Unit Name: Fort St. John Group
Unit Type: Lithostratigraphic
Usage: Currently in use
Age Interval: ? Albian - younger (112 - 0 ma)
Province/Territory: Alberta; British Columbia; Northwest Territories; Yukon Territory
Originator: Dawson, G.M., 1881.
Northeastern British Columbia. For specific localities refer to included formations.
The thickness of the Fort St. John has been reported as being 700 to 2,000 m (2,300 to 6,500 ft). It is present over large areas of the Peace and Pine river foothills of northeastern British Columbia and Alberta, north to the Liard River valley and into the Kotaneelee River area of the Yukon and Northwest Territories.
The group consists mainly of dark marine shales which may be concretionary. These shales may be gypsiferous and at places contain bentonite beds. They are interbedded with fine to coarse grained sandstones (some of which are glauconitic), siltstones and chert-pebble conglomerates.
The group overlies the Bullhead Group or may be in unconformable contact with older Paleozoic sediments. The upper contact is with the Dunvegan Formation (Upper Cretaceous). The Fort St. John Group consists of the following formations: Foothills, northeastern British Columbia, Cruiser, Goodrich, Hasler, Commotion, Gates, Moosebar; Peace River Plains, Shaftesbury, Peace River, Spirit River, Bluesky; Liard River Area, Sully, Sikanni, Lepine, Scatter, Garbutt; Fort Liard, N.W.T., Sully, Sikanni, Lépine, Scatter, Garbutt.
Dawson (1881) originally referred the "lower dark shales" of the Peace and Pine River valleys to the Fort St. John shales. McLearn (1918) defined the St. John Formation to include all strata between the Bull Head Mountain sandstone below and Dunvegan sandstones above. McLearn (1932) revised this and included only strata found between the Gates Formation and the Dunvegan Formation. Wickenden and Shaw (1943) reverted to McLearn's (1918) interpretation and raised the Fort St. John to group status.
Anan-Yorke and Stelck, 1978; Dawson, 1881; Douglas and Norris, 1959; Hage, 1944; McLearn, 1918, 1932; McLearn and Kindle, 1950; Stott, 1960, 1968a, 1968b; Wickenden and Shaw, 1943
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: D.R. Braman; D.F. Stott
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 18 May 2004