Cenozoic regolith in the interior of South Africa

The focus of this synthesis of Cenozoic regolith addresses the neotectonic context and changing palaeo-environmental conditions within the interior of southern Africa. The long-term geomorphological development of the southern African subcontinent since the early Cretaceous has resulted in the erosion of kilometres of rock, much of that cover being removed during the erosion cycle that formed the African Surface. Geological deposits representing that long period of weathering and erosion by drainage systems are rarely preserved. Continued landscape incision by Post-African erosion cycles during the Cenozoic did leave more widespread surficial deposits representing a variety of sedimentary environments and weathering regimes. The development of the Vaal-Orange drainage system and its residual fluvial terrace deposits provides a framework for the pulsed uplift of the interior that triggered episodes of river incision. Epeirogenic movement along axes of relative uplift across the subcontinent, drainage disruption and the subsidence and infilling of the Kalahari Basin are addressed. The Pleistocene sedimentary cover including widespread aeolian deposits in the arid Kalahari region and older windblown deposits extending eastward from the Vaal and Orange valleys, mass movement and colluvial cover associated with slope development, calcareous tufa deposits and karst processes, peat accumulation and lacustrine sediments are described. Weathering profiles and pedogenic duricrust profiles represent hiatus events in the long record of landscape development. The characteristics, occurrence and formation of calcrete, silcrete-dorbank, ferricrete and lateritic profiles is described. The changing palaeo-climatic conditions spanning the terminal Mesozoic and Cenozoic periods are outlined to contextualise the controls on geomorphological processes and accretion of geological materials on land surfaces of different ages across the interior region.