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  • Usage in publication:
    • Sumas Mountain subgroup [informal]
  • Modifications:
    • Named
  • Dominant lithology:
    • Limestone
    • Shale
    • Graywacke
    • Argillite
  • AAPG geologic province:
    • Cascades province
Publication:

Danner, W.R., 1977, Paleozoic rocks of northwest Washington and adjacent parts of British Columbia, IN Stewart, J.H., Stevens, C.H., and Fritsche, A.E., eds., Paleozoic paleogeography of the western United States; Pacific Coast paleogeography symposium I: Society of Economic Paleontologists and Mineralogists, Pacific Section, Pacific Coast Paleogeography Symposium, Bakersfield, CA, April 22, 1977, 1, p. 481-502.


Summary:

Sumas Mountain subgroup [informal], lower subgroup of Chilliwack Group. Consists of limestone with shale, graywacke, argillite, minor amounts of chert and thick section of volcanic rocks. Limestone ranges from argillaceous micrites to layered skeletal reefs and reef breccia. Structure includes isoclinal folds and imbricate faults. Thickness ranges from 610 to 915 m. Underlies Red Mountain subgroup [informal] (new) of Chilliwack Group. Age is Devonian, based on fossil evidence.
Type area: Doaks Creek quarry on east side of Red Mountain, and quarry exposures on Sumas Mountain, Whatcom Co., WA.
["Subgroup" not recognized as a formal stratigraphic rank term (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). Considered informal and should not be capitalized.]

Source: Modified from GNU records (USGS DDS-6; Menlo 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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