The Cliff House Sandstone is a late

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...

stratigraphic unit comprising

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

s in the western

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

Description

The Cliff House Sandstone consists of fine grained white to orange calcareous

. It intertongues with the underlying

Menefee Formation The Menefee Formation is a lower Campanian geologic formation found in Colorado and New Mexico, United States. Description The Menefee Formation consists of fluvial sandstone, shale, and coal. Based on ammonite biostratigraphy, the age of the Me ...

and the overlying

Lewis Shale The Lewis Shale is a geologic formation in the Western United States. It preserves fossils dating back to the Campanian to Maastrichtian stages of the late Cretaceous period. Description The Lewis Shale is an olive-gray marine shale with som ...

. Where the Lewis Shale pinches out in the southwest

San Juan Basin The San Juan Basin is a geologic structural basin located near the Four Corners region of the Southwestern United States. The basin covers 7,500 square miles and resides in northwestern New Mexico, southwestern Colorado, and parts of Utah a ...

, the formation is indistinguishable from the

Pictured Cliffs Formation The Pictured Cliffs Formation is a Campanian geologic formation in the San Juan Basin of New Mexico. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus. Des ...

and the name "Pictured Cliffs" is applied to the entire sequence of massive sandstone. The formation is exposed at

Mesa Verde National Park Mesa Verde National Park is an American national park and UNESCO World Heritage Site located in Montezuma County, Colorado. The park protects some of the best-preserved Ancestral Puebloan archaeological sites in the United States. Established ...

, where it forms the prominent cliffs around Cliff House, for which it is named. It is also prominent at

Chaco Canyon Chaco Culture National Historical Park is a United States National Historical Park in the American Southwest hosting a concentration of pueblos. The park is located in northwestern New Mexico, between Albuquerque and Farmington, in a remote ca ...

. At Chaco Canyon, the formation can be divided into three informal members. These are a lower massive marine sandstone deposited in a high-energy environment; a middle unit deposited in deeper water that contains some

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

beds; and an upper sandstone deposited in a beach and bar environment. The formation is part of the

Mesaverde Group The Mesaverde Group is a Late Cretaceous stratigraphic group found in areas of Colorado, New Mexico, Utah, and Wyoming, in the Western United States. History The Mesaverde Formation was first described by W.H.Holmes in 1877 during the Hayden ...

of the

, which records a regression-transgression sequence of the

Western Interior Seaway The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, and the Western Interior Sea) was a large inland sea that split the continent of North America into two landmasses. The ancient sea, ...

. The Cliff House Sandstone was deposited during the return of the sea as near-shore sand.

History of investigation

The Cliff House Sandstone was first described by W.H.Holmes in 1877 during the

Hayden Survey Ferdinand Vandeveer Hayden (September 7, 1829 – December 22, 1887) was an American geologist noted for his pioneering surveying expeditions of the Rocky Mountains in the late 19th century. He was also a physician who served with the Union Ar ...

as the "Upper Escarpment" of the

Mesaverde Formation The Mesaverde Group is a Late Cretaceous stratigraphic group found in areas of Colorado, New Mexico, Utah, and Wyoming, in the Western United States. History The Mesaverde Formation was first described by W.H.Holmes in 1877 during the Hayden ...

. A.J. Collier redesignated this unit in 1919 as the Cliff House Sandstone and raised the Mesaverde Formation to group rank.

Stratigraphy

Fossil content

Outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial ...

s of the formation in

have produced fossil

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...

teeth, along with the jaws, teeth and fins of ''

Enchodus ''Enchodus'' (from el, ἔγχος , 'spear' and el, ὀδούς 'tooth') is an extinct genus of aulopiform ray-finned fish related to lancetfish and lizardfish. Species of ''Enchodus'' flourished during the Late Cretaceous, and survived the ...

'' and Chimaeroid (

cartilaginous fish Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue ...

) egg cases. The latter have not yet been connected to a particular species of fish. At Chaco Canyon, the lower beds produce shells and casts from clams, ammonites (including possible ''Placenticeras''), snails, and shark's teeth. Trace fossils classified as ''

Ophiomorpha ''Ophiomorpha'' is an ichnotaxon, usually interpreted as a burrow of an organism (specifically a crustacean) living in the near-shore environment. The burrow lining is more or less smooth on the inside, and densely to strongly mammalated or nod ...

nodosa'' are common and are thought to have been produced by ''Callianasa'' shrimp. The middle unit hyas fewer trace fossils but more ''

Inoceramus ''Inoceramus'' (Greek: translation "strong pot") is an extinct genus of fossil marine pteriomorphian bivalves that superficially resembled the related winged pearly oysters of the extant genus '' Pteria''. They lived from the Early Jurassic ...

'', while the upper beds are rich in invertebrate shells, shark teeth, and bone debris from marine lizards.

References

Bibliography

* * * * * * * {{Chronostratigraphy of Colorado, Mesozoic state=expanded Cretaceous formations of New Mexico Geologic formations of Colorado Upper Cretaceous Series of North America Campanian Stage Sandstone formations of the United States Fossiliferous stratigraphic units of North America Paleontology in Colorado Mesa Verde National Park