Stratigraphy and paleoenvironments of Bed III and Bed IV, Olduvai Gorge, Tanzania: Working toward a chronostratigraphic resolution

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 Bed I and Bed II, leaving the upper Bed III and Bed IV considerably understudied. As such, little work has been done to make interpretations on the role of environment in the evolution of hominins in the past ∼1.2 Ma, the time of deposition of the upper beds. 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. The stratigraphic sections measured for this study contain volcaniclastic lithologies that range from claystone, siltstone, sandstone, to conglomerate, as well as tuffs. Bed III contains mainly red volcaniclastic channelized fluvial sandstones and conglomerates. Bed IV contains primarily covered recessive slopes and gray volcaniclastic channelized fluvial sandstones and conglomerates. Overall, the columns represent fluvial-dominated systems. Further research on the depositional processes of Bed III and Bed IV for localities that span the entire gorge will allow us to make large-scale paleoenvironmental reconstructions, which have important implications for the evolution of Homo erectus. This work 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.