Linking basin evolution to plate tectonic processes in (northern) Africa

Abstract

Several sedimentary basins in Africa are classified as intracratonic basins, but no conclusive formation mechanism has been identified for these basin types. Tectonic subsidence curves may help in unraveling formation mechanisms or identify tectonic forcing for these basins. This thesis presents and analyses basin subsidence curves for basins in the interior of Africa and near its passive margins. A backstripping program has been written to solve the backstripping equations needed to make the tectonic subsidence curves from the well data. Results of backstripping 77 wells from 13 basins in Africa are presented. The results are interpreted to identify phases of fast and slow tectonic subsidence and it is investigated whether these can be related to plate tectonic events from the Cambrian to the present. The tectonic subsidence curves of the Ghadames, Illizi, Timimoun, Algeria Regional, Murzuq, Al Kufrah, Iullemmeden, (Upper Egypt), Taoudeni and Zaire basins largely characterize intracratonic basins, Chad and partly Upper Egypt resemble rift basins, and Mozambique and Tanzania Coastal show strong similarity to passive margin basins. The results of the correlations show that the tectonic subsidence curves of the Tanzania Coastal and Mozambique passive margin basins can be correlated to the Africa-Antarctica break-up initiated at 176 Ma (Tanzania Coastal Basin) and to the India-Madagascar break-up at 90 Ma (Mozambique Basin). Many of the North African intracratonic basins show indications that can be correlated to tectonic events occurring at the margins of Africa, i.e. the Hercynian Unconformity and Alpine events. But there are no very clear signals of how far into the plate interior these events have affected the basins.