Red River Formation
|Red River Formation
Stratigraphic range: Caradoc to Ashgill
|Sub-units||Fort Garry Member
Cat Head Member
Dog Head Member
|Underlies||Stony Mountain Formation|
|Thickness||up to 215 metres (710 ft)|
|Named for||Red River of the North|
|Named by||A.F. Foerste, 1929|
The Red River Formation is composed of the following subdivisions from top to base: 
- Fort Garry Member: crystalline and micritic dolomite with an argillaceous dolomite breccia in the middle
- Selkirk Member: fossiliferous dolomitic limestone
- Cat Head Member: cherty dolomite, becoming calcareous to the south
- Dog Head Member: fossiliferous dolomitic limestone
The Red River Formation reaches a maximum thickness of 215 metres (710 ft) in the center of the Williston Basin. At the along the Manitoba outcrop belt, it is 150 metres (490 ft) thick and thins out northwards.
Relationship to other units
The Red River Formation is slightly unconformably overlain by the Stony Mountain Formation and sharply overlays the Winnipeg Formation in Manitoba, the Deadwood Formation in western Saskatchewan and the Canadian Shield in northern Manitoba.
- Lexicon of Canadian Geologic Units. "Formation". Retrieved 2010-02-01.
- Foerste, A.F., 1929. The Ordovician and Silurian of the American arctic and sub-arctic regions. Denison Univ. Sci. Lab J., v. 24, p. 27-79.
- Foerste, A.F., 1929b. The cephalopods of the Red River Formation of southern Manitoba. Denison Univ. Sci. Lab J., v. 24, p. 129-235.