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Spearfish Formation

SPEARFISH FORMATION--Red shale, red siltstone, and white gypsum beds; gypsum beds especially abundant near base.
State Wyoming
Name Spearfish Formation
Geologic age Phanerozoic | Paleozoic Mesozoic | Permian Triassic-Early(?) Triassic-Middle(?) Triassic-Late
Primary rock type mudstone
Secondary rock type evaporite
Other rock types
Lithologic constituents
Major
Sedimentary > Clastic > Mudstone > Shale
Sedimentary > Clastic > Siltstone
Minor
Sedimentary > Chemical > Evaporite > Gypsum
Map references
Love, J.D. and Christiansen, Ann Coe, 1985, Geologic Map of Wyoming: U.S. Geological Survey.
Unit references
Love, J.D. and Christiansen, Ann Coe, 1985, Geologic Map of Wyoming: U.S. Geological Survey.
Counties Crook - Weston