Benton Shale

The Benton Shale (also Benton Formation or Benton Group) is a geologic formation in Montana, Wyoming, North Dakota, South Dakota, Colorado, Kansas, and Nebraska.[1] It preserves fossils dating to the Cretaceous Period. The term Benton Limestone has also been used to refer to the chalky portions of the strata, especially the upper beds of the strata presently classified as Greenhorn Limestone. The Benton classification is obsolete in some regions, having been replaced by the ascending sequence Graneros Shale, Greenhorn Limestone, and Carlile Shale.[2][3]

Benton Shale Stratigraphic range: Cretaceous
Gray shale (Benton Shale; Colorado Springs, Colorado)
Type	Formation
Underlies	Niobrara Formation
Overlies	Dakota Sandstone
Lithology
Primary	Shale
Other	Limestone, sandstone, bentonite
Location
Region	Montana, Wyoming, North Dakota, South Dakota, Colorado, Nebraska
Country	United States
Type section
Named for	Fort Benton, Montana

The classification derives its name from Fort Benton, a small city in Montana on the Upper Missouri River.

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  Concretionary cone-in-cone structures in Benton Shale
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  Gray shale (Benton Shale)
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  Gray shale and bentonites (Benton Shale)