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

Originator: Walcott, 1920.

Type Locality:
On the northern slopes of Sullivan Peak, Glacier Lake Valley, Banff National Park, Alberta.

Distribution:
As re-defined by Aitken and Greggs (1967) the Arctomys Formation is 235 m (771 ft) thick at the type section. It thickens northward to 336 m (1,100 ft) at Mount Robson; at Mount Assiniboine to the southeast it is 40 m (132 ft) thick; and at its most southerly recognized occurrence at White Man Mountain it is 102 m (335 ft) thick.

Locality Data:
Thickness(m): Minimum 40, Maximum 336, Typical 235.

Lithology:
Red, grey, green, platy shales, generally recessive weathering. The shales often exhibit mudcracks, ripple marks and salt casts.

Relationship:
The Arctomys is gradationally overlain by the Waterfowl Formation; its lower contact with the Pika Formation is also gradational.

History:
The Arctomys Formation was established by Walcott for a sequence of laminated limestones (now the Waterfowl Formation) underlain by a thicker succession of red and green shales. However, Walcott rarely adhered to his definition; he generally excluded the upper (Waterfowl) beds, or added Pika beds below. Later authors have settled on the lithologic usage described below (Aitken and Greggs, 1967).

References:
Aitken, J.D. and Greggs, R.G., 1967. Upper Cambrian formations, southern Rocky Mountains of Alberta, an interm report; Geological Survey of Canada, Paper 66-49, 91 p.
Walcott, C.D., 1920. Explorations and field work of the Smithsonian Institute in 1919. Smithsonian Miscellaneous Collections, vol. 72, no. 1, pp. 1-16.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: R.G. Greggs
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 28 Mar 2014