Elk Point Group

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Elk Point Group
Stratigraphic range: Early to Middle Devonian
Blue halite (Prairie Evaporite Formation, Middle Devonian; Potash Saskatchewan-Lanigan Mine, Saskatchewan, Canada) 2.jpg
Blue halite (Prairie Evaporite Formation, upper Elk Point Group, Middle Devonian) from Saskatchewan
Type Geological formation
Sub-unitsUpper and Lower Elk Point Group
Underlies Beaverhill Lake Group, Manitoba Group
Overlies Precambrian to Silurian formations [1]
Thicknessup to 610 metres (2,000 ft) [2]
Lithology
Primary dolomite, halite, anhydrite
Other Limestone, shale, potash
Location
Coordinates 53°54′19″N110°37′49″W / 53.9053°N 110.6304°W / 53.9053; -110.6304 (Elk Point Group)
RegionNorthern plains
CountryFlag of Canada (Pantone).svg  Canada Flag of the United States.svg  United States
Type section
Named for Elk Point
Named byJ.R. McGehee [3]

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 Dakota in the United States. It has been subdivided into numerous formations, [4] number of which host major petroleum and natural gas reservoirs. [5]

Contents

Lithology

The formations of the Elk Point Group are composed primarily of carbonate rocks (dolomite and limestone) and evaporitic rocks (halite, anhydrite and potash), with lesser amounts of dolomitic mudstone and shale. [2]

Paleontology

Some of the carbonate formations of the Elk Point Group contain rich assemblages of marine invertebrate fossils, including many species of brachiopods, gastropods, bivalves, cephalopods, crinoids, ostracods and corals. The evaporitic formations are unfossiliferous or contain a few spores and algal remains. [2]

Environment of Deposition

The formations of the Elk Point Group were deposited in a marine embayment that stretched from an open ocean in the present-day Northwest Territories of Canada to North Dakota in the United States, covering an area roughly half as large as that covered by today's Mediterranean Sea. At times of low water levels and excessive evaporation, halite and other evaporite minerals were deposited in sabkha, supratidal flat and coastal lagoon environments, and at times of higher water levels carbonate platform sedimentation and reef growth were dominant. [1] [4]

Distribution and Thickness

The Elk Point Group extends from the southern boundary of the Northwest Territories through northwestern British Columbia, Alberta, Saskatchewan, and southwestern Manitoba in Canada, and continues into eastern Montana and North Dakota in the United States. [1] It reaches a maximum thickness of about 610 metres (2,000 ft) in eastern Alberta. [2]

Stratigraphy

The Elk Point Group was named for the town of Elk Point, Alberta by J.R. McGehee in 1949. [3] Core from a well that was drilled near Elk Point has been designated as the type section (Anglo-Canadian Elk Point No. 11, 2-11-57-5W4). [1] The group is subdivided into the Lower and Upper Elk Point Group, each of which is further subdivided into formations according to the dominant lithologies, [1] [2] as shown in the tables below.

The Lower Elk Point Group comprises all strata lying below the Winnipegosis Formation (in the south) or the Keg River Formation (in the north) and is present only in the deepest parts of the basin. The Upper Elk Point Group, which is present throughout the basin, includes those formations and all overlying formations to the base of the Manitoba Group (in the south) or the Beaverhill Lake Group (in the north). [1]

Subdivisions

In northern Alberta and central Alberta, the Elk Point Group contains the following subdivisions, from top to base:

Sub-unit Age LithologyMax.
Thickness		Reference
Watt Mountain Formation Givetian red and green shale, sandstone, anhydrite, dolomite, limestone 74.4 m (240 ft) [2]
Gilwood Member Givetian coarse quartz and feldspathic sandstone 15.2 m (50 ft) [2]
Presqu'ile Formation Givetian crystalline dolomite 300 m (980 ft) [2]
Sulphur Point Formation Givetian fossiliferous limestone, green shale 106 m (350 ft) [2]
Muskeg Formation Givetian anhydrite, salt, dolomite, limestone 270 m (890 ft) [2]
Zama Member Givetian sucrosic dolomite 24 m (80 ft) [2]
Keg River Formation Givetian porous dolomite, wackestone limestone, includes the Rainbow Member (dolomitized reef)300 m (980 ft) [2]
Contact Rapids Formation Eifelian to Givetian argillaceous dolomite, dolomitic shale 48.8 m (160 ft) [2]
Chinchaga Formation Eifelian to Givetian anhydrite, crystalline dolomite, quartz sandstone, dolomitic shale, halite 76 m (250 ft) [2]
Cold Lake Formation Eifelian halite, dolomitic shale 117 m (380 ft) [2]
Ernestina Lake Formation Eifelian red shale (base), carbonates, anhydrite (top)23 m (80 ft) [2]
Lotsberg Formation Eifelian halite, calcareous shale 229 m (750 ft) [2]
La Loche Formation (Basal red beds) Eifelian red dolomitic or calcareous shales, silty or sandy, quartzose sandstone 30 m (100 ft) [2] [5] [6]
In southern Alberta

The Elk Point Group is dolomitic and is not differentiated.

