MINERALOGY AND PALEOSOL MICROMORPHOLOGY FROM THE EARLY MIOCENE SONGHOR LOCALITY IN KENYA

The Songhor fossil site in western Kenya contains a diverse and well preserved assemblage of Early Miocene (~19.6 Ma) vertebrate fossils, including early primates. In this study, we analyzed thin sections from paleosols (fossil soils) that were described in the field at Songhor in 2015. Our goal is to determine the mineralogy and micromorphology of these paleosols in order to better understand site formation and paleoenvironmental conditions. Observations were made from seven thin sections using plane- and cross-polarized light on a petrographic microscope. Initial observations indicate the presence of igneous minerals such as feldspars, plagioclases, pyroxenes, and micas. Feldspathoids and carbonates are also noted, with the major feldspathoid hypothesized to be nepheline and the carbonate identified as secondary calcite. This suite of minerals is consistent with the weathering of reworked nepheline lavas and agglomerates associated with the nearby Tinderet Volcano, a natrocarbonitite complex. Pedofeatures that were observed include primary void space, subangular to angular blocky micropeds, hydrolysis of primary minerals, b-fabrics, and translocated clay. These features collectively indicate that pulses of sedimentation were separated by moderate stages of subaerial weathering. Our ongoing work will include a more comprehensive mineralogical characterization and will result in a detailed paleoenvironmental reconstruction for this significant locality.