WARMING PHASES IN SOUTHERN AFRICA DURING THE LAST 150,000 YEARS - AN OVERVIEW

Firmly based palaeoenvironmental data for southern Africa prior to 40, 000 yr B.P. are sparse. The only site which is likely to be able to pr ovide useful information for Isotope Stage 6 is the Pretoria Saltpan; warming at the end of this stage appears to have been rapid and to hav e been associated with increased precipitation in the interior of the sub-continent. In contrast, dry conditions appear to have prevailed in the southwestern areas during the warmest phases of Isotope Stage 5. This regional difference first became apparent during the Pliocene. Du ring the Last Glacial Maximum temperatures based on isotope ratios rea ched their lowest values of 5-6-degrees-C below present, in the southe rn part of the subcontinent, and widespread dryness prevailed. Warming became quite rapid after 16,000 yr B.P. and was almost everywhere ass ociated with a marked increase in wetness to around (or even above) pr esent levels. This warming phase continued until the beginning of the Holocene; the terminal Pleistocene was, however, marked by desiccation in the arid western areas. Of special interest is the Holocene altith ermal, which can be placed between 7000 and 6500 yr B.P. The extent of the temperature rise cannot be specified with any precision, but prob ably did not exceed the Holocene mean by more than 2-degrees-C. In the southern Cape and Karoo more summer rain apparently occurred than dur ing Isotope Stage 2 and in the early Holocene, and this trend towards year-round rainfall appears to have become increasingly pronounced thr ough the later Holocene until about 2000 yr B.P. This argues, in a gen eral way, for an increase in the proportion of summer rainfall with ri sing temperature in the present winter rainfall areas of southern Afri ca.