Freshwater shell deposits in the northwestern Cape Province: further evidence for a widespread wet phase during the late Pleistocene in Southern Africa

The deposits consist of a small, freshwater gastropod, Tomichia ventricosa , and occur at elevations of up to 10 m above the floor of a large (10 km by 8 km) pan, Swartkolkvloer, 50 km south-west of Brandvlei in the north-western Cape Province, a marginally arid area. They are of two types. The older, which are fairly well-consolidated coquinas (shell limestones) of broken shells, are interbedded with shingle. The other type, which consists largely of whole shells only weakly cemented together, displays aeolian-type cross-bedding. Both types are low in magnesium, indicating freshwater conditions. The formation of the pan is attributed to deflation during glacial episodes of the Pleistocene when wind action was greatly enhanced. As a lake it had an area, at its highest level, of about 120 km super(2).