The Southesk Formation is a stratigraphic unit of

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, wher ...

(late

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. It is present on the western edge of the

Western Canada 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 ...

in the Rocky Mountains and foothills of Alberta and southeastern British Columbia. It was named for the Southesk River in Jasper National Park by D.J. McLaren in 1955. The formation consists primarily of

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 ...

and it preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

of marine animals such as

stromatoporoid Stromatoporoidea is an extinct clade of sea sponges common in the fossil record from the Ordovician through the Devonian. They were especially abundant and important reef-formers in the Silurian and most of the Devonian.Stock, C.W. 2001, Stro ...

s and rugose corals.

Lithology and thickness

The Southesk Formation was deposited in reefal environments.Weissenberger, J.A.W. and McIlreath, I.A. 1989. Southesk Cairn reef complex, Upper Devonian (Frasnian), Alberta. In: Reefs: Canada and adjacent areas, H.H.J. Geldsetzer, N.P. James and G.E. Tobbutt (eds.), Canadian Society of Petroleum Geologists, Memoir 13, p. 535-542. It is commonly between 150 and 260 m (490 and 850 feet) thick, and reaches a maximum of about 300 m (1000 feet) in the Flathead area of southeastern British Columbia. It has been subdivided into four members, shown in descending order below.

Distribution and relationship to other units

The Southesk Formation is discontinuously present in the

Canadian Rockies The Canadian Rockies (french: Rocheuses canadiennes) or Canadian Rocky Mountains, comprising both the Alberta Rockies and the British Columbian Rockies, is the Canadian segment of the North American Rocky Mountains. It is the easternmost part ...

from Jasper National Park to the Flathead area of southeastern British Columbia. It is also present in the subsurface beneath the adjacent plains to the east. It conformably overlies the

Cairn Formation The Cairn Formation is a geologic formation of Late Devonian (Frasnian) age in the Western Canada Sedimentary Basin. It was named for the Cairn River near its junction with the Southesk River in Jasper National Park by D.J. McLaren in 1955.McLaren, ...

or, in the Crows Nest Pass area, the Borsato Formation. At its margins it may interfinger with the Perdrix and Mount Hawk Formations. In the mountains it is

unconformably An unconformity is a buried erosional or non-depositional 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 o ...

overlain by the Sassenach, the Alexo or, rarely, the Palliser Formation. It is overlain by the Crowfoot Formation in the plains.

References

* {{Western Canadian Sedimentary Basin, Canadian Rockies=yes Western Canadian Sedimentary Basin Devonian Alberta Paleontology in Alberta Geologic formations of Alberta Stratigraphy of British Columbia Devonian southern paleotropical deposits Frasnian Stage Dolomite formations Fossiliferous stratigraphic units of North America

Lithology and thickness

Distribution and relationship to other units

See also

References