Holocene Environmental Change at Wonderwerk Cave, South Africa: Insights from Stable Light Isotopes in Ostrich Eggshell

Abstract

Sparse records and discontinuous and/or poor chronologically resolved data hinder construction of reliable palaeoenvironmental sequences for the interior of South Africa. Wonderwerk Cave occupies a central position in the interior where the Kalahari Thornveld/dry woodland vegetation and generally arid conditions are expected to be sensitive to subtle past climate perturbations, and evidence from this site has been key to forming views on environmental change in the interior. A compilation of existing data including principal component analysis of pollen suggested broad trends, ranging from variably arid and open in the early Holocene to moister conditions from about 7500 to 5000 years, followed by aridity thereafter. In an effort to better establish the nature and timing of shifts from the Late Pleistocene sequence onwards, we analyse carbon and oxygen isotope ratios in a robust sample of ostrich eggshell from Wonderwerk Cave. The resulting data are then placed within a temporal framework established by Bayesian modelling of existing radiocarbon dates and compared against shifts in the Wonderwerk cultural sequence. Several shifts and trends in aridity include an arid to moist shift in layer 4b near 6000 years, coincident with a cultural shift within the Wilton assemblage, and thereafter an aridification trend culminating at about 2000 years with the appearance of the ceramic LSA.