Stony Mountain Formation
Encyclopedia
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.
South (Williston Basin
)
North
. It reaches a maximum thickness of 45 metres (147.6 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 (98.4 ft).
overlain by the Stonewall Formation
and sharply overlays the Red River Formation
or the Herald Formation
.
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
unit of Ashgill age
Geochronology
Geochronology is the science of determining the age of rocks, fossils, and sediments, within a certain degree of uncertainty inherent to the method used. A variety of dating methods are used by geologists to achieve this, and schemes of classification and terminology have been proposed...
in the Western Canadian Sedimentary Basin
Western Canadian Sedimentary Basin
The Western Canadian Sedimentary Basin is a vast sedimentary basin underlying of Western Canada including southwestern Manitoba, southern Saskatchewan, Alberta, northeastern British Columbia and the southwest corner of the Northwest Territories. It consists of a massive wedge of sedimentary rock...
.
It takes the name from the community Stony Mountain, Manitoba
Stony Mountain, Manitoba
Stony Mountain is a small community in Manitoba, Canada located approximately north of Winnipeg on Provincial Highway 7. The town is located in the Rural Municipality of Rockwood and is the location of Stony Mountain Ski Area...
, and was first described in the town quarry by D.B. Dowling in 1900.
Subdivisions
The Stony Mountain Formation is divided in the following sub-units:South (Williston Basin
Williston Basin
The Williston Basin is a large intracratonic sedimentary basin in eastern Montana, western North and South Dakota, and southern Saskatchewan known for its rich deposits of petroleum and potash. The basin is a geologic structural basin but not a topographic depression; it is transected by the...
)
- Penitentiary Member: argillaceous dolomiteDolomiteDolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
- Gunn Member: interbedded calcareous shaleShaleShale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
and fossilFossilFossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
iferous limestoneLimestoneLimestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
North
- Gunton Member: crystalline dolomite
- Lower Stony Mountain: argillaceous dolomite
Distribution
The Stony Mountain Formation occurs throughout the Williston BasinWilliston Basin
The Williston Basin is a large intracratonic sedimentary basin in eastern Montana, western North and South Dakota, and southern Saskatchewan known for its rich deposits of petroleum and potash. The basin is a geologic structural basin but not a topographic depression; it is transected by the...
. It reaches a maximum thickness of 45 metres (147.6 ft) in the sub-surface at the Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
/United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
border, and thins out towards the east, north and west. In Manitoba
Manitoba
Manitoba is a Canadian prairie province with an area of . The province has over 110,000 lakes and has a largely continental climate because of its flat topography. Agriculture, mostly concentrated in the fertile southern and western parts of the province, is vital to the province's economy; other...
, where it is exposed at the surface in the erosion belt, it has a thickness of 30 metres (98.4 ft).
Relationship to other units
The Stony Mountain Formation is slightly unconformablyUnconformity
An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe...
overlain by the Stonewall Formation
Stonewall Formation
The Stonewall Formation is a stratigraphical unit of Late Ordovician to Early Silurian age in the Western Canadian Sedimentary Basin.It takes the name from Stonewall, Manitoba, and was first described in the Stonewall quarry by E.M...
and sharply overlays the Red River Formation
Red River Formation
The Red River Formation is a stratigraphical unit of Upper Ordovician age in the Western Canadian Sedimentary Basin.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...
or the Herald Formation
Herald Formation
The Herald Formation is a stratigraphical unit of Late Ordovician age in the Western Canadian Sedimentary Basin.It was defined in well Imperial Herald 1-31-1-20W2M by the Lower Paleozoic Names and Correlations Committee of the Saskatchewan Geological Society in 1958.-Lithology:The Herald Formation...
.