Red River Formation

The Red River Formation is a stratigraphical unit of Late Ordovician age in the Williston Basin.

Red River Formation
Stratigraphic range: Caradoc to Ashgill
TypeGeological formation
Sub-unitsFort Garry Member
Selkirk Member
Cat Head Member
Dog Head Member
UnderliesStony Mountain Formation
OverliesWinnipeg Formation
Thicknessup to 215 metres (710 ft)[1]
Lithology
Primarylimestone, dolomite
OtherBreccia
Location
Coordinates51.9482°N 98.0563°W / 51.9482; -98.0563 (Red River Formation)
RegionWCSB
Williston Basin
Country Canada
 United States
Type section
Named forRed River of the North
Named byA.F. Foerste
Year defined1929

It takes the name from the Red River of the North, and was first described in outcrop in the Tyndall Stone quarries and along the Red River Valley by A.F. Foerste in 1929.[2][3]

Lithology

Subdivisions

The Red River Formation is composed of the following subdivisions from top to base: [1]

  • 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

Distribution

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.[1]

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.[1]

The lower Red River Formation is equivalent to the Yeoman Formation, while the Fort Garry Member correlates with the Herald Formation.

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References
  1. Lexicon of Canadian Geologic Units. "Formation". Archived from the original on 2009-04-16. Retrieved 2010-02-01.
  2. 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.
  3. Foerste, A.F., 1929b. The cephalopods of the Red River Formation of southern Manitoba. Denison Univ. Sci. Lab J., v. 24, p. 129-235.
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