Eldon Formation

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Eldon Formation
Stratigraphic range: Middle Cambrian
~509–500  Ma
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Mount-Yamnuska2-Szmurlo.jpg
The Eldon Formation forms the cliffs of Mount Yamnuska in Alberta
Type Formation
Underlies Pika Formation
Overlies Stephen Formation, Snake Indian Formation
ThicknessUp to 500 metres (1640 ft) [1]
Lithology
Primary Limestone, dolomite
Other Mudstone
Location
Coordinates 51°18′8.5″N115°55′45″W / 51.302361°N 115.92917°W / 51.302361; -115.92917 (Eldon Formation) Coordinates: 51°18′8.5″N115°55′45″W / 51.302361°N 115.92917°W / 51.302361; -115.92917 (Eldon Formation)
Region Canadian Rockies
CountryFlag of Canada (Pantone).svg  Canada
Type section
Named forEldon Switch on the Canadian Pacific Railway in Banff National Park, Alberta
Named by Charles Doolittle Walcott in 1908 [2]

The Eldon Formation is a stratigraphic unit that is present on the western edge of the Western Canada Sedimentary Basin in the southern Canadian Rockies of southwestern Alberta and southeastern British Columbia. [3] It is a thick sequence of massive, cliff-forming limestones and dolomites that was named for Eldon Switch on the Canadian Pacific Railway near Castle Mountain in Banff National Park by Charles Doolittle Walcott, [1] [2] who discovered the Burgess Shale fossils. The Eldon Formation was deposited during Middle Cambrian time, and it includes fossil stromatolites. [1] The Eldon forms the scenic cliffs at the top of Castle Mountain, and can also be seen at Mount Yamnuska and other mountains in Banff and Yoho National Parks. [4]

Stratigraphy The study of rock layers and their formation

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 two related subfields: lithostratigraphy and biostratigraphy.

Western Canadian Sedimentary Basin

The Western Canadian Sedimentary Basin (WCSB) is a vast sedimentary basin underlying 1,400,000 square kilometres (540,000 sq mi) 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 extending from the Rocky Mountains in the west to the Canadian Shield in the east. This wedge is about 6 kilometres (3.7 mi) thick under the Rocky Mountains, but thins to zero at its eastern margins. The WCSB contains one of the world's largest reserves of petroleum and natural gas and supplies much of the North American market, producing more than 16,000,000,000 cubic feet (450,000,000 m3) per day of gas in 2000. It also has huge reserves of coal. Of the provinces and territories within the WCSB, Alberta has most of the oil and gas reserves and almost all of the oil sands.

Canadian Rockies mountain range in Canada

The Canadian Rockies or Canadian Rocky Mountains comprise the Canadian segment of the North American Rocky Mountains. They are the eastern part of the Canadian Cordillera, which is a system of multiple ranges of mountains which runs from the Canadian Prairies to the Pacific Coast. The Canadian Rockies mountain system comprises the southeastern part of this system, lying between the Interior Plains of Alberta and northeastern British Columbia on the east to the Rocky Mountain Trench of BC on the west. The southern end borders Idaho and Montana of the United States. In geographic terms, the boundary is at the Canada–United States border, but in geological terms it might be considered to be at Marias Pass in northern Montana. The northern end is at the Liard River in northern British Columbia.

Contents

Lithology and deposition

The Eldon Formation is a thick sequence of cliff-forming carbonate rocks that was deposited during the Middle Cambrian time. It originally formed as limestone and calcareous mudstone in the intertidal to supratidal zone along the western margin of the North American Craton. [3] [5] It was subsequently altered to dolomite and dolomitic mudstone in some areas. [1]

Carbonate rock

Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite (different crystal forms of CaCO3) and dolomite, also known as dolostone, which is composed of the mineral dolomite (CaMg(CO3)2).

Limestone Sedimentary rocks made of calcium carbonate

Limestone is a carbonate sedimentary rock that is often composed of the skeletal fragments of marine organisms such as coral, foraminifera, and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). A closely related rock is dolomite, which contains a high percentage of the mineral dolomite, CaMg(CO3)2. In fact, in old USGS publications, dolomite was referred to as magnesian limestone, a term now reserved for magnesium-deficient dolomites or magnesium-rich limestones.

Calcite carbonate mineral

Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). The Mohs scale of mineral hardness, based on scratch hardness comparison, defines value 3 as "calcite".

Distribution and stratigraphic relationships

The Eldon Formation is present in the southern Rocky Mountains of southwestern Alberta and southeastern British Columbia. It reaches a maximum thickness of about 500 metres (1,640 feet) at Mount Bosworth on the Alberta-British Columbia border. The Eldon conformably overlies the Stephen Formation, which hosts the fossils of the Burgess shale, in the south, and the Snake Indian Formation in the north. It is conformably overlain by the Pika Formation. The Eldon grades into the Earlie Formation to the east, the Chancellor Formation to the west, and the Titkana Formation to the north. It is probably equivalent to the Windsor Mountain Formation to the south. [1] [3] [6]

Mount Bosworth mountain in Canada

Mount Bosworth is located in the Canadian Rockies on the border of Alberta and British Columbia. The mountain is situated immediately northwest of Kicking Horse Pass and straddles the shared border of Banff National Park with Yoho National Park. It was named in 1903 after George Morris Bosworth, an executive and long-time employee of the Canadian Pacific Railway.

