Cody Shale

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.

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


 * 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.