Vanguard Formation

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

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)[1]
Lithology
Primary	Shale, sandstone
Location
Coordinates	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)

It takes the name from Vanguard, and was first defined by R.L. Milner and G.E. Thomas in 1954.^[2]

Lithology

The Vanguard Formation is composed of calcareous shale with a median quartzose sandstone. ^[1]

Distribution

The Vanguard Formation Lateral reaches a maximum thickness of 180 metres (590 ft) in the Williston Basin along the Saskatchewan/Montana border.^[1]

Relationship to other units

The Vanguard Formation is unconformably overlain by the Mannville Group and disconformably overlays the Shaunavon Formation.^[1]

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