Siltite, argillite, dolostone, and quartzite; Middle Proterozoic Wallace Formation; northern Belt province (IDY3n;0)

State	Idaho
Name	Siltite, argillite, dolostone, and quartzite; Middle Proterozoic Wallace Formation; northern Belt province
Geologic age	Early Middle Proterozoic
Original map label	Y3n; Y?n
Comments	Lower Wallace correlates with Empire Fm, middle Wallace with Helena Fm, lower part of upper Wallace with Snowslip Fm, and upper part of upper Wallace with Shepard Fm in Montana (ID078). ID079 lists sedimetary types as (ascending): carbonate mud and mudcracked silt-mud couplets (100m), hummocky silt (250 m), pinch and swell couples, couplets (450 m), microlaminae (400 m), mudcracked couplets (400 m), carbonate mud (250 m), microlaminae (150m). Pinch and swell couples, couplets, and microlaminae are graded beds with very fine sand to dark clay-sized terriginous, dolomitic, or carbonaceous sediments. Carbonates occur as dolomitic mud, oolite, and stromatolitic beds with molar-tooth structure, formed by gas generation, accumulation, and escape.
Primary rock type	siltstone
Secondary rock type	meta-argillite
Other rock types	dolostone (dolomite); quartzite
Lithologic constituents	Major Metamorphic > Argillite (Bed)black, carbonaceous argillite Sedimentary > Clastic > Siltstone (Bed)siliciclastic, dolomitic, or carbonaceous Minor Sedimentary > Carbonate > Dolostone (Bed)micritic, oolitic, or stromatolitic Metamorphic > Quartzite (Bed)siliciclastic, dolomitic, or carbonaceous
Map references	Bond, J.G., Kauffman, J.D., Miller, D.A., and Venkatakrishnan, Ramesh, 1978, Geologic map of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, with contributions from U.S. Geological Survey, scale 1:500,000.
Unit references	Bond, J.G., Kauffman, J.D., Miller, D.A., and Venkatakrishnan, Ramesh, 1978, Geologic map of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, with contributions from U.S. Geological Survey, scale 1:500,000. Anderson, H.E. and Parrish, R.R., 2000, U-Pb geochronological evidence for the geological history of the Belt-Purcell Supergroup, southeastern British Columbia; Chapter 7: in Lydon, J.W., Hoy, T., Slack, J.F., and Knapp, M.E., eds., The Geological Environment of the Sullivan Deposit, British Columbia: Geological Association of Canada, Mineral Deposits Division, Special Publication No 1., p. 113-126. Miller, F.K., Burmester, R.F., Miller, D.M., Powell, R.E., and Derkey, P.D., 1999, Digital geologic map of the Sandpoint 1o x 2o quadrangle, Washington, Idaho, and Montana: U.S. Geological Survey Open-File Report OF 99-144, scale 1:250,000 with report, 71 p. [http://pubs.er.usgs.gov/publication/ofr99144] Harrison, J.E., Griggs, A.B., and Wells, J.D., 1986, Geologic and structure maps of the Wallace 1o x 2o quadrangle, Montana and Idaho: U.S. Geological Survey Map I-1509-A, scale 1:250,000. [http://pubs.er.usgs.gov/publication/i1509A] Griggs, A.B., 1973, Geologic map of the Spokane quadrangle, Washington, Idaho, and Montana: U.S. Geological Survey Map I-768, scale 1:250,000. [http://pubs.er.usgs.gov/publication/i768] Winston, D. and Link, P.K., 1993, Middle Proterozoic rocks of Montana, Idaho and eastern Washington: The Belt Supergroup: in Link, P.K., ed., Middle and Late Proterozoic stratified rocks of the western U.S. Cordillera, Colorado Plateau, and Basin and Range province: in Reed, J.C., Jr., Bickford, M.E., Houston, R.S., Link, P.K., Rankin, D.W., Sims, P.K., and Van Schmus, W.R., eds., Precambrian: Conterminous U.S.: Boulder, Colorado, Geological Society of America, The Geology of North America, v. C-2, p. 467-517.
Geographic coverage	Benewah - Bonner - Boundary - Kootenai - Latah - Shoshone