Bullhead Group 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 Lower Cretaceous 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...

.

It was first defined by F.H. McLearn in 1918.

Lithology

Bullhead Group has conglomerate

Conglomerate (geology)

A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...

 with rounded pebbles of chert

Chert

Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...

, quartz

Quartz

Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

 and quartzite

Quartzite

Quartzite is a hard metamorphic rock which was originally sandstone. Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts. Pure quartzite is usually white to gray, though quartzites often occur in various shades of pink...

 at the base, then grades to 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,...

, siltstone

Siltstone

Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...

 and mudstone

Mudstone

Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...

. Coal

Coal

Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

 is present in the Peace River

Peace River (Canada)

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 flows into the Slave River, a tributary of the Mackenzie River. The Mackenzie is the 12th longest river in the world,...

 area.

The sediments are deposited in a piemontal

Foothills

Foothills are geographically defined as gradual increases in elevation at the base of a mountain range. They are a transition zone between plains and low relief hills to the adjacent topographically high mountains.-Examples:...

 fan environment, as well as alluvial plain and transitional. Deltaic

River delta

A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...

 and marine

Ocean

An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...

 sediments are found north of Peace River

Peace River, Alberta

Peace River is a town in northwestern Alberta, Canada, situated along the banks of the Peace River, at its confluence with the Smoky River, the Heart River and Pat's Creek. It is located northwest of Edmonton, and northeast of Grande Prairie, along Highway 2. The Peace River townsite is nearly ...

.

Distribution

The Bullhead Group has a thickness of 900 metres (2,952.8 ft) in the foothills of the northern Canadian Rockies

Canadian Rockies

The Canadian Rockies comprise the Canadian segment of the North American Rocky Mountains range. They are the eastern part of the Canadian Cordillera, extending from the Interior Plains of Alberta to the Rocky Mountain Trench of British Columbia. The southern end borders Idaho and Montana of the USA...

 in British Columbia

British Columbia

British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...

 and thins out to 100 metres (328.1 ft) in the Peace River

Peace River, Alberta

Peace River is a town in northwestern Alberta, Canada, situated along the banks of the Peace River, at its confluence with the Smoky River, the Heart River and Pat's Creek. It is located northwest of Edmonton, and northeast of Grande Prairie, along Highway 2. The Peace River townsite is nearly ...

 area. North of Fort St. John

Fort St. John, British Columbia

The City of Fort St. John is a city in northeastern British Columbia, Canada. A member municipality of the Peace River Regional District, the city covers an area of about 22 km² with 22,000 residents . Located at Mile 47, it is one of the largest cities along the Alaska Highway. Originally...

 it is not present.

The most complete section is found in the type locality of the Gething Formation

Gething Formation

Gething Formation is a stratigraphical unit of Lower Cretaceous age in the Western Canadian Sedimentary Basin.It was first described in the Peace River Canyon by F.H. McLearn in 1923. The canyon was partly inundated in 1968 by the Williston Lake after the construction of the W. A. C. Bennett Dam...

, in the Peace River

Peace River (Canada)

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 flows into the Slave River, a tributary of the Mackenzie River. The Mackenzie is the 12th longest river in the world,...

 Canyon downstream of the W. A. C. Bennett Dam

W. A. C. Bennett Dam

The W. A. C. Bennett Dam is a large hydroelectric earthfill dam on the Peace River in northern British Columbia, Canada. The dam, located 19 kilometres west of Hudson's Hope, and 85 kilometres northwest of Chetwynd, is named after the late former premier W. A. C. Bennett, and came on-line in 1968...

, west of Hudson's Hope

Hudson's Hope, British Columbia

Hudson's Hope is a district municipality in northeastern British Columbia, Canada, in the Peace River Regional District. It covers an area of with a population of 1,157 people. Having been first settled in 1805, it is the third oldest community in the province, although it was not incorporated...

.

Relationship to other units

The group is conformably overlain by the Fort St. John Group

Fort St. John Group

The Fort St. John Group is a stratigraphical unit of Lower Cretaceous age in the Western Canadian Sedimentary Basin.It takes the name from the city of Fort St. John, British Columbia and was first defined by George Mercer Dawson in 1881.-Lithology:...

 shales and unconformably

Unconformity

An unconformity is a buried erosion 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 of time before deposition of the younger, but the term is used to describe...

 underlain by Jurassic to Triassic deposits, forming a regional angular un-conformity with the Nikanassin Formation

Nikanassin Formation

The Nikanassin Formation is a stratigraphical unit of late Jurassic age. It is part of the Western Canadian Sedimentary Basin and is found in western Alberta, Canada....

, Fernie Group and Kootenay Group.

The Bullhead Group contains, from top to base the following Formations:

• Bluesky Formation
  Bluesky Formation
  The Bluesky Formation is a stratigraphical unit of Lower Cretaceous age in the Western Canadian 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:...
  
  
• Gething Formation
  Gething Formation
  Gething Formation is a stratigraphical unit of Lower Cretaceous age in the Western Canadian Sedimentary Basin.It was first described in the Peace River Canyon by F.H. McLearn in 1923. The canyon was partly inundated in 1968 by the Williston Lake after the construction of the W. A. C. Bennett Dam...
  
  
• Cadomin Formation
  Cadomin Formation
  The Cadomin Formation is a stratigraphical unit of early Cretaceous age. It is part of the Western Canadian Sedimentary Basin and is found in western Alberta, Canada....