Lateral facies and paleosol changes in the lower Okote Member (Koobi Fora Formation) at Ileret, Kenya

Early Pleistocene sediments and interbedded paleosols of the lower Okote Member preserve a diversity of archaeological and paleontological sites that include, for example, ungulate bone with cut marks, hominin fossils, and several trackways showing the footprints of hominins and other fauna. Previous detailed sedimentological and taphonomic studies has led to a comprehensive model of site formation explaining the excellent preservation of the footprint horizons. These data have been used to interpret hominin behavioral ecology along the shoreline of an ancient lake margin. However, other published reconstructions favor that the paleogeography was predominated by an alluvial system, which accumulated multiple meter-scale, fining-upward sequences. These sequences represent crevasse splays active adjacent to a main feeder channel or series of feeder channels. In this study, we examine previously published and new outcrop observations to compare the two contrasting paleogeographic interpretations. We also provide new geochemical analyses on pedogenic carbonate nodules and bulk paleosol samples from outcrop sites separated by 5 km at Ileret. These new data are used to assess if paleo-vegetation and /or iron mineral assemblages are correlated with different depositional environments, and to understand how the ancient landscape may have varied at sites relatively proximal and distal to the basin axis.