干旱区生态环境知识资源中心

Continuous sedimentary archives that allow paleoclimatic and paleoenvironmental reconstructions are rare in regions with a markedly and climate. This study demonstrates the potential of southwestern Kalahari pans in their function as valuable geoarchives based on the survey of five different pans in Namibia and South Africa. Our sedimentological investigations and comprehensive C-14 dating of core material reveal that pans contain an up to few meters thick sedimentary filling of siliciclastic and evaporitic sediments. An age-depth model was developed for each of the studied pans indicating a quasi-continuous accumulation of sediments since the Late Pleistocene. Sedimentary processes in the pans are mainly controlled by local runoff, evaporation and to a minor degree by aeolian transport resulting in a net accumulation. Sedimentological and geochemical analyses reveal the shift and/or extension of monsoonal summer and westerlies-driven winter rain. Elevated sedimentation rates during the Last Glacial Maximum (LGM) in some of the pans indicate an expansion of the winter rainfall belt, which is caused by Antarctic sea ice expansion. Post-LGM climate changes were induced by large-scaled spatial fluctuations of summer and winter rain that resulted in varying precipitation intensities and wind strengths. The detailed study of the paleoenvironmental information recorded in these sedimentary archives provides unique insights into the response of the southwestern Kalahari to past climatic changes and enabled an improved spatial and temporal resolution of existing models of past rainfall zone shifts in southern Africa.