Fort St. John Group

Fort St. John Group Stratigraphic range: Lower Cretaceous PreЄ Є O S D C P T J K Pg N
Type	Geological formation
Sub-units	Cruiser Formation, Goodrich Formation, Hasler Formation, Gates 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 2,000 metres (6,560 ft)^[1]
Lithology
Primary	Shale
Other	Sandstone, siltstone and conglomerates
Location
Region	Northeast British Columbia Northwest Alberta Southern Yukon Southern Northwest Territories
Country	Canada
Type section
Named for	Fort St. John
Named by	George Mercer Dawson, 1881

The Fort St. John Group is a stratigraphic unit of Lower Cretaceous age in the Western Canada Sedimentary Basin.^[2] It takes the name from the city of 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 environment. Bentonite is present in the shale, and it is interbedded with sandstone, siltstone and 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 700 metres (2,300 ft) to 2,000 metres (6,560 ft).

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 disconformably on older units.

Subdivisions

The Fort St. John Group is subdivided into the following formations:

Canadian Rockies foothills of British Columbia

Sub-unit	Age	Lithology	Max. Thickness	Reference
Cruiser Formation	Albian - Cenomanian	marine shale, argillaceous siltstone and fine grained marine sandstone	230 m (750 ft)	^[3]
Goodrich Formation	late Albian	fine-grained, laminated sandstone, mudstone partings	400 m (1,310 ft)	^[4]
Hasler Formation	middle to late Albian	marine shale and siltstone, minor sandstone and pebble conglomerate	265 m (870 ft)	^[5]
Commotion Formation	early to middle Albian	sandstone, shale and conglomerate	490 m (1,610 ft)	^[6]
Gates Formation	early Albian	massive well-sorted sandstone, carbonaceous sandstone, mudstone, siltstone, coal	263 m (860 ft)	^[7]
Moosebar Formation	early Albian	marine shale and siltstone	289 m (950 ft)	^[8]

Peace River Country

Sub-unit	Age	Lithology	Max. Thickness	Reference
Shaftesbury Formation	Albian	friable shale, fish scale siltstone, bentonite, ironstone	400 m (1,310 ft)	^[9]
Peace River Formation	middle Albian	Paddy Member - greywacke, coal Cadotte Member - coarse to fine marine sandstone Harmon Member - dark, fissile, non-calcareous shale	60 m (200 ft)	^[10]
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	348 m (1,140 ft)	^[11]
Bluesky Formation	early Albian	brown, fine to medium grained, glauconitic, porous sandstone	46 m (150 ft)	^[12]

Liard River and Fort Liard Area

Sub-unit	Age	Lithology	Max Thickness	Reference
Sully Formation	early to Late Cretaceous	marine shale and siltstone	300 m (980 ft)	^[13]
Sikanni Formation	early Cretaceous	fine-grained, calcareous, glauconitic sandstone, argillaceous siltstone and shale	240 m (790 ft)	^[14]
Lepine Formation*	middle to late Albian	silty mudstone, sideritic concretions	900 m (2,950 ft)	^[15]
Scatter Formation*	early to middle Albian	Bulwell Member - glauconitic sandstone Wildhorn Member - silty mudstone Tussock Member - glauconitic sandstone, silty mudstone	375 m (1,230 ft)	^[16]
Garbutt Formation*	early Aptian	Lower Garbutt - mudstone, siltstone, siderite, bentonite Upper Garbutt - mudstone, sideritic weathering, argillaceous siltstone, laminated sandstone	290 m (950 ft)	^[17]
Chinkeh Formation	Barremian to early Albian	sandstone with marine shale, conglomeratic base	discontinuous	^[18]

*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 mudstone with fine grained marine sandstone interbeds.

References

↑ Lexicon of Canadian Geologic Units. "Fort St. John Group". Retrieved 2009-02-11.
↑ 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.
↑ Lexicon of Canadian Geologic Units. "Cruiser Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Goodrich Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Hasler Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Commotion Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Gates Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Moosebar Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Shaftesbury Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Peace River Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Spirit River Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Bluesky Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Sully Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Sikanni Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Lepine Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Scatter Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Garbutt Formation". Retrieved 2009-02-11.
↑ Lexicon of Canadian Geologic Units. "Chinkeh Formation". Retrieved 2010-01-09.

Western Canadian Sedimentary Basin

Hydrocarbon history	Oil sands and heavy oil Frontier exploration and development Natural gas liquids Natural gas

Depositional regions	Southern Alberta Central Alberta Northwestern Alberta Plains South-central Canadian Rockies foothills North-east Plains North-central foothills Liard River Fort Nelson Northern Rocky Mountains Fort St. John Saskatchewan Western Manitoba

Liard River area	Wapiti GRP Kotaneelee FM Dunvegan FM Ft. St. John GRP Sully FM SikanniFM Lepine FM Buckinghorse FM Scatter FM Garbutt FM Liard FM Toad FM Grayling FM Ishbel GRP Fantasque FM Kindle FM Mattson FM Golata FM Debolt FM Prophet FM Besa River FM Dunedin FM Stone FM Wokpash FM Muncho-McConnell FM Nonda FM Kechica FM Atan FM Canadian Shield

Fort Nelson area	Wapiti GRP Kotaneelee FM Dunvegan FM Ft. St. John GRP Sully FM SikanniFM Buckinghorse FM Scatter FM Belloy FM Rundle GRP Debolt FM Shunda FM Pekisko FM Banff FM Exshaw FM Kotcho FM Tetcho FM Trout River FM Kakisa FM Redknife FM Jean Marie MBR Fort Simpson FM Horn River FM Muskwa FM Waterways FM Slave Point FM Watt Mountain FM Muskeg FM Sulphur Point FM Presqu'ile FM Pine Point FM Keg River FM Chinchaga FM Canadian Shield

Northwest plains	Paskapoo FM Scollard FM Wapiti GRP Smoky GRP Puskwaskau FM Badheart FM Muskiki FM Cardium FM Kaskapau FM Pouce Coupe MBR Doe Creek MBR Dunvegan FM Fort St. John GRP Shaftesbury FM Peace River FM Spirit River FM Bullhead GRP Bluesky FM Gething FM Cadomin FM Nikanassin FM Fernie GRP Rock Creek MBR Poker Chip Shale Nordegg MBR Schooler Creek GRP Baldonnel FM Charlie Lake FM Halfway FM Doig FM Montney FM Belloy FM Stoddart GRP Taylor Flat FM Kiskatinaw FM Golata FM Rundle GRP Debolt FM Shunda FM Pekisko FM Banff FM Exshaw FM Wabamun FM Trout River FM Kakisa FM Redknife FM Jean Marie MBR Woodbend GRP Irteton FM Fort Simpson FM Leduc FM Duvernay FM Cooking Lake FM Beaverhill Lake GRP Waterways FM Swan Hills FM Fort Vermilion FM Elk Point GRP Watt Mountain FM Gillwood MBR Presqu’ile FM Sulphur Point FM Pine Point FM Muskeg FM Zama MBR Black Shale Keg River FM Rainbow MBR Chinchaga FM Cold Lake FM Ernestina FM Basal Red Beds Granite Wash Canadian Shield

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