Lithic raw material units based on magnetic properties: A blind test with Armenian obsidian and application to the Middle Palaeolithic site of Lusakert Cave 1

Gilliane F. Monnier, Ellery Frahm, Joshua M. Feinberg, Gilbert B. Tostevin, Boris Gasparyan, Daniel S. Adler

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Classification of lithic artifacts’ raw materials based on macroscopic attributes (e.g., color, luster, texture) has been used to pull apart knapping episodes in palimpsest assemblages by attempting to identify artifacts produced through the reduction of an individual nodule. These classes are termed “raw material units” (RMUs) in the Old World and “minimum analytical nodules” in the New World. RMUs are most readily defined for lithic artifacts in areas with distinctive cherts and other siliceous raw materials, allowing pieces from different nodules to be recognized visually. Opportunities to apply RMUs, however, are strongly limited at sites where lithic material visual diversity is low. The magnetic properties of obsidian, which result from the presence of microscopic iron oxide mineral grains, vary spatially throughout a flow. Consequently, obsidian from different portions of a source (i.e., different outcrops or quarries) can vary in magnetic properties. This raises the possibility that magnetic-based RMUs (mRMUs) for obsidian artifacts could be effective to distinguish individual scatters from multiple production episodes and offer insights into spatial patterning within a site or specific occupation periods. First, we assess the potential of mRMUs using obsidian pebbles from Gutansar volcano in Armenia. Second, we evaluate the validity of this approach based on a double-blind test involving an experimental assemblage of Gutansar obsidian flakes. Cluster analysis can successfully discern flakes from obsidian specimens containing high concentrations of iron oxides. Obsidian with more magnetic material has more opportunities for that material to vary in unique ways (e.g., grain size, morphology, physical arrangement). Finally, we apply the mRMU approach to obsidian artifacts from the Middle Palaeolithic site of Lusakert Cave 1 in Armenia and compare the results to traditional RMU studies at contemporaneous sites in Europe. In particular, we seek – but do not find – differences between retouch flakes (which reflect rejuvenation of tools) and the other small debris (which reflect other reduction activities). This result likely reflects the local landscape, specifically the abundance of obsidian and, thus, little pressure to curate and retouch tools. As this approach is applied to additional sites, such findings will play a central role in regional assessments about the nature and timing of the Middle to Upper Palaeolithic “transition” and the relationship, or lack thereof, between technological behaviors and presumed population dynamics.

Original languageEnglish (US)
Pages (from-to)102-123
Number of pages22
JournalJournal of Archaeological Science
StatePublished - Oct 1 2016

Bibliographical note

Funding Information:
We are indebted to numerous colleagues for their contributions. We thank Benik Yeritsyan and Pavel Avetisyan, Institute for Archaeology and Ethnography, National Academy of Sciences, Republic of Armenia, for continued support of our research in Armenia. Thanks also to our many Armenian friends who make such research possible. We recognize the generous financial support provided to Adler for the Hrazdan Gorge Palaeolithic Project by the Norian Armenian Programs Committee (University of Connecticut, 2008–2015), two Large Faculty Grants (University of Connecticut, 2008 and 2012), and the L.S.B. Leakey Foundation (2010 and 2011). The LKT1 excavations were directed by Adler and Yeritsyan, with labor provided by undergraduates in the University of Connecticut's Field School in Armenian Prehistory, directed by Adler, and graduate students in the Old World Archaeology Program. A portion of the GVC obsidian specimens was collected with the assistance of Khachatur Meliksetian and Sergei Karapetian, Institute of Geological Sciences, National Academy of Sciences, Republic of Armenia. Frahm's work was supported by the University of Sheffield's Department of Archaeology; the NARNIA Project, a Marie Curie network funded by the European Union and FP7 (Grant # 265010 ); and the Department of Earth Sciences, Department of Anthropology, and Institute for Rock Magnetism at the University of Minnesota-Twin Cities . Liev Frahm provided research assistance, as did Michelle J. Muth during the pilot study. Her work on this project was supported by the NSF's Research Experience for Undergraduates program and the University of Minnesota's Earth Sciences Summer Internship program. One pXRF instrument used in this study is owned by the Department of Archaeology, University of Sheffield with funding secured by Roger Doonan, and the other is part of the research infrastructure of the University of Minnesota's Wilford Laboratory of North American Archaeology, directed by Katherine Hayes. We received invaluable help from Mike Jackson and Peter Sølheid at the Institute for Rock Magnetism. The editor as well as two anonymous reviewers provided comments that helped to us to clarify the final manuscript. This is IRM contribution #1604.

Publisher Copyright:
© 2016 Elsevier Ltd


  • Lithic analysis
  • Middle Palaeolithic
  • Minimum analytical nodules
  • Obsidian characterization
  • Raw material units
  • Rock magnetism
  • Southern Caucasus


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