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An Abrupt Temperautre and Hydroclimate Transition in Southeast Africa During Glacial Termination V: The Organic Geochemical Record from Lake Malawi

Africa's climate became progressively drier and more variable in the last few million years (e.g., deMenocal, 2004). Of particular interest, is a shift to drier and more variable conditions in the Olorgesailie Formation (Kenya) between 500 and 300 thousand years ago (ka) in which Potts et al. (2018) observed a turnover of ~85% of large-body mammalian fauna to smaller-body related taxa, suggesting that the shift was an evolutionary response to better adapt to the changing climate. However, a hiatus in the Olorgesailie record means that the cause of this faunal shift is still an outstanding question. Here, we analyze Lake Malawi drill core MAL 05–1 (~11ºS, 34ºE) to investigate if a specific climatic event stands out as a possible driver of the dramatic change observed in the East African mammal community. We use organic geochemical proxies including branched glycerol diaklyl glycerol tetraethers (GDGTs), leaf wax carbon and deuterium isotopic records to develop high-resolution temperature, vegetation, and precipitation records, respectively, between 600 and 200 ka. Results show a dramatic and abrupt temperature increase of ~6°C occurring in less than 3000 years during Glacial Termination V, which is the Marine Isotope Stage (MIS) 12 to MIS 11 transition at ~430 ka. Notably, this deglacial warming coincides with enriched leaf wax deuterium isotopic values suggesting a shift to more arid conditions in interglacial MIS 11 than in glacial MIS 12. Results also show another abrupt warming period in which temperature increased ~9°C around MIS 7 (~240 ka). We propose that the major warming and drying during Termination V in East Africa represents a significant abrupt change in the climate of eastern Africa and was a likely driver of the major faunal turnover noted in the Olorgesailie Basin.
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