Stony Mountain Formation

Short description: Stratigraphical unit of Ashgill age

Stony Mountain Formation
Stratigraphic range: Ashgill

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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°55′06″N 97°31′35″W﻿ / ﻿49.9184°N 97.5265°W﻿ / 49.9184; -97.5265﻿ (Stony Mountain Formation)
Region| WCSB
Williston Basin
Country|  Canada
United States
Type section
Named for| Stony Mountain, Manitoba
Named by| D.B. Dowling, 1900

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

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]

## Contents

* 1 Lithology
* 1.1 Subdivisions
* 2 Distribution
* 3 Relationship to other units
* 4 References

## 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

1. ↑ 1.0 1.1 1.2 1.3 Lexicon of Canadian Geologic Units. "Stony Mountain Formation". http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:014604. 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.

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