Investigating the application of Raman spectroscopy of carbonaceous material in sedimentary lithic artifacts for archaeological provenancing applications in the Canadian Rockies

The chemical compositions of toolstones composed of clastic and chemical sedimentary rock are often not distinct among procurement locations. However, sedimentary toolstone sources may show variations in the structural characteristics of the included carbonaceous material (CM) related to differences in their postdepositional histories, providing a potential proxy by which procurement locations, rather than individual rock units, can be assessed as raw material sources for archaeological lithics. Here, we apply a well-established method for investigating the nature of CM in sedimentary rocks, Raman spectroscopy of carbonaceous material (RSCM), to an archaeological case study. We test if the technique can be used to differentiate among toolstones from two procurement areas along the eastern slopes of the Canadian Rocky Mountains potentially used by pre-European contact Indigenous inhabitants of the Hummingbird Creek Site (FaPx-1). Artifacts found during excavations at Hummingbird Creek visually appear to match toolstone-grade rocks in the site's vicinity. We analyzed source material from two localities: (1) the local toolstone around FaPx-1 and (2) a toolstone procurement area similar to 45 km away associated with many precontact workshop sites. To test if the artifacts have compositions consistent with the local toolstones, we analyzed artifacts and potential source materials with RSCM as well as their major, minor, and trace element composition using X-ray fluorescence (XRF). Our work is guided by the elimination of source locations using indirect geochemical proxies in accordance with the exclusionary Provenance Hypothesis. Both the structural and the chemical characteristics of the artifacts are similar to those of geologic samples from the nonlocal source location and are not consistent with samples collected locally, permitting the exclusion of local materials and suggesting that the inhabitants of FaPx-1 used a variety of toolstones to manufacture the artifacts from materials that do not appear to be readily available near the site.

Automated summary

By analyzing toolstones and artifacts from different locations using Raman spectroscopy and X-ray fluorescence techniques, this study excludes local materials as potential sources for artifacts found at the Hummingbird Creek Site, suggesting that the inhabitants may have utilized various hard-to-obtain toolstones for crafting.