Unit Name: Ross Lake Shale
Unit Type: Lithostratigraphic
Rank: Undefined
Status: Formal
Usage: Currently in use
Age Interval: Middle Cambrian (513 - 499 ma)
Province/Territory: Alberta; British Columbia

Originator: Walcott, C.D., 1917a, p. 4.

Type Locality:
Cliffs on east side of Ross Lake, 6.5 km (4 mi) northwest of Lake Louise, Alberta, at 51 deg 26'N, 116 deg 18'W.

Distribution:
The Ross Lake is 2.4 m (8 ft) thick at the type section. Westward, it pinches out before reaching the crest of the Kicking Horse Rim. Eastward, it thickens to 7.8 m (26 ft) near Clearwater Pass before merging with the Mount Whyte Formation. Northward, along the structural grain it thickens to 78.2 m (257 ft) in the Chaba River section near Fortress Lake, before passing into the Snake Indian Formation (equivalent to the Cathedral).

Lithology:
At and near the type section grey-green shale with a few limestone nodules; highly fossiliferous. Thickens northward and becomes an alternation of shale units with thin bedded lime mudstone units, arranged in small scale cycles. It is recessive weathering relative to the limestones above and below.

Relationship:
The Ross Lake Member may be regarded as a tongue of the largely detrital Mount Whyte Formation that extends westward into the carbonate mass of the Cathedral Formation. It is the central unit of the Cathedral, and is underlain and overlain by unnamed members.

History:
Erected by Walcott as a member of the Ptarmigan Formation (abandoned). Deiss (1939) and subsequent workers have treated the Ross Lake as the middle member of the Cathedral Formation.

Other Citations:
Aitken, 1971; Deiss, 1939; Rasetti, 1951; Walcott, 1917a.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: L.V. Hills; J.D. Aitken
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 29 Apr 2003