A Paleotectonic Atlas of the African Plate: Permian to Recent

Abstract

The fragmentary release of petroleum data defining the deep structure and stratigraphy of African basins has been integrated with existing literature to compile 19 tectonic maps over key geological intervals from Permian to Recent times. African plate margins range in their age of opening from Late Triassic (off Lebanon), through Early/Middle Jurassic (Eastern Mediterranean, Central Atlantic, Somali Basin) and Cretaceous (West Africa) to ongoing (northern Red Sea). Their opening follows propagational trends, for example, from the eastern Mediterranean to Guinea and from the Somali Basin in a “smile” shape around southern Africa, eventually to Guinea. Just under half of African margins are rifted margins. North Africa margins are controlled initially by transforms, while volcanic rifted margins dominate in southern Africa. The most debated ocean, the eastern Mediterranean, is demonstrated through well and seismic interpretations to have commenced spreading in late Early to early Middle Jurassic times. Much of West African Cretaceous tectonics, including the generation of strike–slip fault systems, is related to the counter-rotation of Africa versus South America initiated through South Atlantic opening, partly driven by the Bouvet and Tristan Plumes. From the Aptian onward, Africa receives a series of transpressional shocks, largely derived from the Tethyan margin. The most pronounced such event occurs in the Santonian, which is a global-scale event, with? Turonian events in the Indian Ocean also affecting East Africa. Africa is segmented by many interior rifts, with these developed on all mapped intervals, though with peaks of activity in the Permian (South Africa), Late Triassic (North Africa), Early Cretaceous (Central Africa), and Neogene (East Africa). In the Early Cretaceous, a tensional regime is imposed which creates a series of NW-SE trending rifts across the plate: this switches gradually to a N-S rift trend in the Cenozoic. Passive rifts show a high degree of inheritance and can be orientated both perpendicular and parallel to associated strike–slip faults. This type of rift dominates in the Mesozoic, with active plume-related rifts becoming the principal type as mantle activity becomes a more dominant control in the Cenozoic. The Early Cretaceous Sirt Basin is viewed as an isolated plume-related rift, later evolving into a strike–slip associated rift. Analogue-driven hypotheses are proposed for the origin of the more poorly controlled African rifts, such as the Western Desert of Egypt. The formation of the various elements of petroleum systems are responses to these tectonics. For example, geographical trends in basin restriction and potential anoxia are observed to follow the propagational trends of continental breakup.