- Usage in publication:
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- Basin rhyolite
- Modifications:
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- Original reference
- Dominant lithology:
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- Rhyolite
- AAPG geologic province:
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- South Park basin
Summary:
p. 100-101. Basin rhyolite [of Basin Ridge group]. Yellowish-buff to gray and characteristically aphanitic except for a few widely scattered phenocrysts of biotite and feldspar. Maximum thickness measured 300 feet. Relationship with underlying rocks not definite, but near southern end of Basin Ridge, rhyolite thought to lie either directly on Pierre shale or very nearly so. Age is Tertiary.
Caps central part of Basin Ridge and occupies center of Basin Ridge syncline, Park Co., central CO. Known in outcrops extending from about middle of east line of sec. 20, T. 9 S., R. 76 W., to northern bdry. of sec. 27, T. 10 S., R. 76 W., South Park, Park Co., central CO. Average width of outcrop is 2 mi.
Source: US geologic names lexicon (USGS Bull. 1200, p. 230-231).
For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.
Asterisk (*) indicates published by U.S. Geological Survey authors.
"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).
Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).