Verlorenvlei - The first continuous Holocene high-resolution lake sediment record from the Winter Rainfall Zone of South Africa

Abstract:

Verlorenvlei is a coastal lake in the Winter Rainfall Zone of the Western Cape Province of South Africa. Up to now several attempts have been made to recover sediment cores from this lake. However, no continuous high-resolution record covering large parts of the Holocene has been available so far. Within the project RAIN (Regional Archives for Integrated iNvestigations) it was possible to recover a 14.2 m paired parallel core from the central part of Verlorenvlei. Investigations on recent surface sediment distributions (elemental composition and grain sizes) indicate that this sediment core is very well suited for paleoenvironmental reconstructions. Using a set of 23 radiocarbon ages, a chronology for the past 9,000 cal BP was established which suggests continuous sedimentation over this period.

Preliminary lithological and geochemical investigations show that this record can be used for sea level reconstructions as the lake was periodically inundated by the ocean during the past 9,000 cal BP. This is recorded in distinctly elevated Ca and Sr contents as well as the occurrence of marine indicator species (snail and mussel shells) in parts of the sediment core. Thin, pale grey layers of fine sediment occurring at various sediment depths seem to reflect event related deposits. In terms of lithology, geochemical and magnetic composition, the upper 50 cm clearly differ from the rest of the record and indicate increased sediment supply from the catchment, which is likely linked to anthropogenic farming activities.

In conclusion, the newly recovered sediment record from Verlorenvlei offers excellent potential for a detailed, high-resolution reconstruction of sea level changes, climate variations and anthropogenic impact during the past 9,000 cal BP in an area in which natural archives are very scarce or poorly dated.