The Search for the Primary Source of Kings Canyon/La Poudre Pass Obsidian in Colorado

Summary

This is an abstract from the "SAA 2019: General Sessions" session, at the 84th annual meeting of the Society for American Archaeology.

During field survey in 2011, archaeologists for the Medicine Bow-Routt National Forest discovered obsidian nodules contained in ancient alluvial gravels of the Miocene North Park formation in Jackson County, Colorado. The Northwest Research Obsidian Studies Laboratory in Corvallis, Oregon, analyzed this obsidian using ED-XRF and determined that it was previously uncharacterized by their lab. It was subsequently named Kings Canyon obsidian, after a local place name near the geologic source. Further discussions with archaeologists in the northern Colorado revealed that the obsidian was previously known from archaeological contexts. In fact, another obsidian lab had named it La Poudre Pass obsidian. Forest Service archaeologists then embarked upon a search for the primary source, which led to the Never Summer Mountains in Rocky Mountain National Park. Geochemical analyses of vitrophyre from Specimen Mountain proved inconclusive. Isotopic dating using the 40Ar/39Ar method on obsidian and fine-grained volcanic rock samples from the Kings Canyon gravels returned ages consistent with the age of the Oligocene Never Summer Igneous complex. These results suggest that the Kings Canyon/La Poudre Pass obsidian may have a broad geographic distribution across north-central Colorado.

This Resource is Part of the Following Collections

• Society for American Archaeology 84th Annual Meeting, Albuquerque, NM (2019)

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Record Identifiers

Abstract Id(s): 23089