Understanding Subsidence Mechanisms of the Intracontinental Palaeozoic Basins of North Africa

There are a number of large Palaeozoic basins situated on the accretionary crust of North Africa where the subsidence mechanism is unknown and poorly studied. The present theories within the literature explaining the subsidence tend not to explain the duration or areal extent of the subsidence seen. This talk proposes a new theory for the subsidence mechanism which created these basins. This theory is based on the idea that accretionary crust lacks a thick mantle lithosphere when it accretes because it formed through collision of island arcs. The lithosphere thickens as it cools which causes subsidence. This has been tested by comparing the tectonic subsidence curves generated from backstripping wells in the Ghadames and Al Kufrah basins with those generated using forward modelling. The modelling produces a good fit to the magnitude of the subsidence and acts over the same time period. However, there is a discrepancy in the shape of the curves with the forward model predicting higher initial subsidence rates and slower subsidence rates later. This may be because the lithosphere growth is slowed by higher heat production in the crust or greater insulation from the crust than used in the forward modelling.