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. 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 to .

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

Peace River Country

Liard River and Fort Liard, Northwest Territories, Fort Liard Area

*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

{{Western Canadian Sedimentary Basin, Northwest_Plains=yes, Fort_Nelson=yes, Liard_River=yes Lower Cretaceous Series of North America Cretaceous Alberta Cretaceous British Columbia Cretaceous Northwest Territories Cretaceous Yukon Geologic groups of Alberta Geologic groups of British Columbia Geologic groups of the Northwest Territories Geologic groups of Yukon Shale groups of Canada Siltstone groups Sandstone groups of Canada Conglomerate groups