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Morrison Formation, Unkpapa Sandstone, Sundance Formation, and Gypsum Spring Formation

Morrison Formation (Late Jurassic)- Light-gray to green and variegatedred, brown, yellow, or lavender, silceous claystone, shale, and siltstone containing interbedded sandstone and fresh-water limestone lenses. Thickness up to 150 ft (46 m). Unkpapa Sandstone (Late Jurassic)- White, massive to thin-bedded, fine-grained, argillaceous sandstone. May be variegated to banded red, yellow, brown, or lavender. Thickness up to 267 ft (81 m). Sundance Formation (Late to Middle Jurassic)- Greenish-gray, yellow, tan, red to orange, and white, variegated, interbedded, fine- to coarse-grained sandstone, siltstone, clay, and limestone. Thickness 250-350 ft (76-107 m). Gypsum Springs Formation (Middle Jusassic)- Massive white gypsum and minor maroon siltstone and shale. Thickness up to 40 ft (12 m).
State South Dakota
Name Morrison Formation, Unkpapa Sandstone, Sundance Formation, and Gypsum Spring Formation
Geologic age Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late
Primary rock type sandstone
Secondary rock type siltstone
Other rock types claystone; clay or mud; shale; limestone; evaporite
Lithologic constituents
Major
Sedimentary > Clastic > Sandstone (Bed)
Sedimentary > Clastic > Siltstone (Bed)
Sedimentary > Clastic > Mudstone > Claystone (Bed)
Sedimentary > Clastic > Mudstone > Claystone (Bed)
Sedimentary > Clastic > Mudstone > Shale (Bed)
Minor
Sedimentary > Carbonate > Limestone (Bed)
Sedimentary > Chemical > Evaporite > Gypsum (Bed)
Map references
Martin, J. E., Sawyer, J. F., Fahrenbach, M. D., Tomhave, D. W., and Schulz, L. D., 2004, Geologic Map of South Dakota: South Dakota Geological Survey
Unit references
Martin, J. E., Sawyer, J. F., Fahrenbach, M. D., Tomhave, D. W., and Schulz, L. D., 2004, Geologic Map of South Dakota: South Dakota Geological Survey
Counties Butte - Custer - Fall River - Lawrence - Meade - Pennington