Mancos Shale


The Mancos Shale or Mancos Group is a Late 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 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 correspondences with the Colorado Group classification of the Great Plains region; as such, various units of the Colorado Group are recognized within the Mancos.

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:

Subunits

The Mancos occurs with the following subunit names :