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Vanguard Formation
Stratigraphic range: Callovian to Oxfordian PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Sub-units	Masefield Shale Roseray Formation Rush Lake Shale
Underlies	Mannville Group
Overlies	Shaunavon Formation
Thickness	up to 180 metres (590 ft)
Lithology
Primary	Shale, sandstone
Location
Coordinates	49°22′N 107°47′W / 49.36°N 107.79°W / 49.36; -107.79 (Vanguard Formation)
Region	WCSB, Williston Basin
Country	Canada  United States
Type section
Named for	Vanguard, Saskatchewan
Named by	Milner & Thomas
Year defined	1954
Vanguard Formation (Canada)

The Vanguard Formation is a stratigraphical unit of Callovian to Oxfordian age in the Western Canadian Sedimentary Basin.

It takes the name from Vanguard, and was first defined by R.L. Milner and G.E. Thomas in 1954.

Lithology

The Vanguard Formation is composed of calcareous shale with a median quartzose sandstone.

Distribution

The Vanguard Formation Lateral reaches a maximum thickness of 180 metres (590 ft) in the Williston Basin along the Saskatchewan/Montana border.

Relationship to other units

The Vanguard Formation is unconformably overlain by the Mannville Group and disconformably overlays the Shaunavon Formation.

It is equivalent to the Ellis Group in Montana and North Dakota.

Subdivisions

In south-western Saskatchewan, Vanguard has group status, and includes the following subdivisions (of formation rank):

• Masefield Shale: calcareous shale
• Roseray Formation: quartzose glauconitic sandstone
• Rush Lake Shale: calcareous shale with Gryphaea and Kepplerites ammonite fossils

References

1. ^ Lexicon of Canadian Geologic Units. "Vanguard Formation". Retrieved 2010-01-01.
2. Milner, R.L. and Thomas, G E., 1954. Jurassic System in Saskatchewan. In: Western Canada Sedimentary Basin. American Association of Petroleum Geologists, p. 250-267

• Geologic formations of Saskatchewan
• Shale formations
• Jurassic Saskatchewan
• Oil-bearing shales in Canada
• Western Canadian Sedimentary Basin