THE QUATERNARY PALEOENVIRONMENTAL HISTORY OF THE KALAHARI, SOUTHERN AFRICA

In the absence of closed sites, fossiliferous strata and regional or e ven local stratigraphic frameworks, Quaternary scenarios for the Kalah ari have been developed only in the past 20 years based on deductive g eomorphological studies. Landforms studied include palaeo-lakes, caves , pans, dry valleys and spring deposits, all indicative of wetter epis odes. Attempts to establish the presence of episodes of aridity from t he 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 c orpus of 239 radiocarbon dates, of which nearly half, using calcrete a s the dating medium, require careful interpretation. One of the most i mportant findings is that the entire Kalahari experienced a wetter epi sode from 16,000-13,000 B.P., followed by a period of lowering water t ables and return to the present climatic mean. The Kalahari is thus ou t of phase with Africa north of the Equator, and with other major sub- tropical deserts. This has implications for global palaeo-climatic mod elling, although the phenomenon could be explained by the orbital forc ing 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