Stony Mountain Formation

(Redirected from Gunn Member)

The Stony Mountain Formation is a stratigraphical unit of Ashgill age in the Western Canadian Sedimentary Basin.

Stony Mountain Formation
Stratigraphic range: Ashgill
TypeGeological formation
UnderliesStonewall Formation
OverliesRed River Formation
Thicknessup to 45 metres (150 ft)[1]
Lithology
Primarydolomite, shale
OtherAnhydrite, limestone
Location
Coordinates49°55′06″N 97°31′35″W / 49.9184°N 97.5265°W / 49.9184; -97.5265 (Stony Mountain Formation)
RegionWCSB
Williston Basin
Country Canada
 United States
Type section
Named forStony Mountain, Manitoba
Named byD.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

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Subdivisions

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The Stony Mountain Formation is divided in the following sub-units: [1]

South (Williston Basin)
North
  • Gunton Member: crystalline dolomite
  • Lower Stony Mountain: argillaceous dolomite

Distribution

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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

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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

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  1. ^ a b c d Lexicon of Canadian Geologic Units. "Stony Mountain Formation". Retrieved 2010-02-04.
  2. ^ 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.