Phosphoria through Lodgepole Formation: Phosphoria, Quadrant, Amsden, Heath, Otter, Kibbey, Mission Canyon, and Lodgepole Formations

Phosphoria Formation (Pp): Gray and tan dolomite, cherty limestone, bedded chert, siltstone, sandstone, and gray to black phosphatic and dolomitic shale. Marine shelf and offshore marine. Thickness as much as 255 m (837 ft). Quadrant Formation (PAq): Very light gray, yellowish or pinkish, well-sorted sandstone or quartzite, locally interbedded with subordinate limestone beds. Marine. Generally, thickness as much as 140 m (460 ft), but as much as 800 m(2,625 ft) in southwestern-most Montana. Amsden Formation (PAMa): Red shale, light gray limestone, and cherty and sandy limestone. Coastal plain or marine. Thickness as much as 180 m (590 ft). Heath Formation (Mh): Black, fissile, commonly petroliferous shale with subordinate sandstone, gypsum, and coal. Restricted marine to coastal plain. Thickness as much as 150 m (492 ft). Otter Formation (Mo): Green, grayish green, gray, and subordinate reddish brown shale interbedded with light brown or gray limestone. Open and semirestricted marine. Thickness as much as 150 m (492 ft). Kibbey Formation (Mk): Red, quartzose sandstone, siltstone, and shale, locally with subordinate thin gypsum beds and limestone bed in middle part. Intertidal and subtidal. Thickness as much as 105 m (345 ft). Mission Canyon Formation (Mmc): Gray, massive limestone with chert beds and nodules, and solution breccia zones. Shallow marine. Thickness as much as 520 m (1,706 ft). Lodgepole Formation (Ml): Woodhurst Member (upper part of formation): light gray, well-bedded limestone, typically with much dark chert, interbedded with thinner calcareous mudstone beds. Paine Member (middle part of formation):dark gray, thin-bedded, silty or fossiliferous limestone. Cottonwood Canyon Member (lower part of formation): black shale with basal conglomeratic lag deposit. Shallow marine. Thickness as much as 305 m (1000 ft).
State Montana
Name Phosphoria through Lodgepole Formation: Phosphoria, Quadrant, Amsden, Heath, Otter, Kibbey, Mission Canyon, and Lodgepole Formations
Geologic age Permian through Mississippian
Lithologic constituents
Major
Sedimentary > Clastic > Sandstone (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed)
Sedimentary > Carbonate > Limestone (Bed)
Minor
Sedimentary > Clastic > Mudstone > Shale > Black-shale (Bed)
Sedimentary > Clastic > Mudstone (Bed, Calcareous)
Sedimentary > Carbonate > Dolostone (Bed)
Sedimentary > Clastic > Siltstone (Bed)
Sedimentary > Clastic > Conglomerate (Bed)
Sedimentary > Clastic > Mudstone > Shale > Phosphatic-shale (Bed)
Incidental
Sedimentary > Coal (Bed)
Sedimentary > Chemical > Evaporite > Gypsum (Bed)
Sedimentary > Chemical > Chert (Bed)
References

Vuke, S.M., Porter, K.W., Lonn, J.D., and Lopez, D.A., 2007, Geologic Map of Montana - Compact Disc: Montana Bureau of Mines and Geology: Geologic Map 62-C, 73 p., 2 sheets, scale 1:500,000. This map was digitized in 2012 as a result of a contract between the U.S. Geological Survey and the Montana Bureau of Mines and Geology.

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Counties Broadwater