Unit Name: Bakken Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Kinderhookian (359.2 - 348 ma)
Province/Territory: Alberta; Manitoba; Saskatchewan; North Dakota; South Dakota; Wyoming
Originator: Williston Basin Correlations Committee, reported by Nordquist, W., 1953.
Type Locality:
The Amerada Bakken No. 1 well, in C SWNW, Sec. 12, Twp. 157N, Rge. 95W, in Williams County, North Dakota, between 2,930.6 and 2,962.7 m (9,615 and 9,720 ft).
Distribution:
Strata to which the name is applied are found in Manitoba, Saskatchewan and parts of Alberta, Montana, North and South Dakota, and Wyoming. It varies in thickness from a minimum of about 3 m (10 ft) to a maximum of about 40 m (131 ft).
Lithology:
A tripartite unit composed of a medial calcite, or rarely dolomite cemented fine, quartzose sandstone and siltstone with ripples, cross-bedding and flaser bedding, as well as interlamination of sandstone and claystone and local occurrences of oolitic calcarenite. The upper and lower members are black, organic rich shales that contain an impoverished fauna and flora dominated by conodonts, lingulids and palynomorphs. In parts of Alberta there is a basal sandstone as well.
Relationship:
For the most part the Bakken is disconformable with underlying strata regardless of whether they belong to the Upper Devonian Wabamun, Big Valley, Torquay or Three Forks formations, but its upper contact varies from conformable to unconformable with the superjacent Madison Group. The unconformity is recognized as a progressively deeper westward truncation of the members until the Madison lies directly on Lower Bakken. In Alberta the lower black shale and basal sandstone together form the Exshaw Formation. The Bakken is equivalent wholly or in part to the Englewood of the Dakotas, Montana and Wyoming, as well as to the Sappington of southwestern Montana.
Other Citations:
Brindle, 1960, Christopher, 1961; Harker and McLaren, 1958; MacQueen and Sandberg, 1970; Nordquist, 1953; Penner, 1958.
References:
Williston Basin Nomenclature Committee, 1953
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: D.M. Kent
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 12 Mar 2009