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  • Usage in publication:
    • Shallow Creek Quartz Latite*
  • Modifications:
    • Named
  • Dominant lithology:
    • Breccia
  • AAPG geologic province:
    • San Juan Mountains province
Publication:

Steven, T.A., and Ratte, J.C., 1964, Revised Tertiary volcanic sequence in the central San Juan Mountains, Colorado; Article 132, IN Geological Survey Research 1963; short papers in geology and hydrology; Articles 122-170: U.S. Geological Survey Professional Paper, 475-D, p. D54-D63. [Available online from the USGS PubsWarehouse: http://pubs.er.usgs.gov/pubs/pp/pp475D]


Summary:

Named for exposures in drainage basins of Rat Creek, Miners Creek, and Shallow Creek 2 to 4 1/2 mi west of Creede, Mineral Co, CO, San Juan Mountain province. Consists largely of volcanic breccias. Thin lava flows make up less than 10 percent of the formation. Is porphyritic with small phenocrysts set in an aphanitic groundmass. Is irregularly altered, and oxidized and burnt in appearance, or irregularly altered to clay and crisscrossed with quartz and carbonate veinlets. Assigned to the middle Tertiary. Is about the same age as Bachelor Mountain Rhyolite and La Garita Quartz Latite. Formed prior to Farmers Creek Rhyolite and to Huerto Formation.

Source: GNU records (USGS DDS-6; Denver GNULEX).


Map showing publication footprint
  • Usage in publication:
    • Shallow Creek unit*
  • Modifications:
    • Revised
  • AAPG geologic province:
    • San Juan Mountains province
Publication:

Lipman, P.W., Sawyer, D.A., and Hon, K., 1989, Central San Juan caldera cluster; Road log 3, South Fork to Lake City, IN Chapin, C.E., and Zidek, Jiri, eds., Field excursions to volcanic terranes in the western United States; Volume 1, Southern Rocky Mountain region: New Mexico Bureau of Mines and Mineral Resources Memoir, no. 46, p. 330-349., Produced for the International Association of Vocanology and Chemistry of the Earth's Interior (IAVCEI) General Assembly held in Santa Fe, New Mexico, June 25 - July 1, 1989


Summary:

Revised to informal status and assigned to Carpenter Ridge Tuff. Study is in Creede area, Mineral Co, CO, San Juan Mountain province. Unit now interpreted as landslide and talus breccia derived from northwest wall of Bachelor caldera (in La Garita Mountains) during its subsidence. Breccias are composed of precaldera (Conejos-age) hornblende-bearing dacitic lavas. Table Mountain was one of source stratovolcanoes for dacitic lavas. Bachelor caldera was source of Carpenter Ridge. Previous workers interpreted unit to be a primary volcanic accumulation. Unit had similar origin as breccias of Phoenix Park (revised to informal status) and Outlet Tunnel (reinstated to informal status) units both of Carpenter Ridge. Oligocene 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 ([ ]).

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