Stephen Formation

The Stephen Formation is a geologic formation exposed in the Canadian Rockies of British Columbia. Its rocks were formed during the middle Cambrian. It is famous for the exceptional preservation of soft-bodied fossils: the Burgess Shale biota. The formation overlies the Cathedral escarpment, a submarine cliff; consequently it is divided into two quite separate parts, the 'thin' sequence deposited in the shallower waters atop the escarpment, and the 'thick' sequence deposited in the deeper waters beyond the cliff. Because the 'thick' Stephen Formation represents a distinct lithofacies, some authors suggest it warrants its own name, and dub it the Burgess Shale Formation. The stratigraphy of the Thin Stephen Formation has not been subject to extensive study, so except where explicitly mentioned this article applies mainly to the Thick Stephen Formation.

The Snake Indian Formation is a stratigraphic unit of Middle Cambrian age that is present on the western edge of the Western Canada Sedimentary Basin in the northern Canadian Rockies of Alberta and British Columbia. It was named for Snake Indian River in Jasper National Park by E.W. Montjoy and J.D. Aitken in 1978. The type locality was established on Chetamon Mountain.

Related Research Articles

Bullhead Group is a stratigraphic unit of Lower Cretaceous age in the Western Canada Sedimentary Basin of northeastern British Columbia and western Alberta. It was first defined by F.H. McLearn in 1918 as the Bullhead Mountain Formation, but later was upgraded to group status. It consists of the Cadomin and Gething Formations, although some early workers included the Bluesky Formation and others in the group.

Palliser Formation

The Palliser Formation is a stratigraphic unit of Late Devonian (Famennian) age in the Western Canada Sedimentary Basin. It is a thick sequence of limestone and dolomitic limestone that is present in the Canadian Rockies and foothills of western Alberta. Tall cliffs formed of the Palliser Formation can be seen throughout Banff and Jasper National Parks.

The Mist Mountain Formation is a latest Jurassic to earliest Cretaceous geologic formation in the Western Canada Sedimentary Basin of southeastern British Columbia and southwestern Alberta. It was named for outcrops along a western spur of Mist Mountain in the Canadian Rockies of Alberta. It contains economically important coal reserves that are mined in southeastern British Columbia.

The Elk Point Group is a stratigraphic unit of Early to Middle Devonian age in the Western Canada and Williston sedimentary basins. It underlies large area that extends from southern boundary of the Northwest Territories in Canada to North Dakota in the United States. It has been subdivided into numerous formations, many which host major petroleum and natural gas reservoirs.

The Lynx Formation or Lynx Group is a stratigraphic unit of Late Cambrian (Dresbachian) age in the Western Canada Sedimentary Basin. It is present in the Canadian Rockies of Alberta and British Columbia. It was originally described as the Lynx Formation by Charles Doolittle Walcott in 1913, based on and named for outcrops on the slopes of Lynx Mountain on the continental divide east of Mount Robson. It was subdivided into five formations and elevated to group status by J.D. Aitken and R.G. Greggs in 1967. The name Lynx Formation continues to be used in areas where some or all of the subdivisions cannot be distinguished. All of the formations in the Lynx Group include fossil trilobites and some contain the stromatolite Collenia.

Morrissey Formation

The Morrissey Formation is a stratigraphic unit of Late Jurassic (Portlandian) age in the Western Canada Sedimentary Basin. It is named for outcrops on Morrissey Ridge, 16 kilometres (10 mi) southeast of Fernie, British Columbia, and is present in southeastern British Columbia and southwestern Alberta.

Gog Group

The Gog Group is a stratigraphic unit in the Western Canada Sedimentary Basin. It is present in the western main ranges of the Canadian Rockies in Alberta and British Columbia, and in the Cariboo Mountains and in the central Purcell Mountains in southwestern British Columbia. It was named by C.F. Deiss in 1940 for a type locality near Mount Assiniboine.

The Flume Formation is a geologic formation in the Western Canada Sedimentary Basin in Alberta, Canada. It was deposited as an extensive carbonate platform along the western edge of the basin during Late Devonian (Frasnian) time and the reefs of the Cairn Formation subsequently developed on it.

The Skoki Formation is a stratigraphic unit of Early to Middle Ordovician age that is present on the western edge of the Western Canada Sedimentary Basin in the Canadian Rockies of Alberta and British Columbia. It was named for Skoki Mountain near Lake Louise in Banff National Park by Charles Doolittle Walcott in 1928. The Skoki Formation is fossiliferous and includes remains of brachiopods and other marine invertebrates, as well as conodonts and oncolites.

