Comparison of climate and environment on the edge of the Palaeo-Agulhas Plain to the Little Karoo (South Africa) in Marine Isotope Stages 5–3 as indicated by speleothems

Abstract

Given the steep present-day climatic gradients in southern South Africa, comparative studies of its coastal and inland paleoclimate provide important insight into the region's spatial climate dynamics. We present a comparative study of new speleothem stable oxygen (δ18O) and carbon (δ13C) isotopic composition from Efflux Cave (EC; 113–19 ka, hiatus between 105 and 94 ka) in the Little Karoo inland basin and Herolds Bay Cave (HBC; 93–62 ka) at the boundary between the Cape coastal lowlands and the Palaeo-Agulhas Plain. Gaussian kernel based cross-correlation analyses against palaeoclimate proxy records show that rainfall seasonality at EC is related to rainfall amount in the South African interior, whereas HBC is similar to the South African east coast. Our new proxy records, corroborated by archaeological evidence from the Cape coastal lowlands and the Little Karoo, suggest that in both regions, surface water was readily available and grassland ecosystems with variable amounts of C4 and C3 grasses as well as fynbos communities could be found nearby. Cross-correlation analyses of the new records from EC and HBC compared to previously published speleothem records from southern South Africa show only limited statistical correlation. However, there are some similarities in overall trends of palaeoclimate change in the Cape coastal lowlands and the Little Karoo whereby Marine Isotope Stage (MIS) 5b (mainly Greenland Interstadial 22) and 4 generally have more summer rainfall and higher abundances of C4 vegetation than MIS 5a and MIS 3.