Geologic units in Montezuma county, Colorado

Additional scientific data in this geographic area

Dakota Sandstone and Burro Canyon Fm (Cretaceous) at surface, covers 30 % of this area

Sandstone, shale, and conglomerate. In northwest and west-central: Lower Cretaceous. In southwest: Lower and Upper Cretaceous.

Mancos Shale (Cretaceous) at surface, covers 21 % of this area

In northwest and west-central: Intertongues complexly with units of overlying Mesaverde Group or Fm; lower part consists of a calcareous Niobrara equivalent and Frontier Sandstone and Mowry Shale Members; in areas where the Frontier and Mowry Members (Kmfm), or these and the Dakota Sandstone (Kfd) are distinguished, map unit (Km) consists of shale above Frontier Member. In Southwest: Lower part contains Juana Lopez Member (Kmj)

Menefee Fm and Point Lookout Sandstone (Cretaceous) at surface, covers 10 % of this area

Sandstone, shale, and coal; sandstone

Cliff House Sandstone (Cretaceous) at surface, covers 9 % of this area

Cliff House Sandstone

Morrison Fm, Summerville Fm, and Entrada Sandstone (Jurassic) at surface, covers 8 % of this area

Summerville Fm: Shale and siltstone

Eolian deposits (Quaternary) at surface, covers 7 % of this area

Includes dune sand and silt and Peoria Loess

Morrison, Wanakah, and Entrada Fms (Jurassic) at surface, covers 5 % of this area

Morrison, Wanakah, and Entrada Fms

Dolores Fm (Triassic) at surface, covers 2 % of this area

Red siltstone, shale, sandstone, and limestone-pellet conglomerate

Mancos Shale--Juana Lopez Member (Cretaceous) at surface, covers 2 % of this area

Calcareous sandstone; a thin but persistent unit distinguished only locally

Modern alluvium (Quaternary) at surface, covers 2 % of this area

Includes Piney Creek Alluvium and younger deposits

Laramide intrusive rocks (Tertiary-Cretaceous) at surface, covers 1 % of this area

Mainly intermediate to felsic compositions; some mafic

Morrison Fm (Jurassic) at surface, covers 1 % of this area

Variegated claystone, mudstone, sandstone, and local beds of limestone

Cutler Fm (Permian) at surface, covers 1 % of this area

Arkosic sandstone, siltstone, and conglomerate

Gravels and alluviums (Quaternary) at surface, covers 0.5 % of this area

Includes Broadway and Louviers Alluviums

Older gravels and alluviums (Quaternary) at surface, covers 0.3 % of this area

Includes Slocum, Verdos, Rocky Flats, and Nussbaum Alluviums in east, and Florida, Bridgetimber, and Bayfield Gravels in southwest

Glen Canyon Group and Chinle Fm (Jurassic-Triassic) at surface, covers 0.2 % of this area

In southwest, Glen Canyon Group consists of Navajo Sandstone, Kayenta Fm (red siltstone, shale, and sandstone) and Wingate Sandstone; Chinle is red siltstone

Landslide deposits (Quaternary) at surface, covers 0.2 % of this area

Locally includes talus, rock-glacier, and thick colluvial deposits

Cliff House Sandstone (Campanian) at surface, covers < 0.1 % of this area

Transgressive marine sandstone.

Middle Tertiary intrusive rocks (Tertiary) at surface, covers < 0.1 % of this area

Intermediate to felsic compositions

Menefee Formation (Campanian to Santonian) at surface, covers < 0.1 % of this area

Mudstone, shale, and sandstone; coal-bearing.

Mancos Shale (Cenomanian to Campanian) at surface, covers < 0.1 % of this area

Divided into Upper and Lower parts by Gallup Sandstone.

Point Lookout Sandstone (Campanian to Santonian) at surface, covers < 0.1 % of this area

Regressive marine sandstone in McKinley and Sandoval Counties; the lower, Hosta Tongue, of Point Lookout is transgressive and is separated from main body by the Satan Tongue of Mancos Shale.

Alluvium (Holocene to upper Pleistocene) at surface, covers < 0.1 % of this area

Alluvium

Mancos Shale, lower part (Turonian and Cenomanian) at surface, covers < 0.1 % of this area

Mancos Shale, lower part

Morrison Formation (Brushy Basin and Salt Wash Members) (Late Jurassic) at surface, covers < 0.1 % of this area

Morrison Formation (Brushy Basin and Salt Wash Members).

Dakota Sandstone (Cenomanian) at surface, covers < 0.1 % of this area

Includes Oak Canyon, Cubero, and Paguate Tongues; includes Clay Mesa Tongue of Mancos Shale.

Morrison Formation (Upper Jurassic) at surface, covers < 0.1 % of this area

Upper Jurassic nonmarine rocks.

Dakota Ss and Cedar Mtn. or Burro Canyon Formations (Cretaceous) at surface, covers < 0.1 % of this area

Dakota Ss and Cedar Mtn or Burro Canyon Formations.

Alluvium and colluvium (Quaternary) at surface, covers < 0.1 % of this area

Alluvium and colluvium

Glen Canyon Group (Early Jurassic) at surface, covers < 0.1 % of this area

Glen Canyon Group (Navajo Ss, Kayenta Fm, and Wingate Ss). Includes Rainbow Bridge.