Late Holocene environments at verlorenvlei, Western Cape Province, South Africa

Abstract

Abstract Evidence on late Quaternary palaeoenvironments of the western and southwestern Cape of South Africa has facilitated detailed reconstructions mainly for the mountains, where organic sediment accumulation has been favoured by relatively humid climates. On the lowlands, particularly those of the west coast region, the search for sites traditionally regarded as suitable for the accumulation of sediments containing preserved fossil pollen has commenced only more recently. This area of the Western Cape Province has, however, provided Quaternary scientists with a rich archaeological record that has yet to be tested against independent lines of palaeoecological evidence. A sequence of sediments which have accumulated in what is today a large freshwater coastal lake, Verlorenvlei, has been sampled at Grootdrift, 15 km inland of the coast. A series of seven sediment cores was extracted during 1991 and three of these have now been sub-sampled, radiocarbon dated and subjected to a range of palaeoenvironmental techniques, in particular pollen analysis, sedimentology and geochemistry. Three pollen diagrams are presented which reveal the vegetation history of both the immediate Grootdrift environment and the wider catchment during several periods over the last 5500 years. A mid-Holocene higher sea-level is evident in two of the cores which were examined for pollen throughout their length. The surrounding area appears at this time to have been somewhat more arid than today. Following a hiatus in sedimentation some time after 4300 BP, the marine conditions at the site disappear and are replaced by fresh water as the dominant hydrological and ecological influence. Around the time of colonial occupation of the region, some 300 years ago, lacustrine conditions prevailed at Grootdrift and greater moisture availability is indicated in the catchment. During the last 300 years, the picture revealed by high resolution palynology of the third core is one of progressive levels of human disturbance both in and around the Verlorenvlei. Evidence from a textural and geochemical analysis of the sediments is consistent with the interpretation based on fossil pollen. The implications of this information are examined against the archaeology and palaeoecology of several cave sites in the vicinity of the vlei. The consistency apparent in the range of types of evidence suggests that some reliance can be placed on the mid-late Holocene palaeoenvironmental reconstruction at Verlorenvlei. The paper thus provides insight into the nature of the complex interactions between late Holocene climate change, sea-level fluctuation, vegetation change, vlei hydrology and human activity in the Western Cape coastal region.