The Shaunavon Formation is a stratigraphical

Stratigraphy

Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....

 unit of Bathonian

Bathonian

In the geologic timescale the Bathonian is an age or stage of the Middle Jurassic. It lasted from approximately 167.7 Ma to around 164.7 Ma...

 age

Geochronology

Geochronology is the science of determining the age of rocks, fossils, and sediments, within a certain degree of uncertainty inherent to the method used. A variety of dating methods are used by geologists to achieve this, and schemes of classification and terminology have been proposed...

 in the Western Canadian Sedimentary Basin

Western Canadian Sedimentary Basin

The Western Canadian Sedimentary Basin is a vast sedimentary basin underlying of Western Canada including southwestern Manitoba, southern Saskatchewan, Alberta, northeastern British Columbia and the southwest corner of the Northwest Territories. It consists of a massive wedge of sedimentary rock...

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It takes the name from the town of Shaunavon

Shaunavon, Saskatchewan

The town of Shaunavon is situated in Southwest Saskatchewan at the junction of Highways 37 and 13. It is 110 kilometres from Swift Current, 163 kilometres from the Alberta border and 74 kilometres from the Montana border. Shaunavon was established in 1913 and settled along a railroad line...

, 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.

Lithology

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

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

 in the lower part with an oolitic

Oolite

Oolite is a sedimentary rock formed from ooids, spherical grains composed of concentric layers. The name derives from the Hellenic word òoion for egg. Strictly, oolites consist of ooids of diameter 0.25–2 mm; rocks composed of ooids larger than 2 mm are called pisolites...

 bed at the top. The upper member consists of calcareous sandstone

Sandstone

Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...

 and oolitic limestone, shell coquina

Coquina

Coquina is a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically sorted fragments of the shells of either molluscs, trilobites, brachiopods, or other invertebrates. For a sediment to be considered to be a coquina, the average size of the...

 and argillaceous limestone with interbeds of gray and green shale

Shale

Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...

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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

Petroleum

Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

 is produced from the Shaunavon Formation in south-eastern Saskatchewan

Saskatchewan

Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....

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Distribution

The Shaunavon Formation reaches a maximum thickness of 48 metres (157.5 ft). It occurs in the sub-surface in south-western Saskatchewan

Saskatchewan

Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....

. In the Williston Basin

Williston Basin

The Williston Basin is a large intracratonic sedimentary basin in eastern Montana, western North and South Dakota, and southern Saskatchewan known for its rich deposits of petroleum and potash. The basin is a geologic structural basin but not a topographic depression; it is transected by the...

 it appears present in Montana

Montana

Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

 and North Dakota

North Dakota

North Dakota is a state located in the Midwestern region of the United States of America, along the Canadian border. The state is bordered by Canada to the north, Minnesota to the east, South Dakota to the south and Montana to the west. North Dakota is the 19th-largest state by area in the U.S....

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

Weyburn, Saskatchewan

Weyburn is a city in southeastern Saskatchewan, Canada. It is located on the Souris River southeast of the provincial capital of Regina and is north of the border with the United States. The name is reputedly a corruption of the Scottish "wee burn," referring to a small creek. The city is...

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

Manitoba

Manitoba is a Canadian prairie province with an area of . The province has over 110,000 lakes and has a largely continental climate because of its flat topography. Agriculture, mostly concentrated in the fertile southern and western parts of the province, is vital to the province's economy; other...

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Relationship to other units

The Shaunavon Formation is conformably overlain by the Sawtooth Formation and conformably overlays the Gravelbourg Formation

Gravelbourg Formation

The Gravelbourg Formation is a stratigraphical unit of Bajocian age in the Western Canadian Sedimentary Basin.It takes the name from the town of Gravelbourg, and was first described in well Tidewater Eastend Crown No. 1 by R.L. Milner and G.E. Thomas in 1954.-Lithology:The Gravelbourg Formation is...

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It is equivalent to the Sawtooth Formation in southern Alberta

Southern Alberta

Southern Alberta is a region located in the Canadian province of Alberta. As of the year 2004, the region's population was approximately 272,017. The primary cities are Lethbridge and Medicine Hat...

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

Montana

Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

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