GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 168-4
Presentation Time: 9:00 AM-6:30 PM


KEARNEY, John C.1, JOHNSON, Claudia C.1 and NJAU, Jackson, K.2, (1)Department of Geological Sciences, Indiana University, 1001 E. Tenth St., Bloomington, IN 47405-1405, (2)Stone Age Institute, Indiana University, Bloomington, IN 47407; Department of Geological Sciences, Indiana University, 1001 E. Tenth St., Bloomington, IN 47405-1405,

Hominin fossils and stone artifacts can be found in a range of ancient environments in East Africa, but many hominin sites are found in and around ancient lake basins for reasons varying from taphonomy to hominin resource utilization. These lake deposits are extensively studied to extract imperative fine-scale climate data, allowing for interpretations to be made about the role of a changing climate on the evolution of early humans. Such is the case for Olduvai Gorge, Tanzania, arguably one of the most important archaeological sites that exposes nearly continuous deposits from the past ~2 million years. The oldest deposits are termed Bed I and Bed II and consist primarily of lacustrine facies, while the overlying deposits, termed Bed III and Bed IV, consist primarily of soil and fluvial facies. Much of the geologic research of the past several decades has focused on the older lacustrine deposits, and the younger deposits of Bed III and Bed IV have been comparatively understudied. In order to make detailed paleoenvironmental reconstructions of Bed III and Bed IV, stratigraphic sections need to be measured and correlated. Here I present previously unmeasured stratigraphic sections from the Side Gorge using field data collected in the summer of 2016. Thick paleosols in these sections indicate extended periods of time of little to no deposition that allowed for soil formation, and intermittent conglomerates indicate relatively shorter periods of time of rapid deposition by high-energy streams and floods. These conglomerates are further characterized quantitatively using paleocurrent directions measured in the field, stream energy using clast composition and size, and provenance using optical petrography and X-ray diffraction. These methods allow for detailed paleoenvironmental reconstructions to be made in exposed deposits that lack the ideal fine-scale resolution of lacustrine deposits.