PALEOENVIRONMENTAL INTERPRETATION OF DRILL CORE FROM TUGEN HILLS, KENYA USING X-RAY DIFFRACTION

Regions of significant archeological and paleontonological deposits can be used to help better understand early hominin behavior in relation to environmental changes through paleoenvironmental reconstruction. Using X-ray diffraction (XRD) of lacustrine sediments obtained from core material recovered during the Hominin Sites and Paleolakes Drilling Project (HSPDP) at Lake Baringo-Tugen Hills in central Kenya, a region known for many paleontological and archeological discoveries, we can reconstruct a high-resolution record of paleoclimatic and tectonic histories during the Plio-Pleistocene. XRD analysis enables us to identify the mineralogical trends from the ~227m core, in order to understand the geochemical evolution of the basin. This will be one step in reconstructing orbitally-induced environmental changes, and how those changes influenced vertebrate and hominin evolution. This will improve our understanding of the environmental context of hominin evolution, especially with respect to hypothesized influences of Milankovich-scale orbital variations. Preliminary results indicate discrete zones of zeolite mineral groups, suggesting paleolake basin geochemistry evolution. Quartz and diatom-rich intervals are distinct from zeolitic zones, providing a mineralogical record of salinity variance. The zeolite mineralogy of the lower 100m of the core is nearly exclusively dominated by phillipsite, whereas the upper 120m have significant variations with clear zones including phillipsite, clinoptilolite, analcime, and chabazite, along with diatomaceous intervals that are zeolite-free. This suggest greater amplitude of environmental fluctuations later in the history of the core. Variation in source volcaniclastics is an alternative explanation. Furthermore, hkl reflections of clay-rich bulk samples suggest varying relative abundances of kaolinite and smectite. As we extract clay fractions and analyze the clay mineralogy in further detail, this ratio may provide an indication of the basin’s paleoweathering intensity. This method will provide essential information to supplement the many other paleolimnological proxies being investigated by the HSPDP team.