Bullhead 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 ...

Lower Cretaceous Lower may refer to: * ''Lower'' (album), 2025 album by Benjamin Booker * Lower (surname) * Lower Township, New Jersey *Lower Receiver (firearms) * Lower Wick Gloucestershire, England See also * Nizhny {{Disambiguation ...

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 Canada 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 ba ...

of northeastern

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

and western

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 ...

. It was first defined by F.H. McLearn in 1918 as the Bullhead Mountain Formation, but later was upgraded to group status. It consists of the

Cadomin Cadomin is a Hamlet (place), hamlet in west-central Alberta, Canada, within Yellowhead County. It is along the McLeod River in the Rocky Mountain Foothills, foothills of the Rocky Mountains, approximately south of Hinton, Alberta, Hinton near ...

and Gething Formations, although some early workers included the

Bluesky Formation The Bluesky Formation is a stratigraphic unit of Lower Cretaceous age in the Western Canada Sedimentary Basin. It takes the name from the hamlet of Bluesky, and was first described in Shell's ''Bluesky No. 1'' well by Badgley in 1952. Lithology ...

and others in the group.Stott, D.F. 1965. Lower Cretaceous Bullhead and Fort St John Groups, between Smoky and Peace Rivers, Rocky Mountain foothills, Alberta and British Columbia. Geological Survey of Canada, Bulletin 152, 279 p. .

Lithology

Bullhead Group includes the conglomerate and quartzose

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 ...

s of the Cadomin Formation at the base, and grades to

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

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

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...

seams of the overlying Gething Formation. Those sediments were deposited in

alluvial fan An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to Semi-arid climate, semiar ...

braided river A braided river (also called braided channel or braided stream) consists of a network of river channel (geography), channels separated by small, often temporary, islands called ''braid bars'' or, in British English usage, ''aits'' or ''eyots''. ...

deltaic A river delta is a landform, archetypically triangular, created by the deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or with a body of stagnant water. The creati ...

and

coastal plain A coastal plain (also coastal plains, coastal lowland, coastal lowlands) is an area of flat, low-lying land adjacent to a sea coast. A fall line commonly marks the border between a coastal plain and an upland area. Formation Coastal plains can f ...

environments.

Distribution

The Bullhead Group is present in the foothills of the

Northern Rocky Mountains The Northern Rocky Mountains, usually referred to as the Northern Rockies, are a subdivision of the Canadian Rockies comprising the northern half of the Canadian segment of the Rocky Mountains. While their northward limit is easily defined as th ...

and the adjacent plains, extending from the

Tuchodi River The Tuchodi River is a stream in the Northern Rocky Mountains of northern British Columbia, Canada. The river flows through the Northern Rocky Mountains Provincial Park in a northeasterly direction to the Muskwa River. Its name comes from Slavey p ...

of British Columbia in the north to the

Smoky River The Smoky River is a river in western Alberta, Canada. It is a major tributary of the Peace River (Canada), Peace River. The name refers to the presence of "smouldering beds of coal in the riverbank" noted by the Cree people, an Indigenous peop ...

of Alberta in the south. It thins eastward from about in the western foothills of northeastern British Columbia to about in the Peace River plains, reaching zero near Fort St. John. The most complete section is found in the type locality of the Gething Formation in the

Peace River The Peace River () is a river in Canada that originates in the Rocky Mountains of northern British Columbia and flows to the northeast through northern Alberta. The Peace River joins the Athabasca River in the Peace-Athabasca Delta to form the ...

Canyon immediately downstream from the W. A. C. Bennett Dam.Glass, D.J. (editor) 1997. Lexicon of Canadian Stratigraphy, vol. 4, Western Canada including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba. Canadian Society of Petroleum Geologists, Calgary, 1423 p. on CD-ROM. .

Relationship to other units

The Bullhead Group overlies a major regional

unconformity 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 ...

caused by pre-Bullhead erosion. It rests unconformably on the Fernie Formation, the Nikanassin Formation, the

Minnes Group The Minnes Group, originally named the Minnes Formation, is a geologic unit of latest Jurassic to earliest Cretaceous age in the Western Canada Sedimentary Basin. It is present in the northern foothills of the Canadian Rockies and the adjacent ...

or the Kootenay Group, depending on the location and the extent of the erosion. It is overlain conformably by the

glauconitic Glauconite is an iron potassium phyllosilicate (mica group) mineral of characteristic green color which is very friable and has very low weathering resistance. It crystallizes with a monoclinic geometry. Its name is derived from the Greek () m ...

sandstones and marine shales at the base of the Fort St. John Group.

References

{{WCSB, Northwest_Plains=yes Western Canadian Sedimentary Basin Cretaceous British Columbia Geologic groups of British Columbia Barremian Stage Aptian Stage Albian Stage Geologic groups of Alberta Cretaceous Alberta Coal groups Conglomerate groups Sandstone groups of Canada Siltstone groups