Investigating the Kinematics of the African Topography: Constraints on the Spatio-temporal Evolution of Surface Uplift
Résumé
The African topography is characterized by elevated regions (> 1000 m), such as over the South-African Plateau, and is quite intriguing because it does not relate to any orogenic and convergent setting. Several models have been proposed in the past to account for these topographic anomalies. However, clear geological constraints were lacking to discriminate among the proposed scenarios and mechanisms. For this purpose, we have collected available data to quantify the silico-clastic fluxes of sediments preserved in the margins. In addition, we have gathered and re-interpreted paleogeographic constraints to qualitatively assess the spatio- temporal evolution of the continental surface, and denudation can be estimated from LT thermochronology. This database covers the whole continent, over the last ~180 Ma. To interpret these data and place quantitative constraints on the spatio-temporal evolution of surface uplift, we derive erosion and transport laws that apply at such great spatial and temporal scales. These laws are implemented in a numerical model that tests the possible histories of surface uplift consistent with the data. This study thus places crucial constraints on the possible mechanisms responsible for the observed topography. Finally, our approach should be applicable to other contexts, such as those related to the development of orogenic plateaus.