Stonewall Formation
Stratigraphic range: Ashgill to Alexandrian PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Underlies	Interlake Group
Overlies	Stony Mountain Formation
Thickness	up to 34 metres (110 ft)[1]
Lithology
Primary	dolomite
Other	Sandstone, anhydrite
Location
Coordinates	50°07′07″N 97°43′26″W / 50.1186°N 97.7239°W / 50.1186; -97.7239 (Stonewall Formation)
Region	WCSB Williston Basin
Country	Canada
Type section
Named for	Stonewall, Manitoba
Named by	E.M. Kindle, 1914

The Stonewall Formation is a stratigraphical unit of Late Ordovician to Early Silurian age in the Western Canadian Sedimentary Basin.

It takes the name from Stonewall, Manitoba, and was first described in the Stonewall quarry by E.M. Kindle in 1914.^[2]

Lithology

The Stonewall Formation is composed of finely crystalline dolomite, with a basal argillaceous and sandy dolomite (the Williams Member). Two thin sandstone beds occur in the middle and at the top of the formation. ^[1] In the central Williston basin, the base is marked by an anhydrite bed.

Distribution

The Stonewall Formation occurs at surface in the Manitoba outcrop belt and in the sub-surface in the Williston Basin.^[1] It reaches a maximum thickness of 34 metres (110 ft).

Relationship to other units

The Stonewall Formation is overlain by the Interlake Group (conformably in the south, disconformably in the north) and sharply overlays the Stony Mountain Formation.^[1]