Mancos Shale

Mancos Shale
Stratigraphic range: Mid Albian-Campanian ~
Mancos Shale at its type location just north of Mancos, Colorado
Type	Geologic formation
Sub-units	See text
Underlies	Mesaverde Formation
Overlies	Dakota Group
Lithology
Primary	Shale
Location
Coordinates	37.353°N 108.297°W / 37.353; -108.297
Region	Arizona, Colorado, New Mexico, Utah, Wyoming
Country	United States
Extent	Basin and Range, Colorado Plateau & San Juan Mountains Provinces
Type section
Named for	Mancos, Colorado
Mancos Shale (the United States) Mancos Shale (Colorado)

Mancos Shale badlands in Capitol Reef National Park, southern Utah.

Mancos Shale and Mowry Shale oil and gas fields within the Uinta Basin and Piceance Basin

Stratigraphic column showing the relationship of the Mancos and Mowry shales

Tununk Member of the Mancos Shale below the capping Ferron Sandstone Member. West side of the San Rafael Swell, Emery County, Utah.

The Mancos Shale or Mancos Group is a Late Cretaceous (Upper Cretaceous) geologic formation of the Western United States.

The Mancos Shale was first described by Cross and Purington in 1899 and was named for exposures near the town of Mancos, Colorado.

Geology

It is dominated by mudrock that accumulated in offshore and marine environments of the Cretaceous North American Inland Sea. The Mancos was deposited during the Cenomanian (locally Albian) through Campanian ages, approximately from 95 Ma to 80 Ma.

Stratigraphically the Mancos Shale fills the interval between the Dakota and the Mesaverde Group.

The lower marine Mancos Shale conformably intertongues with terrestrial sandstones and mudstones classified as Dakota and in its upper part grades into and intertongues with the Mesaverde Group. The shale tongues typically have sharp basal contacts and gradational upper contacts. Whereas in the plains east of the Rocky Mountains certain mappable marine shales are identified as formations (e.g., Skull Creek, Graneros), correlated deposits within the distribution of the Mancos are named as tongues of the greater Mancos Formation.

Thus, the classification broadly corresponds with the Colorado Group classification of the Great Plains region; as such, various units of the Colorado Group are recognized within the Mancos in those areas where their distinct facies can be recognized.

Occurrences

The Mancos occurs in the Basin and Range Province, the Colorado Plateau Province, and the San Juan Mountains Province.

Structural basins

It also occurs in the following structural basins:

Black Mesa Basin Estancia Basin Green River Basin

Orogrande Basin Paradox Basin Piceance Basin

San Juan Basin Uintah Basin

Subunits

The Mancos occurs with the following subunit names (listed alphabetically): (bold: principle reference section at the type location)

Anchor Mine Tongue (CO, UT), Aspen Member (UT, WY), Black Butte Tongue (WY), Blue Gate Member (UT), Fairport Member (CO) Blue Hill Member (CO, NM), Buck Tongue (CO, UT), Bull Point Sandstone Member (UT), Carlile Member (NM), Clay Mesa Tongue (NM), Cortez Member (CO) Cooper Arroyo Sandstone Member (NM), D-Cross Tongue (NM), Devils Grave Sandstone [Member] (CO), El Vado Sandstone Member (NM), Emery Sandstone Member (UT), Fairport Member (CO)

Ferron Sandstone Member (CO, UT), Fort Hays Limestone Member (CO), Frontier Formation (CO, UT), Garley Canyon Sandstone Member (UT), Graneros Member (CO, NM), Greenhorn Member (NM), Hartland Shale Beds (NM), Hopi Sandy Member (AZ), Horsehead Tongue (NM), Hunt Creek Sandstone [Member] (CO), Juana Lopez Member (CO, NM), Loyd Sandstone Member (CO), Masuk Member (UT) or Masuk Tongue (UT), Meeker Sandstone Member (CO), Montezuma Valley Member [Carlile] (CO) Morapos Sandstone Member (CO),

Mowry Member (UT) or Mowry Shale (CO, UT), Mulatto Tongue (NM), Muley Canyon Sandstone Member (UT), Niobrara Member (CO, NM), Pescado Tongue (AZ, NM), Rangely Tongue (CO, UT), Rio Salado Tongue (NM), Sanastee Sandstone Member (NM), Satan Tongue (NM), Semilla Sandstone Member (NM), Smoky Hill Member (CO) Tocito Sandstone Lentil (CO, NM), Tununk Member (UT), Whitewater Arroyo Tongue (NM), Wildcat Canyon Sandstone Member (UT), Wind Rock Tongue (AZ).

See also

• List of fossiliferous stratigraphic units in Arizona
• List of fossiliferous stratigraphic units in Colorado
• List of fossiliferous stratigraphic units in New Mexico
• List of fossiliferous stratigraphic units in Utah
• List of fossiliferous stratigraphic units in Wyoming