A Lipid Biomarker Record of Plio-Pleistocene Hydroclimatic Change from the Baringo-Tugen Hills-Barsemoi Basin, Kenya

The Plio-Pleistocene (50 Ma) encompasses several major transitions in the frequency and amplitude of orbital-scale global climate cycles. While trends in ice volume are well-characterized, the dearth of continental cores spanning the onset of regular Northern Hemispheric glaciation (~2.7 Ma) hampers our understanding of tropical terrestrial hydroclimates and their dependence on high-latitude processe. Hominid fossil-rich eastern African strata are of particular interest, as paired geochemical-sedimentological and anthropological analyses present an opportunity to investigate the environmental context of early hominin evolution. To this end, the Hominin Sites and Paleolakes Drilling Project recovered a nearly continuous core from an upper Pliocene section of the Baringo-Tugen Hills-Barsemoi region spanning ~3.32.6 Ma, including the intensification of Northern Hemispheric glaciation and the onset of 41-kyr glacial-interglacial cycles as well as developments in key Australopithecine, Paranthropus, and Homo lineages. Here, we present a suite of new geochemical data, including compound-specific lipid biomarker indices and selected x-ray fluorescence elemental ratios, signals of precipitation amount, vegetation type, weathering intensity, and lake depth on sub-orbital timescales (~2 kyr resolution). We assess whether changes in high-latitude climatein particular, the ~2.7 Ma onset of Northern Hemisphere glaciationmay have forced transitions in African rainfall variability from precession- to obliquity-dominated periodicities, as well as synchronicity between eastern African climate and global trends. This multi-proxy approach enables a better separation of hydrologic and tectonic influences on climate, potentially yielding a significant advance in our understanding of sub-Saharan conditions during a key geologic and evolutionary transition.