Unit Name: Vanguard Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Callovian - Oxfordian (164.7 - 155.6 ma)
Province/Territory: Saskatchewan
Originator: Milner, R.L. and Thomas, G.E., 1954.
Type Locality:
Southwestern Saskatchewan. No type section was defined; however, the authors divided the formation into three members, lower, middle and upper, with type sections. Christopher (1974) formally raised these members to formation status and the Vanguard to group status. The formations were named the Rush Lake Shale, Roseray Formation and Masefield Shale, and are described under those headings.
Distribution:
The Vanguard Formation lies generally south of Latitude 51 deg N in southern Saskatchewan. From the sub-Cretaceous erosional edge Its thickens to 180 m (590 ft) southward into the Williston Basin centre, along the border of Montana and North Dakota.
Locality Data:
Thickness(m): Minimum 0, Maximum 180.
Lithology:
The Vanguard Formation as a whole is dominantly a green-grey, variably calcareous shale, medially divided by a glauconitic, calcareous, fine-bedded, fine-grained quartzose sandstone corresponding to the middle member. The lower member is generally fossiliferous, containing mostly pelecypods, especially Gryphaea. The ammonite Kepplerites is found locally in southeastern Saskatchewan.
Relationship:
The Vanguard Formation overlies the Shaunavon Formation disconformably and is severely truncated under the Cretaceous Mannville Group. The base and contact is marked by a calcite-cemented sandstone less than 1 m (3 ft) thick, and an abundance of Gryphaea costidensus (nebrascensis). As a whole the formation correlates with the Ellis Group, made up of the Rierdon and Swift formations south of the International border.
Other Citations:
Christopher, 1974; Milner and Thomas, 1954.
References:
Christopher, J.E., 1974. The upper Jurassic Vanguard and Lower Cretaceous Mannville groups of southwestern Saskatchewan Saskatchewan Dept. Min. Res., Rept. 151.
Milner, R.L. and Thomas, G E., 1954. Jurassic System in Saskatchewan. In: Western Canada Sedimentary Basin Amer. Assoc. Petrol. Geol., p. 250-267
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.E. Christopher
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 16 Feb 2009