Ten seconds in the field: rapid Armenian obsidian sourcing with portable XRF to inform excavations and surveys

Abstract

Armenia has one of the most obsidian-rich natural and cultural landscapes in the world, and the lithic assemblages of numerous Palaeolithic sites are predominantly, if not entirely, composed of obsidian. Recent excavations at the Middle Palaeolithic cave of Lusakert 1 recovered, on average, 470 obsidian artifacts daily. After sourcing more than 1700 artifacts using portable XRF (pXRF) in our field house, our team sought to shift pXRF-based obsidian sourcing into the field itself, believing that the geological origins of artifacts would be useful information to have on-site during an excavation or survey. Despite increasing use of portable instruments, previous studies have principally focused on collections in museums and other archives, and as a result, obsidian sourcing has remained embedded in post-excavation studies. One critical factor in the uptake of obsidian sourcing in the field is the time needed to measure each artifact, frequently 2–6 min in previous studies. Here we report our two methods of obsidian sourcing, including source matching done automatically by the pXRF instrument's onboard software, in only 10 s. Our tests with Armenian geological specimens and Palaeolithic artifacts demonstrate the high efficacy of our two methods, which are sufficiently fast to become syncopated with our excavation and survey activities. By reducing measurement times from a mode of 300 s in recent studies to just 10 s, here we show how (and why) to shift pXRF-based obsidian sourcing from the context of “white lab coats” to that of “muddy boots.”