Paleoclimate and paleoenvironment reconstruction of early Miocene Tinderet sites in western Kenya, and its implications for hominoid evolution.

Early Miocene Tinderet sites in western Kenya preserve some the earliest occurrences of large bodied hominoids like Proconsul. The sites preserve different catarrhine fossil assemblages, with some species found in all sites while others found in one site. To better assess this variation, a detailed paleoenvironmental and paleoclimatic reconstruction was done for Tinderet sites in Koru 16, Koru 21 and Kapurtay New. The stratigraphy demonstrates that these sites sample a non-steady landscape that experienced periodic sediment input from volcanic eruptions. The lithology is comprised of interbedded ash and weakly developed paleosols that possess somewhat similar microand macromorphology. Paleoenvironmental reconstructions using stable carbon isotope from paleosol organic matter indicate the presence of C3 vegetation with a likely contribution from C4 biomass which was used in conjunction with the presence of microcharcoal from Koru and Kapurtay New to infer an environment with open patches or canopy breaks. Forest structure reconstruction in Koru 16 suggests a tropical seasonal forest with young and mature trees. Paleoclimate reconstructions using geochemical proxies predict mean annual precipitation of >1000 mm/yr. which indicates humid conditions. Taken together, the results suggest a seasonally dry climate, and that differences in the hominoid assemblages between the sites may not be related to differences in environment or vegetation structure since this appears to be a constant factor across the localities.