Variation of Relief, Siliciclastic Flux and Stratigraphic Architecture of Sedimentary Basins: A Database for the African Passive Margins

Rouby, Delphine¹, François Guillocheau¹, Yael Guyomard¹, Stephane Bonnet¹, Olivier Dauteuil¹, Cecile Robin¹, Michel Guiraud² (1) University of Rennes, Rennes, France (2) Biogeosciences Dijon, Dijon, France

The dynamic of siliciclastic flux entering sedimentary basins reflects the response of continental relief to climatic and/or tectonic perturbations via the growth of sedimentary sys­tems ensuring the transit of sediments toward the basin. The aim of this project is to deter­mine, using the natural example of the southern african passive margins, the scales of vari­ations of the siliciclastic supply and their consequences on the sedimentary record. We use sedimentology, sequence and seismic stratigraphy and quantitative geomorphology to analyse of the 3D geometry of erosion/sedimentation systems, that is (i) identify key geo­morphologic and stratigraphic surfaces, (ii) correlate them between the continent and basin,

(iii) determine and compare volumes of solid sediments eroded and preserved for each time steps defined by the key surfaces. We are currently developing a database describing the geometry of sedimentary basins of african margins. We present here a preliminary version of the database based only published data including: (i) a global evaluation of sedimentary volumes preserved in basins of the west african margin (from Niger delta to South Africa) based on a 3D geometry of the total thickness of these basins; (ii) a more detailed evalua­tion of volumes preserved in basins from Senegal to Somalia based on series homogenized 2D cross-sections; (iii) a detailed quantification and comparison of volumes of sediments eroded on the continent and preserved in the basin based on the 3D geometry of two sedi­mentary systems (including their drainage areas) of southern Africa (Limpopo and Orange basins).