The Beaverhill Lake Group is a geologic unit of

Middle Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wher ...

Late Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

(late

Givetian The Givetian is one of two faunal stages in the Middle Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Eifelian Stage and followed by the Frasnian Stage. It is named after the town of Givet in ...

Frasnian The Frasnian is one of two faunal stages in the Late Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Givetian Stage and followed by the Famennian Stage. Major reef-building was under way during t ...

) age in the

Western Canada Sedimentary Basin The Western Canadian 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 ...

that is present in the southwestern

Northwest Territories The Northwest Territories (abbreviated ''NT'' or ''NWT''; french: Territoires du Nord-Ouest, formerly ''North-Western Territory'' and ''North-West Territories'' and namely shortened as ''Northwest Territory'') is a federal territory of Canada. ...

, northeastern

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost Provinces and territories of Canada, province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include ...

and

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

. It was named by the geological staff of

Imperial Oil Imperial Oil Limited (French: ''Compagnie Pétrolière Impériale Ltée'') is a Canadian petroleum company. It is Canada's second-biggest integrated oil company. It is majority owned by American oil company ExxonMobil with around 69.6 percent ...

in 1950 for Beaverhill Lake, Alberta, based on the core from a

well A well is an excavation or structure created in the ground by digging, driving, or drilling to access liquid resources, usually water. The oldest and most common kind of well is a water well, to access groundwater in underground aquifers. T ...

that they had drilled southeast of the lake, near Ryley, Alberta (Anglo-Canadian Beaverhill Lake No. 2, 11-11-50-17W4).

Petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crude ...

is produced from the Swan Hills Formation of the Beaverhill Lake Group in the Swan Hills area of

northern Alberta Northern Alberta is a geographic region located in the Canadian province of Alberta. An informally defined cultural region, the boundaries of Northern Alberta are not fixed. Under some schemes, the region encompasses everything north of the ce ...

Lithology

The Beaverhill Lake Group consists of

anhydrite Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with t ...

and

carbonate rock Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite (different crystal forms of CaCO3), and dolomite rock (also known as doloston ...

s at the base (the Fort Vermillion Formation), overlain by interbedded sequences of

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an a ...

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especia ...

argillaceous Clay minerals are hydrous aluminium phyllosilicates (e.g. kaolin, Al2 Si2 O5( OH)4), sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces. Clay mineral ...

micritic

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...

and dolomite. The group becomes thicker and more shaly to the west.

Distribution and thickness

The Beaverhill Lake Group is present beneath the plains of the southwestern Northwest Territories, northeastern British Columbia and Alberta. It reaches a maximum thickness of about in

central Alberta Central Alberta is a region located in the Canadian province of Alberta. Central Alberta is the most densely populated rural area in the province. Agriculture and energy are important to the area's economy. Geography Central Alberta is bordere ...

Outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficia ...

s of one of its formations (the Waterways) can be seen along the Athabasca and Clearwater Rivers in the

Fort McMurray Fort McMurray ( ) is an urban service area in the Regional Municipality of Wood Buffalo in Alberta, Canada. It is located in northeast Alberta, in the middle of the Athabasca oil sands, surrounded by boreal forest. It has played a significa ...

area.Norris, A.W. 1963. Devonian stratigraphy of northeastern Alberta and northwestern Saskatchewan. Geological Survey of Canada, Memoir 313.

Stratigraphy

;

Central Alberta Central Alberta is a region located in the Canadian province of Alberta. Central Alberta is the most densely populated rural area in the province. Agriculture and energy are important to the area's economy. Geography Central Alberta is bordere ...

; Swan Hills area In

and northeastern

the unit has

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondary ...

status and is not subdivided.

Environment of deposition

The formations of the Beaverhill Lake Group were deposited in an

embayment A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a gulf, sea, sound, or bight. A cove is a small, circular bay with a ...

that extended from an open

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

in the present-day

in Canada, to

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

in the United States. An extensive reef complex called the Presqu'ile Barrier had developed across the mouth of the embayment, blocking it from the open ocean and restricting the inflow of sea water. Low water levels and excessive evaporation led to the deposition of the anhydrite-rich Fort Vermillion Formation at the base of the group in northern areas. Water levels then increased throughout the embayment, and the overlying

s were deposited in reefs (Swan Hills Formation), and in

carbonate platform A carbonate platform is a sedimentary body which possesses topographic relief, and is composed of autochthonic calcareous deposits. Platform growth is mediated by sessile organisms whose skeletons build up the reef or by organisms (usually mic ...

and basin environments (Waterways Formation).Wendte, J. and Uyeno, T. 2005. Sequence stratigraphy and evolution of Middle to Upper Devonian Beaverhill Lake strata, south-central Alberta. Bulletin of Canadian Petroleum Geology. v. 53, no. 3, p. 250-354.

Relationship to other units

The Beaverhill Lake Group is conformably underlain by the formations of the

Elk Point Group The Elk Point Group is a stratigraphic unit of Early to Middle Devonian age in the Western Canada and Williston sedimentary basins. It underlies a large area that extends from the southern boundary of the Northwest Territories in Canada to North ...

. In most areas it is conformably overlain by the formations of the

Woodbend Group The Woodbend Group is a stratigraphical unit of Frasnian age in the Western Canadian Sedimentary Basin. It was first described in the ''British American Pyrcz No. 1'' well by Imperial Oil geological staff in 1950. Lithology The Formation is co ...

