The Pleistocene/Holocene transition in South Africa: evidence for the Younger Dryas event

Evidence for the Younger Dryas (YD) "cold episode" event and other complexities in the warming up of world climates at the end of the Pleistocene is rather sparse outside the North Atlantic region. There are indications from a number of studies, however, that it was indeed a worldwide event. Seeking evidence to define the Pleistocene/Holocene transition in southern Africa, the oxygen isotope ratios in shell fragments of the giant land snail, Achatina sp. (as derived from dated strata in the archaeological excavations of the Bushman Rock Shelter in the Transvaal region of South Africa), were measured. A sequence of colder episodes, including what we believe to be the YD event, is indicated, and there is evidence as for an earlier (Older Dryas?) event as well. We also measured the oxygen isotope ratios of modern land snail shells from South Africa and showed that they exhibit a good correlation with latitude, enabling us to make some deductions as to the general climatic conditions during the Pleistocene/Holocene transition compared to today.