An Early Pleistocene Phytolith Record from Wonderwerk Cave, Northern Cape, South Africa

Abstract

Grass silica short cell phytoliths were sampled from the four lowermost archaeological strata in excavation 1 at Wonderwerk Cave and offer an independent record of climatic change during an episode of Early Stone Age hominin occupation at the cave. Linked to differences in growing season temperature and the geographic distribution of C3 and C4 grasses in southern Africa, fossil grass phytoliths were used to trace palaeoenvironmental shifts at the site. The results suggest that Early Pleistocene environmental conditions at the cave fluctuated: between wetter and drier summer–rainfall growing conditions (C4) towards the end of the Olduvai subchron and the beginning of the subsequent interval of reversed polarity, to mostly dry and cooler winter–rainfall growing conditions (C3), that continued throughout the interval. It ended with a shift towards increased summer rainfall aridity at around one million years ago. The fluctuation between markedly wetter and drier C4 conditions at the cave (NADP-me grass types vs. NAD-me grass types) does not support the premise that the expansion of C4 grasslands was always coupled with increased aridity.