164-9 Two Decades of Obsidian Provenance Studies in the Central Andes: What Have We Learned?

Session: Advances and Applications of Geochemistry in Archaeology

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Abstract:

Since 2004 I have studied obsidian sources and artifacts in the Peruvian Andes to understand how people in the past migrated and interacted across a vast and rugged landscape. In this talk I will share some highlights from the past two decades of collaborative obsidian research with my co-authors and other colleagues.

Despite being relatively small, localized geologic features located within rugged mountain landscapes, many of South America’s obsidian sources had been discovered and were being transported long distances by the terminal Pleistocene and early Holocene. Among these was the Alca source in southern Peru. From initial use by terminal Pleistocene hunter-gatherers in the high Andes and on the desert Pacific coast, to widespread distribution by complex societies, Alca was one of the most important raw materials used for stone tools in South America. Extensive field mapping and analysis using neutron activation analysis and x-ray fluorescence (XRF) showed that the Alca source had geographically patterned geochemical variation over an extensive region. This feature has permitted high-resolution provenance determination of artifacts at many archaeological sites to investigate how people extracted and distributed obsidian through time.

As knowledge of obsidian sources in the Andean landscape has grown by leaps and bounds, the advent of non-destructive portable (p)-XRF has greatly increased the number of artifacts archaeologists can analyze. I will provide some examples of how these developments have helped reveal landscape learning processes by past people, detect long-distance transfers of Alca and other obsidians indicating past migrations or exchanges, and track the rise and decline of complex societies and social and economic networks.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-5403

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