PHANEROZOIC TECTONICS OF AFRICA: AN OVERVIEW

The environmental evolution of Africa is closely tied to its geologic history. This presentation will provide an overview of African Phanerozoic tectonics and will briefly introduce some of the current studies being conducted to investigate the associated, resulting structures.

At the end of the Proterozoic, Africa was centrally located within the Gondwana Supercontinent and was situated at extremely high latitudes. Only the northwestern and southernmost tips of Africa were located along the Gondwana margin. Throughout the Cambrian and into the Silurian, Gondwana drifted northward over the South Pole, and glacial tillites were deposited throughout Africa. Paleozoic tectonic activity in Africa was dominated by several collisional events. The Hercynian orogeny, which marked the closure of the Paleothethys ocean around 350-280 Ma, lead to localized folding and thrusting along Africa’s northwestern edge. Additionally, at about the same time, the Paleopacific plate was subducting beneath southern Africa, leading to the formation of the Cape Fold Belt.

Rifting of Gondwana began in the Late Carboniferous and became more widespread by the middle-late Jurassic. In Africa, rifting was primarily accommodated along tectonic sutures and mobile belts dating back to the collision and amalgamation of Archean and Proterozoic cratons. These tectonic boundaries provided zones of weakness and were reactivated by extensional processes. Basins developed along the edges and within the interior of the African plate. By the early Cretaceous, the Central, East, and West African Rift systems had begun to form, followed by the development of the Red Sea-Gulf of Aden-East African Rift in the middle Cenozoic. Extension and rifting in East Africa continues today. The African continent has remained in a fairly stable position over the last 200 Ma, possibly due to the lack of slab pull affects at its margins.

In conjunction with the AfricaArray program, current studies of African tectonics are focused on investigating the lithospheric structure of Precambrian cratons, examining the crustal and upper mantle structure of rift systems, and imaging mantle upwellings. Significant effort is being made to tie these investigations to those in other fields, such as geochemistry and paleoclimatology.