In Saskatchewan, Manitoba and Montana
Sub-unit Age LithologyMax.
Thickness		Reference
Dawson Bay Formation Givetian dolomitic mudstone, crystalline limestone, argillaceous carbonate, bituminous limestone, dolomite, anhydrite, halite 50 m (160 ft) [2]
Prairie Evaporite Formation Givetian halite, anhydrite, dolomite, dolomitic mudstone, limestone, potash 218 m (720 ft) [2]
Winnipegosis Formation Givetian dolomite, bituminous carbonates, anhydrite 100 m (330 ft) [2]
Ashern Formation Eifelian to Givetian argillaceous dolomite and dolomitic shale and siltstone; minor anhydrite 55 m (180 ft) [2]
Meadow Lake Formation Eifelian dolomite with mudstone interbeds, limestone and sandstone at base56 m (180 ft) [2]

Relationship to Other Units

The Elk Point Group is conformably overlain by the Manitoba Group in Manitoba and Saskatchewan, and by the Beaverhill Lake Group in Alberta. It rests unconformably on Precambrian basement rocks in northern Alberta, on Cambrian strata in northeastern Alberta and in Saskatchewan, and on Ordovician to Silurian [1] formations in western Alberta, Saskatchewan and southwestern Manitoba. [2] In the Northwest Territories, some of its uppermost units are exposed at surface or are unconformably overlain by Cretaceous strata. [1]

The Lower Elk Point Group is equivalent to the Stone Formation and its equivalents, and the Headless and Nahanni Formations, in northerneastern British Columbia and the southwestern Northwest Territories. In the same areas, the Upper Elk Point includes the Pine Point Group, and is equivalent to parts of the Horn River Formation, Besa River Formation, and others. [2]

Petroleum and Natural Gas

The porous carbonate rocks of the Elk Point Group host major petroleum and natural gas reservoirs. As of 1994, the Initial Established Recoverable Petroleum Reserves and the Cumulative Petroleum Production for the group were estimated at 339.3 and 240.4 million cubic metres, respectively. For natural gas, the Initial Established Marketable Reserves and the Cumulative Production were estimated at 142.7 and 79.5 billion cubic metres, respectively. [5]

Related Research Articles

The Leduc Formation is a stratigraphic unit of Late Devonian (Frasnian) age in the Western Canada Sedimentary Basin. It takes its name from the city of Leduc, and it was formally described from the B.A. Pyrz No. 1 well in central Alberta, between the depths of 1,623.7 m (5,327 ft) and 1,807.5 m (5,930 ft), by Imperial Oil Limited in 1950. Supplementary information came from a complete section of the formation that was cored in Imperial Oil's Leduc No. 530 well between 1,633 m (5,358 ft) and 1,863 m (6,112 ft).

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 natural gas reservoirs in the Zama lake and Rainbow Lake areas of northwestern Alberta.

The Wabamun Formation is a stratigraphic unit of Late Devonian (Famennian) age in the Western Canada Sedimentary Basin. It takes the name from Wabamun Lake and was first described in the Anglo Canadian Wabamun Lake No. 1 well by Imperial Oil in 1950.

The Exshaw Formation is a stratigraphic unit in the Western Canada Sedimentary Basin. It takes the name from the hamlet of Exshaw, Alberta in the Canadian Rockies, and was first described from outcrops on the banks of Jura Creek north of Exshaw by P.S. Warren in 1937. The formation is of Late Devonian to Early Mississippian age as determined by conodont biostratigraphy, and it straddles the Devonian-Carboniferous boundary.

<span class="mw-page-title-main">Horn River Formation</span>

The Horn River Formation is a stratigraphic unit of Devonian age in the Western Canadian Sedimentary Basin.

<span class="mw-page-title-main">Palliser Formation</span>

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 Beaverhill Lake Group is a geologic unit of Middle Devonian to Late Devonian age in the Western Canada Sedimentary Basin that is present in the southwestern Northwest Territories, northeastern British Columbia and Alberta. It was named by the geological staff of Imperial Oil in 1950 for Beaverhill Lake, Alberta, based on the core from a well that they had drilled southeast of the lake, near Ryley, Alberta.

The Manitoba Group is a stratigraphical unit of middle to late Devonian age in the Western Canadian Sedimentary Basin.

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.

