental slivers overprinted by volcanism or Eocene oceanic plateaus [START_REF] Jackson | The Yermak Plateau: Formed at a triple junction[END_REF]Engen et al., 2008;[START_REF] Faleide | Structure and evolution of the continental margin off Norway and the Barents[END_REF]. The YermakPLATEAU experienced volcanic influence during its construction, and it might have recently been rejuvenated as indicated by high heat-flow values (Okay and Crane, 1992). Using seismic reflection data, [START_REF] Berglar | Initial opening of the Eurasian Basin, Arctic Ocean[END_REF] identified rotated fault blocks at the NE YermakPLATEAU margin, bounded by major listric normal faults, and half-grabens filled with syn-rift sediments. Based on these observations, [START_REF] Berglar | Initial opening of the Eurasian Basin, Arctic Ocean[END_REF] interpret this region as a rifted continental margin, implying that the NE YermakPLATEAU is of continental origin. While part of the Yermak PLATEAUmight be continental, the northern section and the Morris Jesup Rise may have formed a continuous volcanic massif when the propagating rift arrived at the Spitsbergen or de Geer fault zone (Okay and Crane, 1992).

J o u r n a l P r e -p r o o f Barents 98-line 3E (after Breivik et al. 2003).

The northern segment around Mohns Ridge

The Greenland side of this segment has been studied through four wide-angle seismic profiles: AWI-20030200 to AWI20030500 (Figures 21 & 28) (Schlindwein et al., 1999a and[START_REF] Schlindwein | east Greenland from integrated geophysical studies 104[END_REF][START_REF] Voss | Continent-ocean transition and voluminous magmatic underplating derived from P-wave velocity modelling of the East Greenland continental margin[END_REF][START_REF] Voss | Variations in magmatic processes along the East Greenland volcanic margin[END_REF]. The northernmost profile (AWI-20030200) samples a margin with only small amounts of magma and an oceanic crust thinning over a very short distance (120 km) until magnetic anomaly C21 (47.1 Ma). The southern seismic transect (AWI-20030500) is associated with a sedimentary basin of up to 7 km depth beneath flood basalts [START_REF] Voss | Variations in magmatic processes along the East Greenland volcanic margin[END_REF]. The continental region of about 30 km thickness shows volcanic edifices and some magmatic underplating landward of the COB magmatic underplate. Initial oceanic crustal thickness decreases from 9-13 km in the south to 5 km in J o u r n a l P r e -p r o o f the north [START_REF] Voss | Variations in magmatic processes along the East Greenland volcanic margin[END_REF]. The thickness of the HVLC increases towards the south up to a maximum of 15 km. In comparison, along the conjugate profiles LVMT4 and LVMT1 offshore the Lofoten, the oceanic crust is 1-2 km thicker while continental crustal thickness is similar [START_REF] Tsikalas | Crustal structure of the Lofoten-Vester\aalen continental margin, off Norway[END_REF] (Figure 28). Along both a HVLC extends from the C23 anomaly to underneath the continent, with its maximum thickness of 5-8 km at the COT [START_REF] Voss | Variations in magmatic processes along the East Greenland volcanic margin[END_REF][START_REF] Tsikalas | Crustal structure of the Lofoten-Vester\aalen continental margin, off Norway[END_REF]. Along this part of the Greenland margin, break-up related SDR packages decrease in volume both northward and southward from a central point around 75°N [START_REF] Franke | Polyphase magmatism during the formation of the northern East Greenland continental margin[END_REF].

The north-south differences in the distribution of the HVLC along the basin are proposed to result from either a transfer zone that acted as a barrier to northward magma flow, or a second magmatic event associated with the separation of the Jan Mayen microcontinent from Greenland [START_REF] Voss | Variations in magmatic processes along the East Greenland volcanic margin[END_REF]. [START_REF] Korenaga | Crustal structure of the southeast Greenland margin from joint refraction and reflection seismic tomography[END_REF][START_REF] Holbrook | Mantle thermal structure and active upwelling during continental breakup in the North Atlantic[END_REF][START_REF] Voss | Variations in magmatic processes along the East Greenland volcanic margin[END_REF][START_REF] Tsikalas | Crustal structure of the Lofoten-Vester\aalen continental margin, off Norway[END_REF].( a The Vøring Transform Marginal PLATEAU is situated north of the East Jan Mayen FZ [START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF]. Wide-angle seismic data indicate a magmatically overprinted continental crust for the plateau [START_REF] Mjelde | Lower crustal seismic velocity-anomalies; magmatic underplating or serpentinized peridotite? Evidence from the Vøring Margin, NE Atlantic[END_REF][START_REF] Berndt | High velocity breakup related sills in the Vøring Basin, off Norway[END_REF]. A high velocity layer interpreted to be mafic intrusions/underplate is underlying the plateau with a highly J o u r n a l P r e -p r o o f variable thickness of up to 8 km [START_REF] Mjelde | Lower crustal seismic velocity-anomalies; magmatic underplating or serpentinized peridotite? Evidence from the Vøring Margin, NE Atlantic[END_REF]. The flexed continental crust is dilated by numerous feeder-dikes of the thick overlying SDR sequences [START_REF] Abdelmalak | The ocean-continent transition in the mid-Norwegian margin: Insight from seismic data and an onshore Caledonian field analogue[END_REF].

The conjugate of the VøringPLATEAU would be situated at the NE-Greenland margin (Loncke et al., 2019).

The central segment around the Aegir and Kolbeinsey ridges and the Greenland-Iceland-Faroe Ridge

This segment was the object of several wide-angle seismic surveys mostly concentrating on the origin of the Icelandic magmatic province and the Jan Mayen Microcontinent (e.g. ARK -Weigel et al., 1995, Vøring 96 -Raum, 2000;FIRE -Richardson et al., 1998;iSIMM Faroe line -Roberts et al., 2009) (Figure 29 and 30). North of the Greenland-Iceland Faroe Ridge (GIFR), the ARK 1988-3 line [START_REF] Weigel | Investigations of the East Greenland continental margin between 70° and 72° N by deep seismic sounding and gravity studies[END_REF] shows 35 km thick continental crust beneath the Greenland margin (Figure 30). Still onshore, the 15km-deep Jameson Land BASIN is crossed with the basement high forming Liverpool Land to the east of it. From there, the continental crust thins seaward and is underlain by a HVLC that [START_REF] Weigel | Investigations of the East Greenland continental margin between 70° and 72° N by deep seismic sounding and gravity studies[END_REF] propose to result from magmatism. The adjacent oceanic crust is 6-7 km thick [START_REF] Weigel | Investigations of the East Greenland continental margin between 70° and 72° N by deep seismic sounding and gravity studies[END_REF]. Conjugate to this line is profile JKMR-95 L3 crossing the western margin of the Jan Mayen Microcontinent (Figure 29). The oceanic crust on this line is 9-10 km thick in the west but thins to 5 km towards the Jan Mayen Microcontinent [START_REF] Kodaira | Evolution of oceanic crust on the Kolbeinsey Ridge, north of Iceland, over the past 22 Myr[END_REF]) (Figure 30). Line JKMR-95L3 connects eastward with OBS 2000 Line 8, showing a 17km-thick crust beneath the Jan Mayen Microcontinent [START_REF] Mjelde | Crustal transect across the North Atlantic[END_REF]. There is no evidence for a HVLC, which is why [START_REF] Kodaira | Evolution of oceanic crust on the Kolbeinsey Ridge, north of Iceland, over the past 22 Myr[END_REF] proposed the western margin of the Jan Mayen Microcontinent to be non-volcanic. The exact outline of the Jan Mayen Microcontinent is still disputed (see the various proposed continent ocean boundaries in [START_REF] Funck | Crustal structure[END_REF], it extends from south of the island of Jan Mayen to somewhere north of Iceland [START_REF] Gaina | Palaeocene-Recent plate boundaries in the NE Atlantic and the formation of the Jan Mayen microcontinent[END_REF]. The microcontinent has a crustal thickness of about 17 km and elevated lower crustal velocities and basaltic flows on its eastern side [START_REF] Kodaira | Evolution of oceanic crust on the Kolbeinsey Ridge, north of Iceland, over the past 22 Myr[END_REF]. Further to the east, profile Vøring-96 8B images 7-8 km-thick oceanic crust [START_REF] Raum | Crustal structure of the southern part of the Vöring Basin, mid-Norway margin, from wide-angle seismic and gravity data[END_REF]. In the south, KRISE line 7 is located at the continent-ocean transition zone of the Jan Mayen Microcontinent [START_REF] Brandsdottir | Evolution of a Divergent Plate Boundary; From the Active Kolbeinsey Ridge, N-Iceland to the Exinct Aegir Ridge, Norway Basin[END_REF] linking with OBS 2000 Line 1 and in its extension Vøring-96 8A [START_REF] Breivik | Rates of continental breakup magmatism and seafloor spreading in the Norway Basin-Iceland plume interaction[END_REF][START_REF] Raum | Crustal structure and evolution of the Faeroe, Møre and Vøring margins from wideangle seismic and gravity data[END_REF][START_REF] Raum | Crustal structure of the southern part of the Vöring Basin, mid-Norway margin, from wide-angle seismic and gravity data[END_REF] (Figure 30) at the mid-Norwegian continental margin. This 160km-wide margin is underlain by a HVLC of up to 4 km thickness.

