Subsidence, extension and thermal history of the West African margin in Senegal

The subsidence of the Atlantic margin in Senegal clearly shows two rapid stages related to the formation of (1) the Central Atlantic during the early Jurassic (around 200 Ma), and (2) the Equatorial Atlantic during the Cretaceous (100 Ma). A simple model of extension is used to interpret the subsidence history and to derive the thermal evolution of this basin. The present-day gravity, bathymetry, bottom hole temperatures (BHT) in oil exploration boreholes and heat flow density are used to control the validity of the model. Two cross sections from the outcropping basement to oceanic crust are used, one in Casamance and the other one at the south to latitude of Dakar. The model can fully explain the first-order subsidence history as well as the present-day observations, and therefore can provide valuable information about the thermal evolution of sediments and about the structure of the continental crust along the margin. Comparisons with the opposite margin in North America (Blake Plateau and Carolina trough) indicate a rather different evolution (the North American margin did not undergo the second stage of rifting) and a different crustal structure (crustal thinning is less important on the African margin).