Abstract
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 contains inter-stratified stone tool industries associated with the Earlier, 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 assemblages amenable for sourcing lithic artifacts. Petrographic analysis of sixty-two lithologic samples collected in primary and secondary positions reveal discriminatory differences. More precisely, five outcrops have quartzites with unique mineral assemblages, five outcrops have meta-granites with unique mineral assemblages, 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 discriminate source materials using mineralogy, which implies that sourcing lithic artifacts is possible. For proof of concept, we assign the source/s of previously described fuchsitic quartzite artifacts from three archaeological sites at Oldupai to two nearby outcrops. Additional archaeological testing will allow researchers to glean new understandings of hominin behavior and stone procurement in the Oldupai paleobasin.
Highlights
Rocks used for artifact manufacture are alternatively known as lithic raw materials and occur as mineral aggregates of igneous, metamorphic, and sedimentary origin that are nonrenewable and spatially exhaustible over a non-geological timeframe (Kyara, 1996)
We characterize a range of lithologies that were available to hominins at Oldupai Gorge using a combination of thin section petrography, Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS), and Electron Probe Micro Analysis (EPMA)
By characterizing the range and variability of lithic raw materials that were available to Pleistocene hominins, we have demonstrated that there are unique mineralogical identifiers even among similar lithologies
Summary
Rocks used for artifact manufacture are alternatively known as lithic raw materials and occur as mineral aggregates of igneous, metamorphic, and sedimentary origin that are nonrenewable and spatially exhaustible over a non-geological timeframe (Kyara, 1996). Raw material characterization and sourcing through comparative study of geological specimens and artifacts. Raw Material Characterization at Oldupai (Weigand et al, 1977; Shotton and Hendry, 1979) can provide insights into stone selection and procurement strategies (Stout et al, 2005), transportation costs (Kyara, 1999), technological façonnage (Mason and Aigner, 1987), functional suitability (Ebright, 1987), anthropogenic usage (Courtenay et al, 2019), landuse behavior (Tactikos, 2005), population movements (Reimer, 2018), and social networks of trade and exchange (Lebo and Johnson, 2007). Ten samples were subsequently analyzed using SEM-EDS and EPMA to complement petrographic observations
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