Late Quaternary climate and environmental reconstruction based on lake and peat sediments from the central southern Cape region of South Africa

This thesis aims at reconstructing environmental and climatic, and particularly hydrological changes in South Africa during the Late Quaternary. Hydrogen isotopes from leaf wax-derived n-alkanes and oxygen isotopes from hemicellulose-derived sugars were analysed in a first step on modern reference material from South Africa in order to evaluate the potential of both biomarker isotopes as well as coupling them in a paleohygrometer for robust paleohydrological reconstruction. In a second step, two sediment archives, i.e., Lake Voёlvlei and the peatland Vankervelsvlei, located at Africa’s southern Cape coast were identified as ideally suited for paleoenvironmental and -climatic reconstruction. Both records have been analysed using a broad multi-proxy approach including well-established sedimentological and geochemical proxies as well as innovative biomarker isotopes and the paleohygrometer approach in high temporal resolution. For the first time in this region, this combination of proxies was used to draw a coherent picture of moisture availability and precipitation sources along South Africa’s southern Cape coast. During the Holocene, hydroclimate variability was driven by contributions from Easterly- and locally-derived precipitation leading to moist conditions and a year-round precipitation regime from ~7.5 to ~5.0 ka and from ~3.0 ka until present day. Drier conditions accompanied by a shift to a winter rainfall regime occurred from ~5.0 to ~3.0 ka. Comparisons with other regional records support these results, but the driving forces behind this climate variability are still subject of considerable debate. On Late Quaternary timescales, low sea level caused the coastline to migrate south of its present position leading to increased continentality and dry conditions during glacial periods. During interglacial periods, the coastline was approximately where it is situated in recent times due to high sea level leading to more humid conditions at Vankervelsvlei.