Greyson shale (MTpCAg;0)

State	Montana
Name	Greyson shale
Geologic age	Proterozoic \| Mesoproterozoic
Original map label	pCg
Primary rock type	meta-argillite
Secondary rock type	quartzite
Other rock types	limestone
Lithologic constituents	Major Metamorphic > Metasedimentary > Metaclastic > Argillite (Greenschist) Minor Sedimentary > Carbonate > Limestone (Bed)Weakly metamorphosed limestones. Metamorphic > Metasedimentary > Metaclastic > Quartzite (Greenschist)
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	Ruppel, E.T., O'Neill, J.M., and Lopez, D.A., 1993, Geologic map of the Dillon 1o x 2o quadrangle, Idaho and Montana: U.S. Geological Survey Miscellaneous Investigations Series Map I-1803-H, scale 1:250,000. [http://pubs.er.usgs.gov/publication/i1803H] Tysdal, R.G., Ludington, Steve, and McCafferty, A.E., 1996, Mineral and energy resource assessment of the Helena National Forest, west-central Montana: U.S. Geological Survey Open-File Report 96-683-A, 322 p., 6 plates. [http://pubs.er.usgs.gov/publication/ofr96683A] Knechtel, M.M. and Patterson, S.H., 1956, Bentonite deposits in marine Cretaceous formations, Hardin district, Montana and Wyoming: U.S. Geological Survey Bulletin 1023, 116 p. [http://pubs.er.usgs.gov/publication/b1023] Mudge, M.R., and Earhart, R.L., 1983, Bedrock geologic map of part of the northern disturbed belt, Lewis and Clark, Teton, Pondera, Glacier, Flathead, Cascade and Powell Counties, Montana: U.S. Geological Survey Miscellaneous Geologic Investigations Seri [http://pubs.er.usgs.gov/publication/i1375] 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. McMannis, W.J., 1963, LaHood Formation--A coarse facies of the Belt Series in southwestern Montana: Geological Society of America Bulletin, v. 74, no. 4, p. 407-436. Skipp, Betty, and Peterson, A.D., 1965, Geologic map of the Maudlow quadrangle, southwestern Montana: U.S. Geological Survey Miscellaneous Investigations Series Map I-452, 2 sheets, scale 1:24,000. [http://pubs.er.usgs.gov/publication/i452] Whipple, J.W., 1992, Geologic map of Glacier Park, Montana: U.S. Geological Survey Miscellaneous Investigations Series Map I-1508-F, 1 sheet, scale 1:100,000. [http://pubs.er.usgs.gov/publication/i1508F] Earhart, R.L., Mudge, M.R., and Connor, J.J., 1984, Belt Supergroup lithofacies in the Northern Disturbed Belt, northwest Montana, in McBane, J.D., and Garrison, P.B., eds., Northwest Montana and adjacent Canada--Montana Geological Society 1984 Field Con Keefer, W.R., 1972, Geologic of the west half of the Neihart 15-minute quadrangle, central Montana: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-726, scale 1:62,500. [http://pubs.er.usgs.gov/publication/i726]
Geographic coverage	Broadwater - Jefferson - Lewis and Clark - Meagher