2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 136-3
Presentation Time: 9:00 AM-6:30 PM


KEARNEY, John1, JOHNSON, Claudia C.1, NJAU, Jackson1, TOTH, Nick2 and SCHICK, Kathy2, (1)Geological Sciences, Indiana University, 1001 E. 10th St, Bloomington, IN 47405, (2)Stone Age Institute, Indiana University, PO Box 5097, Bloomington, IN 47407, kearneyj@indiana.edu

Olduvai Gorge, Tanzania is an important paleoanthropological site that has yielded significant hominin fossils and stone artifacts. Much of the paleoenvironmental research conducted in the past several decades has been focused on the stratigraphically lower Beds I and II, leaving the upper Beds III and IV considerably understudied. In this study, I use lithology and optical petrology on samples from select localities near archaeological sites MNK and VEK in the Side Gorge to begin a detailed stratigraphic analysis on these upper beds to determine depositional environment so that accurate correlations can be made across the gorge. Bed III has traditionally been differentiated from Bed IV in the eastern portion of the gorge by its distinct red color. This characteristic is not present in the western portion of the gorge, where the beds are combined and referred to as Beds III-IV (undivided), and thus Bed III needs to be redefined based on environmental processes. While the lower Beds I and II of this study area contain primarily lacustrine deposits, the upper Beds III and IV are dominated by fluvial deposits and disconformities represented by paleosols. In the localities studied here, the base of Bed III is overlying a tuff of mafic composition at the top of Bed II. Bed III contains primarily red volcaniclastic sandstone and conglomerate. The top of Bed III contains a thick red conglomerate that is scouring an underlying paleosol. The contact between Bed III and Bed IV is marked by an erosional surface on top of the red conglomerate. Bed IV contains primarily gray volcaniclastic channel sandstone and conglomerate, as well as covered recessive slopes. Further research on the depositional processes will allow us to use these criteria to differentiate Beds III and IV in the western portion of the gorge and make large-scale paleoenvironmental reconstructions, which have important implications for the evolution of Homo erectus. This will lead to further interpretations of how hominins utilized and interacted with their environment, and how it may have played a role in the evolution of our recent ancestors.