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  • Usage in publication:
    • Chalmers quartz monzonite
  • Modifications:
    • Named
  • Dominant lithology:
    • Quartz monzonite
  • AAPG geologic province:
    • South Park basin
Publication:

Stark, J.T., Johnson, J.H., Behre, C.H., Jr., Powers, W.E., Howland, A.L., and Gould, D.B., 1949, Geology and origin of South Park, Colorado: Geological Society of America Memoir, 33, 188 p.


Summary:

Named for Chalmers Ridge, which is 2 mi long, rises 200 ft above Park floor in sec 13, T11S, R76W, Park Co, CO in South Park basin. No type locality designated. Forms rounded hills. Intrudes Mesozoic sediments. Known only as float. Is a fine-grained equigranular rock with the visible quartz, feldspar, biotite, and hornblende. Varies from pinkish gray through bluish gray to olive green. Microscopically is porphyritic with subhedral phenocrysts of plagioclase, orthoclase, quartz, feldspar, biotite, and hornblende. Of early Tertiary age. Geologic map.

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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