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Bulletin 2064–II
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Geology and Stratigraphy of the Challis Volcanic Group and Related Rocks, Little Wood River Area, South-Central Idaho

By Richard F. Sanford

With a section on Geochronology by Lawrence W. Snee

The Challis volcanic field is the largest of several Eocene volcanic fields in the Pacific Northwest of the United States and Canada. In the Little Wood River area of Idaho, rock types in the Eocene Challis Volcanic Group include andesite lava flows and tuff breccia, dacite lava flows and flow breccia, volcaniclastic sedimentary rocks, lithic tuff, nonvolcanic conglomerate, and rhyolite dikes.

Version 1.0

Posted May 2005

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