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- Usage in publication:
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- Cressman's Gulch Formation
- Modifications:
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- Named
- Dominant lithology:
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- Gneiss
- Quartzite
- AAPG geologic province:
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- Southern Rocky Mountain region
Summary:
Named for Cressman's Gulch, Ralston Buttes quad, Jefferson Co, CO in the Southern Rocky Mountain region. Type area designated along mountain front in NW1/4 SE1/4 sec 17, T3S, R70W. Called layered lime-silicate gneiss in earlier reports. Consists of amphibolitic and tactitic gneiss. Includes Chase Ranch Quartzite Member, a 10 to 20-ft-thick fine-grained, massive to thin-bedded quartzite that occurs at different stratigraphic positions in the formation. Tactitic rocks produce bone-like structures upon weathering. Quartz pods and stringers frequent. Pegmatites are as much as 25 ft thick. Ranges from 50-800 ft thick. Absence to west due to unconformity at base of overlying Junction Formation (new). Geologic map. Cross section. Precambrian age.
Source: GNU records (USGS DDS-6; Denver GNULEX).
- Usage in publication:
-
- Cressman's Gulch Formation
- Modifications:
-
- Overview
- AAPG geologic province:
-
- Southern Rocky Mountain region
Summary:
Chase Ranch Quartzite Member of Cressman's Gulch Formation is one of several units defined in a narrow belt along east-central Front Range, near Golden, Jefferson County, Colorado (Southern Rocky Mountain region). Of doubtful use elsewhere. Assumed direction of stratigraphic sequence is debatable. Belongs with pre-1,700 m.y. metamorphic complex, or of Precambrian X 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 ([ ]).