J o u r n a l P r e -p r o o f Orange transparent areas represent the location of volcanic provinces [START_REF] Whittaker | Long-term interaction between mid-ocean ridges and mantle plumes[END_REF] and green transparent areas represent transform marginal plateaus [START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF]. 1988Line 3 (after Weigel et al. 1995); (b) JMKR-95 Line 3 (after Kodaira et al., 1998a); (c) OBS 2000 Line 8 (after Mjelde et al., 2008);(d) Vøring 96 Line 8B (after [START_REF] Raum | Crustal structure and evolution of the Faeroe, Møre and Vøring margins from wideangle seismic and gravity data[END_REF]; (e) KRISE Line 7 (after [START_REF] Brandsdottir | Evolution of a Divergent Plate Boundary; From the Active Kolbeinsey Ridge, N-Iceland to the Exinct Aegir Ridge, Norway Basin[END_REF]; (f) OBS 2000 Line 1 (after [START_REF] Breivik | Rates of continental breakup magmatism and seafloor spreading in the Norway Basin-Iceland plume interaction[END_REF]; (j) Vøring 96 Line 8A (after [START_REF] Raum | Crustal structure and evolution of the Faeroe, Møre and Vøring margins from wideangle seismic and gravity data[END_REF][START_REF] Raum | Crustal structure of the southern part of the Vöring Basin, mid-Norway margin, from wide-angle seismic and gravity data[END_REF].

J o u r n a l P r e -p r o o f

A second transect chosen in this margin segment is located along the Greenland-Iceland-Faroe Ridge including Iceland itself (Figures 29 and31). Located at the Greenland margin, SIGMA Line 1 extends onto the Greenland-Iceland Ridge and shows a crust exceeding 30 km in thickness with a HVLC with velocities up to 7.5 km/s extending at least for 150 km from the coast and possibly even farther towards Iceland [START_REF] Holbrook | Mantle thermal structure and active upwelling during continental breakup in the North Atlantic[END_REF]. The COT zone is probably located landward of the western end of the profile. Spanning Iceland, the ICEMELT line indicates that the crustal thickness increases from 25 km in the north to 38-40 km in the southern central part [START_REF] Darbyshire | Crustal structure above the Iceland mantle plume imaged by the ICEMELT refraction profile[END_REF]. In the young volcanic regions, the upper crust is only 5 km thick, but ridge jumps may have doubled the upper crustal layer thickness locally [START_REF] Darbyshire | Crustal structure above the Iceland mantle plume imaged by the ICEMELT refraction profile[END_REF]. Lower crustal velocities, between 7.1 km/s and 7.35 km/s are higher than in normal oceanic crust, which can be explained by elevated temperatures in the mantle. East of Iceland, the transition between the continental Faroe block and the thickened oceanic crust of the Faroe-Iceland Ridge was mapped by the FIRE profile [START_REF] Richardson | Crustal structure beneath the Faroe Islands and the Faroe-Iceland Ridge[END_REF]. The lower part of the crust beneath the Faroe Islands exhibits high velocities that may relate to magmatic underplating or mafic intrusions [START_REF] Richardson | Crustal structure beneath the Faroe Islands and the Faroe-Iceland Ridge[END_REF]. To the north, the iSIMM Faroes profil was acquired with a very dense seismometer spacing of 2 to 5 km and was able constrain a narrow COT zone of only 50 km width and large amounts of intrusives and extrusives within the transition zone [START_REF] Roberts | Imaging igneous rocks on the North Atlantic rifted continental margin[END_REF]. J o u r n a l P r e -p r o o f

The southern segment along the Reykjanes Ridge

This segment was imaged by three wide-angle seismic profiles of the SIGMA experiment [START_REF] Korenaga | Crustal structure of the southeast Greenland margin from joint refraction and reflection seismic tomography[END_REF][START_REF] Holbrook | Mantle thermal structure and active upwelling during continental breakup in the North Atlantic[END_REF][START_REF] Hopper | Structure of the SE Greenland margin from seismic reflection and refraction data: Implications for nascent spreading center subsidence and asymmetric crustal accretion during North Atlantic opening[END_REF] showing the magma-rich nature of the margin(Figure 32).SIGMA 2 is located closest to the Iceland HotSpotand shows 27-km-thick crust at the continent-ocean boundary (COB), from where the oceaniccrust thins to about 10 km over a distance of 150 km [START_REF] Holbrook | Mantle thermal structure and active upwelling during continental breakup in the North Atlantic[END_REF]. The profile SIGMA 3 is located further away from Iceland showing an initial oceanic crustal thickness of 16 km at COB thinning gradually to 8 km over a distance of 170 km. The southernmost profile SIGMA 4 also has an initial oceanic crustal thickness of 16 km but here the thinning to 8-9 km occurs over only 75 km, reflecting the increasing distance to the Iceland plume [START_REF] Holbrook | Mantle thermal structure and active upwelling during continental breakup in the North Atlantic[END_REF].

