The Manitoba Group 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: lithostrati ...

unit of middle to late

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

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 older ...

in the Western Canadian Sedimentary Basin. The group takes its name from the province of Manitoba, and was first defined by A.D. Baillie in 1953.

Lithology

The Manitoba Group is composed of alternating cycles of

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

, carbonate and evaporite.

Distribution

The Manitoba Group occurs in outcrop in southwestern Manitoba and in the sub-surface in southern Saskatchewan, North Dakota and Montana. It reaches a maximum thickness of in outcrop and up to in the sub-surface.

Subdivisions

The following formationas are recognised, from top to bottom: *The Souris River Formation appears in the upper part of the Manitoba Group, is of Givetian to

Frasnian The Frasnian is one of two faunal stages in the Late Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Givetian Stage and followed by the Famennian Stage. Major reef-building was under way during th ...

age and consists of thin shale-carbonate-evaporite cycles. *The Hubbard Evaporite is recognised at the top of the Montana Group in the Elk Point Basin. Its age is Givetian *The Dawson Bay Formation is the lower part of the Manitoba Group. It is of Givetian age and consists of red shale (the "Second Red Bed") and a sequence of limestone and

dolomitic Dolomite () is an anhydrous carbonate mineral composed of calcium magnesium carbonate, ideally The term is also used for a sedimentary carbonate rock composed mostly of the mineral dolomite. An alternative name sometimes used for the dolomiti ...

limestone.

Relationship to other units

The Manitoba Group is conformably overlain by the Duperow Formation and disconformably overlays the

Prairie Evaporite Formation The Prairie Evaporite Formation, also known as the Prairie Formation, is a geologic formation of Middle Devonian (Givetian) age that consists primarily of halite (rock salt) and other evaporite minerals. It is present beneath the plains of north ...

Winnipegosis Formation The Elk Point Group is a stratigraphic unit of Early to Middle Devonian age in the Western Canada and Williston sedimentary basins. It underlies a large area that extends from the southern boundary of the Northwest Territories in Canada to North ...

of the

Elk Point Group The Elk Point Group is a stratigraphic unit of Early to Middle Devonian age in the Western Canada and Williston sedimentary basins. It underlies a large area that extends from the southern boundary of the Northwest Territories in Canada to Nor ...

. The lower Manitoba Group is equivalent to the

Muskeg Formation The Muskeg Formation is a geologic formation of Middle Devonian (Givetian) age in the Western Canada Sedimentary Basin. It extends from the plains of northwestern Alberta to northeastern British Columbia, and includes important petroleum and natur ...

in northern Alberta, while the upper part correlates with the Beaverhill Lake Formation.

References

{{Western Canadian Sedimentary Basin, Saskatchewan=yes Geologic groups of Saskatchewan Geologic groups of Manitoba Devonian southern paleotropical deposits Middle Devonian Series Upper Devonian Series