Holocene aeolian activity in the southwestern Kalahari Desert, southern Africa: significance and relationships to late-Pleistocene dune-building events

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Abstract
Little is known about the timing of dune-building episodes in the southwestern Kalahari Desert. Previously, arid phases when dune activity occurred have been inferred from gaps in chronologies derived from information that attests to former humid periods. To redress this, optically stimulated luminescence (OSL) dating was applied to sediment samples taken from a range of aeolian landforms in the SW Kalahari. Four periods of dune building are identified in the late Pleistocene and Holocene. Holocene aeolian activity at 6 ka and 1-2 ka led to the construction of localised dune forms, in contrast to late Pleistocene times when the extensive field of linear dunes that dominates the region was emplaced. Late-Holocene aridity was however sufficient to allow rapid emplacement of the lunette dune at Witpan. The record of aeolian activity is evaluated in the context of humid chronologies and an ocean-atmosphere model of Holocene climate change, with good agreement obtained. It is concluded that the application of optical dating to a range of aeolian landforms has the potential to establish the style as well as timing of dune-building. It is also demonstrated that the climate during dune-building periods must have differed significantly from the prevailing semi-arid climate with drought periods of today, which may have been the predominant climate regime through much of the Holocene.