The Pierre Shale is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

or series in the

Upper Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cret ...

which occurs east of the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in great-circle distance, straight-line distance from the northernmost part of Western Can ...

in the

Great Plains The Great Plains is a broad expanse of plain, flatland in North America. The region stretches east of the Rocky Mountains, much of it covered in prairie, steppe, and grassland. They are the western part of the Interior Plains, which include th ...

, from Pembina Valley in

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

. The Pierre Shale was described by

Meek Meekness is an attribute of human nature and behavior that has been defined as an amalgam of righteousness, inner humility, and patience. Meekness has been contrasted with humility alone insomuch as humility simply refers to an attitude towards o ...

and

Hayden Hayden may refer to: Places Inhabited places in the United States * Hayden, Alabama *Hayden, Arizona *Hayden's Ferry, former name of Tempe, Arizona *Hayden, California, former name of Hayden Hill, California *Hayden, Colorado *Hayden, Idaho *Hayde ...

in 1862 in the Proceedings of the Academy of Sciences (Philadelphia). They described it as a dark-gray

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

, fossiliferous, with veins and seams of

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate Hydrate, dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk ...

, and

concretions A concretion is a hard and compact mass formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular shapes a ...

iron oxide An iron oxide is a chemical compound composed of iron and oxygen. Several iron oxides are recognized. Often they are non-stoichiometric. Ferric oxyhydroxides are a related class of compounds, perhaps the best known of which is rust. Iron ...

. The Pierre Shale is about 3,138 feet (956m) thick at the type locality. It overlies the Niobrara division and underlies the Fox Hills beds. It was named for an occurrence near Fort Pierre on the

Missouri River The Missouri River is a river in the Central United States, Central and Mountain states, Mountain West regions of the United States. The nation's longest, it rises in the eastern Centennial Mountains of the Bitterroot Range of the Rocky Moun ...

South Dakota South Dakota (; Sioux language, Sioux: , ) is a U.S. state, state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Dakota people, Dakota Sioux ...

. The Pierre Shale is of marine origin and was deposited in the

Western Interior Seaway The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, or the Western Interior Sea) was a large inland sea (geology), inland sea that existed roughly over the present-day Great Plains of ...

. It is correlative with other marine shales that occur farther west, such as the Bearpaw Shale,

Mancos Shale 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, C ...

and the

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 some t ...

. It correlates with the Lea Park Formation in

central Alberta Central Alberta is a region located in the Canadian province of Alberta. Central Alberta is the most densely populated rural area in the province. Agriculture and energy are important to the area's economy. Geography Central Alberta is bordered ...

. The Pierre is overlain by marginal marine deposits of the

Fox Hills Formation The Fox Hills Formation is a Cretaceous geologic formation in the northwestern Great Plains of North America. It is present from Alberta on the north to Colorado in the south. Fossil remains of dinosaurs, including tyrannosaurs, as well as lar ...

. Most of the formation was deposited in the

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. Campa ...

Age Age or AGE may refer to: Time and its effects * Age, the amount of time someone has been alive or something has existed ** East Asian age reckoning, an Asian system of marking age starting at 1 * Ageing or aging, the process of becoming older ...

of the

late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

. However, the discovery of fossils of ''

Baculites baculus ''Baculites'' is an extinct genus of heteromorph Ammonitida, ammonite cephalopods with almost straight shells. The genus, which lived worldwide throughout most of the Late Cretaceous, and which briefly Paleocene ammonites, survived the Cretaceous ...

'' in the uppermost beds of the Pierre Shale in the

Raton, New Mexico Raton ( ) is a city in and the county seat of Colfax County, New Mexico, Colfax County in northeastern New Mexico, United States. The city is located just south of Raton Pass. The city is also located about 6.5 miles south of the New Mexico–Col ...

area show that deposition continued here into the early

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

Mineral resources

The Pierre Shale is the host formation for commercial

petroleum Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring un ...

deposits in the Florence and Canon City fields in

Fremont County, Colorado Fremont County is a county located in the U.S. state of Colorado. As of the 2020 United States census, 2020 census, the population was 48,939. The county seat is Cañon City, Colorado, Cañon City. The county is named for 19th-century explorer ...

, and the

Boulder Oil Field The Boulder Oil Field was an oil field, in the area of Boulder, Colorado. Some history Ute Indians were the first to discover oil, in Colorado. The McKenzie Well still stands, near Boulder, and Isaac Canfield found it in 1901, by dowsing, ...

Boulder County, Colorado Boulder County is a county located in the U.S. state of Colorado of the United States. As of the 2020 census, the population was 330,758. The most populous municipality in the county and the county seat is Boulder. Boulder County comprises th ...

. More recently, natural gas has been extracted in the

Raton Basin The Raton Basin is a geologic structural basin in southern Colorado and northern New Mexico. It takes its name from Raton Pass and the town of Raton, New Mexico. In extent, the basin is approximately east-west, and north-south, in Huerfano an ...

in southern

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

. The shale formation is usually too impermeable for hydrocarbon extraction, but produces in areas where it is naturally fractured or fractured by artificial means.

Paleofauna

Reptiles

Dinosaurs

Mosasaurs

Plesiosaurs

Pterosaurs

Turtles

Fish

Bony fish

Cartilaginous fish

Marine vertebrates

* '' Gillicus'' * ''

Pseudocorax ''Pseudocorax'' is an extinct genus of mackerel sharks that lived during the Late Cretaceous. It contains six valid species that have been found in Europe, the Middle East, North Africa, and North America. It was formerly assigned to the family ...

'' * ''

Carcharias ''Carcharias'', also known as sand tiger sharks, is a genus of mackerel sharks belonging to the family Carchariidae, of which it is the only extant member. Once bearing many prehistoric species, all have gone extinct with the exception of the cri ...

Invertebrates

Annelids

Arthropods

Bivalves

Brachiopods

Cephalopods

Echinoderms

Gastropods

Scaphopods

References

{{Authority control Upper Cretaceous Series of North America Cretaceous Alberta Cretaceous Colorado Cretaceous Kansas Cretaceous Montana Cretaceous geology of Nebraska Cretaceous formations of New Mexico Cretaceous geology of South Dakota Cretaceous geology of Wyoming Campanian Stage Oil-bearing shales in Canada Oil-bearing shales in the United States Great Plains