Unit Name: Bear Rock Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Late Silurian - Middle Devonian (422.9 - 385.3 ma)
Age Justification: Fauna virtually nonexistent; some ostracodes (Moellaritia canadensis), brachiopods and colonial corals.
Province/Territory: Northwest Territories

Originator: Hume and Link, 1945.

Type Locality:
Type section is in the Canol area on Bear Rock which is at the junction of the Great Bear and Mackenzie rivers at Fort Norman, Northwest Territories. (Ca. 64 deg 56'N, 125 deg 45'W).

Distribution:
The Bear Rock is 66 to 90 m (215 to 295 ft) thick at the type section and reaches a maximum subsurface thickness of more than 1,500 m (4,920 ft) in the Candel et al. Dahadinni M-43A and IOE et al. Dahadinni I-70 wells in the Dahadinni map-area (95N). The Bear Rock Fm is not mapped south of 62 deg 30'N or west of 130 deg W and is bounded eastward by the Canadian Shield. Northward it does not extend beyond about 68 deg N. Over most of its extent the Bear Rock is about 305 to 763 m (1,000-2,500 ft) thick.

Lithology:
At the type section the Bear Rock is subdivided into three parts; a lower part of white weathering gypsiferous lensing dolomite, a thin middle part of indistinctly bedded grey dolomite and limestone and a thick upper part of dolomitic limestone breccia. South and west of the type section in the Mackenzie Mountains, the Bear Rock is almost entirely limestone breccia in outcrop with no evaporites. In the subsurface the Bear Rock is a sequence of interbedded anhydrite and dolomite (Law, 1971).

Relationship:
The Bear Rock unconformably overlies the Mount Kindle Fm and in places the Delorme Fm and is overlain by the Hume Fm and Ebbutt Member of the Willow Lake Fm. Westward the Bear Rock passes to the Arnica, Landry and Manetoe Formations and southward to the lower part of the Chinchaga Fm. Northward it passes to limestone of the Gossage Fm. It, along with the Franklin Mountain Fm, is unconformably overlain by the Gilmore Lake Member (Langton Bay Fm) in parts of the Anderson Plain Area. The Fitzgerald Fm is probably equivalent to part of the Bear Rock.

Other Citations:
Balkwill and Yorath, 1970a, 1970b; Cook and Aitken, 1971; Douglas and D.K. Norris, 1961; Gabrielse et al., 1973; Hume and Link, 1945; Law, 1971; Lawrence, 1973; Perry and Lenz, 1978.

References:
Hume, G.S. and Link, T.A., 1945. Canol geological investigations in the Mackenzie River area, Northwest Territories and Yukon (Report and Three Maps); Geological Survey of Canada, Paper 45-16, 87 p. + Preliminary Map 45-16A, Lower Mackenzie River Area, Northwest Territories and Yukon, Sheet 1, Scale: 1 inch to 8 miles; Preliminary Map 45-16B, Lower Mackenzie River Area, Northwest Territories and Yukon, Sheet 2, Scale: 1 inch to 8 miles; and Preliminary Map 45-16C, Lower Mackenzie River Area, Northwest Territories and Yukon, Sheet 3, Scale: 1 inch to 8 miles.
Law, James, 1971. Regional Devonian geology and oil and gas possibilities, upper Mackenzie River area; Canadian Society of Petroleum Geologists (CSPG), Bulletin of Canadian Petroleum Geology, vol. 19, no. 2 (June), pp. 437-484.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 2, Yukon Territory and District of Mackenzie; L.V. Hills, E.V. Sangster and L.B. Suneby (editor)
Contributor: L.V. Hills; D.W. Morrow
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 19 Mar 2009