The Shaunavon Formation is a

stratigraphic unit A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features ( facies) that characteriz ...

Bathonian In the geologic timescale the Bathonian is an age (geology), age and stage (stratigraphy), stage of the Middle Jurassic. It lasted from approximately 168.2 ±1.2 annum, Ma to around 165.3 ±1.1 Ma (million years ago). The Bathonian Age succeeds ...

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

Western Canadian Sedimentary Basin The Western Canada Sedimentary Basin (WCSB) underlies of Western Canada including southwestern Manitoba, southern Saskatchewan, Alberta, northeastern British Columbia and the southwest corner of the Northwest Territories. This vast sedimentary b ...

. It takes the name from the town of Shaunavon, and was first described in the ''Tidewater A.O. Eastend Crown No. 1'' well, drilled south-west of the settlement, by R.L. Milner and G.E. Thomas in 1954.Milner, R.L. and Thomas, G E., 1954. Jurassic System in Saskatchewan. In: Western Canada Sedimentary Basin

American Association of Petroleum Geologists The American Association of Petroleum Geologists (AAPG) is one of the world's largest professional geological societies with about 17,000 members across 129 countries. The AAPG works to "advance the science of geology, especially as it relates to ...

, p. 250-267

Lithology

The Shaunavon Formation is composed of two members. The lower member consists of buff microcrystalline massive

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) ...

in the lower part with an oolitic bed at the top. The upper member consists of calcareous

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

and oolitic limestone, shell

coquina Coquina () is a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically sorted fragments of mollusks, trilobites, brachiopods, or other invertebrates. The term ''coquina'' comes from the S ...

and argillaceous limestone with interbeds of gray and green

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 ...

. Dolomitisation can occur in both members. Lenticular beds separated by sedimentation breaks are common in the upper member. Channels also occur in the upper Shaunavon.

Hydrocarbon production

Oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) and lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturate ...

is produced from the Shaunavon Formation in south-western

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 ...

Distribution

The Shaunavon Formation reaches a maximum thickness of . It occurs in the sub-surface in south-western

. 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 appears present in

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

and

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 ...

as the lower part of the Sawtooth Formation and Piper Formation. East of

Weyburn Weyburn is the tenth-largest city in Saskatchewan, Canada. The city has a population of 11,019. It is on the Souris River southeast of the provincial capital of Regina, Saskatchewan, Regina and is north from the North Dakota border in the ...

, it grades into the shaley facies of the Melita Formation of

Manitoba Manitoba is a Provinces and territories of Canada, province of Canada at the Centre of Canada, longitudinal centre of the country. It is Canada's Population of Canada by province and territory, fifth-most populous province, with a population ...

Relationship to other units

The Shaunavon Formation is conformably overlain by the Sawtooth Formation and conformably overlays the Gravelbourg Formation. It is equivalent to the Sawtooth Formation in

southern Alberta Southern Alberta is a region located in the Canadian province of Alberta. In 2016, the region's population was approximately 291,112. The primary cities are Lethbridge and Medicine Hat. The region is known mostly for agricultural production, but o ...

, as well as to the Bowes member and Firemoon Member of the Piper Formation in

References

{{Western Canadian Sedimentary Basin, Saskatchewan=yes Geologic formations of Saskatchewan Jurassic Saskatchewan Western Canadian Sedimentary Basin