Planation Surfaces of the East African Rift as a Record of Vertical Movements and Denudation Measurement Since 60 Ma

The objective of this presentation is (1) to reconstruct the different steps of the East African Rift growing and mainly the domes, (2) to discuss their relationships with mantle dynamics and (3) to use planation surfaces for measuring the denudation through time (volume of eroded sediments incoming in sedimentary basins). The African relief – including the East African Rift Domes - results from two major types of planation surfaces, etchplains (weathering surfaces by laterites) and pediplains/pediments. These planation surfaces are stepped along plateaus with different elevations. The stepping of the pediment-type planation surfaces records a local base level fall due to local uplift. The present-day topography of the East African Rift is younger than 40-30 Ma. (1) The very long wavelength uplift (1000-2000 km) of the East African Dome started around 34 Ma (Eocene-Oligocene boundary). (2) The uplift rate increased during Late Miocene times (11-6 Ma) with the incision of large pediplains well dated on the Congolese side of the East African Dome.