Type Locality:

In the vicinity of Cowles Lake (65°57'N, 113°17'W), District of Mackenzie.

Distribution:

From 3,000 to 6,000 m (10,000-20,000 ft). It is found in the Bear Province of the Canadian Shield, south of Coronation Gulf.

Lithology:

Fraser and Tremblay (1969) and Fraser (1974) subdivided the group into five formations. In ascending order these are: 1) Odjick Formation, 640-2,300 m (2,100-7,500 ft); predominantly thick-bedded quartzite and interlayered, argillite with a few beds of carbonate and quartz-pebble conglomerate and locally, andesitic flows; 2) Rocknest Formation, 700-1,700 m (2,300-5,500 ft), principally thick-bedded dolomite interbedded with argillite; 3) Recluse Formation, 600-1,900+ m (2,000-6,500+ ft); red and black shale and slate, concretionary argillite, thick-bedded greywacke, and siltstone; 4) Cowles Lake Formation, about 800 m (2670 ft); medium- to thick-bedded grey limestone and grey or red argillite, intercalated with finely interlaminated limestone and argillite; and 5) Takiyuak Formation, 400+ m (1,200+ ft); uniform, reddish feldspathic to lithic arenite and siltstone.

Relationship:

The Epworth Group rests unconformably (angular) on Archean rocks. It is laterally equivalent to the Goulburn Group and to the Great Slave Supergroup. It is, in part, unconformably overlain by the Hornby Bay Group.

Remark:

Hoffman (1981a) proposed to elevate the rank of the "Recluse Formation" (Fraser, 1974) to that of a group, retaining its original stratigraphic limits. Instead of elevating the rank of the venerable name "Epworth" to a supergroup, Hoffman (1981a) proposed that they return to O'Neill's well-described original definition (O'Neill, 1924, p. 21-2, 45-7), that is the Odjick and Rocknest formations, but retain its current rank as Epworth Group. It is considered to be part of the Coronation Supergroup (Hoffman, 1981a).

Other Citations:

Fraser, 1964; Fraser et al., 1970; Hoffman, 1973b.

References:

Fraser, J.A. and Tremblay, L.P., 1969. Correlation of Proterozoic strata in the northwestern Canadian Shield; Canadian Journal of Earth Sciences = Journal Canadien des Sciences de la Terre, vol. 6, no. 1, pp. 1-9.

Fraser, J.A., 1964. Geological notes on northeastern District of Mackenzie, Northwest Territories: Geological Survey of Canada, Paper 63-40, 20 p.

Fraser, J.A., 1974. The Epworth Group Rocknest area, District of Mackenzie; Geological Survey of Canada, Paper 73-39, 23 p.

Fraser, J.A., Donaldson, J.A., Fahrig, W.F., and Tremblay, L.P., 1970. Helikian basins and geosynclines of the northwestern Canadian Shield, pp. 213-238: in Baer, A.J. (ed.), Symposium on basins and geosynclines of the Canadian Shield, Geological Survey of Canada, Paper 70-40, 265 p.

Hoffman, P.F., 1973b. Evolution of an early Proterozoic continental margin; the Coronation Geosyncline and associated aulacogens of the northwestern Canadian Shield: Philosophical Transactions Royal Society London, Series A, vol. 273, pp. 547-581.

Hoffman, P.F., 1981a. Revision of stratigraphic nomenclature, foreland thrust-fold belt of Wopmay Orogen, District of Mackenzie; in Current Research, Part A, Geological Survey of Canada, Paper 81-1A, p. 247-250.

O'Neill, J.J., 1924. Report of the Canadian Arctic Expedition 1913-1918, v. II: Geology and Geography, Part A: The geology of the Arctic coast of Canada, west of the Kent Peninsula, Government Printer, Ottawa, pp. 1A-107A.