Cody Shale

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Cody Shale
Stratigraphic range: Late Cretaceous
TypeSedimentary
Sub-unitssee text
UnderliesMesaverde Formation
OverliesFrontier Formation
Thickness500-1000 m
Lithology
Primaryshale
Location
RegionMontana folded belt province, Central Montana uplift, , Powder River basin, Wind River basin
CountryUnited States
ExtentWyoming, Idaho, Montana
Type section
Named forCody, Wyoming
Named byC. 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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