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

2025-06-04T20:24:56Z

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

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{{Short description|Stratigraphic Group in Western Canada}}
{{Infobox Rockunit
| name = Fort St. John Group
| type = [[Geological formation]]
| age = {{Fossil range|Lower Cretaceous}}
| period = Early Cretaceous
| prilithology = [[Shale]]
| otherlithology = [[Sandstone]], [[siltstone]] and [[Conglomerate (geology)|conglomerates]]
| namedfor = [[Fort St. John, British Columbia|Fort St. John]]
| namedby = [[George Mercer Dawson]], 1881
| region = Northeast {{flag|British Columbia}} Northwest {{flag|Alberta}} Southern {{flag|Yukon}} Southern {{flag|Northwest Territories}}
| country = {{flag|Canada}}
| subunits = Cruiser Formation, Goodrich Formation, Hasler Formation, Gates Formation, [[Moosebar Shale Formation|Moosebar Formation]], Shaftesbury Formation, [[Peace River Formation]], [[Spirit River Formation]], [[Bluesky Formation]], Sully Formation, Sikanni Formation, Lepine Formation, Scatter Formation, Garbutt Formation, Buckinghorse Formation
| underlies = [[Dunvegan Formation]]
| overlies = [[Bullhead Group]]
| thickness = up to {{convert|2000|m|ft|-1}}<ref name=lexicon>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:005170 | title = Fort St. John Group | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
}}
The '''Fort St. John Group''' is a [[Stratigraphy|stratigraphic]] unit of [[Lower Cretaceous]] [[Geochronology|age]] in the [[Western Canadian Sedimentary Basin|Western Canada Sedimentary Basin]].<ref name=Mossop19>{{Cite web | url = http://www.ags.gov.ab.ca/publications/wcsb_atlas/a_ch19/ch_19.html |title = The Geological Atlas of the Western Canada Sedimentary Basin, Chapter 19: Cretaceous Mannville Group of the Western Canada Sedimentary Basin | author = Mossop, G.D. and Shetsen, I., (compilers), Canadian Society of Petroleum Geologists and Alberta Geological Survey | year = 1994 | access-date = 2013-08-01 | url-status = dead | archive-url = https://web.archive.org/web/20130814133127/http://www.ags.gov.ab.ca/publications/wcsb_atlas/a_ch19/ch_19.html | archive-date = 2013-08-14 }}</ref> It takes the name from the city of [[Fort St. John, British Columbia|Fort St. John]], [[British Columbia]] and was first defined by [[George Mercer Dawson]] in 1881.

==Lithology==
The Fort St. John Group is mostly composed of dark [[shale]] deposited in a [[Marine (ocean)|marine]] environment. [[Bentonite]] is present in the shale, and it is interbedded with [[sandstone]], [[siltstone]] and [[Conglomerate (geology)|conglomerates]].

==Distribution==
The Fort St. John Group occurs in the subsurface in the [[Peace River Country]] of northeastern [[British Columbia]] and north-western [[Alberta]], in southern [[Yukon]] and southern [[Northwest Territories]]. It has a thickness of {{convert|700|m|ft|-1}} to {{convert|2000|m|ft|-1}}.

==Relationship to other units==
The Fort St. John Group is conformably overlain by the [[Dunvegan Formation]] and conformably underlain by the [[Bullhead Group]] or may rest [[unconformity|disconformably]] on older units.

===Subdivisions===
The Fort St. John Group is subdivided into the following formations:
====[[Canadian Rockies]] foothills of [[British Columbia]]====
{|class="wikitable"
|-
! [[Geological unit|Sub-unit]] !! [[Geochronology|Age]] !! Lithology !! Max. Thickness !! Reference
|-
| Cruiser Formation || [[Albian]] - [[Cenomanian]] || [[marine (ocean)|marine]] [[shale]], argillaceous [[siltstone]] and fine grained marine [[sandstone]] || {{convert|230|m|ft|-1|abbr=on}}
|<ref>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:003606 | title = Cruiser Formation | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
|-
| Goodrich Formation || late [[Albian]] || fine-grained, laminated [[sandstone]], [[mudstone]] partings || {{convert|400|m|ft|-1|abbr=on}}
|<ref>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:005709 | title = Goodrich Formation | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
|-
| Hasler Formation || middle to late [[Albian]] || marine [[shale]] and [[siltstone]], minor [[sandstone]] and pebble [[Conglomerate (geology)|conglomerate]] || {{convert|265|m|ft|-1|abbr=on}}
|<ref>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:006336 | title = Hasler Formation | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
|-
| Commotion Formation || early to middle [[Albian]] || [[sandstone]], [[shale]] and [[Conglomerate (geology)|conglomerate]] || {{convert|490|m|ft|-1|abbr=on}}
|<ref>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:003249 | title = Commotion Formation | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
|-
| Gates Formation || early [[Albian]] || massive well-sorted [[sandstone]], carbonaceous sandstone, [[mudstone]], [[siltstone]], [[coal]] || {{convert|263|m|ft|-1|abbr=on}}
|<ref>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:005478 | title = Gates Formation | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
|-
| Moosebar Formation || early [[Albian]] || marine [[shale]] and [[siltstone]] || {{convert|289|m|ft|-1|abbr=on}}
|<ref>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:010101| title = Moosebar Formation| author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
|-
|}

