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Map showing publication footprint
  • Usage in publication:
    • West Fork Formation*
  • Modifications:
    • Named
  • Dominant lithology:
    • Siltite
    • Limestone
  • AAPG geologic province:
    • Idaho Mountains province
Publication:

Ruppel, E.T., 1975, Precambrian Y sedimentary rocks in east-central Idaho, IN Ruppel, E.T., Ross, R.J., Jr., and Schleicher, David, Precambrian and lower Ordovician rocks in east-central Idaho: U.S. Geological Survey Professional Paper, 889-A, p. A1-A23.


Summary:

Unit is named the West Fork Formation of the Lemhi Group. Consists of mostly thick-bedded to massive, cross-laminated, ripple-marked, medium to dark greenish-gray siltite, with lenticular algal limestone. Has blocky fracture. Thickness is 460 m. Gradationally overlies the Inyo Creek Formation; gradationally underlies the Big Creek Formation. Age is Precambrian Y. (B1520)

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


Map showing publication footprint
  • Usage in publication:
    • West Fork Formation*
  • Modifications:
    • Age modified
  • AAPG geologic province:
    • Idaho Mountains province
Publication:

Hobbs, S.W., 1980, The Lawson Creek Formation of Middle Proterozoic age in east-central Idaho, IN Contributions to stratigraphy: U.S. Geological Survey Bulletin, 1482-E, p. E3-E9.


Summary:

Age of the West Fork Formation is revised from Precambrian Y to Proterozoic Y.

Source: 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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