PALEOENVIRONMENTAL HISTORY AND REGIONAL INTERPRETATION FOR THE HOMINOID-BEARING LOCHERANGAN LOCALITY IN WEST TURKANA, KENYA

A nuanced understanding of paleoenvironment is essential to understanding archaeology, anthropology, and human evolutionary history. The Turkana Basin in northern Kenya preserves a sedimentary record tracing the physical and cultural evolution of our species. However, the paleoenvironmental history that accompanied and drove these evolutions becomes increasingly challenging to reconstruct further into the past, particularly in the Miocene­­­­­. Because Lower Miocene records are spatially limited, understanding of the broader depositional systems and precise paleoenvironmental interpretation is limited. We know that across East Africa, Lower Miocene hominoids were adapted for a wetter environment than the modern savannah and there is evidence of both lacustrine and large-scale fluvial systems in parts of Turkana at this time. The goal of this research is to integrate the previously undescribed but highly fossiliferous Lower Miocene Locherangan locality in West Turkana, Kenya into the broader paleoenvironmental context of this time period. A new, high-resolution stratigraphic section promotes basin-wide correlations with the other Lower Miocene records and subsequent geochemical analyses provide increasingly precise paleoenvironmental context. Locherangan is dominated by fine-grained lithologies, episodically overprinted by pedogenesis. Sparse sands near the top of the 50.3 m, continuous section contain the bulk of the terrestrial vertebrate assemblage. Analysis of carbon content, ostracod taphonomy, and δ¹⁸O and δ¹³C isotopes from ostracod valves provide further insight into the environment. Total organic carbon data suggest that pedogenic overprint may reduce the inorganic carbon content and increase organic carbon content. Though diagenesis and pedogenesis compromise the preservation of many ostracods and alter the carbon content, both tools provide valuable information about the dynamic nature of the lacustrine margin preserved in this section. From an evolutionary standpoint, this research provides valuable environmental contexts for the hominoids Afropithecus turkanensis and Simiolus enjienssi that were excavated at Locherangan in the 1980s.