The Survey Peak Formation is a stratigraphic unit of latest Cambrian to earliest Ordovician age. It is present on the western edge of the Western Canada Sedimentary Basin in the Canadian Rockies of Alberta and British Columbia. It was named for Survey Peak near Mount Erasmus in Banff National Park by J.D. Aitken and B.S. Norford in 1967. The Survey Peak Formation is fossiliferous and includes remains of trilobites and other marine invertebrates, as well as conodonts, stromatolites, and thrombolites.

The Sulphur Mountain Formation is a geologic formation of Early to Middle Triassic age. It is present on the western edge of the Western Canada Sedimentary Basin in the foothills and Rocky Mountains of western Alberta and northeastern British Columbia. It includes marine fossils from the time shortly after the Permian-Triassic extinction event.

Beattie Peaks Formation

The Beattie Peaks Formation is a geologic formation of Early Cretaceous (Valanginian) age in the Western Canada Sedimentary Basin that consists primarily of marine mudstone. It is present in the northern foothills of the Canadian Rockies and the adjacent plains in northeastern British Columbia.

Monteith Formation

The Monteith Formation is a geologic formation of Early Cretaceous (Valanginian) age in the Western Canada Sedimentary Basin that consists primarily of sandstone. It is present in the northern foothills of the Canadian Rockies and the adjacent plains in northeastern British Columbia and west-central Alberta.

The Kootenay Group, originally called the Kootenay Formation, is a geologic unit of latest Jurassic to earliest Cretaceous age in the Western Canada Sedimentary Basin that is present in the mountains and foothills of southeastern British Columbia and southwestern Alberta. It includes economically important deposits of high-rank bituminous and semi-anthracite coal, as well as plant fossils and dinosaur trackways.

The Kananaskis Formation is a geologic formation that is present on the western edge of the Western Canada Sedimentary Basin in the southern Canadian Rockies of western Alberta. Named after the Kananaskis Range near Banff, it was deposited during the Late Pennsylvanian sub-period of the Carboniferous period. Some of its strata host fossils of marine invertebrates.

The Pika Formation is a stratigraphic unit of Middle Cambrian age that is present on the western edge of the Western Canada Sedimentary Basin in the Canadian Rockies of Alberta and British Columbia. It was named for Pika Peak near Lake Louise in Banff National Park by C.F. Deiss in 1939. It is fossiliferous and preserves several genera of trilobites. Outcrops of the Pika Formation can be seen in Banff and Jasper National Parks.

The Arctomys Formation is a stratigraphic unit of late Middle Cambrian age. It is present on the western edge of the Western Canada Sedimentary Basin in the Canadian Rockies of Alberta and British Columbia. It was named for Arctomys Peak near Mount Erasmus in Banff National Park by Charles Doolittle Walcott in 1920. Outcrops of the Arctomys can be seen in Banff and Jasper National Parks.

The Titkana Formation is a stratigraphic unit of Middle Cambrian age that is present on the western edge of the Western Canada Sedimentary Basin in the northern Canadian Rockies of Alberta and British Columbia. It was named for Titkana Peak near Mount Robson by Charles Doolittle Walcott in 1913. The Titkana Formation is generally unfossiliferous.

References

  1. 1 2 3 4 5 Glass, D.J. (editor) 1997. Lexicon of Canadian Stratigraphy, vol. 4, Western Canada including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba. Canadian Society of Petroleum Geologists, Calgary, 1423 p. on CD-ROM. ISBN   0-920230-23-7.
  2. 1 2 Walcott, C.D. 1908. Nomenclature of some Cambrian Cordilleran formations. Smithsonian Miscellaneous Collections, vol. 53, no. 1, 14 pp.
  3. 1 2 3 Slind, O.L., Andrews, G.D., Murray, D.L., Norford, B.S., Paterson, D.F., Salas, C.J., and Tawadros, E.E., Canadian Society of Petroleum Geologists and Alberta Geological Survey (1994). "The Geological Atlas of the Western Canada Sedimentary Basin (Mossop, G.D. and Shetsen, I., compilers), Chapter 8: Middle Cambrian and Early Ordovician Strata of the Western Canada Sedimentary Basin" . Retrieved 2018-07-13.CS1 maint: Multiple names: authors list (link)
  4. ↑ Leckie, D.A. 2017. Rocks, ridges and rivers – Geological wonders of Banff, Yoho, and Jasper National Parks. Brokenpoplars, Calgary, Alberta, 217 pp. ISBN   978-0-9959082-0-8.
  5. ↑ Aitken, J.D. 1971. Control of lower Paleozoic sedimentary facies by the Kicking Horse Rim, southern Rocky Mountains, Canada. Bulletin of Canadian Petroleum Geology, vol. 19, no. 3, p. 557-569.
  6. ↑ Alberta Geological Survey, 2013. "Alberta Table of Formations; Alberta Energy Regulator" . Retrieved 1 May 2018.
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