The Ellis Group 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 ...

Bajocian In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.9 ±0.8 Ma to around 168.2 ±1.2 Ma (million years ago). The Bajocian Age succeeds the Aalenian Age and precedes the Bathonia ...

- Oxfordian

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 ...

Alberta Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...

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 ...

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

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 ...

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

Fort Ellis Fort Ellis was a United States Army fort established August 27, 1867, east of present-day Bozeman, Montana. Troops from the fort participated in many major campaigns of the Indian Wars. The fort was closed on August 2, 1886. History The fort wa ...

, and was first described in outcrop in the Rocky Creek Canyon by A.C. Peale in 1893.Peale, A.C., 1893. The Paleozoic section in the vicinity of Three Forks, Montana.

United States Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...

, Bulletin 110, p.9-56.

Lithology

The Ellis Group is composed of

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 ...

and

sandstones Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains, cemented together by another mineral. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed o ...

deposited in a marine and transitional environment.

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 Sawtooth Formation in southeastern

Distribution

The Ellis Group laterally occurs in the subsurface 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 ...

and northern and central

. It is typically , but thickens on either side of the Sweetgrass Arch and reaches up to in southeastern Alberta.

Subdivisions

The Ellis Group includes the following formations, from top to bottom:

Relationship to other units

The Ellis Group is

unconformably 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 o ...

overlain by the shales and sandstones of the

Mannville Group The Mannville Group is a stratigraphic unit of Cretaceous age in the Western Canadian Sedimentary Basin. It takes the name from the town of Mannville, Alberta, and was first described in the ''Northwest Mannville 1'' well by A.W. Nauss in 1945. ...

and rests on the

carbonate A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...

s of the

Rundle Group The Rundle Group is a stratigraphic unit of Mississippian age in the Western Canadian Sedimentary Basin. It takes the name from Mount Rundle (itself taking the name from Robert Terrill Rundle), and was first described in outcrops at the nort ...

. It grades westwards to the shales of the Fernie Group, and eastwards to the shale, sandstones and limestones of the

Vanguard The vanguard (sometimes abbreviated to van and also called the advance guard) is the leading part of an advancing military formation. It has a number of functions, including seeking out the enemy and securing ground in advance of the main force. ...

and Shaunavon Formations.

References

{{Western Canadian Sedimentary Basin, Saskatchewan=yes, South AB=yes, state=expanded Geologic groups of Montana Geologic groups of Wyoming Jurassic Canada Jurassic Montana Jurassic United States Bajocian Stage Oxfordian Stage Shale formations of the United States Sandstone groups of the United States Geologic groups of Alberta Geologic groups of Saskatchewan Shale groups of Canada Sandstone groups of Canada