PALEOSOL ANALYSIS OF A MIDDLE MIOCENE PRIMATE FOSSIL SITE IN WEST TURKANA, KENYA

The Turkana Basin of northern Kenya in eastern Africa hosts sedimentary strata that preserve fossils and climatic information critical to understanding primate evolution. In this study, we analyzed paleosols to reconstruct the paleoenvironment associated with the Esha fossil site (13.8 Ma) in the Lothidok Formation, West Turkana. Paleosols were systematically described from a stratigraphic interval that includes newly discovered primate fossils. Macroscopic features described in the field include paleosol horizons, structure, Munsell color, mottling, presence of root traces or burrows, grain size, and mineralogy. A total of 19 samples were recovered in the summers of 2022 and 2023 for elemental and isotopic analysis from four different paleosols. Two of which are correlated laterally and directly underlie the new primate fossil layer, and two stratigraphically higher than the fossil layer. X-ray fluorescence on prepared bulk samples was used to estimate elemental weathering of each profile. The random forest proxy for mean annual precipitation (RF-MAP) indicates that precipitation levels at the time of soil development were 500-1000 mm— correlative to modern day African woodland and savanna ecosystems. This suggests that the paleoenvironment of Esha was neither a grassland nor a closed canopy forest and indicates a dryer and less forested environment than the Early Miocene localities in the Lothidok formation of West Turkana. Elevated calcium and sodium oxide concentrations in some samples are attributed to diagenetic zeolitization and calcite cementation. The presence of these minerals produces artificially low rainfall estimates compared to unaltered samples. Ongoing work includes organic carbon stable isotope analysis for paleovegetation reconstruction, and petrographic and mineralogical analysis to better differentiate well preserved from diagenetically altered samples.