Cainozoic environmental change in southern Africa,with special emphasis on the last 200 000 years

Abstract

Since the end of the Cretaceous, Africa's latitudinal drift has been relatively small and has not significantly modified the general pattern of stepwise cooling and aridification that has characterized the Cainozoic era. Tectonic uplift has, in contrast, strongly influenced regional climates in east and southern Africa, especially during the late Neogene, and has accentuated the east-west moisture gradient which has prevailed, with minor interruptions, since the Oligocene. In common with most other midlatitude regions, southern African environments responded dramatically to the global episode of cooling and drying between 2.8 and 2.6 myr which ushered in the cyclical fluctuations of the Pleistocene. The establishment of a winter rainfall regime in the southwestern part of the subcontinent probably dates from around 2.6 myr. In the north east, new proxy data spanning the last 200 000 years indicate that summer rainfall varied in relation to receipts of solar insolation at precessional frequencies. Superimposed upon these cyclical changes were a number of less regular variations which, on the basis of the larger body of evidence available for the Holocene, elicited specific localized responses. These diachronistic changes argue for the involvement of factors other than solar insolation alone in the more recent evolution of southern African climates.