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(U-Th)/He zircon and archaeological ages for a late prehistoric eruption in the Salton Trough (California, USA)

Schmitt, Axel K. and Martín, Arturo and Stockli, Daniel F. and Farley, Kenneth A. and Lovera, Oscar M. (2013) (U-Th)/He zircon and archaeological ages for a late prehistoric eruption in the Salton Trough (California, USA). Geology, 41 (1). pp. 7-10. ISSN 0091-7613.

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U-Th and (U-Th)/He zircon geochronology redefines the timing of volcanic activity in the Salton Trough (Southern California, USA), the subaerial extension of the incipiently oceanic Gulf of California. U-series disequilibrium corrected (U-Th)/He zircon analyses for a granophyre ejecta clast from the Red Island rhyolite dome indicate an eruption age of 2480 ± 470 a (calendric dates between 0 and 940 Before Common Era, BCE; error at 95% confidence). This eruption age is supported by U-Th zircon crystallization ages for two obsidian-bearing lavas: Red Island (the host for the granophyre) and Obsidian Butte, a prehistoric quarry for obsidian that is widely distributed in southern California and northern Mexico archaeological sites. Lavas and granophyre display overlapping zircon crystallization age distributions that support field and compositional evidence that they are cogenetic and contemporaneous. The (U-Th)/He eruption age is younger and significantly more precise than previous ages for these volcanoes, and is the first indication that the eruption of obsidian flows coincided with human presence in the region. A late prehistoric eruption age agrees with the absence of the Obsidian Butte lithic source among early prehistoric cultural artifacts, previously attributed to submergence of the quarry location during hypothesized persistent flooding by ancient Lake Cahuilla.

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Farley, Kenneth A.0000-0002-7846-7546
Additional Information:© 2012 Geological Society of America. Received 16 May 2012. Revision received 6 June 2012. Accepted 11 June 2012. Published online 15 October 2012. We thank W. Elders for providing sample I70–24, L. Hedges and R. Kislitsyn for (U-Th)/He analytical assistance, and H. Zou and C. Shen for whole-rock U-Th isotope data. M. Dahdul, J. Dietler, M.C. Hall, D. Laylander, S., Shackley, and A. Porcayo-Michelini shared helpful insights into obsidian archaeology. We thank reviewers C. Bacon, T. Fischer, and editors A. Barth and S. Wyld. This work was supported by grants through UC-MEXUS (University of California Institute for Mexico and the United States) CN 07-60 and National Science Foundation MARGINS grant EAR-0948162. The ion microprobe facility at the University of California–Los Angeles is partly supported by a grant from the Instrumentation and Facilities Program, Division of Earth Sciences, National Science Foundation.
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University of California Institute for Mexico and the United States (UC-MEXUS)CN 07-60
NSF Division of Earth Sciences, Instrumentation and Facilities ProgramUNSPECIFIED
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Official Citation: Axel K. Schmitt, Arturo Martín, Daniel F. Stockli, Kenneth A. Farley, and Oscar M. Lovera (U-Th)/He zircon and archaeological ages for a late prehistoric eruption in the Salton Trough (California, USA) Geology, January 2013, v. 41, p. 7-10, first published online 15 October 2012, doi:10.1130/G33634.1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36794
Deposited By: Ruth Sustaita
Deposited On:08 Feb 2013 16:53
Last Modified:03 Mar 2020 13:01

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