Three and half million year history of moisture availability of South West Africa: Evidence from ODP site 1085 biomarker records

Ocean Drilling Program Site 1085 provides a continuous marine sediment record off southern South West Africa for at least the last three and half million years. The n-alkane ∂ ¹³C record from this site records changes in past vegetation and provides an indication of the moisture availability of SW Africa during this time period. Very little variation, and no apparent trend, is observed in the n-alkane δ ¹³C record, suggesting stable long-term conditions despite significant changes in East African tectonics and global climate. Slightly higher n-alkane δ ¹³C values occur between 3.5 and 2.7Ma suggesting slightly drier conditions than today. Between 2.5 and 2.7Ma there is a shift to more negative n-alkane δ ¹³C values suggesting slightly wetter conditions during a ~0.2Ma episode that coincides with the intensification of Northern Hemisphere Glaciation (iNHG). From 2.5 to 0.4Ma the n-alkane δ ¹³C values are very consistent, varying by less than ±0.5‰ and suggesting little or no long-term change in the moisture availability of South West Africa over the last 2.5 million years. This is in contrast to the long-term drying trend observed further north offshore from the Namib Desert and in East Africa. A comparison of the climate history of these regions suggests that Southern Africa may have been an area of long-term stability over the last 3.5 Myrs.