Unit Name: Cadomin Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Early Cretaceous (145.5 - 99.6 ma)
Province/Territory: Alberta; British Columbia

Originator: Mackay, 1929a, b, c; 1930.

Type Locality:
No type section specified by Mackay, but named for exposures in the vicinity of Cadomin, west-central Alberta (Sec. 5, Twp. 47, Rge. 23W5M).

Ranges from less than 1 m to over 170 m (3 to over 558 ft). Generally thicker and coarser to the west. Recognized in the foothills of Alberta and British Columbia between 49°N and about 56°30'N. Eastern limit appears to be an erosional escarpment trending slightly west of north (McLean, 1977a) and diverging from the foothills trend to the north. West of the escarpment the formation is recognized in the subsurface.

Characterized by conglomerate. Average clast size 1 to 5 cm (0.4 to 2 in), up to 40 cm (16 in). Matrix is generally fine- to coarse-grained sand, and cement is silica. Chert and quartzite are the predominant clast lithologies, but sandstone is present in some areas. The conglomerate is usually hard, resistant to erosion and forms prominent outcrops. More than one bed of conglomerate occurs in some sections, with interbedded sandstone, siltstone and mudstone, often with a high carbonaceous content and occasionally coal beds, particularly in sections north of the Smoky River. Average clast size generally thicker and coarser grained than overlying sandstone beds.

Rests disconformably on the Kootenay Group, Nikanassin Formation, Minnes Group and Fernie Group. Overlain abruptly to gradationally by the Gladstone and Gething formations. May be equivalent in part to the Cut Bank Sandstone of southern Alberta, the Deville (Detrital) and the Ellerslie formations in the central plains, and possibly the basal beds of the McMurray Formation in the northeastern Alberta Plains. The Cadomin replaces the name Dalhousie sandstone in the eastern foothills of southern Alberta.

First introduced by Mackay (1929) in the Cadomin area and correlated with the Blairmore Conglomerate of the southern Alberta Foothills. Use extended to the foothills of northeastern British Columbia (Alberta Study Group, 1954; Stott, 1960a).

* Parent is Blairmore Group in Alberta; Bullhead Group in Brtish Columbia.

Other Citations:
Stott, 1968b, 1973.

Alberta Study Group, 1954. Lower Cretaceous of the Peace River region. In: Western Canada Sedimentary Basin; Clark, L.M. (Ed.). Amer. Assoc. Petrol. Geol., p. 268-278.
Mackay, B.R., 1929a. Mountain Park Sheet, West of Fifth Meridian, Alberta; Geological Survey of Canada, "A" Series Map 208A, Scale: 1:63 360 or 1 Inch to 1 Mile.
Mackay, B.R., 1929b. Cadomin, Alberta; Geological Survey of Canada, Map 209A.
Mackay, B.R., 1929c. Brule Mines coal area, Alberta; Geological Survey of Canada, Summ. Rept. 1928, Part B, p. 1-29.
Mackay, B.R., 1930. Stratigraphy and structure of bituminous coal fields in the vicinity of Jasper Park, Alberta. Can. Inst. Min. and Metall., Trans., v. 33, p. 473-509.
McLean, J.R., 1977a. The Cadomin Formation; stratigraphy, sedimentology and tectonic implications; Canadian Society of Petroleum Geologists (CSPG), Bulletin of Canadian Petroleum Geology, vol. 25, no. 4 (August), pp. 792-827.
Stott, D.F., 1960a. Cretaceous rocks between Smoky and Pine rivers, Rocky Mountain Foothills, Alberta and British Columbia; Geological Survey of Canada, Paper 60-16.
Stott, D.F., 1968b. Lower Cretaceous Bullhead and Fort St. John groups, between Smoky and Peace rivers, Rocky Mountain Foothills, Alberta and British Columbia; Geological Survey of Canada, Bulletin 152, 279 p.
Stott, D.F., 1973. Lower Cretaceous Bullhead Group between Bullmoose Mountain and Tetsa River, Rocky Mountain Foothills, northeastem British Columbia; Geological Survey of Canada, Bulletin 219, 228 p. + 5 figures in back pocket.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: J.R. McLean
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 21 Jul 2009