imported>Volcanoguy: removed Category:Siltstone formations; added Category:Siltstone groups using HotCat

2025-06-04T20:18:30Z

removed Category:Siltstone formations; added Category:Siltstone groups using HotCat

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{{Short description|Stratigraphic Group in Western Canada}}
{{Infobox Rockunit
| name = Bullhead Group
| image =
| caption =
| type = [[Geological formation]]
| age = {{Fossil range|Barremian|Albian}}
| period = Early Cretaceous
| prilithology = [[Conglomerate (geology)|Conglomerate]], [[sandstone]], [[siltstone]] and [[mudstone]]
| otherlithology = [[Coal]]
| namedfor =
| namedby = F.H. McLearn<ref name=McLearn>McLearn, F.H., 1923. Peace River Canyon Coal Area, British Columbia; [[Geological Survey of Canada]], Summary Report 1922, Part B, pp. 1-46.</ref>
| region = [[British Columbia]], [[Alberta]]
| country = [[Canada]]
| coordinates = {{coord|56.01|-122.14|name=Bullhead Group|display=inline,title}}
| unitof =
| subunits = [[Gething Formation]]<br />[[Cadomin Formation]]
| underlies = [[Fort St. John Group]]
| overlies = [[Nikanassin Formation]], [[Fernie Group]], [[Minnes Group]], [[Kootenay Group]]
| thickness = up to {{convert|900|m|ft|-1}}<ref name=Glass />
| extent =
| area =
| map =
| map_caption =
}}
'''Bullhead Group''' is a [[stratigraphic unit]] of [[Lower Cretaceous]] [[Geochronology|age]] in the [[Western Canadian Sedimentary Basin|Western Canada Sedimentary Basin]] of northeastern [[British Columbia]] and western [[Alberta]].<ref name=Mossop19>{{Cite web|url=http://ags.aer.ca/reports/atlas-of-the-western-canada-sedimentary-basin.htm|title=The Geological Atlas of the Western Canada Sedimentary Basin, Chapter 19: Cretaceous Mannville Group of the Western Canada Sedimentary Basin|others=Compiled by Mossop, G.D. and Shetsen, I.|author=Canadian Society of Petroleum Geologists and Alberta Geological Survey|year=1994|accessdate=2016-06-20|archive-url=https://web.archive.org/web/20160701131122/http://ags.aer.ca/reports/atlas-of-the-western-canada-sedimentary-basin.htm|archive-date=2016-07-01|url-status=dead}}</ref> It was first defined by F.H. McLearn in 1918 as the Bullhead Mountain Formation,<ref name="McLearn" /> but later was upgraded to group status. It consists of the [[Cadomin Formation|Cadomin]] and [[Gething Formation]]s, although some early workers included the [[Bluesky Formation]] and others in the group.<ref name=Stott>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}}.</ref>

==Lithology==
Bullhead Group includes the [[Conglomerate (geology)|conglomerate]] and quartzose [[sandstone]]s 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]], [[river delta|deltaic]] and [[coastal plain]] environments.<ref name="Stott" />

==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 {{convert|900|m|ft|sp=us}} in the western foothills of northeastern British Columbia to about {{convert|100|m|ft|sp=us}} in the Peace River plains, reaching zero near [[Fort St. John, British Columbia|Fort St. John]]. The most complete section is found in the [[type locality (geology)|type locality]] of the Gething Formation in the [[Peace River (Canada)|Peace River]] Canyon immediately downstream from the [[W. A. C. Bennett Dam]].<ref name=Glass>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}}.</ref>

==Relationship to other units==
The Bullhead Group overlies a major regional [[unconformity]] caused by pre-Bullhead erosion.<ref name="Stott" /> 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 [[glauconite|glauconitic]] sandstones and marine shales at the base of the [[Fort St. John Group]].<ref name="Glass" />

==References==
{{reflist}}

{{WCSB|Northwest_Plains=yes}}

[[Category:Western Canadian Sedimentary Basin]]
[[Category:Cretaceous British Columbia]]
[[Category:Geologic groups of British Columbia]]
[[Category:Barremian Stage]]
[[Category:Aptian Stage]]
[[Category:Albian Stage]]
[[Category:Geologic groups of Alberta]]
[[Category:Cretaceous Alberta]]
[[Category:Coal groups]]
[[Category:Conglomerate groups]]
[[Category:Sandstone groups of Canada]]
[[Category:Siltstone groups]]

Bullhead Group - Revision history

imported>Volcanoguy: removed Category:Siltstone formations; added Category:Siltstone groups using HotCat