Stonewall Formation
Encyclopedia
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. Kindle in 1914.
, with a basal argillaceous and sandy dolomite (the Williams Member). Two thin sandstone
beds occur in the middle and at the top of the formation.
In the central Williston basin, the base is marked by an anhydrite
bed.
. It reaches a maximum thickness of 34 metres (111.5 ft).
.
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 Late Ordovician to Early Silurian 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 Stonewall, Manitoba
Stonewall, Manitoba
Stonewall is a town in the Canadian province of Manitoba with a population of 4,376 as of the 2006 census. The town is situated approximately north of Winnipeg on PTH 67. It is known for its limestone quarries. The local festival is the Quarry Days which is usually held over three days in August...
, and was first described in the Stonewall quarry by E.M. Kindle in 1914.
Lithology
The Stonewall Formation is composed of finely crystallinedolomiteDolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
, with a basal argillaceous and sandy dolomite (the Williams Member). Two thin sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
beds occur in the middle and at the top of the formation.
In the central Williston basin, the base is marked by an anhydrite
Anhydrite
Anhydrite is a mineral – anhydrous calcium sulfate, CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the orthorhombic barium and strontium sulfates, as might be expected from the...
bed.
Distribution
The Stonewall Formation occurs at surface in the Manitoba outcrop belt and in the sub-surface in 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 34 metres (111.5 ft).
Relationship to other units
The Stonewall Formation is overlain by the Interlake Group (conformably in the south, disconformably in the north) and sharply overlays the Stony Mountain FormationStony Mountain Formation
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...
.