Unit Name: Charlie Lake Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Carnian (228.7 - 216.5 ma)
Province/Territory: Alberta; British Columbia

Originator: Clark, 1957.

Type Locality:
In the subsurface Peace River Plains of northeastern British Columbia, Pacific Fog St. John No. 16 well, in 2-18-84-19W6M, between 1,297.2 and 1,575.2 m (4,256 and 5,168 ft). Surface reference section at Brown Hill, on the north side of Peace River-Williston Lake Reservoir, NTS 11-E/ 94-B-2 (Colquhoun, 1962).

Attains a thickness of 405 m (1,328 ft) in foothills exposures near the headwaters of Schooler Creek, north of the Williston Lake Reservoir. In the subsurface foothills and plains the Charlie Lake varies from zero in the extreme east and north to over 550 m (1,804 ft) adjacent to the foothills south of Peace River. Thinning to east is in part due to erosional effects and in part to deposition. The Charlie Lake occurs in the Peace River Plains as far east as Grande Prairie and in foothills exposures between the Muskwa and Sukunka rivers. Hess (1968) demonstrated an approximate mid-Charlie Lake unconformity at the base of the Coplin Member, effecting a division between an 'upper' and 'lower' Charlie Lake. Generally the lower Charlie Lake sediments dip southwest at a considerably greater rate, displaying the angular nature of the "Coplin Unconformity". Hess stated that it "is the most pronounced break in upper Triassic sedimentation in northeast British Columbia. It progressively truncates from southwest to northeast every member of the lower Charlie Lake and, in turn, is truncated by the Pre-Cretaceous Unconformity. It seems reasonable to assume that the Coplin Unconformity also truncated the Halfway, however, there is no way of knowing for certain since this part of the Triassic section was removed by Pre-Gething erosions."

Foothills exposures consist of a variable sequence of yellowish brown to yellow pale grey to orange-brown weathering, dolomitic to calcareous sandstone, siltstone, sandy limestone, dolostone and lesser amounts of intraformational and/or solution breccia. In the subsurface plains to the east the formation is dominated by massive anhydrites, red dolomitic siltstones, evaporitic dolomites and minor halite. The Charlie Lake displays a transition from evaporitic facies in the east to sandstone and carbonate facies in the west. In the subsurface several oil and gas producing members have been defined - the Coplin, Inga, Boundary Lake and Nancy (Fitzgerald and Peterson, 1967; Armitage, 1962; and Hess, 1968). Members are not recognized with any degree of certainty in foothills exposures.

The Charlie Lake Formation is gradationally overlain in exposures by pale grey weathering, cliff forming limestone and calcareous dolostone of the Baldonnel Formation north of the Peace River-Williston Lake Reservoir area. Between the Peace River-Williston Lake Reservoir and Sukunka River it is abruptly overlain by dark greyish brown weathering limestone and dolomitic siltstone of the Ducette Member of the Baldonnel Formation. In the subsurface it is overlain by secondary dolomites of the Baldonnel Formation. In easternmost areas it is unconformably overlain by the Jurassic Fernie Formation and in northern regions, by the Cretaceous Fort St. John Group. It is gradationally underlain in the foothills by pale to medium grey to yellowish grey sandstone, siltstone and lesser dolostone of the Liard Formation. It is conformably underlain in the subsurface plains and eastern foothills by the Halfway Formation, except in the far east, where it rests disconformably on the Doig Formation (formerly referred to as the Toad-Grayling Formation). The formation is equivalent to the lower half to two thirds of the deeper water Ludington Formation to the west and northwest. In the Jasper-Banff area of Alberta it is equivalent to the Starlight Evaporite Member of the Whitehorse Formation. It is part of Schooler Creek Group.

Name proposed by Clark (1957) for subsurface unit in Fort St. John area of northeastern British Columbia. Name formally proposed and type section designated by Hunt and Ratcliffe (1959). Facies recognized and name extended to include foothills exposures between Muskwa and Sukunka rivers by Pelletier (1964), Colquhoun (1962) and Gibson (1971, 1975).

Other Citations:
Armitage, 1962; Clark, 1957; Colquhoun, 1962; Fitzgerald and Peterson, 1967; Gibson, 1971, 1975; Hess, 1968; Hunt and Ratcliffe, 1959; Pelletier, 1964.

Clark, L.M., 1957. Fort St. John sets pace for Peace River gas fields; Oil and Gas Journal, vol. 55, no. 33, pp. 132-144.
Colquhoun, D.J., 1962. Triassic stratigraphy in the vicinity of Peace River Foothills, British Columbia; in, 4th Annual Field Trip Guidebook; Edmonton Geololgical Society, pp. 57-88.

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.W. Gibson
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 03 Nov 2009