MINERALS AS CLIMATE CHANGE PROXIES: DEVELOPING A PALEOENVIRONMENTAL INTERPRETATION OF THE BTB TUGEN HILLS DRILL CORE; PART OF THE HOMININ SITES AND PALEOLAKES DRILLING PROJECT

Paleolake basins of the East African Rift have been documented to hold many of the most important archaeological and paleontological sites regarding human evolution. Reconstructing paleoenvironmental conditions will help us to better understand how vertebrate and hominin evolution was affected by environmental change during the Pliocene and Pleistocene (~3.4-2.5 Ma). Changes in the mineralogical makeup of the sediments reflect environmental changes. A ~227m core was drilled in May-June 2013 at the Hominin Sites & Paleolakes Drilling Project site located in the Lake Baringo-Tugen Hills basin, a location of numerous paleontological and archeological discoveries. In total, 1272 ~4cm³ samples were taken approximately every 16 cm throughout the length of the core. Samples were prepared and analyzed by X-ray diffraction using a Panalytical XPERT PRO MPD operating at 45kV and 40mA to identify bulk mineralogy and assess trends over time. Calcite, Mg-calcite, dolomite, phillipsite, and analcime have been identified in core samples as phase indicators. Carbonates and zeolites appear to be mutually exclusive, and preliminary results suggest clear mineralogical intervals in which one dominates over the other. Mineralogical zones may represent episodes of changing paleolake chemistry, between relatively fresh and saline conditions. The mineralogical record will provide insight as to the influences climate and tectonics had on the geochemical evolution of Lake Baringo at this time. Integrating this dataset with the other proxies under investigation will be required to create a high-resolution record. As we move towards completion of a high-resolution dataset, mineralogical trends associated with climatic regimes of aridity recognized by paleosol formation and zeolite occurrences will allow for reconstruction of paleoenvironmental conditions.