Palaeoenvironmental Reconstruction from Near-Surface Pan Sediments: An Example from Lebatse Pan, Southeast Kalahari, Botswana

Recent studies of pan sediment stratigraphy in southern Africa have indicated the potential of geophysical and geochemical analyses for elucidating the evolution of pans and the environmental conditions under which formation took place. We have investigated three cores, of 1.8 to 2.6 m in length, from Lebatse Pan in southeast Kalahari, Botswana, and compare the results with the few other similar studies available. Through the sedimentological characteristics of Lebatse we identify cycles of deposition, chemical precipitation and post-depositional alteration under shifting environmental conditions from c . 60,000 years ago to the present. Four periods are separated by depositional hiatuses, marking dry conditions during which deflation of the pan cannot be excluded. During the two oldest periods the sequence of finely laminated, magnesia-rich sediments suggests deposition in a permanent shallow waterbody under evaporative conditions, causing chemical precipitation of dolomite from groundwater. Less evaporative conditions are inferred for the third period of deposition between hiatuses H2 and H1. The youngest period, ¹⁴C-dated to 29,000 years BP, is characterised by water-logged conditions and the development of reed beds. It is believed to have been laid down under fluctuating water levels. The cycles of deposition exhibited in the pan cores appear synchronous with wetter periods in the Southern Kalahari, indicated by the limited evidence currently available.