Sand ramps in the Golden Gate Highlands National Park, South Africa: Evidence of periglacial aeolian activity during the last glacial

Abstract

Sand ramps have been identified in a side-valley on the southern side of the Little Caledon River in the Golden Gate Highlands National Park, Free State, South Africa. The site lies in the foothills of the northern Drakensberg (Maluti) Mountains, and this study aims to explore the potential of such deposits to add to the sparse palaeoenvironmental record of the region. Up to 11 m of aeolian sand, banked against north-facing slopes, is exposed by fluvial incision through the deposits, revealing interbedded fluvial lenses and palaeosols. The region is currently devoid of significant aeolian sediment transport or deposition, and supports well-developed grassland vegetation; these deposits testify to former conditions different from those of today, which would have been characterised by depleted vegetation and a different wind and/or climatic regime. Biogenic proxies are absent from the deposits, but Optically-Stimulated Luminescence (OSL) dating of the sediments reveals that they accumulated at intervals throughout much of the last glacial event, from around 45 to 16 ka. These dates are consistent with those of vegetation changes from palaeoecological sites elsewhere in the region, and also with dated evidence for niche glaciation further south in the high Drakensberg. Evidence from this study supports significant landscape changes in the Drakensberg during the last glacial, with the foothills in the region of Golden Gate Highlands National Park subject to aeolian processes under a periglacial environment.