The conjugate margin of the Faroe-Hatton-Rockall PLATEAUwas sampled along several profiles (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][START_REF] Parkin | Influence of the Iceland mantle plume on oceanic crust generation in the North Atlantic[END_REF][START_REF] Vogt | The Hatton Basin and continental margin: Crustal structure from wide-angle seismic and gravity data[END_REF][START_REF] Shannon | Structural setting, geological development and basin modelling in the Rockall Trough[END_REF]. Figure 32 shows a conjugate reconstruction for SIGMA line 3 [START_REF] Hopper | Structure of the SE Greenland margin from seismic reflection and refraction data: Implications for nascent spreading center subsidence and asymmetric crustal accretion during North Atlantic opening[END_REF] and the iSIMM Hatton dip line [START_REF] White | Crustal structure of the Hatton and the conjugate east Greenland rifted volcanic continental margins, NE Atlantic[END_REF]. Although the original crustal thickness might have been over 50 km, the crustal thickness at the landward limit of the profiles is about 32 km on the Greenland side and only 24 km on the Hatton Bank side, probably due to previous rifting events [START_REF] Ziegler | Chapter 30 -Post-Hercynian plate reorganization in the Tethys and Arctic -North Atlantic domains[END_REF][START_REF] Doré | Principal tectonic events in the evolution of the northwest European Atlantic margin[END_REF]Funck et al., 2017). Spreading rates along the margins are asymmetric in the oceanic crust, where only 65 km of crust was accreted between Chron C22 and the COB on the Hatton margin and up to 140 km during the same period at the SE Greenland margin, when using the interpretation of [START_REF] Funck | Crustal structure[END_REF] for the position of the COB. The high amount of flood basalts and thick oceanic crustal thickness of up to 18 km can be explained by either high mantle temperature potential [START_REF] White | Magmatism at rift zones: The generation of volcanic continental margins and flood basalts[END_REF] or the pre-break-up rifting in the neighboring Hatton BASIN [START_REF] Armitage | The importance of rift history for volcanic margin formation[END_REF]. In that case, hot mantle material from upwelling during the previous rifting event can spread laterally to already slightly extended lithosphere before the breakup [START_REF] Armitage | The importance of rift history for volcanic margin formation[END_REF].

J o u r n a l P r e -p r o o f

Discussion

This review of main conjugate deep seismic profiles along the Atlanticmarginsallows for discussion of the unresolved questionsregarding rifting and continental margin formation identified in the introduction. As a summary and base for the discussion, the original crustal thickness, oceanic crustal thickness, and approximate beta factors are provided in Table 2.

1) What are the factors leading to the development of either volcanic or magma-poor margins and during which phase?

The continental margins of the Atlantic cover the full range of passive margins from highly volcanic to magma-poor margin types (Figure 33). Continental margins along the volcanic parts show a distinctively different structure to non-volcanic ones. First of all, they tend to be J o u r n a l P r e -p r o o f narrower, e.g. the Argentine volcanic rifted margin reveals a scarcity of rift basins and abrupt thinning of the continental crust [START_REF] Franke | Margin segmentation and volcano-tectonic architecture along the volcanic margin off Argentina/Uruguay, South Atlantic[END_REF][START_REF] Schnabel | The structure of the lower crust at the Argentine continental margin, South Atlantic at 44°S[END_REF][START_REF] Becker | Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup[END_REF]. Except for the locations rift-perpendicular basins (e.g. Colorado, Salado), there is no evidence of significant crustal thinning prior to break-up along most of the Argentine margin. In our compilation the magma-poor Galicia margin and the Flemish Cap and Nova Scotia margins are wider (e. g. [START_REF] Dean | Deep structure of the oceancontinent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: The IAM-9 transect at 40°20′N[END_REF][START_REF] Funck | Crustal structure of the northern Nova Scotia rifted continental margin (eastern Canada)[END_REF]. Second, zones of upper mantle exhumed at the seafloor and serpentinizedby water intruding through cracks and faults have been discovered so far only at magma-poor margins. These zones are characterized by seismic velocities higher than lower crustal velocities and lower than unserpentinizedmantle.

Deep reflections observed in wide-angle seismic data might originate from a serpentinization front rather than from the Moho (Minshull et al., 1998;Minshull, 2009). These zones are clearly imaged along the margins of the southern North Atlantic [START_REF] Dean | Galicia Bank ocean-continent transition zone: new seismic reflection constraints[END_REF] and northern parts of the American margin of the Central Atlantic [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]. None of the wide-angle seismic models from volcanic margins along the Atlantic Ocean revisited in this study show indications for serpentinizedmantle material between the extrusive SDR sequences and HVLC bodies (e.g. [START_REF] Bauer | Deep structure of the Namibia continental margin as derived from integrated geophysical studies[END_REF][START_REF] Korenaga | Crustal structure of the southeast Greenland margin from joint refraction and reflection seismic tomography[END_REF][START_REF] Planert | The wide-angle seismic image of a complex rifted margin, offshore North Namibia: Implications for the tectonics of continental breakup[END_REF].

The first oceanic crust accreted along magma-poor margins can be unusually thin, as for example at the Nova Scotia margin [START_REF] Funck | Crustal structure of the northern Nova Scotia rifted continental margin (eastern Canada)[END_REF] and correspondingly it could be expected that oceanic crust accreted at volcanic margins is overthickened. However, this is complicated as layers of magmatic underplate might be present underneath the crust, as for example along the US continental margin (LASE study group, 1984). Our comparison shows thick oceanic crust is accreted in the N-E Atlantic, and thin oceanic crust in the western Central Atlantic.

J o u r n a l P r e -p r o o f

Figure 33: Location of the wide-angle seismic profiles reviewed in this study. Red and white polygons are volcanic margin parts (red) and magma-poor margins (white) [START_REF] Lundin | Magmatism and extension rates at rifted margins[END_REF]. Green polygons depict TMP from Loncke et al., 2020. (a -Rif-Tell Fold Belt (Bumby and Guiraud, 2005);b -Atlas Fold Belt (Bumby and Guiraud, 2005); c -West African Fold Belt [START_REF] J O U R N A L P R E -P R O O F Sougy | West African fold belt[END_REF]d -Borboruna Fold Belt (Assumpção et al., 2013); e -Dom Feliciano Fold Belt [START_REF] Reuber | Control of Precambrian-to-Paleozoic orogenic trends on along-strike variations in Early Cretaceous continental rifts of the South Atlantic Ocean[END_REF]; f -Damara Fold Belt [START_REF] Reuber | Control of Precambrian-to-Paleozoic orogenic trends on along-strike variations in Early Cretaceous continental rifts of the South Atlantic Ocean[END_REF]; g -Gariep Fold Belt [START_REF] Reuber | Control of Precambrian-to-Paleozoic orogenic trends on along-strike variations in Early Cretaceous continental rifts of the South Atlantic Ocean[END_REF]; h -Cape Fold Belt [START_REF] Reuber | Control of Precambrian-to-Paleozoic orogenic trends on along-strike variations in Early Cretaceous continental rifts of the South Atlantic Ocean[END_REF] 2: Crustal thickness, beta-factor and oceanic thickness from the seismic profiles reviewed in this study. (1 -Voss et al., 2009;2 -Tsikalas et al., 2008;3 -Holbrook et al., 2001;4 -Staples et al., 1997;5 -Holbrook et al., 2001;6 -White and Smith, 2009;7 -Funck et al., 2003;8 -Whitmarsh et al., 1996;9 -Van Avendonk et al., 2006;10 -Chian et al., 1999;11 -Lau et al., 2006;12 -Dean et al., 2000;13 -Funck et al., 2004;14 -Biari et al., J o u r n a l P r e -p r o o f 2015; 15 -LASE Studygroup, 1984;16 -Klingelhoefer et al., 2009;17-Loureiro et al., 2018;18 -Contrucci et al., 2004;19 -Evain et al. 2015 ;20 -Becker et al., 2014 ;24 -Schinkel et al., 2007 ;23 -Becker et al., 2014 ;24 -Bauer et al., 2000). (a) From [START_REF] Szwillus | Global Crustal Thickness and Velocity Structure From Geostatistical Analysis of Seismic Data[END_REF] What is the influence of inheritance in margin break-up?

