XRF ANALYSIS OF LATE MIOCENE SEDIMENT FROM THE LOCHERANGAN LOCALITY, TURKANA BASIN OF WESTERN KENYA

The Locherangan locality, located on the western margin of the Turkana Basin, northern Kenya, is a unique deposit from the Late Miocene. Fieldwork in 2016 provided additional sedimentological and stratigraphical data in high-resolution detail, adding to previous paleoenvironmental and paleoclimatic analysis of Locherangan. The stratigraphy at Locherangan is ~50 meters thick and has 36 distinct lithological units including crystalline bentonites, lacustrine clays, and paleosols. The section records deposition on a fluctuating lake margin as the sediments represent both subaerial and subaqueous environments. Bulk geochemical analyses of sediments provide data that can inform the reconstruction of past environments and climates. Geochemical proxies, particularly focused on paleosols from the section, were applied to a preliminary sample set from this section in order to understand more about the conditions surrounding paleosol formation. This study provides preliminary geochemical data for sediments from the Locherangan section. 55 different powdered sediment samples were analyzed using two different methods of x-ray fluorescence (XRF), portable XRF (pXRF) and conventional XRF (XRF). pXRF has the advantage of being faster, more cost-effective, and the analysis can be conducted in the field, although it was not in this study. Conversely, XRF has the advantage of historically being more accurate and it can analyze a greater range of elements that are needed for interpretation of paleosols such as Mg and Na. This study compared results generated on the same samples by the two analytical techniques. Ultimately, comparison between the two methods is advantageous as it could allow for future in situ field measurements on outcrops using pXRF, which could guide subsequent field sampling for follow up XRF in the lab.