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Wallace formation

Wallace formation: A heterogeneous unit that includes dark-gray argillite, arenaceous and argillaceous limestone, in part dolomitic, and gray limy quartzite, with shale and sandstone in large areas. The argillaceous and sandy or quartzitic rocks are commonly slightly calcareous. The dominantly carbonate-rich rocks contain "molar tooth" or segregation structures. Commonly characterized by thin laminae. Locally red rocks near the top may represent a transition into the Missoula group.
StateMontana
NameWallace formation
Geologic ageProterozoic | Mesoproterozoic
Original map labelpCw
Primary rock typemeta-argillite
Secondary rock typecarbonate
Other rock typesquartzite
Lithologic constituents
Major
Metamorphic > Metasedimentary > Metaclastic > Argillite (Greenschist)
Minor
Metamorphic > Metasedimentary > Metaclastic > Quartzite (Greenschist)
Sedimentary > Carbonate (Greenschist)Weakly metamorphosed limestone, dolomitic limestone, and dolomite.
Map references
Ross, P.R., Andrews, D.A., and Witkind, I.J., 1955, Geologic map of Montana: U.S. Geological Survey, 2 sheets, scale 1:500,000.
Unit references
Richards, P.W. and Rogers, C.P., Jr., 1951, Geology of the Hardin area, Big Horn and Yellowstone Counties, Montana: U.S. Geological Survey Oil and Gas Investigations Map OM-111, 2 sheets, scale 1:63,360 (Reprinted 1975).
Lewis, R.S., 1998, Geologic map of the Montana part of the Missoula West 30' x 60' quadrangle: Montana Bureau of Mines and Geology Open File Report 373, 20 p, scale 1:100,000.
Lonn, J.D., and McFadden, M.D., 1999, Geologic map of the Wallace 30' x 60' quadrangle: Montana Bureau of Mines and Geology Open File Report 388, 15 p., scale 1;100,000.
Harrison, J.E., Griggs, A.B., and Wells, J.D., 1986, Geologic and structure maps of the Wallace 1° x 2° quadrangle, Montana and Idaho: Montana Bureau of Mines and Geology Montana Atlas Series 4-A, scale 1:250,000.
Harrison, J.E., Cressman, E.R., and Whipple, J.W., 1992, Geologic and structure maps of Kalispell 1° x 2° quadrangle, Montana and Alberta, British Columbia: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-2267, scale 1:250,000.
Harrison, J.E., 1972, Precambrian Belt basin of northwestern United States--Its geometry, sedimentation and copper occurrences: Geological Society of America Bulletin, v. 83, no. 5, p. 1215-1240.
Whipple, J.W., Connor, J.J., Raup, O.B., and McGimsey, R.G., 1984, Preliminary report on the stratigraphy of the Belt Supergroup, Glacier National Park and adjacent Whitefish Range, Montana, in McBane, J.D., and Garrison, P.B., eds., Northwest Montana an
Harrison, J.E., 1984, Stratigraphy and lithocorrelation of the Wallace Formation, in Hobbs, S.W., ed., The Belt--Abstracts with summaries, Belt Sympsium II, 1983: Montana Bureau of Mines and Geology Special Publication 90, p. 24-26.
Geographic coverageFlathead - Lake - Lincoln - Mineral - Missoula - Sanders

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