Our review highlights that the influence ofinheritance on the position and style of rifting is still highly debated. While some oceanic basins developed preferentially along old sutures from previous Wilson Cycles (e. g. [START_REF] Piqué | The central Atlantic rifting: Reactivation of Palaeozoic structures?[END_REF] other rifts broke through old cratons (Newman and White, 1999). A good example for the first is the northern Central Atlantic, which opened at least during two Wilson cycles along similar axes [START_REF] Wilson | Did the Atlantic close and then re-open?[END_REF]Pique and Laville, 1996;[START_REF] Whalen | Supercontinental inheritance and its influence on supercontinental breakup: The Central Atlantic Magmatic Province and the breakup of Pangea[END_REF][START_REF] Peace | A review of Pangaea dispersal and Large Igneous Provinces -In search of a causative mechanism[END_REF][START_REF] Thomas | Tectonic inheritance at multiple scales during more than two complete Wilson cycles recorded in eastern North America[END_REF]. In some places, margins which formed along old suture zones, still show the presence of remaining subducted conjugate slabs, e.g. East Greenland [START_REF] Schiffer | A sub-crustal piercing point for North Atlantic reconstructions and tectonic implications[END_REF].

Conversely, rifting brokethrough the Greenland Craton despite the existence of highlythinned continental crust at the nearby HattonBASIN.Such behavior may be explained by the cooling and corresponding strengthening of the lithospheric mantle when rifting stops for a sufficient amount oftime before the new rift develops (Newman and White al., 1999;England, 1986).

When extension reoccurs, a new rift will develop next to the extinct one, preferring the then less competent lithosphere. Based on numerical modeling [START_REF] Armitage | The importance of rift history for volcanic margin formation[END_REF], propose that a first rifting episode directly influences the rifting style of following episodes. For example, during the interrifting period the thermal anomaly located at the older Hatton BASINrift might have produced melt flowing into the NE-Atlantic rift producing volcanism and thick oceanic crust, and therefore could be a cause of magmatism during the break-up of the NE-Atlantic [START_REF] Armitage | The importance of rift history for volcanic margin formation[END_REF].

The late Cretaceous/Early Cenozoic rifting in the NE Atlantic saw two configurations. In the north, it widely followed the generally N-S trend of the Caledonides, while in the south it rifted a craton and crossed the NagssugtoqidianOrogenealmost orthogonally. Similarly, in the Austral South Atlantic the Late Jurassic/Early Cretaceous rift crossed the Gondwana Fold Belt in Argentina/South Africa nearly orthogonally and went parallel to the Dom Feliciano Belt at the latitude of Brazil and Angola. The arms of the Proterozoic-Cambrian Pan-African Fold Belt (Damara F.B.-orthogonal, Kaoko, (Gariep), Ribeira F.B.-parallel) are arranged to form an orogenic triple junction at the point where the Walvis Ridge intersects with the Namibian shore [START_REF] Clemson | The Namib rift: A rift system of possible Karoo age, offshore Namibia. In The oil and gas habitats of the South Atlantic[END_REF], i.e. at the position of the Etendeka lavas. At the intersection of propagating rifts with pre-existing suture zones, the production of magmatism probably increased (Koopmann et al., 2014a;[START_REF] Schiffer | A sub-crustal piercing point for North Atlantic reconstructions and tectonic implications[END_REF][START_REF] Peace | A review of Pangaea dispersal and Large Igneous Provinces -In search of a causative mechanism[END_REF]Petersen et al., 2018). Where rifts stagnated at a barrier such as a suture zone, such excess magmatism may contribute to the formation of LIPs (Foulger at al., 2019, Peace, 2019).

J o u r n a l P r e -p r o o f

Based on a concept from Courtillot, 1982, Reuber andMann (2019) proposed that where orogenic fabric trends parallel to the north-south SouthAtlantic rift direction, narrow (55-90 km) rift zones with modest continental beta factors of 2.5-3.5 develop, while a basement fabric trending near-orthogonally to the north-south South Atlantic rift direction results in wider (185-220 km) rift zones with higher beta factors of 4.3-5. These authors explain that greater amounts of stretching are needed to rupture the orthogonal, orogenic, basement fabric, while smaller amounts of rifting are needed to stretch the weaker and parallel, orogenic, basement fabric (Figure 34). This hypothesis holds true for the South Atlantic where wider, locked zones in the South Atlantic like the rift-orthogonal Salado suture zone or Damara foldbelt, exhibit higher beta factors and narrower rift zones like the rift-parallel Dom Feliciano and Kaokofoldbelts whichexhibit lower beta factors (Figures 32 and33). The central Atlantic is characterized by the margin parallel West African Fold Belt and the Variscan and Iapetus sutures along the north American margin, which opened in a single phase [START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF]. The NE Atlantic opened along pre-existing structures, however other factors such as changing stress directions were influential [START_REF] Schiffer | Structural inheritance in the North Atlantic[END_REF]. South Atlantic like the rift-orthogonal Salado suture zone or Damara foldbelt exhibit higher beta factors. Narrower rift zones like the rift-parallel Dom Feliciano and Kaokofoldbelts exhibit lower beta factors. Regional trends of pre-existing, orogenic basement fabrics are shown by the gray lines (After Reuberand Mann., 2019).

3) What are the origins and the mechanisms of formation of transform marginal plateaus?

TMPs are located at the boundary of two oceanic basins of different ages, for example the Demerara and Guinea PLATEAUS; the Walvis and Sao Paulo PLATEAUS and the Yermack and Morris-JesupPLATEAUS, the Hatton-Rockall PLATEAU; the Falkland-Malvinas PLATEAU (Mercier de Lepinay et al., 2016;Loncke et al., 2020 and references therein).

Although widespread, the architecture and layout of marine marginal plateaus have not yet been satisfactorilyunderstood. By definition, they are associated with a transform margin. These transform segments might have formed at rift propagation barriers, or between two opening basins forming transfer zones during opening and break-up. Most of these plateaus have experienced volcanism at one stage of their evolution and are considered, at least for part of their surface area, as volcanic margins [START_REF] Elliott | Influence of margin segmentation upon the break-up of the Hatton Bank rifted margin, NE Atlantic[END_REF]2009;[START_REF] Berndt | Controls on the tectonomagmatic evolution of a volcanic transform margin: the Vøring Transform Margin, NE Atlantic[END_REF]Planert et al., 2016;[START_REF] Reuber | Demerara Rise, offshore Suriname: Magma-rich segment of the Central Atlantic Ocean, and conjugate to the Bahamas hot spot[END_REF][START_REF] Abdelmalak | The T reflection and the deep crustal structure of the Vøring Margin, offshore midNorway[END_REF][START_REF] Schimschal | The Falkland Plateau in the context of Gondwana breakup[END_REF][START_REF] Lizarralde | Crustal structure across the Brunswick magnetic anomaly, offshore Georgia, from coincident ocean bottom and multi-channel seismic data[END_REF]. However, a marginal ridge system is not always present on sheared edges. For example, oceanwardthe crust in front of SW Newfoundland thins from 20 to 6 km in thickness without creating a ridge [START_REF] Reid | Crustal structure of northern Baffin Bay: Seismic refraction results and tectonic implications[END_REF]. Their genesis has been linked to a thermally induced uplift by heat transfer from the oceanic crust into the neighboring continental crust [START_REF] Bird | Shear margins: Continent-ocean transform and fracture zone boundaries[END_REF][START_REF] Parsiegla | Southern African continental margin: Dynamic processes of a transform margin[END_REF] or to the uplift of crustal segments as a result of transpressive movements [START_REF] Parsiegla | Southern African continental margin: Dynamic processes of a transform margin[END_REF]. Also, as observed in the Red Sea, a compressional front can precede the tip of a propagating rift [START_REF] Bonatti | Oscillatory spreading explanation of anomalously old uplifted crust near oceanic transforms[END_REF]. When this front impacts against an oblique barrier such as a fracture zone, the crust along the barrier may be compressively uplifted [START_REF] Crane | The role of fracture zones during early Red Sea rifting: structural analysis using Space Shuttle radar and LANDSAT imagery[END_REF] (Figure 35).

