Abstract

Two major colluvia have been differentiated in eastern southern Africa: a lower (Bovu) (>30 ka) and an upper (Mphunga) (<30 ka). Existing stratigraphic models, based on 14C dating of pedogenic carbonates in paleosols and on archaeological and faunal inference, indicate that deposition of the upper colluvium is climate-dependent, associated with micropedimentation processes operating under semi-arid climatic conditions during the late Pleistocene Hypothermal (ca.30-12 ka); mid- to late Holocene radiocarbon dates of pedogenic carbonates derived from several sites in the upper colluvium are thought to be erroneous. Four new 14C dates derived from wood and organic detritus interbedded with the upper colluvium in the Mkhondvo valley in Swaziland indicate that colluviation occurred throughout the late Holocene, did not cease at ca. 10-12 ka, and is ongoing. Dated profiles are used to provide the first reliable estimates of denudation rates in badland areas in southern Africa; rates at Mkhondvo show rapidly accelerating erosion during the latter part of the past 1 ka. These results indicate that colluvium genesis in eastern southern Africa is more complex than previously envisaged and, though probably strongly influenced by climatic regime, is highly sensitive to other factors. Colluvial stratigraphic models in eastern southern Africa need to be reevaluated in the light of this new evidence.

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