BioArchive Tswaing Crater

This project is part of the joint research initiative of the German and South African earth science communities Inkaba yeAfrica

Scope
The Tswaing crater was formed 220,000 years BP by a meteorite impact and as a result of subsequent groundwater inflow and rainfall a lake evolved in the centre of the closed crater basin (A). Due to the lack of in- and outflow the lake environment is strongly controlled by the local climate. At present the lake receives water from precipitation and groundwater seepage during summer, whereas evaporation predominates in winter causing an increased salinity (B) and water column stratification. In consequence, the 2 – 3 m deep, alkaline lake is anoxic below 50 cm water depth and microbes as well as cyanobacteria (C) are the predominating organisms in this extreme environment. 

With a thickness of approximately 90 m the sediments of the Tswaing crater lake represent an important record for the global climate change on the southern hemisphere over the last 200,000 years and contain detailed information on the evolution of the lake ecosystem. During the first phase of the project the climatic variations of South Africa were reconstructed in a multi-proxy approach [Kirsten et al., 2007. South African Journal of Geology 110, 311 – 326]. Analyses of lipid biomarkers and their isotopic signature provided first insights into the carbon cycle and its variations during the last 14,000 years which were closely linked to climate changes.
Currently, we examine these variations and the evolution of the lake ecosystem in a more detailed study by the application of compound-specific hydrogen isotopes on selected lipid biomarkers aiming specifically at the understanding of hydrological changes such as variations in the precipitation and evaporation. Moreover, the climatic effect on the evolution of the lake environment and the biocoenosis will be elucidated.

Participants
 

• H. Wilkes
• F. Schmidt
• H. Oberhänsli (Section 3.3)
• I. Kristen

Partners
 

• T. Partridge, University of the Witwatersrand, South Africa

Funding

Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum