Abstract This work integrates the available geological information and geochronology data for the Cretaceous–Recent magmatism in the South Atlantic, represented by onshore and offshore magmatic events, including the oceanic islands along the transform faults and near the mid-ocean ridge. The analysis of the igneous rocks and their tectonic settings allows new insights into the evolution of the African and Brazilian continental margins during the South Atlantic opening. Following the abundant volcanism in the Early Cretaceous, the magmatic quiescence during the Aptian–Albian times is a common characteristic of almost all Brazilian and West African marginal basins. However, rocks ascribed to the Cabo Granite (104 Ma) are observed in NE Brazil. In West Africa, sparse Aptian–Albian ages are observed in a few coastal igneous centres. In the SE Brazilian margin, an east–west alkaline magmatic trend is observed from Poços de Caldas to Cabo Frio, comprising igneous intrusions dated from 87 to 64 Ma. Mafic dyke swarms trending NW also occur in the region extending from the Cabo Frio Province towards the Central Brazilian Craton. On the West African side, Early Cretaceous–Recent volcanism is observed in the Walvis Ridge (139 Ma), the St Helena Ridge (81 Ma) and the Cameroon Volcanic Line (Early Tertiary–Recent). Volcanic islands such as Ascencion (1.0–0.65 Ma), Tristão da Cunha (2.5–0.13 Ma) and the St Helena islands (12 Ma) most probably correspond to mantle plumes or hot spots presently located near the mid-Atlantic spreading centre. Within the South America platform and deep oceanic regions, the following volcanic islands are observed: the Rio Grande Rise (88–86 Ma), Abrolhos (54–44 Ma), the Vitória–Trindade Chain (no age), Trindade (2.8–1.2 Ma) and Fernando de Noronha (12–1.5 Ma). There are several volcanic features along the NW–SE-trending Cruzeiro do Sul Lineament from Cabo Frio to the Rio Grande Rise, but they have not been dated. The only known occurrence of serpentinized mantle rocks in the South Atlantic margin is associated with the Saint Peter and Saint Paul Rocks located along the São Paulo Fracture Zone. The Cameroon Volcanic Line in NW Africa is related to the magmatism that started in the Late Cretaceous and shows local manifestations up to the Present. The compilation of all available magmatic ages suggests an asymmetrical evolution between the African and South America platforms with more pre-break-up and post-break-up magmatism observed in the Brazilian margin. This is most likely to have resulted from the different geological processes operating during the South Atlantic Ocean opening, shifts in the spreading centre, and, possibly, the rising and waning of mantle plumes. Supplementary material: A complete table with radiometric dates that have been obtained by universities, government agencies and research groups is available at: www.geolsoc.org.uk/SUP18596

Abstract New seismic and well data in the deep-water basins of Campos, Santos, South Kwanza and Benguela, supported by plate reconstructions, help answer fundamental questions on the rifting history of the central South Atlantic, specifically on the amount and effect of fault-related deformation, and on when and where sea-floor spreading started. The Paraná mantle plume played a fundamental role – dynamically raising the plate, prolonging continental rifting by heat-softening the crust and, after break-up, delaying the onset of marine conditions. Previous discrepancies in extension and subsidence have been solved, and the location and age of the continent–ocean boundary can now be determined. Rifting involved approximately 450 km of homogeneous pure shear, equivalent to a β factor (lithosphere stretching factor) of 4.5. Break-up occurred at 123 Ma (Barremian–Aptian boundary), 7–8 Ma later than the southern South Atlantic but 6 Ma before widespread salt deposition. The mid-Atlantic ridge was initially subaerial, marked by a volcanic high. Sea-floor spreading was at a rate of 24 mm year −1 , similar to syn-rift deformation prior to break-up. Transcontinental strike-slip shear zones are not evident but a major NW–SE lithospheric lineament associated with a failed triple junction arm had a major influence on the magmatic history, both prior to and after break-up. Supplementary material: A4 versions of the seismic sections shown in Figures 6 & 7 are available at http://www.geolsoc.org.uk/SUP18563 .

Abstract The tectonosedimentary development of the South Atlantic is compared with the Central Atlantic margins, which are associated with major episodes of magmatism during the Mesozoic continental break-up. Subsequently, the Cenozoic break-up in the North Atlantic led to the formation of the volcanic Norwegian–Greenland conjugate margins. The DSDP boreholes in the magma-poor Iberian–Newfoundland margins have confirmed the occurrence of exhumed mantle at the ocean–continent transition. This possibility has been suggested for the South Atlantic margins, but still lacks confirmation from drilling. The Red Sea and the Gulf of Aden may be considered as natural laboratories to study the break-up processes and formation of divergent continental margins. Using key geological and geophysical data, we compare some of the structures observed in incipient stages of basin formation between the African and the Arabian plates with the structures observed in older sedimentary basins associated with the Gondwana break-up. We also analyse deep seismic reflection profiles and potential field data at the continent–ocean boundary of these conjugate margins, using palinspastic reconstructions to define the corresponding seismic pairs. We conclude that the Red Sea and the Gulf of Aden display remarkable differences to the Iberian–Newfoundland margins, and notable similarities with the South Atlantic margins.

Abstract Salt–sediment interplay in the Santos Basin is investigated integrating seismic interpretation, kinematic restoration and analogue modelling. Deformation within the post-salt sequence results from thin-skinned gravitational gliding and spreading, driven primarily by halokinesis, greatly affected by massive sediment inflows. The impressive landward-dipping listric Cabo Frio Fault controls the major depocentres updip, whereas salt-cored folds accommodate downdip shortening. Sediment supply from confluent directions creates a complex interference pattern of superposed folds with intervening polygonal minibasins. A new structure is identified (termed the ‘Ilha Grande Gravitational Cell’), a linked system of updip extension and downdip contraction detached on salt, comprising the Cabo Frio Fault and minibasins. It moves to the SE, with eastern and western borders suggesting lateral gradients of slippage. This thin-skinned feature results from the differential load imposed by a thick prograding wedge over the ductile salt and is independent of pre-salt structures. The post-salt sequence moves basinwards due to halokinesis, thereby changing position relative to the pre-salt sequence, which implies that any present-day correspondence between pre- and post-salt structures may not attest to linkage in the past. Application of kinematic restoration techniques allows the true position and geometry of the key elements through time, improving petroleum systems assessment.

Abstract Understanding the genesis of the very peculiar 600 km-wide Santos Basin–São Paulo Plateau system and its narrow conjugate Namibe Margin is a kinematic and structural problem. Several hypotheses have been proposed in order to explain the genesis of this system that imply the same amount of horizontal movement. We investigate the consequences of the horizontal movement in the Santos Basin, based in plate kinematic reconstructions. The kinematic history of this system that we present here, based on the interpretation of seismic profiles and kinematic constraints, has the following consequences: (1) there is no evidence of a ridge jump sensu stricto but, rather, a southwards propagation in the Central Segment of the South Atlantic that starts in the northern part, between the NE Brazilian and Gabonese margins; (2) the Namibe margin evolved as a transform passive margin; (3) the opening direction of the Santos Basin–São Paulo Plateau system is oblique to the general opening motions of the South American and African plates; and (4) this opening is younger (6 Ma) than those of the other basins of the Central Segment of the South Atlantic.