Cody Shale

Cody Shale
Stratigraphic range: Late Cretaceous
Type Sedimentary
Sub-units see text
Underlies Mesaverde Formation
Overlies Frontier Formation
Thickness 500-1000 m
Lithology
Primary shale
Location
Region Montana folded belt province, Central Montana uplift, Big Horn basin, Powder River basin, Wind River basin
Country United States
Extent Wyoming, Idaho, Montana
Type section
Named for Cody, Wyoming
Named by C. T. Lupton, 1916[1]

The Cody Shale is a Late Cretaceous geologic formation. It is mapped in Wyoming, Idaho, and Montana.

The formation is described by W.G. Pierce as follows: upper part is buff, sandy shale and thinly laminated buff sandstone; lower part is dark gray, thin-bedded marine shale.[2]

The formation is divided into many members that vary regionally. Alphabetically:[3]

  • Ardmore Bentonite Beds (WY)
  • Belle Fourche Member (MT, WY)
  • Carlile Member (MT, WY)
  • Claggett Member (MT, WY)
  • Eldridge Creek Member (MT)
  • Gammon Ferruginous Member (MT, WY)
  • Greenhorn Calcareous Member (MT)
  • Niobrara Member (MT, WY)
  • Sage Breaks Member (WY)
  • Shannon Sandstone Member (MT, WY)
  • Steele Member (WY)
  • Sussex Sandstone Member (WY)
  • Telegraph Creek Member (MT, WY)
  • Wallace Creek Tongue (WY)

Certain members rise to formation rank in other areas; for example, the Greenhorn is classified as a formation in a number of states, particularly in Colorado and Kansas.

References

  1. ↑ Lupton, C.T., 1916, Oil and gas near Basin, Big Horn County, Wyoming, IN Contributions to economic geology, 1915; Part 2, Mineral fuels: U.S. Geological Survey Bulletin, 621-L, p. L157-L190.
  2. ↑ Pierce, W.G., 1997, Geologic map of the Cody 1 degree x 2 degrees quadrangle, northwestern Wyoming: U.S. Geological Survey, Miscellaneous Geologic Investigations Map I-2500, scale 1:250000.
  3. ↑ "Geologic Unit: Cody". National Geologic Database. Geolex — Unit Summary. United States Geological Survey. Retrieved 2018-06-29.


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