Stony Mountain Formation
The Stony Mountain Formation is a stratigraphical unit of Ashgill age in the Western Canadian Sedimentary Basin.
| Stony Mountain Formation | |
|---|---|
| Stratigraphic range: | |
| Type | Geological formation |
| Underlies | Stonewall Formation |
| Overlies | Red River Formation |
| Thickness | up to 45 metres (150 ft)[1] |
| Lithology | |
| Primary | dolomite, shale |
| Other | Anhydrite, limestone |
| Location | |
| Coordinates | 49.9184°N 97.5265°W |
| Region | WCSB Williston Basin |
| Country | .svg.png.webp){kind=small} Canada United States |
| Type section | |
| Named for | Stony Mountain, Manitoba |
| Named by | D.B. Dowling, 1900 |
It takes the name from the community Stony Mountain, Manitoba, and was first described in the town quarry by D.B. Dowling in 1900.[2]
Lithology
Subdivisions
The Stony Mountain Formation is divided in the following sub-units: [1]
- South (Williston Basin)
- Penitentiary Member: argillaceous dolomite
- Gunn Member: interbedded calcareous shale and fossiliferous limestone
- North
- Gunton Member: crystalline dolomite
- Lower Stony Mountain: argillaceous dolomite
Distribution
The Stony Mountain Formation occurs throughout the Williston Basin.[1] It reaches a maximum thickness of 45 metres (150 ft) in the sub-surface at the Canada/United States border, and thins out towards the east, north and west. In Manitoba, where it is exposed at the surface in the erosion belt, it has a thickness of 30 metres (100 ft).
Relationship to other units
The Stony Mountain Formation is slightly unconformably overlain by the Stonewall Formation and sharply overlays the Red River Formation or the Herald Formation.[1]
References
- Lexicon of Canadian Geologic Units. "Stony Mountain Formation". Retrieved 2010-02-04.
- Dowling, D.B., 1900. Report on the Geology of the West Shore and Islands of Lake Winnipeg; Geological Survey of Canada, Annual Report 1898, Volume XI, Part F, with Map 664.