Numerical experiments and observations from the Red Sea indicate that spreading after continental rifting starts with sporadic seafloor spreading triggered by local asthenospheric upwelling in cells around 130 km apart [START_REF] Bonatti | Punctiform initiation of seafloor spreading in the Red Sea during transition from a continental to an oceanic rift[END_REF][START_REF] Corti | Transition from continental break-up to punctiform seafloor spreading: How fast, symmetric and magmatic[END_REF]. A contrary mechanism with unzipping from south to north has been proposed for the South Atlantic [START_REF] Franke | Margin segmentation and volcano-tectonic architecture along the volcanic margin off Argentina/Uruguay, South Atlantic[END_REF]. Final rifting along the NE Greenland margin most likely also included opening along sporadic spreading cells [START_REF] Franke | Polyphase magmatism during the formation of the northern East Greenland continental margin[END_REF]. Systematic mapping of SDR sequences along the Argentine/Uruguay continental margins shows that the volume of magma emplaced is highest close to transfer zones and that the width of the SDR wedges decreases in the direction of rifting in each individual margin segment [START_REF] Franke | Margin segmentation and volcano-tectonic architecture along the volcanic margin off Argentina/Uruguay, South Atlantic[END_REF]. A conceptual model from Koopmann et al., (2014a) proposes that once a rift arrives at a transfer zone rifting might come to a halt, volcanism temporarily diminishes, and heat accumulates in the mantle. When the next segment starts opening the accumulated heat may result in excess magmatism (Koopmann et al., 2014a). In this case, this accumulated heat might be responsible for the volcanism along TMPs but also in a top-down approach it might cause elevated heat regions in the mantle to develop at the position of rift barriers [START_REF] Franke | Rifting, lithosphere breakup and volcanism: Comparison of magma-poor and volcanic rifted margins[END_REF]. This might explain earlier observations of the existence of mantle plumes close to J o u r n a l P r e -p r o o f triple junctions observed by [START_REF] Burke | Plume-Generated Triple Junctions: Key Indicators in Applying Plate Tectonics to Old Rocks[END_REF]. The absence of TMP along some sheared margins might be explained by a different rifting style or the rift not halting for a longer period of time and thus not leading to the accumulation of heat in the mantle. However, some TMP seem to have developed at the terminus of a segment before reaching the transfer zone (e.g. Demerara/Guinea) and others after resuming opening when the transfer zone has been overcome (e. g. Hatton). This might be explained in some cases by rift barrierswhichallow the focusing of mantlemelts and later the localization of transferfaults, and in other cases, the transformfaultsallow the compartmentalization of meltcells.The exact relationship between mantle melting cells, localization of TMP and transform faults will need to be studied in more detail in the future.

A number of recent studies also show that the transition from continental to oceanic crust on sheared continental margins is by no means as abrupt as shown in previous studies. The Ascension Fracture Zone in the Gulf of Guinea shows an approximately 70 km zone of a 'proto-oceanic' crust [START_REF] Turner | Structure and composition of the ocean-continent transition at an obliquely divergent transform margin, Gulf of Guinea, West Africa[END_REF]. Along the Agulhas-Falkland Fracture Zone, there is a 50 km wide transition zone between the continental and oceanic crust [START_REF] Parsiegla | Southern African continental margin: Dynamic processes of a transform margin[END_REF]. This relatively broad transition zone observed along these margins can result from readjustments in the opening direction during oblique rifting for example due to a plate reorganisation [START_REF] Acocella | The role of transfer structures on volcanic activity at CampiFlegrei (Southern Italy)[END_REF][START_REF] Farangitakis | Analogue Modeling of Plate Rotation Effects in Transform J o u r n a l P r e -p r o o f Margins and Rift-Transform Intersections[END_REF]. [START_REF] Crane | The role of fracture zones during early Red Sea rifting: structural analysis using Space Shuttle radar and LANDSAT imagery[END_REF]. One side of the intersection will be uplifted while the other side will be under oblique extension.

J o u r n a l P r e -p r o o f

Conclusions and outlook

This study presents a compilation of deep seismic data along the Atlantic continental margins and selected conjugate or near-conjugate profiles based on plate kinematic reconstructions. It therefore allows comparison of asymmetry of rifting, influence of volcanism and the presence of serpentinized upper mantle material at the different margin segments. Some factors such as wide-angle seismic model quality and the plate reconstructional pole choice will influence our results, however as we are studying model features on a scale larger than 10-20 kilometers our results remain valid. The comparison of deep seismic models from the literature allows for the testing and validation of existing hypotheses about rifting and the opening of an oceanbasins. Our review shows that only magma-poor margins exhibit zones that have been qualified by the original authors of the studies as zones of serpentinized upper mantle material, exhumed during rifting. For magma rich margin segments the volume of volcanic material increases towards transfer zones, where rifting probably comes to a halt and leads to local heating of the upper mantle. Once the barrier was broken, rifting resumed with a lesser amount of volcanism. Highly oblique or shear margins are often associated with transform marginal plateaus and mostly include large quantities of volcanic material.

In the future more and denser spaced deep seismic profiles located along conjugate margins will be needed to explore rifting in true 3D geometry. Plate kinematic reconstructions taking plate deformation into account will be helpful to assess the finer degrees of asymmetry of margin pairs. Lastly, seismicreflectionprofiling will be needed to better account for the volume of volcanic material and associated variability along continental margins.

Figure 1 :

 1 Figure 1: Schematic representation of the progress of knowledge from top to bottom :the early view of (a) Mackenzie, 1978 and (b) Wernick, 1985, new concepts of (c) Reston 2005, (d) Ranero and Perez-Gussinye 2010, (e) Peron-Pinvindic et al., 2013 and (f)[START_REF] Clerc | Rifted margins: Ductile deformation, boudinage, continentward-dipping normal faults and the role of the weak lower crust[END_REF]. (g) and (h) shows schematic representation of the architecture of a slowly extended magma-poor marginand a rapidly extended magma-rich margin(after Franke., 2013;[START_REF] Peron-Pinvidic | Structural comparison of archetypal Atlantic rifted margins: A review of observations and concepts[END_REF][START_REF] Sutra | How does the continental crust thin in a hyperextended rifted margin? Insights from the Iberia margin[END_REF][START_REF] Doré | RESEARCH FOCUS: Hyperextended continental margins-Knowns and unknowns[END_REF][START_REF] Peron-Pinvidic | Rifted Margins: State of the Art and Future Challenges[END_REF]

Figure 2 :

 2 Figure 2: (a) -(f) Reconstruction of the Central Atlantic with rotational poles from Matthews et al., 2016. The fixed plate is Africa. (g) Topography and bathymetry map of the Atlantic region.

Figure 3 :

 3 Figure 3: (a) Seafloor bathymetry from the ETOPO1 dataset (b) Magnetic anomalies of the seafloor from the EMAG2 grid (doi:10.7289/V5H70CVX). (c) Age of the seafloor(Müller et al., 2016).

