Déformations très grandes longueursd’onde de l’Afrique au cours du Cénozoique

International audienceThe African continent is characterized by a bimodal topography. The900-1100 m elevation peak mainly corresponds to the Southern African(Kalahari Plateau) and the East African Domes, whereas the 300-400 mpeak is the mean elevation of the Sahara. Those reliefs are characterizedby very long wavelength (x1000 km), similar to the scale of mantledynamics. The origin of this relief, dynamic topography or more localcontrols (e.g. old lithospheric inheritance), are highly debated and moregeological controls are required.To answer those questions - in the frame of the TopoAfrica project -we performed a geomorphical study of Africa coupled with the tectonosedimentarystudy of the sedimentary basins or the magmatism.(1) Most of the African reliefs are younger than the Early-Middle Eocene(55-40 Ma).(2) The only significative old relief of Africa is the Southern AfricanPlateau that experienced a two steps evolution, a first uplift during LateCretaceous contemporaneous with high erosion under humid climaticconditions, followed by a second uplift during Late Eocene - Early Oligocene.The present-day arid to semi-arid climate could explain its preservation.(3) Most of Africa is uplifted during Miocene times (20-10 Ma), age ofmost of the present-day reliefs.(4) The African magmatic provinces (Virunga-Kivu, Cameroon VolcanicLine, Hoggar, Aïr...) are associated with local uplifts that startedaround Late Eocene times (40-35 Ma).The relationships of those reliefs with the migration of the African plateover the African superswell will be discussed