HR: 11:20h
AN: PP22A-05    [Abstracts]
TI: New Insights Into the Climate and Vegetation History of the subtropical Crater Lake 'Tswaing', South Africa, for the Last 300,000 Year
AU: * Kristen, I
EM: kristen@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AU: Fuhrmann, A
PP22A-05 AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AU: Haug, G H
PP22A-05 AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AU: Horsfield, B
PP22A-05 AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AU: Oberhänsli, H
PP22A-05 AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AU: Partridge, T C
PP22A-05 AF: Climatology Research Group University of the Witwatersrand, 12 Cluny Road Forest Town, Johannesburg, 2193 South Africa
AU: Thorpe, J
PP22A-05 AF: University College London Department of Geography, 26 Bedford Way, London, WC1H 0AP United Kingdom
AU: Wilkes, H
PP22A-05 AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AB: Deeper time palaeoclimate reconstructions are still rare on the continental southern hemisphere. Here we present new biogeochemical data from a core retrieved in crater lake 'Tswaing' (formerly 'Pretoria saltpan'). This opens a novel chance to get a more detailed view into climate variability of the subtropical region of South Africa on the glacial/interglacial time scale.
The crater 'Tswaing' was formed around 220±52 kyr ago by a meteorite impact. However, new U/Th analyses of authigenic carbonates provide preliminary evidence that the lake might be older than 300 kyr.
Today the basin contains a shallow (< 3 m water depth), hypersaline (pH ~10) lake with a diameter of about 300 m in an about 1 km wide crater. Hence, the lake catchment is small with no water in- or outflow. Therefore, the lake is sensitive for variations in rainfall and probably wind stress. Our 90 m composite core profile consists of partly fine-laminated lake sediments intercalated with mudflow deposits. Previous investigations and our new data reveal a considerable variability of bulk geochemical proxies such as total inorganic carbon (TIC), total organic carbon (TOC) and the C/N ratio. The upper half of the core is dominated by fluctuations in TOC while TIC controls the variation in the lower half of the core. These data argue for substantial changes in the depositional environment of the lake system. They are complemented by facies analyses in thin sections, major element patterns derived from μXRF scanning , the carbon isotopic composition of the bulk sediment, maceral analysis, and lipid biomarkers of the organic material in the sediments. First results allow to distinguish intervals with completely different ecosystems and hydrology during lake history. Intervals with dinoflagellates and algae as main primary producers alternate with phases dominated by bacteria and ciliates feeding on them. Future detailed analyses will provide new insights into the development of these climate sensitive lacustrine habitats as well as the surrounding vegetation in the catchment area over two to four glacial cycles.
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 1055 Organic and biogenic geochemistry
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4942 Limnology (0458, 1845, 4239)
DE: 9305 Africa
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005