Figure 4 :

 4 Figure 4: A) Topographic and bathymetric map of the Atlantic Ocean from ETOPO1 bathymetry grids[START_REF] Amante | ETOPO1 arc-minute global relief model: procedures, data sources and analysis[END_REF]. B) Overview of the central Atlantic Ocean located between the Pico and Gloria fracture zones to the north and the 15°20 0N, and Guinea fracture zones to the south (thick black lines), bathymetry and topography from ETOPO1 bathymetry grids[START_REF] Amante | ETOPO1 arc-minute global relief model: procedures, data sources and analysis[END_REF]. The position of the salt (light yellow) is taken from[START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF],[START_REF] Davison | Central Atlantic margin basins of North West Africa: Geology and hydrocarbon potential (Morocco to Guinea)[END_REF],[START_REF] Tari | 8 -The conjugate margins of Morocco and Nova Scotia[END_REF]. Major magnetic anomalies are from[START_REF] Sahabi | Un nouveau point de départ pour l'histoire de l'Atlantique central[END_REF] and[START_REF] Labails | An alternative early opening scenario for the Central Atlantic Ocean[END_REF]. Offshore CAMP volcanism is from[START_REF] Coffin | Large igneous provinces: Crustal structure, dimensions, and external consequences[END_REF] and[START_REF] Ernst | Large Igneous Provinces[END_REF]. Going from north to south. Black lines along the North American margin represent wide-angle seismic profiles of the [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][START_REF] Louden | Chapter 2: Plate tectonics[END_REF], LASE, EDGE-801, (LASE Study Group, 1986;[START_REF] Tréhu | Structure of the lower crust beneath the Carolina trough, U.S. Atlantic continental margin[END_REF][START_REF] Austin | Crustal structure of the Southeast Georgia embayment-Carolina trough: Preliminary results of a composite seismic image of a continental suture(?) and a volcanic passive margin[END_REF] Holbrook et al., 1994a[START_REF] Holbrook | Seismic structure of the US Mid Atlantic continental margin[END_REF][START_REF] Lizarralde | Crustal structure across the Brunswick magnetic anomaly, offshore Georgia, from coincident ocean bottom and multi-channel seismic data[END_REF][START_REF] Lizarralde | US mid-Atlantic margin structure and early thermal evolution[END_REF]. Black lines along the North African margin represent wide-angle seismic profiles of the Sismar (c),Mirror (d) and Dakhla (e) cruises(Contrucci et al., 2004b;[START_REF] Klingelhoefer | Tectonophysics Crustal structure of the SW-Moroccan margin from wide-angle and re flection seismic data (the DAKHLA experiment) Part A: Wide-angle seismic models[END_REF][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].

Figure 5 :

 5 Figure 5: Reconstruction of the Central Atlantic at154 Ma (Chron M25) with rotational poles from Matthews et al., 2016. The fixed plate is Africa. Locations of wide-angle seismic profiles are marked by solid lines. Orange transparent polygons represent the location of volcanic provinces. Yellow lines depict segment boundaries.

Figure 6 .

 6 Figure 6. Reconstruction of the Nova-Scotia-Moroccan margin pair. (a) After initial extension, (b) asymmetric seafloor spreading, with exhumation to the west and magmatic accretion to the east, and (c) accretion of thin magmatic oceanic crust (after[START_REF] Biari | Opening of the central Atlantic Ocean: Implications for geometric rifting and asymmetric initial seafloor spreading after continental breakup[END_REF]. Abbreviations are HSM, highly serpentinised mantle; PSM, serpentinised mantle.

Figure 7 :

 7 Figure 7: Reconstruction of the U.S.-Mauritania margin pair. (a) After initial extension, (b) accretion of highly intruded and underplated oceanic crust and seaward dipping reflector sequences on the western margin and slightly intruded oceanic crust on the eastern margin, and (c) accretion of thin normal oceanic crust[START_REF] Biari | Opening of the central Atlantic Ocean: Implications for geometric rifting and asymmetric initial seafloor spreading after continental breakup[END_REF].

Figure 8 :

 8 Figure 8: A) Topographic and bathymetric map of the Atlantic Ocean from ETOPO1 bathymetry grids[START_REF] Amante | ETOPO1 arc-minute global relief model: procedures, data sources and analysis[END_REF]. (B) Overview of the South Atlantic Ocean divided into four segments from the north to the south, the Equatorial segment, the Central segment, the South Segment and the Falkland Segment (e.g Popoff, 1988[START_REF] Moulin | Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)[END_REF]. Bathymetry and topography from ETOPO1 bathymetry grids[START_REF] Amante | ETOPO1 arc-minute global relief model: procedures, data sources and analysis[END_REF]. The Aptian salt as well as SDR structures are from[START_REF] Torsvik | A new scheme for the opening of the South Atlantic Ocean and the dissection of an Aptian salt basin[END_REF]. The large igneous province volcanics are from[START_REF] Coffin | Large igneous provinces: Crustal structure, dimensions, and external consequences[END_REF]. Magnetic anomalies are from[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 along the South American margin represent wide-angle seismic profiles of the Amazon Cone Experiment and the MARGATS cruise (a)(Greenroyd et al., 2008[START_REF] Lizarralde | Crustal structure across the Brunswick magnetic anomaly, offshore Georgia, from coincident ocean bottom and multi-channel seismic data[END_REF]; SalSa experiment (b)[START_REF] Loureiro | Imaging exhumed lower continental crust in the distal Jequitinhonha basin, Brazil[END_REF] SanBa experiment (c) [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]; BGR04-REFR01(d) and BGR98-REFR2 (e) are from[START_REF] Becker | Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup[END_REF] The AWI-20130010 (f) wide-angle seismic profile running from East Falkland to the Georgia BASIN is after[START_REF] Schimschal | The Falkland Plateau in the context of Gondwana breakup[END_REF] On the African conjugate margin (g) represents wide-angle seismic profiles of the ZaïAngo cruise[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]; (h) P2 profile along the Walvis Ridge after[START_REF] Fromm | Interaction between a hotspot and a fracture zone: The crustal structure of Walvis Ridge at 6° E[END_REF] (i) Profile 2 from the MAMBA experiments afterBauer et al., 2000 and (j) Springbok line afterSchinkel et al., 2007.

Figure 9 :

 9 Figure 9: Reconstruction of the South Atlantic at 84 Ma (Chron 34) with rotational poles from Matthews et al., 2016. The fixed plate is Africa. Locations of wide-angle seismic profiles are marked by solid lines. Orange transparent polygons represent the location of volcanic provinces.

Figure 10 :

 10 Figure 10: Reconstruction of the South Atlantic at 130 Ma (a) and at 110 Ma (b) with rotational poles from Matthews et al, 2016. The fixed plate is Africa. Locations of wide-angle seismic profiles are marked by solid lines. AFFZ = Agulhas-Falkland Fracture zone.

Figure 11 :

 11 Figure 11: Deep structure of the Falkland PLATEAU and the Maurice Ewing Bank along profile AWI20130010 (after[START_REF] Schimschal | The Falkland Plateau in the context of Gondwana breakup[END_REF]. For location see Figure10.

Figure 12 :

 12 Figure 12: Deep structure of the Agulhas PLATEAU from profile AWI-20050200 Abbreviations are AFFZ, Agulhas-Falkland Fracture Zone; AP, Agulhas PLATEAU; APA, Agulhas Passage (after Parsiegla et al., 2008).

