Major late cainozoic climatic events and palaeoenvironmental changes in Africa viewed in a world wide context

Abstract

During the Late Cainozoic Africa witnessed big changes of a physical and biological nature. The continent was affected by drift, orographic changes, internal rifting and stepwise cooling of world climate. The climatic variations which occurred are reviewed in this contribution in a wider context, correlating them with events in other continents and in the surrounding oceans. The evidence from former sea levels is not included in this survey. Pronounced global cooling dated at 15.5-14, 10-9, 6.2-5.2, 3.6 and 2.5 m.y. are discussed. These episodes had a considerable influence on the biota of the continent. During these events the climate became progressively colder and drier, while during the interim periods the climate was warmer and more humid. Oceanic evidence indicates that the hyperaridity of the Namib desert in southwestern Africa dates back to the early Late Miocene. The Saharan flora, adapted to aridity, may be of Mid Pliocene or Late Miocene age. The savanna biotope, which is of importance for considerations on human evolution, was widespread in East Africa during the time when glaciations increased rapidly in the Northern Hemisphere. The existence of much older savannas is discussed. Impoverishment and temporary dissection of the tropical and subtropical forests of Africa will have occurred repeatedly during cold periods after the Miocene. A consequence of these changes was that in Early Pliocene time these forests were in the southwestern Cape replaced by “fynbos” (macchia).