Holocene vegetation history and palaeoenvironments at Klaarfontein Springs, Western Cape, South Africa

Abstract

Several sedimenit cores ai-ounid the coastal lake of Verlorenvlei, Westem Cape, have thus far revealed important details of the development of this semi-arid winter-rainfall environment during the late Quatemary. Complex interplay between climate change, sea-level fluctuation and human activities have characterized the Verlorenvlei record and suggests that these environments have been subject to high degrees of disturbance over time. However, due to the discontiniuous nature of the sedimentary record, the Holocene record has remained fragmentary. Investigation of a 6 in vibracore sequence at Klaarfontein (32δ25′26″S; 18δ29′40″E). an artesian spring site some 18 km inland of Eland's Bay. facilitates a more complete Holocene palaeoenivironmental reconstruction. Pollen concentrations in 37 spectra distributed through the 6 m core vary with organic content, but at all depths are stufficient to facilitate interpretation of vegetation history and reveal a high degree of dynamism in the local and regional environments. The lower sediments are characterized by elements strongly indicative of more xeric conditions and the catchment appears to have been dominated by drought-resisting woody shrubs. Local vegetation in the mid-Holocene is consistent with the occurrence of two sealevel transgressions resulting in each case in the development of a salt marsh at the site. The uppermost pollen spectra are all relatively modern (post 200 BP). Grass pollen declines from 1900 BP, possibly as a result of the occupation of the area by pastoralists, although climate change cannot be ruled out. A decline in pollen diversity towards the surface is associated with a further reduction in grass pollen and ani increase in the proportion of succulents, hence offerinig support for the hypothesis of significant colonial and post-colonial disturbance of the vegetation. The evaluation of the pollen sequence at Klaarfontein supports previous palaeoenvironmental reconstructions and at once reveals new insights regarding the complex Holocene limnology, hydrology and geomorphology of the Verlorenvlei system.