The Elk Formation is a stratigraphic unit of the Western Canada Sedimentary Basin that is present in southeastern British Columbia and southwestern Alberta. It is probably of Early Cretaceous age, but in some areas its strata could be as old as Late Jurassic. It includes minor thin coal beds and was named for outcrops near the now-abandoned Elk River coal mine east of Fernie, British Columbia.

<span class="mw-page-title-main">Cairn Formation</span>

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.

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 Perdrix Formation is a geologic formation of Late Devonian (Frasnian) age in the Western Canada Sedimentary Basin. It named for Roche à Perdrix in Jasper National Park, Alberta, by P.E. Raymond in 1930. It includes fossils of marine animals.

The Fairholme Group is a stratigraphic unit of Late Devonian (Frasnian) age. It is present on the western edge of the Western Canada Sedimentary Basin in the Rocky Mountains and foothills of Alberta and British Columbia. It was named for the Fairholme Range near Exshaw in the Canadian Rockies by H.H. Beach in 1943.

<span class="mw-page-title-main">Prairie Evaporite Formation</span> Geologic formation of Givetian age

The Prairie Evaporite Formation, also known as the Prairie Formation, is a geologic formation of Middle Devonian (Givetian) age that consists primarily of halite and other evaporite minerals. It is present beneath the plains of northern and eastern Alberta, southern Saskatchewan and southwestern Manitoba in Canada, and it extends into northwestern North Dakota and northeastern Montana in the United States.

The La Loche Formation is a geologic formation of early Middle Devonian (Eifelian) age in the Western Canada Sedimentary Basin. It is present in northeastern Alberta and northwestern Saskatchewan and was first described by A. W. Norris in 1963, who named it for a Roman Catholic Mission at Lac La Loche. Its type section is located at Contact Rapids on the Clearwater River in Saskatchewan, northwest of Lac La Loche. It is not fossiliferous.

The Purcell Supergroup is composed primarily of argillites, carbonate rocks, quartzites, and mafic igneous rocks of late Precambrian (Mesoproterozoic) age. It is present in an area of about 15,000 km2 in southwestern Alberta and southeastern British Columbia, Canada, and it extends into the northwestern United States where it is called the Belt Supergroup. It was named for the Purcell Mountains of British Columbia by R.A. Daly in 1912. Fossil stromatolites and algal structures are common in some of the Purcell Supergroup rocks, and the Sullivan ore body at Kimberley, British Columbia, a world-class deposit of lead, zinc, and silver, lies within the Alderidge Formation in the lower part of the Purcell.

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.

<span class="mw-page-title-main">Eldon Formation</span> Geologic formation in Canada

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. 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, who discovered the Burgess Shale fossils. The Eldon Formation was deposited during Middle Cambrian time, and it includes fossil stromatolites. 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.

Armit Meadows Ecological Reserve is an ecological reserve located in Porcupine Provincial Forest, Manitoba, Canada. It was established in 2015 under the Manitoba Ecological Reserves Act. It is 2.63 square kilometres (1.02 sq mi) in size.

References

  1. 1 2 3 4 5 6 7 8 Meijer Drees, N.C. 1986. Evaporitic deposits of western Canada. Geological Survey of Canada, paper 85-20.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 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.
  3. 1 2 McGehee, J.R., 1949. Pre-Waterways Paleozoic stratigraphy of Alberta Plains. Bull. American Association of Petroleum Geologists, 33:4, p. 603-613.
  4. 1 2 Mossop, G.D. and Shetsen, I. (compilers). Canadian Society of Petroleum Geologists and Alberta Geological Survey (1994). "The Geological Atlas of the Western Canada Sedimentary Basin, Chapter 10: Devonian Elk Point Group of the Western Canada Sedimentary Basin" . Retrieved 2016-06-20.{{cite web}}: CS1 maint: multiple names: authors list (link)
  5. 1 2 3 Mossop, G.D. and Shetsen, I. (compilers) Canadian Society of Petroleum Geologists (1994). "The Geological Atlas of the Western Canada Sedimentary Basin, Chapter 32: Oil and Gas Resources of the Western Canada Sedimentary Basin" . Retrieved 2016-06-20.{{cite web}}: CS1 maint: multiple names: authors list (link)
  6. ↑ Schneider, C.L.; Grobe, F.J.; Hein (2018-01-24) [2012]. "ERCB/AGS Open File Report 2012-20 Outcrops of the La Loche, Contact Rapids, and Keg River Formations (Devonian) on the Clearwater River: Alberta (NTS 74D/9) and Saskatchewan (NTS 74C/12)" (PDF). Energy Resources Conservation Board Alberta Geological Survey. Her Majesty the Queen in Right of Alberta, 2013. ISBN   978-1-4601-0089-9 . Retrieved 2018-01-24.
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