Investigating the Formation and Evolution of Mega-Paleolakes in the Middle Kalahari of Semi-Arid Botswana From Sedimentary and Geochemical Proxies

Abstract

We investigated the occurrence and evolution of mega-paleolakes in the middle Kalahari Desert in semi-arid Botswana, Africa based on sedimentary and geochemical proxies. The mega-paleolakes covered more than 60,000 km^2 including the present day lower Okavango Delta. This study tested the following working hypotheses (1) environmental conditions leading to the formation of mega-paleolakes and their presence is recorded in sediments of the lower Okavango Delta and can be used to distinguish between lacustrine and fluvial paleoenvironments and (2) more than one paleolake episode will be recorded as lacustrine sedimentation either separated by a disconformity or by fluvial sedimentation. The objectives of the study were to collect sediments from an area of the delta projected to be covered by the mega-paleolake, conduct stratigraphic, geochemical and stable isotope measurements, and evaluate the data for the presence and evolution of a mega-paleolake beyond the present day lake basin settings. Results of the study indicate a possible mega-paleolake in the stratigraphic record based on anomalously high concentrations of total inorganic carbon, suggesting local and regional wet climate. The development of mega-lakes has major ramifications for people and infrastructure of the Okavango Delta as such a reoccurrence in modern times can cause devastation to the region.