, and in northwestern Alberta and northeastern British Columbia it is disconformably overlain by the Muskwa Formation. It is equivalent to the

Souris River Formation The Manitoba Group is a stratigraphical unit of middle to late Devonian age in the Western Canadian Sedimentary Basin. The group takes its name from the province of Manitoba, and was first defined by A.D. Baillie in 1953. Lithology The Manito ...

in southeastern Alberta,

Saskatchewan Saskatchewan ( ; ) is a province in western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on the south by the U.S. states of Montana and North ...

and

Manitoba , image_map = Manitoba in Canada 2.svg , map_alt = Map showing Manitoba's location in the centre of Southern Canada , Label_map = yes , coordinates = , capital = Win ...

, and to the Flume Formation of the

Fairholme Group The Fairholme Group is a stratigraphic unit of Late Devonian (Frasnian) age. It is present on the western edge of the Western Canada Sedimentary Basin in the Rocky Mountains and foothills of Alberta and British Columbia. It was named for the Fairh ...

in the

Canadian Rockies The Canadian Rockies (french: Rocheuses canadiennes) or Canadian Rocky Mountains, comprising both the Alberta Rockies and the British Columbian Rockies, is the Canadian segment of the North American Rocky Mountains. It is the easternmost par ...

. According to D.L Griffin, it is equivalent to the Slave Point Formation and Waterways Formation in northeastern Alberta, with the Slave Point Formation and the lower

Hay River Formation The Hay River Formation is a geologic formation in Northwest Territories. It preserves fossils dating back to the Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end o ...

in the

District of Mackenzie The District of Mackenzie was a regional administrative district of Canada's Northwest Territories. The district consisted of the portion of the Northwest Territories directly north of British Columbia, Alberta, and Saskatchewan on Canada's m ...

, as well as the

Horn River Formation The Horn River Formation (also ''Horn River Shale'') is a stratigraphic unit of Devonian (early Givetian to late Frasnian) age in the Western Canadian Sedimentary Basin. It is a thick sequence of marine sediments that was first described in out ...

and

Fort Simpson Formation The Fort Simpson Formation is a stratigraphical unit of Devonian age in the Western Canadian Sedimentary Basin. It takes the name from the settlement of Fort Simpson, and was first described in well Briggs Turkey Lake No. 1 (located south-east ...

northwest of the Slave Point-

Keg River A keg is a small barrel. Wooden kegs made by a cooper were used to transport nails, gunpowder, and a variety of liquids. A keg is normally now constructed of stainless steel, although aluminium can be used if it is coated with plastic on th ...

facies in northeastern British Columbia and the

.Griffin, D.L., 1965. "The facies front of the Devonian Slave Point - Elk Point sequence in northeastern British Columbia and the Northwest Territories"; Journal of Canadian Petroleum Technology, vol. 4, no. 1, pp. 13-22.

Paleontology

The carbonate rocks of the Beaverhill Lake Group contain rich

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, ...

faunas.Norris, A.W. 1983. Brachiopods (''Schizophoria, Strophodonta'' (''Strophodonta''), ''Nervostrophia, Eostrophalosia'' and ''Devonoproductus'') from the lower Upper Devonian Waterways Formation of northeastern Alberta. Geological Survey of Canada, Bulletin 350. There are also

crinoid Crinoids are marine animals that make up the Class (biology), class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while the unstalked forms are called feather stars or coma ...

ostracod Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typic ...

s and

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secre ...

s, and, in the Swan Hills Formation, stromatoporoids.

Hydrocarbon production

Since 1957

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

has been produced from the Swan Hills Formation of the Beaverhill Lake Group in the Swan Hills area of

, where it includes Devonian

reef A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic component, abiotic processes—deposition (geology), deposition of ...

structures similar to those of the

Leduc Formation The Leduc Formation is a stratigraphic unit of Late Devonian (Frasnian) age in the Western Canada Sedimentary Basin. It takes its name from the city of Leduc, and it was formally described from the B.A. Pyrz No. 1 well in central Alberta, between ...

and the

Rainbow Member A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured circular arc. Rainbows ...

in Alberta.Barss, D.L., Copland, A.B., and Ritchie, W.D., 1970, Middle Devonian Reefs, Rainbow Area, Alberta, in Geology of Giant Petroleum Fields, AAPG Memoir 14, Halbouty, M.T., editor, Tulsa: American Association of Petroleum Geologists, pp. 18-49Hemphill, C.R., Smith, R.I., and Szabo, F., 1970, Geology of Beaverhill Lake Reefs, Swan Hills Area, Alberta, in Geology of Giant Petroleum Fields, AAPG Memoir 14, Halbouty, M.T., editor, Tulsa: American Association of Petroleum Geologists, pp. 50-90

References

{{Western Canadian Sedimentary Basin, Northeast_Plains=yes, Northwest_Plains=yes, South AB=yes Geologic groups of North America Geologic formations of Canada Western Canadian Sedimentary Basin Stratigraphy of Alberta Stratigraphy of British Columbia Stratigraphy of the Northwest Territories Devonian southern paleotropical deposits Middle Devonian Series Upper Devonian Series