Post-Rift Vertical Movements Of The Southern African Margins - Implications For The South African Plateau Uplift

Guillaume Baby (1) , François Guillocheau (1) , Cécile Robin (1) , Massimo Dall’asta (2)

1 GR - Géosciences Rennes
2 TOTAL S.A.

The South African Plateau (SAP) is the world’s largest non-orogenic plateau. It forms a large-scale topographic anomaly which rises from sea level to > 1000 m. Most mechanisms proposed to explain its elevation gain imply mantle processes. The age of the uplift and the different steps of relief growth are still debated. On one hand, a Late Cretaceous uplift is supported both by thermochronological studies and sedimentary flux quantifications. On the other hand, geomorphological studies suggest a Late Cenozoic uplift scenario (<30 Ma). However few attentions were paid to the evolution of the overall geomorphic system, from the upstream erosional system to the downstream depositional system. This study is based on two different approaches: - Onshore, on the mapping and chronology of all the macroforms (weathering surfaces, pediments and pediplains, incised rivers, wave-cut platforms) dated by intersection with the few preserved sediments and the volcanics. - Offshore, on a more classical dataset of seismic lines and petroleum wells, coupled with biostratigraphic revaluations (characterization and dating of vertical movements of the margins - sediment volume measurement). The main result of this study is that the SAP is an old Upper Cretaceous relief (90-70 Ma) reactivated during Oligocene (30-15 Ma) times.

Domaines: Tectonique; Géomorphologie

Guillaume Baby, François Guillocheau, Cécile Robin, Massimo Dall’asta. Post-Rift Vertical Movements Of The Southern African Margins - Implications For The South African Plateau Uplift. Third EAGE Eastern Africa Petroleum Geoscience Forum, EAGE, Nov 2017, Maputo, Mozambique. ⟨10.3997/2214-4609.201702412⟩. ⟨insu-01647592⟩