====[[Peace River Country]]====
{|class="wikitable"
|-
! [[Geological unit|Sub-unit]] !! [[Geochronology|Age]] !! Lithology !! Max. Thickness || Reference
|-
| Shaftesbury Formation || [[Albian]] || friable [[shale]], fish scale [[siltstone]], [[bentonite]], [[ironstone]] || {{convert|400|m|ft|-1|abbr=on}}
|<ref>{{Cite web| url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:013581 | title = Shaftesbury Formation | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
|-
| [[Peace River Formation]] || middle [[Albian]] ||[[Paddy Member]] - [[greywacke]], [[coal]] [[Cadotte Member]] - coarse to fine marine [[sandstone]] [[Harmon Member]] - dark, fissile, non-calcareous [[shale]] || {{convert|60|m|ft|-1|abbr=on}}
|<ref>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:011614 | archive-url= https://archive.today/20120708115131/http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:011614 | url-status = dead | archive-date = 2012-07-08 | title = Peace River Formation | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
|-
| [[Spirit River Formation]] || middle [[Albian]] || [[Notikewin Member]] - fine to medium grained argillaceous [[sandstone]], dark [[shale]], [[ironstone]] [[Falher Member]] - [[greywacke]], [[shale]], [[siltstone]], [[coal]] [[Wilrich Member]] - dark [[shale]] thin [[sandstone]] and [[siltstone]] stringers || {{convert|348|m|ft|-1|abbr=on}}
|<ref>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:014250 | title = Spirit River Formation | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
|-
| [[Bluesky Formation]] || early [[Albian]] || brown, fine to medium grained, [[glauconite|glauconitic]], [[porosity|porous]] [[sandstone]] || {{convert|46|m|ft|-1|abbr=on}}
|<ref>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:001560 | title = Bluesky Formation | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11 | url-status = dead | archive-url = https://archive.today/20120709174851/http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:001560 | archive-date = 2012-07-09}}</ref>
|-
|}

====[[Liard River]] and [[Fort Liard, Northwest Territories|Fort Liard]] Area====
{|class="wikitable"
|-
! [[Geological unit|Sub-unit]] !! [[Geochronology|Age]] !! Lithology !! Max Thickness !! Reference
|-
| Sully Formation || early to Late [[Cretaceous]] || marine [[shale]] and [[siltstone]] || {{convert|300|m|ft|-1|abbr=on}}
|<ref>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:014713 | title = Sully Formation | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
|-
| Sikanni Formation || [[early Cretaceous]] || fine-grained, calcareous, [[glauconite|glauconitic]] [[sandstone]], argillaceous [[siltstone]] and [[shale]] || {{convert|240|m|ft|-1|abbr=on}}
|<ref>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:013765 | title = Sikanni Formation | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
|-
| Lepine Formation* || middle to late [[Albian]] || silty [[mudstone]], [[siderite|sideritic]] concretions || {{convert|900|m|ft|-1|abbr=on}}
|<ref>{{Cite web | url=http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:008392| title = Lepine Formation | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
|-
| Scatter Formation* || early to middle [[Albian]] || [[Bulwell Member]] - [[glauconite|glauconitic]] [[sandstone]] [[Wildhorn Member]] - silty [[mudstone]] [[Tussock Member]] - glauconitic [[sandstone]], silty [[mudstone]] || {{convert|375|m|ft|-1|abbr=on}}
|<ref>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:013367 | title = Scatter Formation| author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
|-
| Garbutt Formation* || early [[Aptian]] || Lower Garbutt - [[mudstone]], [[siltstone]], [[siderite]], [[bentonite]] Upper Garbutt - [[mudstone]], [[siderite|sideritic]] weathering, argillaceous [[siltstone]], laminated [[sandstone]] || {{convert|290|m|ft|-1|abbr=on}}
|<ref>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:005442 | title = Garbutt Formation | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2009-02-11}}</ref>
|-
| Chinkeh Formation || [[Barremian]] to early [[Albian]] || [[sandstone]] with marine [[shale]], conglomeratic base || discontinuous
|<ref>{{Cite web | url = http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:016852 | title = Chinkeh Formation | author = [[Lexicon of Canadian Geologic Units]] | access-date = 2010-01-09}}</ref>
|-
|}
<nowiki>*</nowiki>Buckinghorse Formation is equivalent to the sum of Lepine Formation, Scatter Formation and Garbutt Formation. It occurs north-east of the [[Canadian Rockies]] foothills in [[British Columbia]], between the [[Halfway River]] and [[Muskwa River]]. It is composed of silty [[marine (ocean)|marine]] [[mudstone]] with fine grained marine [[sandstone]] interbeds.

==References==
{{reflist}}

{{Western Canadian Sedimentary Basin|Northwest_Plains=yes|Fort_Nelson=yes|Liard_River=yes}}

[[Category:Lower Cretaceous Series of North America]]
[[Category:Cretaceous Alberta]]
[[Category:Cretaceous British Columbia]]
[[Category:Cretaceous Northwest Territories]]
[[Category:Cretaceous Yukon]]
[[Category:Geologic groups of Alberta]]
[[Category:Geologic groups of British Columbia]]
[[Category:Geologic groups of the Northwest Territories]]
[[Category:Geologic groups of Yukon]]
[[Category:Shale groups of Canada]]
[[Category:Siltstone groups]]
[[Category:Sandstone groups of Canada]]
[[Category:Conglomerate groups]]

Fort St. John Group - Revision history

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