Cooling and drying in northeast Africa across the Pliocene

Terrestrial records suggest that Northeast Africa experienced drying during the Pliocene; however, these records are often incomplete in time and space, and questions about this shift in climate remain. Here, we use marine sediments from Deep Sea Drilling Project (DSDP) Site 231 in the Gulf of Aden to generate a multi-proxy organic geochemical record of northeast African climate spanning 5.3-2 Ma. This new record provides a regional perspective on climate and serves as context for the fossil record of early hominin evolution. We measured leaf wax carbon (delta C-13(wax)) and hydrogen (delta D-wax) isotopic composition and TEX86 (tetraether index of 86 carbons) to investigate past changes in vegetation, aridity, and ocean temperature, respectively. In the earliest Pliocene, we infer warm subsurface ocean temperatures from TEX86, semi-arid conditions on land and extensive C-4 grasslands based on delta D-wax, delta C-13(wax) and previously published pollen. After 5 Ma, ocean temperatures gradually cooled, and at 4.3 Ma there was a transition to arid conditions on land based on delta D-wax and pollen. Grasslands yielded to a mid Pliocene landscape of dry shrublands. This drying appears to be an atmospheric response to cooling ocean temperatures, which may reflect changes in tropical ocean circulation, the intensification of Indian Monsoon winds or perhaps other changes associated with Pliocene cooling. (C) 2016 Elsevier B.V. All rights reserved.