Previous studies have endeavored to use petrophysical traits of obsidian, particularly its magnetic properties, as an alternative to conventional geochemical sourcing, one of the greatest successes in archaeological science. Magnetic approaches, however, have not seen widespread application due to their mixed successes. In a time when geochemical analyses can be conducted non-destructively, in the field, and in a minute or two, magnetic measurements of obsidian must offer novel archaeological insights to be worthwhile, not merely act as a less successful version of geochemistry. To this end, we report the findings of our large-scale study of obsidian magnetism, which includes 734 geological obsidian specimens and 97 artifacts measured for six simple magnetic parameters. Based on our results, we propose, rather than using magnetic properties to source artifacts to a particular obsidian flow (inter-flow sourcing), these properties are best used to differentiate quarrying sites within an individual flow (intra-flow sourcing). Our results also demonstrate that certain magnetic properties are highly affected by ancient knappers' material selection criteria. Furthermore, depending on the spatial scales of variation, which likely vary from flow to flow, we envision several potential applications of this approach, including integration into minimum analytical nodule analysis (MANA). Magnetic data appear to shift the scale of obsidian sourcing from flows to quarries and, in turn, enable new insights into raw-material procurement strategies, group mobility, lithic technology, and the organization of space and production.
Bibliographical noteFunding Information:
We are indebted to numerous colleagues for their roles in this project. Carolyn Dillian lent geological specimens from Glass Mountain. Giorgio Buccellati and Marilyn Kelly-Buccellati are directors of the Urkesh excavations under the International Institute for Mesopotamian Area Studies. Export of Tell Mozan artifacts was approved by the Directorate General of Antiquities and Museums, Syrian Arab Republic. Most Anatolian geological specimens were collected by George “Rip” Rapp, University of Minnesota and Tuncay Ercan, Directorate of Mineral Research and Exploration, Turkey. Additional specimens were collected by M. James Blackman of the Smithsonian, Robert L. Smith of the United States Geological Survey, and James F. Luhr of the Smithsonian. Serial-sectioned specimens were collected by John Whittaker and Kathryn Kamp of Grinnell College. We are grateful for the research assistance of Charissa Johnson (supported by the University of Minnesota's Undergraduate Research Opportunity Program and a Sigma Xi Grant-in-Aid), Amy Hillis (supported by the National Science Foundation's Research Experience for Undergraduates program and the University of Minnesota's Earth Sciences Summer Internship program ), and Steven Newman (as part of the University of Minnesota's Archaeology Laboratory Internship program ). We received invaluable help from Mike Jackson, Julie Bowles, and Peter Sølheid at the Institute for Rock Magnetism. This research was also supported by the Departments of Earth Sciences and Anthropology at the University of Minnesota, the Department of Archaeology at the University of Sheffield , and Marie Curie Network FP7-PEOPLE-2010-ITN: New Archaeological Research Network for Integrating Approaches to Ancient Material Studies (NARNIA). Two anonymous reviewers and the editor are also thanked for their helpful comments that clarified the final manuscript. This is IRM publication #1206.
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- Rock magnetism
- Southwest Asia