South Atlantic continental margins of Africa: a comparison of the tectonic vs climate interplay on the evolution of equatorial west Africa and SW Africa margins

摘要

The comparative review of 2 representative segments of Africa continentalmargin: the equatorial western Africa and the SW Africa margins, helps inanalysing the main controlling factors on their development. Early Cretaceousactive rifting S of the Walvis Ridge resulted in the formation of the SW Africavolcanic margin. The non-volcanic rifting N of the Walvis ridge, led to theformation of the equatorial western Africa margin, with thick and extensive,synrift basins. Regressive erosion of SW Africa prominent shoulder upliftaccounts for high clastic sedimentation rate in Late Cretaceous - Eocene, whiledominant carbonate production on equatorial western Africa shelf suggestslittle erosion of a low hinterland. The early Oligocene climate change hadcontrasted response in both margins. Emplacement of the Congo deep-sea fanreflects increased erosion in equatorial Africa, under the influence of wetclimate, whereas establishment of an arid climate over SW Africa induced adrastic decrease of denudation, and thus reduced sedimentation on the margin.Neogene emplacement of the African superswell beneath S. Africa renewed onshoreuplift on both margins, but it accelerated erosion only in the Congo catchment,due to wetter climate. Neogene high sedimentation rate reactivatedgravitational tectonics that had remained quiescent since late Cretaceous.