The Stonewall Formation is a

stratigraphical Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostrat ...

unit of

Late Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. T ...

to Early Silurian

age Age or AGE may refer to: Time and its effects * Age, the amount of time someone or something has been alive or has existed ** East Asian age reckoning, an Asian system of marking age starting at 1 * Ageing or aging, the process of becoming olde ...

in the

Western Canadian Sedimentary Basin The Western Canadian Sedimentary Basin (WCSB) underlies of Western Canada including southwestern Manitoba, southern Saskatchewan, Alberta, northeastern British Columbia and the southwest corner of the Northwest Territories. This vast sedimentary ...

. It takes the name from

Stonewall, Manitoba Stonewall is a town in the Canadian province of Manitoba with a population of 5,046 as of the 2021 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 ...

, and was first described in the Stonewall quarry by E.M. Kindle in 1914.Kindle, E.M., 1914. The Silurian and Devonian Section of Western Manitoba;

Geological Survey of Canada The Geological Survey of Canada (GSC; french: Commission géologique du Canada (CGC)) is a Canadian federal government agency responsible for performing geological surveys of the country, developing Canada's natural resources and protecting the e ...

, Summary Report 1912, pp. 247-261.

Lithology

The Stonewall Formation is composed of finely crystalline

dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

, with a basal argillaceous and sandy dolomite (the Williams Member). Two thin

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

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, or anhydrous calcium sulfate, is a mineral with the chemical formula 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 t ...

bed.

Distribution

The Stonewall Formation occurs at surface in the Manitoba outcrop belt and in the sub-surface in the

Williston Basin The Williston Basin is a large intracratonic sedimentary basin in eastern Montana, western North Dakota, South Dakota, southern Saskatchewan, and south-western Manitoba that is known for its rich deposits of petroleum and potash. The basin is a ...

. It reaches a maximum thickness of .

Relationship to other units

The Stonewall Formation is overlain by the

Interlake Group The Interlake Formation is a stratigraphical unit of Silurian age in the Western Canadian Sedimentary Basin. It takes the name from the Interlake Region in Manitoba, and was first described in outcrop by A.D. Baillie in 1951.Ballie, A.D., 195 ...

(conformably in the south, disconformably in the north) and sharply overlays the

Stony 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. Dowling in 1900 ...

References

{{Western Canadian Sedimentary Basin, Saskatchewan=yes Ordovician Alberta Ordovician Manitoba Ordovician Saskatchewan Silurian Alberta Silurian Manitoba Silurian Saskatchewan Western Canadian Sedimentary Basin Geologic formations of Manitoba Geologic formations of Saskatchewan Stonewall, Manitoba Ordovician southern paleotropical deposits Dolomite formations Sandstone formations of Canada