Figure 13

 13 Figure 13: (A) Reconstruction of the southern or Austral South Atlantic at 84 Ma with rotational poles from Matthews et al, 2016. The fixed plate is Africa. Locations of wide-angle seismic profiles are marked by solid blue lines. Orange transparent polygons represent the location of volcanic provinces. (B) Reconstruction at 110 Ma.

Figure 14 :

 14 Figure 14: Deep structure of the Uruguay continental margin and the Namibia continental margin (after[START_REF] Bauer | Deep structure of the Namibia continental margin as derived from integrated geophysical studies[END_REF][START_REF] Becker | Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup[END_REF]. (a) reconstruction for break-up (COB), (b) accretion of oceanic crust.

Figure 15 :

 15 Figure 15: Deep structure of the Argentinian and Namibian continental margins(after Schinkel et al., 2007 and[START_REF] Becker | Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup[END_REF]. (a) reconstruction for break-up (COB), (b) accretion of oceanic crust.

Figure 16 :

 16 Figure 16: Reconstruction of the South Atlantic at 104 Ma with rotational poles from Matthews et al, 2016. The fixed plate is Africa. Locations of wide-angle seismic profiles are marked by solid lines.

Figure 17 :

 17 Figure 17: Deep structure of the Brazilian and Zaire continental margin (afterLoureiro et al., 2018 and[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].

Figure 18 :

 18 Figure 18: Deep structure of the Santos BASIN and Namibia margin[START_REF] Evain | Deep structure of the Santos Basin-São Paulo Plateau System, SE Brazil[END_REF][START_REF] Fromm | Interaction between a hotspot and a fracture zone: The crustal structure of Walvis Ridge at 6° E[END_REF]. (a) Reconstruction at 86 Ma, (b) Reconstruction at 112 Ma, (c) reconstruction for break-up (COB), (d) accretion of oceanic crust. Red polygons mark volcanism[START_REF] Whittaker | Long-term interaction between mid-ocean ridges and mantle plumes[END_REF] and green polygons mark transform marginal plateaus[START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF].

Figure 19 :

 19 Figure 19: (a) Reconstruction of the equatorial Atlantic at 106 Ma with rotational poles from Matthews et al., 2016. The fixed plate is Africa. (b) Reconstruction of the equatorial Atlantic at 85 Ma. Locations of wide-angle seismic profiles are marked by solid lines (red lines: MARGATS from[START_REF] Lizarralde | Crustal structure across the Brunswick magnetic anomaly, offshore Georgia, from coincident ocean bottom and multi-channel seismic data[END_REF] Green lines: lines from Greenroyd et al., 2007 and 2008). Orange transparent polygons represent the location of volcanic provinces[START_REF] Whittaker | Long-term interaction between mid-ocean ridges and mantle plumes[END_REF] and green transparent areas TMP[START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF].

Figure 20 :

 20 Figure 20: Deep structure of the DemeraraPLATEAUand the French Guiana continental margin[START_REF] Greenroyd | Crustal structure of the French Guiana margin, West Equatorial Atlantic[END_REF] Greenroyd et al., 2008;[START_REF] Lizarralde | Crustal structure across the Brunswick magnetic anomaly, offshore Georgia, from coincident ocean bottom and multi-channel seismic data[END_REF].

  Figure 21: (A) Topographic and bathymetric map of the Atlantic Ocean from ETOPO1 bathymetry grids[START_REF] Amante | ETOPO1 arc-minute global relief model: procedures, data sources and analysis[END_REF]. (B) and (C) Overview of the North Atlantic Ocean. SDR, extrusive lavas and sills are from[START_REF] Horni | Offshore volcanic facies[END_REF][START_REF] Horni | Regional distribution of volcanism within the North Atlantic Igneous Province[END_REF]. Magnetic anomalies are from[START_REF] Bronner | Magmatic breakup as an explanation for magnetic anomalies at magma-poor rifted margins[END_REF] and[START_REF] Nirrengarten | Kinematic Evolution of the Southern North Atlantic: Implications for the Formation of Hyperextended Rift Systems[END_REF]. Sedimentary basins from[START_REF] Funck | Crustal structure[END_REF],[START_REF] Alves | Diachronous evolution of Late Jurassic-Cretaceous continental rifting in the northeast Atlantic (west Iberian margin)[END_REF],Lundin and Doré (2011), and Tugend et al. (2014): HB (Hatton BASIN); RT (Rockall Trough); PB (Porcupine BASIN); CS (Celtic Sea); WAB (Western Approach BASIN); OK (Orphan Knoll); OB (OrphinBASIN); FPB (Flemish Pass BASIN); JAB (Jeanne d 'Arc BASIN); WB (Whale BASIN); HoB (Horseshoe BASIN); SWB (South Whale BASIN); HoB (Horseshoe BASIN); CB (Carson BASIN); DB (Le DanoisBASIN); PoB (Porto BASIN); PeB (PenicheBASIN); LB (Lusitanian BASIN); AB (AlentejoBASIN); AlB (Algarve BASIN). Black lines along the NE Atlantic margin represent wide-angle seismic profiles of the (a) Barents 98 line 3E (after Breivik et al. 2003) (b) AWI20030200 (after Voss et al., 2009); (c)LVMT (after Tsikalas et al., 2005); (d) ARK 1988-3 (after Weigel et al. 1995); (e) JMKR95-3 (after Kodaira et al., 1998a); (f) OBS2000-8 (after[START_REF] Mjelde | Crustal transect across the North Atlantic[END_REF]; (g) KRISE 7 (after[START_REF] Brandsdottir | Evolution of a Divergent Plate Boundary; From the Active Kolbeinsey Ridge, N-Iceland to the Exinct Aegir Ridge, Norway Basin[END_REF] (h) OBS 2000-1 (after Breivik et al., 2006); (i) Vøring 96 Line 8A (afterRaum, 2002); (j) Vøring 96 Line 8B (after

  suggest a Barremian age (anomaly M5 to M3, ~130 Ma) based on the modeling of magnetic anomalies.Péron-Pinvidic et al. (2007) propose a break-up age of 112 Ma at the Aptian-Albian boundary. These differences in the interpretation of the break-up age can originate J o u r n a l P r e -p r o o f

Figure 23 :

 23 Figure 23: Deep structure of the Newfoundland and Iberian margin(after Funck et al., 2003 and[START_REF] Whitmarsh | The ocean/continent transition beneath the Iberia Abyssal Plain and continental-rifting to seafloor-spreading processes[END_REF]. (a) Reconstruction of the Southern North Atlantic at 125 Ma (b) reconstructed for the initiation of seafloor spreading and (c)at the time of magnetic anomaly M0 (118 Ma).

Figure 24 :

 24 Figure 24: Deep structure of the Newfoundland and Iberian margin (after van[START_REF] Van Avendonk | Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada[END_REF] 2009 and[START_REF] Chian | Deep structure of the oceancontinent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: Ocean Drilling Program (Legs 149 and 173) transect[END_REF].

Figure 25 :

 25 Figure 25: Deep structure of the Newfoundland and Iberian margins (after[START_REF] Lau | Crustal structure across the Grand Banks -Newfoundland Basin Continental Margin -I. Results from a seismic refraction profile[END_REF][START_REF] Dean | Deep structure of the oceancontinent transition in the southern Iberia Abyssal Plain from seismic refraction profiles: The IAM-9 transect at 40°20′N[END_REF]. (a) Reconstruction of the Southern North Atlantic at 125 Ma (b) reconstructed for the initiation of seafloor spreading and (c)at accretion of oceanic crust.

