MULTIPLE EPISODES OF ARIDITY IN SOUTHERN AFRICA SINCE THE LAST INTERGLACIAL PERIOD

There is generally a dearth of evidence of the nature of Quaternary cl imate change within desert systems, which has limited precious interpr etations of past environmental change at low latitudes. The Last Glaci al Maximum has previously been identified as the peak of Late Quaterna ry aridity, when desert systems expanded to five times their present e xtent(1-3), and low-latitude aridity has been described for previous g laciations(4). But little evidence has been derived directly for large desert basins, particularly southern Africa. Here we report new chron ological (optical dating) evidence of arid episodes recorded in aeolia n sediments from the Mega Kalahari sand sea. Episodic aeolian activity is recorded at the northeastern desert margin, whereas more sustained activity is evident from the southwestern desert core. Several signif icant arid events are apparent since the last interglacial period, wit h dune-building (arid) phases at similar to 95-115, 41-46, 20-26 and 9 -16kyr before present. Existing atmospheric general circulation model simulations and independent palaeoclimate data indicate that the chang es in aridity are related to changes in the northeast-southwest summer rainfall gradient, which are in turn related to sea surface temperatu res in the southeastern Atlantic Ocean.