Unit Name: Big Valley Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Famennian (374.5 - 359.2 ma)
Province/Territory: Alberta; Saskatchewan; Montana
Originator: Wonfor and Andrichuk, 1953, 1956.
Type Locality:
Canadian Gulf Rumsey 6-30-33-21W4M, in Alberta, between 1,600.2 and 1,613.9 m (5,250 and 5,295 ft).
Distribution:
The Big Valley Formation averages 15 to 20 m (49 to 66 ft) in thickness in southwestern Saskatchewan and southern Alberta, thickening to 30 to 40 m (98 to 131 ft) in the mountains (Banff-Jasper area), where it is referred to the Costigan Member of the Palliser Formation. To the north it passes into the undifferentiated Wabamun Group; to the south it forms part of the Three Forks of Montana. Locally, in southwestern Alberta facies changes (dolomitization, evaporites) preclude identification of the unit.
Lithology:
Grey, tan and brown micritic limestone, locally bioclastic and commonly fossiliferous (brachiopods, etc.). The limestones are variable, argillaceous and interbeds of grey and green shale occur increasingly toward southeastern Alberta. Chert nodules are locally present. The limestones are variably dolomitized in the Calgary area.
Relationship:
Conformably overlies the Stettler Formation in southern Alberta or the Torquay Formation is southwestern Saskatchewan; the change from dolomites and/or evaporites of the underlying formations to limestones and argillaceous beds of the Big Valley being usually distinctive. The contact with the overlying black share of the Exshaw (Bakken) is abrupt, and may be disconformable Post-Paleozoic erosion has truncated the Big Valley to the northeast; where the Big Valley subcrops it may be overlain by Mesozoic sands and shales.
Other Citations:
Andrichuk, 1960; Andrichuk and Wonfor, 1954; Beales, 1956; Belyea, 1955, 1957, 1964; Raasch, 1956; Sutterlin, 1958; Wonfor and Andrichuk, 1953, 1956.
References:
Wonfor, J.S. and Andrichuk, J.M., 1953. Upper Devonian geologic history in Stettler area, Alberta, Canada, Abstracts of papers submitted for the November meeting in Toronto, Canada. Anonymous, Bulletin of the Geological Society of America, December 1953, Vol. 64, Issue 12, Part 2, pp. 1390-1391
Wonfor, J.S. and Andrichuk, J.M., 1956. The Wabamun Group in the Stettler area; J. Alberta Petrol. Geol., vol .4, pp. 99-111.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: F.A. Stoakes; J. Wendte; J.M. Andrichuk
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 30 Mar 2009