The Carlile Shale is a

Turonian The Turonian is, in the International Commission on Stratigraphy, ICS' geologic timescale, the second age (geology), age in the Late Cretaceous epoch (geology), Epoch, or a stage (stratigraphy), stage in the Upper Cretaceous series (stratigraphy), ...

age Upper/Late Cretaceous series

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 ...

geologic formation in the central-western United States, including 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 ...

region of

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 ...

Kansas Kansas ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the west. Kansas is named a ...

Nebraska Nebraska ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Ka ...

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 ...

North Dakota North Dakota ( ) is a U.S. state in the Upper Midwest, named after the indigenous Dakota people, Dakota and Sioux peoples. It is bordered by the Canadian provinces of Saskatchewan and Manitoba to the north and by the U.S. states of Minneso ...

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 ...

, and

Wyoming Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...

History of investigation

The Carlile Shale was first named by

Grove Karl Gilbert Grove Karl Gilbert (May 6, 1843 – May 1, 1918), known by the abbreviated name G. K. Gilbert in academic literature, was an American geologist. Biography Gilbert was born in Rochester, New York, and graduated from the University of Rochester. ...

for exposures at Carlile Spring, located about west of

Pueblo, Colorado Pueblo ( ) is a List of municipalities in Colorado#Home rule municipality, home rule municipality that is the county seat of and the List of municipalities in Colorado, most populous municipality in Pueblo County, Colorado, United States. The ...

. He described it as a medium gray shale, capped with limestone or sandstone, and assigned it to the Benton Group. By 1931, William Walden Rubey and his coinvestigators had mapped it into

and the

Black Hills The Black Hills is an isolated mountain range rising from the Great Plains of North America in western South Dakota and extending into Wyoming, United States. Black Elk Peak, which rises to , is the range's highest summit. The name of the range ...

. Rubey also first assigned it to the Colorado Group. C.H. Dane assigned it to the Mancos Shale in

in 1948.

Description

The formation is composed of marine deposits of the generally retreating phase (hemi-cycle) of the Greenhorn cycle of 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 ...

, which followed the advancing phase of the same cycle that formed the underlying

Graneros Shale The Graneros Shale is a geologic formation in the United States identified in the Great Plains as well as New Mexico that dates to the Cenomanian Age of the Cretaceous Period. It is defined as the finely sandy argillaceous or clayey ''near-shor ...

and Greenhorn Formation. As such, the lithology progresses from open ocean chalky shale (with thin limestones) to increasing carbonaceous shale to near-shore sandstone. Near the center of the seaway, currents in the remnant shallows sorted skeletal remains into a mass of calcareous sand. The contact between the Carlile Shale and the overlying

Niobrara Formation The Niobrara Formation , also called the Niobrara Chalk, is a geologic formation in North America that was deposited between 87 and 82 million years ago during the Coniacian, Santonian, and Campanian stages of the Late Cretaceous. It is com ...

is marked by an

unconformity An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval ...

in much of the outcrop area, but where an unconformity is not discernible, the boundary is typically placed at the first resistant, fine-grained limestone bed at the base of the Niobrara Formation.

Gallery

Fossil content

Upper Turonian series

plesiosaur The Plesiosauria or plesiosaurs are an Order (biology), order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared in the latest Triassic Period (geology), Period, possibly in the Rhaetian st ...

remains are among the

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s that have been recovered from the strata of its Blue Hill Shale Member in Kansas.Jstor.org: "Probable plesiosaur remains from the Blue Hill Shale (Carlile Formation)" in Kansas"
Kansas Academy of Science, 2009. The Carlile in eastern South Dakota contains shark teeth, fossil wood and leaves, and ammonites.
William A. Cobban and E.A. Merewether (1983), Stratigraphy and paleontology of mid-Cretaceous rocks in Minnesota and contiguous areas. USGS Professional Paper 1253.

Reptiles

Crocodyliforms

Plesiosaurs

Squamates

Fish

Cartilaginous fish

References

{{Chronostratigraphy of Colorado, Mesozoic state=expanded Shale formations of the United States Turonian Stage Cretaceous Colorado Cretaceous Kansas Cretaceous Nebraska Cretaceous formations of New Mexico Cretaceous geology of North Dakota Cretaceous geology of South Dakota Cretaceous geology of Wyoming Upper Cretaceous Series of North America Geologic formations of Colorado Geologic formations of Kansas Geologic formations of Nebraska Geologic formations of North Dakota Geologic formations of South Dakota Geologic formations of Wyoming Limestone formations of the United States Sandstone formations of the United States Siltstone formations of the United States