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Mancos Shale
Stratigraphic range: Mid Albian-Campanian
Mancos Shale badlands in Capitol Reef NP.jpg
Mancos Shale badlands in Capitol Reef National Park, southern Utah.
Type Geologic formation
Sub-units See text
Underlies Mesaverde Formation
Overlies Dakota Group
Primary Shale
Coordinates 37°21′09″N 108°17′49″W / 37.3525426°N 108.2969254°W / 37.3525426; -108.2969254
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 Mowry shale oil gas fields
Mancos Shale and Mowry Shale oil and gas fields within the Uinta Basin and Piceance Basin
Uinta Piceance Basin stratigraphic column
Stratigraphic column showing the relationship of the Mancos and Mowry shales

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.


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 Group and the Mesaverde Formation Group.

The Mancos Shale rests conformably on the 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.

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.


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:

  • Orogrande Basin
  • Paradox Basin
  • Piceance Basin


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).
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