Miocene climate and vegetation changes in the Cape Peninsula, South Africa: evidence from biogeochemistry and palynology

Abstract

Organic material from the Noordhoek area on the western margin of the Cape Peninsula, South Africa, was obtained from a ~ 50 m-long drill-core dominated by fluvio-lacustrine siliciclastic sediments. The aim of this study is to constrain fluctuations in climate and the decline of tropical vegetation elements along the southwestern coast and the Cape Peninsula of South Africa, during the Late Cenozoic phase, when the Benguela upwelling system was established. The approach was to combine palynological, biogeochemical (tetraether lipids) and stable isotope (C, N) studies of the organic-bearing record from the Noordhoek area on the western margin of the Cape Peninsula. Bulk C and N isotope data of sediment organic matter, point to a predominantly C3 higher plant source vegetation. Mean annual air temperature (MAT) from the analyses of tetraether lipids (MBT′–CBT index) was compared with palynomorphs from partly unpublished data of a previously drilled core adjacent to the study site. The palynomorphs are of subtropical affinities, and suggest that an open riparian forest would have existed in the early to middle Miocene of the southwestern coast of South Africa. Together these data sources allow vegetation and climate reconstructions of subtropical conditions during the early to middle Miocene, which comprised fluctuating open riparian forest and swamp vegetation. Temperatures rose in the middle Miocene and were higher than those of the present day.