Oldupai Gorge is located within the Ngorongoro Conservation Area, a UNESCO World Heritage Site in northern Tanzania along the western margin of the East African Rift System. Oldupai’s sedimentary record exhibits a complex sequence of inter-stratified lithic assemblages associated with the Early, Middle, and Later Stone Age. While diachronic technological change is perceptible, the totality of locally available rocks remained largely unchanged through time. Here, thin section petrography, Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy, and Electron Probe Micro Analysis were employed to characterize source lithologies in the Oldupai region. One of our goals was to determine if outcrops have rock types with unique mineral compositions amenable for sourcing lithic artifacts. Geological samples were collected in primary and secondary positions, from which sixty-two samples were selected for analysis. Comparative analyses show that five outcrops have quartzites with unique mineral compositions, seven meta-granite varieties are unique to five individual outcrops, Engelosin phonolite samples are texturally and mineralogically unique, and magmatic samples recovered in secondary position may be sourced to their volcanic center. Our results demonstrate it is feasible to differentiate between source materials using optical mineralogy which implies that sourcing lithic artifacts based on mineral compositions is possible. This is further substantiated by assigning the source/s for previously described fuchsitic quartzite artifacts from three archaeological sites at Oldupai as this raw material type uniquely occurs at two nearby outcrops. Systematic archaeological testing will allow future researchers to glean new understandings of hominin behavior and resource procurement within the Oldupai paleobasin.
