Hasler Formation

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)
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. It takes the name from the city of Fort St. John, British Columbia and was first defined by George Mercer Dawson in 1881.

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.

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).

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.

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

*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.