The quaternary palaeoenvironmental history of the Kalahari, Southern Africa

In the absence of closed sites, fossiliferous strata and regional or even local stratigraphic frameworks, Quaternary scenarios for the Kalahari have been developed only in the past 20 years based on deductive geomorphological studies. Landforms studied include palaeo-lakes, caves, pans, dry valleys and spring deposits, all indicative of wetter episodes. Attempts to establish the presence of episodes of aridity from the vast linear dune fields have not been successful, primarily because the function of linear dunes has been misunderstood. A chronological framework for the past 40,000 years has been established, based on a corpus of 239 radiocarbon dates, of which nearly half, using calcrete as the dating medium, require careful interpretation. One of the most important findings is that the entire Kalahari experienced a wetter episode from 16,000-13,000 B.P., followed by a period of lowering water tables and return to the present climatic mean. The Kalahari is thus out of phase with Africa north of the Equator, and with other major sub-tropical deserts. This has implications for global palaeo-climatic modelling, although the phenomenon could be explained by the orbital forcing hypothesis. The recent use of U/Th dating on cave sinters suggests this pattern extends back into earlier glacial/interglacial cycles. (C) 1996 Academic Press Limited