Portable X-ray fluorescence (pXRF) instruments can source obsidian artifacts once beyond analytical reach, expanding the range of artifact classes included in sourcing research. It is now more straightforward to analyze a “museum quality” tool on display in a gallery than the flaking chips and resharpening debitage recovered with it. That is because a minimum specimen size for artifacts is often mentioned as a drawback of pXRF-based sourcing. Many recent studies reject artifacts smaller than 1 cm and thinner than 3 mm for pXRF analysis. This study concerns whether such guidelines are too restrictive. After examining data from previous research into this issue, this study uses an experimental assemblage of 650 flakes from five obsidian sources to demonstrate two data handling techniques that enable valid and reliable source identifications for artifacts as small as microdebitage. The first involves ratios between quantitative concentrations of well-measured elements with similar X-ray energies, while the second one involves multivariate analysis of elemental data for obsidian flakes across a variety of size classes. As an example, 200 small blades are matched to two chemically similar obsidian sources on the Aegean island of Melos. Distinguishing between them has been treated as a “benchmark” or “litmus test” for evaluating obsidian sourcing techniques. Ultimately, it is demonstrated that debitage, as small as ∼ 1–2 mm and < 10 mg, can be sourced using pXRF. Including small lithic size classes has important consequences. Obsidian tools were continuously resharpened and rejuvenated as they were transported across the landscape. Sourcing microdebitage, not only large artifacts, enables insights into tool maintenance and curation behaviors that would otherwise be invisible.
Bibliographical noteFunding Information:
Many friends and colleagues made this study possible. I thank Pavel Avetisyan, Director of the Institute for Archaeology and Ethnography, Armenia, for his continued support. I direct the Obsidian Resources and Landscapes of Palaeolithic Armenia project jointly with Boris Gasparyan, Institute of Archaeology and Ethnography, and Daniel S. Adler, University of Connecticut. My fieldwork was facilitated by Khachatur Meliksetian and Sergei Karapetian, Institute of Geological Sciences, Armenia, and Suren Kesejyan, Institute of Archaeology and Ethnography. Other obsidian specimens were collected by George “Rip” Rapp, University of Minnesota–Duluth, and the late Tuncay Ercan, General Directorate of Mineral Research and Exploration, Republic of Turkey. I am grateful to the staff of the 6th Ephorate of Prehistoric and Classical Antiquities for making arrangements for me to analyze the obsidian blades. The excavation was conducted by the 6th Ephorate, and my results were included in a 2012 report to the excavators and ephorate director. Funding for me to conduct analyses at the ephorate was provided by the Marie Curie NARNIA project (Grant 265010 ). Artifact photos are included without fee thanks to the exemption granted to scientific studies and publications. The synthetic specimens were made by Vassilis Kilikoglou, National Centre for Scientific Research “Demokritos.” Liev Frahm assisted with their measurement. One of the Niton instruments in this study is owned by the University of Sheffield's Archaeology Department, and the other pXRF is part of the research infrastructure of the Institute for Rock Magnetism, Department of Earth Sciences, University of Minnesota. NAA and EDXRF data were provided by Michael Glascock, Archaeometry Laboratory, MURR. EMPA analyses were conducted in the Electron Microprobe Laboratory, the University of Minnesota. Three anonymous reviewers' comments improved the clarity of the final manuscript.
© 2016 Elsevier Ltd
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- Artifact size limitations
- Chip debris
- Lithic debitage
- Multivariate analysis
- Obsidian sourcing
- Portable X-ray fluorescence
- Stone tool maintenance