Paleogeography of Africa Through Meso-Cenozoic Times: A Focus on the Continental Domain Evolution
Résumé
We developed paleogeographic database of the African plate during MesoCenozoic times. Our objective is to quantify the paleoelevations, and then uplift variations on the continental domain. We first map the shoreline, the bayline, the type of continental systems. We also compile the paleocurrents data available on the fluvial deposits. We define the main river catchments and their divides, based on the paleocurrents data and the location of the river mouths on both lakes and seas. We integrate the boundary conditions such as plate kinematics and magmatism (a magmatism database is also compiled). We define the location of rift shoulders, highs of volcanic arcs, mountain belts, and plateau associated with flood basalts or any other magmatic activity (alkaline small province, kimberlites...). The main tectonic events responsible of relief creations were during: (1) the Late Kimmeridgian-Early Tithonian (155-150 My), (2) the intra Berriasian (145-140 My?), (3) the Austrian deformations (e.g. 130-125 My), (4) the Late Albian to Cenomanian (100-94 My), (5) the Turonian to Maastrichtian (90-65 My) with a paroxysm at the Santonian/Campanian boundary (84 My), (6) the Oligocene-Early Miocene (34-16 My). The topography of Africa during Late Jurassic to Late Cretaceous is mainly controlled by a very long wavelength deformation (x1000 km) showing a maximum in the middle part of North Africa (Mauritania to Sudan) and South Africa and a minimum along the Congo "trough" corresponding to a large lake base-level. This pattern is strongly modified during the Late Cretaceous time by the uplift of the Congo "trough" (Senonian deformations). The last period of uplift occurred during Oligocene and Early Miocene times. These very long wavelength deformations are directly related to the mantle dynamics beneath Africa.