Geomorphic evidence for the late Quaternary palaeoclimates of the middle Kalahari of northern Botswana

Abstract

Summary Geomorphological studies of caves and lakes in northern Botswana since 1973 have yielded a suite of 80 radiometric dates which permit palaeoenvironmental reconstruction of the landscape over the last 45, 000 years. The unique characteristics of the landforms, when interpreted with caution, yield palaeoclimatic information on both northern Botswana and the catchments of the Okavango River in the Angolan Highlands. Several major shifts in precipitation are indicated for the period 45,000–20,000 BP, with dry conditions prevailing at 25,000 BP. The Late Glacial was characterised by humid conditions, especially from 16,000–13,000 BP, whilst the early Holocene was semi-arid, with precipitation peaks circa 6,000–5,000 BP and 2,000 BP. The results contrast sharply with some southern African palaeo-climatic descriptions in print, where many of the inferences have been drawn from studies of the northern hemisphere inter-tropical zone. The implications of the study are briefly discussed in relation to palaeoclimatic models of the whole African continent.