Southesk Formation
{{Infobox rockunit
| name = Southesk Formation
| image =
| caption =
| type = Formation
| age = {{fossil range|Frasnian|Frasnian| late Frasnian}}
| prilithology = Dolomite
| otherlithology = Limestone
| namedfor = Southesk River
| namedby = D.J. McLaren, 1955.Devonian formations in the Alberta Rocky Mountains between Bow and Athabasca rivers. Geological Survey of Canada, Bulletin 35.
| region = Alberta
British Columbia
| country = Canada
| coordinates = {{coord|52|38|00|N|116|58|00|W|name=Saouthesk Formation|display=inline,title}}
| unitof = Fairholme Group
| subunits = Ronde Member
Arcs Member
Grotto Member
Peechee Member
| underlies = Sassenach Formation, Alexo Formation, Palliser Formation, or Crowfoot Formation
| overlies = Cairn Formation, or Borsato Formation
| thickness = Up to about 300 m (1000 feet)Glass, D.J. (editor) 1997. Lexicon of Canadian Stratigraphy, vol. 4, Western Canada including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba, p. 1094. Canadian Society of Petroleum Geologists, Calgary, 1423 p. on CD-ROM. {{ISBN|0-920230-23-7}}.
| extent =
| area =
| map =
| map_caption =
}}
The Southesk Formation is a stratigraphic unit of Late Devonian (late Frasnian) age. It is present on the western edge of the Western Canada Sedimentary Basin 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 and it preserves fossils of marine animals such as stromatoporoids 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.
| class="wikitable" | |||
| Member | Lithology | Max. Thickness | Fossils || Reference |
|---|---|---|---|
| Ronde Member | limestone & silty limestone; present only in limited areas | {{convert|55|m|ft | |
| 1|abbr=on}} | not fossiliferous | ||
| Arcs Member | light grey, medium-bedded, medium-crystalline dolomite | {{convert|74|m|ft | |
| 1|abbr=on}} | minor branching stromatoporoids, foraminifera, & algae | ||
| Grotto Member | thick- to thin-bedded, dark brown to grey, variably argillaceous dolomite | {{convert|67|m|ft | |
| 1|abbr=on}} | branching stromatoporoids; tabulate corals | ||
| Peechee Member | massive, light grey, medium- to coarse-crystalline dolomite; minor limestone & anhydrite | {{convert|300|m|ft | |
| 1|abbr=on}} | bulbous & branching stromatoporoids; tabulate corals |
Distribution and relationship to other units
The Southesk Formation is discontinuously present in the Canadian Rockies 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 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 overlain by the Sassenach, the Alexo or, rarely, the Palliser Formation. It is overlain by the Crowfoot Formation in the plains.{{cite web |last1=Alberta Geological Survey |title=Alberta Table of Formations, May 2019 |url=https://ags.aer.ca/document/INF/Table_of_Formations_2019.pdf |publisher=Alberta Energy Regulator |accessdate=24 March 2020}}
See also
{{Portal |Earth sciences|Canada|Paleontology}}
References
{{reflist}}
- {{cite web|title= Fossilworks: Gateway to the Paleobiology Database|author= ((Various Contributors to the Paleobiology Database))|url= https://www.fossilworks.org|access-date= 17 December 2021}}
{{Western Canadian Sedimentary Basin|Canadian Rockies=yes}}
Category:Western Canadian Sedimentary Basin
Category:Paleontology in Alberta
Category:Geologic formations of Alberta
Category:Geologic formations of British Columbia
Category:Devonian southern paleotropical deposits
Category:Dolomite formations of the United States
Category:Fossiliferous stratigraphic units of North America