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- Usage in publication:
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- Purple Mountain Pumice Breccia
- Modifications:
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- Named
- Dominant lithology:
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- Breccia
- AAPG geologic province:
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- Yellowstone province
Summary:
Named after a park named Purple Mountain on north rim of Madison Canyon, about 1 1/2 mi north of Madison Junction, Yellowstone National Park, WY in the Yellowstone province. No type locality designated. Is a welded, rhyolitic pumice breccia that preceded eruption of Yellowstone Tuff (new). The phenocrysts are quartz, sanidine, and oligoclase. Has two principal outcrop areas: 1) north wall of Madison Canyon, 2) at Stonetop Mountain about 4 mi north of Yellowstone Lake. Ranges from soft coherent tuff to densely indurated rock. Maximum observed thickness is 1,000 ft. Appears to be the product of pyroclastic flows. Assigned a Pliocene age.
Source: GNU records (USGS DDS-6; Denver GNULEX).
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 ([ ]).