TEMPORAL AND SPATIAL CORRELATIONS BETWEEN CHANGES IN PLATE MOTIONS AND THE EVOLUTION OF RIFTED BASINS IN AFRICA

We present the results of a backstripping study, incorporating over 200 wells in 14 different basins or groups of basins located on the African interior or continental margins. These results, presented as mean tectonic subsidence rates averaged over appropriate periods, are compared with the opening histories and changes in plate motions of the Atlantic and Indian Oceans and the Tethys-Mediterranean area for seven time-steps from the Late Jurassic until present. The results indicate a temporal and spatial correlation between phases of rapid subsidence in African basins and changes in plate motions and, therefore, are promising in terms of applicability of large-scale plate motions in the studies of paleo-stresses in sedimentary basins, especially at times of initial rifting and formation of subduction zones. Reactivation of the basins appears to be primarily controlled by the orientation of the basin and underlying basement structures with respect to the stress direction. The basins are preferably formed within weaker zones, mostly Pan-African shear zones, and the distance from the active plate boundary to the weak zone plays a minor role in whether or not it will be reactivated, The presence of three important hot spots, which were active during the early stages of break-up of Gondwana, may have been important in preweakening the lithosphere at their sites. This may have played an additional role in the localization of the basin deformation.