BIOMARKER RECORDS OF PLIO-PLEISTOCENE PALEOCLIMATE FROM THE SOUTHEAST AFRICAN MARGIN

The climate of the Limpopo River catchment, located in southeastern Africa, is sensitive to hydrographic changes in the nearby Agulhas Current (AC) and atmospheric circulation variability driven by large-scale, global climate dynamics. Despite the potential significance of climate’s role in regional hominin evolution, records of Plio-Pleistocene terrestrial climate in southeastern Africa have been limited by a prior lack of drill cores. Here we examine the molecular and isotopic composition of marine and terrestrial biomarkers recovered from deep-sea sediments near the Limpopo River drainage (IODP Site U1478) to provide a continuous record of terrestrial climate in southeastern Africa and its relation to global climate and the AC. Our compound-specific hydrogen isotope (δ²H_wax) record of hydroclimate variability and corresponding haptophyte algae (U^k'₃₇) and marine archaea (TEX₈₆) lipid-based temperature records span from 4.3 to 1.75 ma, encompassing the mid-Pliocene warm period, the Plio-Pleistocene transition, and some developments in early hominin evolution. Our biomarker records document a transition to wetter conditions between 4.3 and 4 Ma that persist into the late Pliocene, followed by increasing aridity at 3 Ma and a shift to higher amplitude variability in hydroclimate that characterizes the latest Pliocene and early Pleistocene. We discuss the connections between Plio-Pleistocene climate change in the Limpopo River catchment and both continental ice sheet and Indian Ocean variability and explore the potential implications of our climate records for the interpretation of early hominin evolutionary transitions in East Africa.