Bullhead Group

Bullhead Group
Stratigraphic range: Barremian–Albian
Type Geological formation
Sub-units Gething Formation
Cadomin Formation
Underlies Fort St. John Group
Overlies Nikanassin Formation, Fernie Group, Minnes Group, Kootenay Group
Thickness up to 900 metres (2,950 ft)[1]
Lithology
Primary Conglomerate, sandstone, siltstone and mudstone
Other Coal
Location
Coordinates 56°01′N 122°08′W / 56.01°N 122.14°W / 56.01; -122.14 (Bullhead Group)Coordinates: 56°01′N 122°08′W / 56.01°N 122.14°W / 56.01; -122.14 (Bullhead Group)
Region  British Columbia
 Alberta
Country  Canada
Type section
Named by F.H. McLearn[2]

Bullhead Group is a stratigraphic unit of Lower Cretaceous age in the Western Canada Sedimentary Basin of northeastern British Columbia and western Alberta.[3] It was first defined by F.H. McLearn in 1918 as the Bullhead Mountain Formation,[2] but later was upgraded to group status. It consists of the Cadomin and Gething Formations, although some early workers included the Bluesky Formation and others in the group.[4]

Lithology

Bullhead Group includes the conglomerate and quartzose sandstones of the Cadomin Formation at the base, and grades to sandstone, siltstone, mudstone, shale and coal seams of the overlying Gething Formation. Those sediments were deposited in alluvial fan, braided river, deltaic and coastal plain environments.[4]

Distribution

The Bullhead Group is present in the foothills of the Northern Rocky Mountains and the adjacent plains, extending from the Tuchodi River of British Columbia in the north to the Smoky River of Alberta in the south. It thins eastward from about 900 meters (3,000 ft) in the western foothills of northeastern British Columbia to about 100 meters (330 ft) 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 Canyon immediately downstream from the W. A. C. Bennett Dam.[1][5]

Relationship to other units

The Bullhead Group overlies a major regional unconformity caused by pre-Bullhead erosion.[4] It rests unconformably on the Fernie Formation, the Nikanassin Formation, the Minnes Group or the Kootenay Group, depending on the location and the extent of the erosion. It is overlain conformably by the glauconitic sandstones and marine shales at the base of the Fort St. John Group.[1][5]

References

  1. 1 2 3 Lexicon of Canadian Geologic Units. "Bullhed Group". Retrieved 2009-02-08.
  2. 1 2 McLearn, F.H., 1923. Peace River Canyon Coal Area, British Columbia; Geological Survey of Canada, Summary Report 1922, Part B, pp. 1-46.
  3. Mossop, G.D. and Shetsen, I., (compilers), Canadian Society of Petroleum Geologists and Alberta Geological Survey (1994). "The Geological Atlas of the Western Canada Sedimentary Basin, Chapter 19: Cretaceous Mannville Group of the Western Canada Sedimentary Basin". Retrieved 2013-08-01.
  4. 1 2 3 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. ISBN 0-660-10208-0.
  5. 1 2 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. ISBN 0-920230-23-7.
This article is issued from Wikipedia - version of the Monday, February 10, 2014. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.