Mega-Lake in the Kalahari: A Late Pleistocene record of the Palaeolake Makgadikgadi system |
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| Authors: | Sallie L Burrough David SG Thomas Richard M Bailey |
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| Institution: | 1. School of Geography and the Environment, OUCE, University of Oxford, South Parks Road, Oxford OX1 3QY, UK;2. Department of Environmental and Geographical Science, University of Cape Town, Rondebosch 7701, South Africa;1. Department of Meteorology and Centre for Past Climate Change, University of Reading, RG6 6BB, UK;2. Environmental Change Institute, University of Oxford, OX1 3QY, UK;1. School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, UK;2. Department of Environmental and Geographical Science, University of Cape Town, Rondebosch 7701, South Africa;1. School of Geography and Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, UK;2. Long Term Ecology Laboratory, Department of Zoology, University of Oxford, UK;3. Department of Environmental and Geographical Science, University of Cape Town, South Africa;1. Department of Geography, Oklahoma State University, Stillwater, OK 74078, USA;2. Department of Plant Sciences, University of the Free State, Bloemfontein, South Africa;3. Centre National de Recherche Scientifique, UMR 5554, Institut des Sciences de l’Evolution de Montpellier, Université Montpellier, Bat. 22, CC061, Place Eugène Bataillon, 34095 Montpellier, Cedex 5, France;4. Institute of Earth Surface Dynamics, Geopolis, University of Lausanne, CH-1015 Lausanne, Switzerland |
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| Abstract: | A distinct series of beach ridges marking the former shorelines of large inter-connected lacustrine basins in the Kalahari can be clearly identified from Landsat imagery and Shuttle Radar Topography Mission (SRTM) data. These basins, which form the terminal sump of the Okavango system in northern Botswana, are now almost completely dry. During the Quaternary they were intermittently occupied by large stable lake bodies and are thought to have periodically filled to a point of coalescence inundating an area that, at its largest extent, encompassed 66,000 km2. Poor chronological control has previously limited the utility of this important palaeo-archive. As part of a region-wide lake palaeo-shoreline research programme, a systematic optically stimulated luminescence (OSL) dating programme has utilised a lightweight hydraulic auger to take samples at depth from relict shoreline features. Twenty drill-sites have generated 140 samples for dating, establishing a firm chronology for multiple lake full phases in all three component basins (Ngami, Mababe and Makgadikgadi) of this mega-lake. This paper presents the final set of ages in the programme, derived from four cores from the western and north-eastern shorelines of Makgadikgadi, and uses these ages to establish a chronology of mega-lake high-stands during the last ～300 ka providing a rare directly dated, long terrestrial record of positive hydrological excursions within the southern hemisphere. |
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