Meso-Cenozoic Source-to-Sink analysis of the African margin of the Equatorial Atlantic

The objective of the Transform Source to Sink Project (TS2P) is to link the stratigraphic architecture of the offshore sedimentary basins of the African margin of the Equatorial Atlantic to the evolution of their source areas on the West African Craton. Alternating transform and oblique segments from Guinea to Nigeria produced a variability along the margin in terms of necking style (i.e. margin width), onshore geology and relief, subsidence/accumulation patterns that we analyzed from subsurface data, geology and geomorphology. It is a low-elevation margin characterized by a dissected marginal upward that is preserved only in the 1200-1900 m high Guinea Rise. This upwarp separated a continental interior (Man-Leo basement domain, southern T aoudeni and lullemmeden intracratonic basins) from the passive margin domain (Liberia, Ivory coast, Ghana and Benin passive margin basins). For the Cretaceous, we compared the long-term stratigraphic trends of each of the margin segment. We produced new paleo-geographic maps since the rifting, delineating domains on the craton and along the margin, which accumulated material resulting from the erosion of the craton and the marginal upwarp. We estimated onshore denudation from thermal histories determined by low temperature thermochronology along 3 transects across the upwarp in Guinea, Ivory Coast and Benin. We are estimating sediment accumulation history in the different margin basins to compare them to the denudation history. For the Cenozoic, we have reconstructed onshore denudation distribution and drainage history from dated and regionally correlated geomorphic markers. We identified contributing areas for each margin segments, over that period, and quantified the volume of sediments produced by denudation. We compared the associated stratigraphic signature of these fluxes along the margin. We show that, 60 Myrs after the rifting, the preservation of the Cenozoic wedge is strongly influenced by the necking style of the margin's segments. Nonetheless, specific stratigraphic events, such as the major unconformity in the Oligocene, are preserved along the whole margin, regardless of the necking style.