The Gypsum Spring Formation is a stratigraphical unit of

Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 161.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relativel ...

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 ...

in the

Williston Basin The Williston Basin is a large intracratonic sedimentary basin in eastern Montana, western North Dakota, South Dakota, southern Saskatchewan, and south-western Manitoba that is known for its rich deposits of petroleum and potash. The basin is a ...

. It takes the name from Gypsum Spring in

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 ...

, and was first described in outcrop in Freemont County by J.D. Love in 1939.Love, J.D., 1939. Geology along the southern margin of the Absaroka Range. Wyoming.

Geological Society of America The Geological Society of America (GSA) is a nonprofit organization dedicated to the advancement of the geosciences. History The society was founded in Ithaca, New York, in 1888 by Alexander Winchell, John J. Stevenson, Charles H. Hi ...

, Spec. Paper 20, p. 45.

Lithology

The Gypsum Spring Formation is composed of massive white

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 ...

in the lower part, and alternating gypsum, red

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 ...

, dolomite and

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

Distribution

The Gypsum Spring Formation reaches a maximum thickness of in central

. It occurs from 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 ...

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 ...

through

and into southern

Saskatchewan Saskatchewan is a Provinces and territories of Canada, province in Western Canada. It is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and to the south by the ...

Relationship to other units

It is equivalent to the upper part of the Watrous Formation and the lower part of the Gravelbourg Formation in

References

{{Western Canadian Sedimentary Basin, Saskatchewan=yes Geologic formations of Saskatchewan Geologic formations of Montana Geologic formations of Wyoming Bajocian Stage Middle Jurassic Series Geologic formations of South Dakota Jurassic geology of South Dakota Jurassic geology of Wyoming Shale formations of Canada Shale formations of the United States Dolomite formations Limestone formations of Canada Limestone formations of the United States