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Multi-technique geochemical characterization of the Alca obsidian source, Peruvian Andes

Kurt Rademaker, Michael D. Glascock, Bruce Kaiser, David Gibson, Daniel R. Lux and Martin G. Yates
Multi-technique geochemical characterization of the Alca obsidian source, Peruvian Andes
Geology (Boulder) (May 2013) 41 (7): 779-782


We report results from comprehensive mapping and multi-technique geochemical characterization of obsidian from the Alca source in the Peruvian Andes (15.3 degrees S, 72.7 degrees W), aimed at understanding patterns of extraction and trade in one of the world's centers of complex civilization. Alca obsidian was among the most economically important and widely distributed volcanic glasses used for stone tool making in South America from ca. 13 ka until recently, yet the geologic source of this material has never been studied comprehensively. Our work establishes Alca as one of the largest obsidian sources in South America and the only Peruvian source known to have patterned intrasource geochemical variability. There are six geochemically distinct Alca subsources exposed from 2710 to 5165 m elevation over >330 km (super 2) of the highlands, an area nearly seven times larger than previously known. Our results now permit provenance determination of artifacts to specific outcrops. We analyzed 252 geologic samples using energy-dispersive X-ray fluorescence, neutron activation analysis, wavelength-dispersive X-ray fluorescence, and nondestructive, portable energy-dispersive X-ray fluorescence. All techniques distinguish the same six Alca subsources, establishing analytical comparability between geochemical methods. Discrimination of Alca obsidian to the subsource level using portable X-ray fluorescence represents a major advance in nondestructive provenance analysis. Further nondestructive analysis of robust sets of obsidian artifacts within Peru will allow high-resolution study of the evolution of central Andean exchange systems.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 41
Serial Issue: 7
Title: Multi-technique geochemical characterization of the Alca obsidian source, Peruvian Andes
Affiliation: University of Maine at Orono, Department of Anthropology, Orono, ME, United States
Pages: 779-782
Published: 20130524
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 24
Accession Number: 2013-047964
Categories: Geochemistry of rocks, soils, and sedimentsIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch maps
S15°18'00" - S15°18'00", W72°42'00" - W72°42'00"
Secondary Affiliation: University of Missouri at Columbia, USA, United StatesBruker Elemental, USA, United StatesUniversity of Maine at Farmington, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201330
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