Figure 26 :

 26 Figure 26: (a) Reconstruction of the North Atlantic at 51 Ma with rotational poles from[START_REF] Matthews | Global plate boundary evolution and kinematics since the late Paleozoic[END_REF]. The fixed plate is North America. Locations of wide-angle seismic profiles are marked by solid lines. (b) Present day bathymetry with extruded lavas (red), sills (blue) and SDR (green) fromÁ Horni et al. (2014; 2017).

Figure 27 :

 27 Figure 27: Deep structure of the SW Barents Sea margin along profile Barents 98-line 3E (after Breivik et al. 2003).

Figure 28 :

 28 Figure 28: Deep structure of the Norwegian and Greenland continental margins (after[START_REF] Korenaga | Crustal structure of the southeast Greenland margin from joint refraction and reflection seismic tomography[END_REF][START_REF] Holbrook | Mantle thermal structure and active upwelling during continental breakup in the North Atlantic[END_REF][START_REF] Voss | Variations in magmatic processes along the East Greenland volcanic margin[END_REF][START_REF] Tsikalas | Crustal structure of the Lofoten-Vester\aalen continental margin, off Norway[END_REF].(a) Reconstruction of the North Atlantic at 51 Ma (b) reconstructed for the initiation of seafloor spreading and (c)at accretion of oceanic crust.

  Figure 28: Deep structure of the Norwegian and Greenland continental margins (after[START_REF] Korenaga | Crustal structure of the southeast Greenland margin from joint refraction and reflection seismic tomography[END_REF][START_REF] Holbrook | Mantle thermal structure and active upwelling during continental breakup in the North Atlantic[END_REF][START_REF] Voss | Variations in magmatic processes along the East Greenland volcanic margin[END_REF][START_REF] Tsikalas | Crustal structure of the Lofoten-Vester\aalen continental margin, off Norway[END_REF].(a) Reconstruction of the North Atlantic at 51 Ma (b) reconstructed for the initiation of seafloor spreading and (c)at accretion of oceanic crust.

Figure 29 :

 29 Figure 29: Location map of the wide-angle seismic profiles shown in Figures 30 and 31.Orange transparent areas represent the location of volcanic provinces[START_REF] Whittaker | Long-term interaction between mid-ocean ridges and mantle plumes[END_REF] and green transparent areas represent transform marginal plateaus[START_REF] Basile | The Jurassic magmatism of the Demerara Plateau (offshore French Guiana) as a remnant of the Sierra Leone hotspot during the Atlantic rifting[END_REF].

Figure 30 :

 30 Figure 30: P-wave velocity models for conjugate profiles in the Jan Mayen region. (a) ARK 1988 Line 3 (after Weigel et al. 1995); (b) JMKR-95 Line 3 (after Kodaira et al., 1998a); (c) OBS 2000 Line 8 (after Mjelde et al., 2008); (d) Vøring 96 Line 8B (after[START_REF] Raum | Crustal structure and evolution of the Faeroe, Møre and Vøring margins from wideangle seismic and gravity data[END_REF]; (e) KRISE Line 7 (after[START_REF] Brandsdottir | Evolution of a Divergent Plate Boundary; From the Active Kolbeinsey Ridge, N-Iceland to the Exinct Aegir Ridge, Norway Basin[END_REF]; (f) OBS 2000 Line 1 (after[START_REF] Breivik | Rates of continental breakup magmatism and seafloor spreading in the Norway Basin-Iceland plume interaction[END_REF]; (j) Vøring 96 Line 8A (after[START_REF] Raum | Crustal structure and evolution of the Faeroe, Møre and Vøring margins from wideangle seismic and gravity data[END_REF][START_REF] Raum | Crustal structure of the southern part of the Vöring Basin, mid-Norway margin, from wide-angle seismic and gravity data[END_REF].

Figure 31

 31 Figure 31: P-wave velocity models along the Greenland-Iceland-Faroe Ridge and the Faroe-Shetland BASIN (FSB). (a) SIGMA line 1 (after Holbrook et al. 2001); (b) ICEMELT line (after Darbyshire et al. 1998); (c) FIRE offshore line (after Richardson et al. 1998); (d) iSIMM Faroe line (after Roberts et al. 2009). Orange colors depict Icelandic type crust including a high degree of volcanic material possibly mixed with continental crustal fragments.

Figure 32 :

 32 Figure 32: Deep structure of the Greenland margin and the RockallTrough: SIGMA Line 3 after Hopper et al. (2003), iSIMM Hatton dip line (W) after Parkin and White (2008) and iSIMM Hatton dip line after White and Smith (2009).(a) Reconstruction of the North Atlantic at 51 Ma (b) reconstructed for the initiation of seafloor spreading and (c)at accretion of crust.

Figure 34 :

 34 Figure 34: A) Modification of the schematic model from[START_REF] Courtillot | Propagating rifts and continental breakup[END_REF] illustrating how a propagating rift is affected by along-strike zones of wider, "locked" zones of continental extension between two plates. B) Model fromReuberand Mann. (2019) showing that the wider, locked zones correspond to areas of pre-rift, orogenic grains that are at right angles or oblique to the Cretaceous South Atlantic opening direction. Wider, locked zones in the

Figure 35 :

 35 Figure 35: Schematic diagram of the deflection of a propagating rift along a continental shear zone (redrawn after[START_REF] Crane | The role of fracture zones during early Red Sea rifting: structural analysis using Space Shuttle radar and LANDSAT imagery[END_REF]. One side of the intersection will be uplifted while the other side will be under oblique extension.

Table 2 .

 2 ).

	Explanation	of	1-24	is	given	in	the	caption	of

J o u r n a l P r e -p r o o f

Acknowledgements

The GMT (Wessel and Smith, 1995) software package was used in the preparation of this paper. The GPlates software from the EarthByte Project was used to create the plate-tectonic reconstructions. We would like to thank Alison Chalm for proofreading the manuscript before resubmission.

J o u r n a l P r e -p r o o f

Geographic domain

Age of opening

Associated magmatic province

Central Atlantic ~195 Ma (1) ~175 Ma (2) 0.8 cm/yr (9) North: Magmapoor South:

Heavily magmatic (SDR, Underplate) Am. : Sable, Shelburne, and Georges Bank basins Af. : Seine, Meseta, Mauritania, Casamance, Caroline basins

1-2 cm/yr (10) Magmatic Danmarks Havn Basin (NE Greenland)

Transform or highly oblique (60-90°)

7 cm/yr [START_REF] Wilson | Did the Atlantic close and then re-open?[END_REF] High magmatism (SDR, Underplate)

3.8 cm/yr (11) 4.7 cm/yr (12) Moderate magmatism. (6) 1 cm/yr [START_REF] Wilson | Did the Atlantic close and then re-open?[END_REF] Magma-poor -Divergent (0-30°) -NAIP Northeast Atlantic ~55.5 Ma (8) 1.5-2.5 cm/yr (13) Strong

Am

Highlights

The comparison of published deep seismic velocity models, plate kinematic reconstructions and geological information allows to assess rifting styles and volcanic influence along the Atlantic Margins. Zones of upper mantle exhumed at the seafloor and serpentinized by water intruding through cracks and faults have been discovered only at magma-poor margins. At magma-rich margins the volume of magma is largest close to transfer zones and decreases in the direction of rifting in each individual margin segment. Sheared margins are often associated with transform marginal plateaus, which have undergone at least one volcanic phase.

J o u r n a l P r e -p r o o f

Declaration of interests

☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

☐The authors declare the following financial interests/personal relationships which may be considered potential competing interests: