Unit Name: Oldman Formation
Unit Type: Lithostratigraphic
Usage: Currently in use
Age Interval: Late Cretaceous (99.6 - 65.5 ma)
Province/Territory: Alberta; Saskatchewan
Originator: Russell and Landes, 1940.
Oldman River, from near confluence with St. Mary River 9.6 km (6 mi) south of Lethbridge, Alberta to the vicinity of Lethbridge.
The Oldman is 328 m (1,000 ft) thick at Lethbridge and thins to 122 m (400 ft) in eastern Alberta. The formation loses its identity in southwestern Saskatchewan, being replaced by shale.
The upper part (Lethbridge Member) consists of carbonaceous sandstones and shales, coal seams and one or more bentonitic beds near the top. The lower member, generally a fresh water deposit, consists of light grey sandstones and shales, with minor greenish, brown and reddish shales, and siltstones. The shales grade from sandy shale to argillaceous sandstone. The sandstones are generally weakly cemented and commonly weather to form "badland" topography. Grain sizes range from fine to coarse. Plant remains are common and the formation is world famous for dinosaurian remains.
The Oldman is underlain by the brackish water Foremost Formation and overlain by the marine Bearpaw Formation. To the west and north of the type area the Oldman and Foremost formations together constitute the Belly River Formation.
The Oldman Formation was known successively as the Pale and Yellow Beds and Pale Beds.
Crockford, 1949; Furnival, 1946; Powers, 1931; Russell and Landes, 1940; Thompson and Oxford, 1953.
Russell, L.S. and Landes, R.W., 1940. Geology of the southern Alberta Plains; Geological Survey of Canada, Memoir 221.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: ASPG Lexicon 1960
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 28 May 2008