Beaverfoot Formation

Beaverfoot Formation
Stratigraphic range: Late Ordovician (Ashgill age)-Early Silurian (Llandovery) ~455–440  Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Formation
Underlies	Cairn Formation or Tegart Formation
Overlies	Mount Wilson Formation
Thickness	Up to about 500 m (1,600 ft) [1]
Lithology
Primary	Dolomite, limestone
Other	Chert
Location
Coordinates	51°07′00″N116°40′00″W / 51.11667°N 116.66667°W / 51.11667; -116.66667 (Beaverfoot Formation)
Approximate paleocoordinates	0°24′S63°12′W / 0.4°S 63.2°W / -0.4; -63.2
Region	British Columbia Alberta
Country	Canada
Extent	Western Canada Sedimentary Basin & Rocky Mountains, British Columbia and Alberta Purcell Mountains, British Columbia
Type section
Named for	Beaverfoot Range
Named by	L.D. Burling
Year defined	1922 [2]
Beaverfoot Formation (Canada) Show map of Canada Beaverfoot Formation (Alberta) Show map of Alberta

The Beaverfoot Formation is a stratigraphic unit of Late Ordovician (Ashgill age) to Early Silurian (Llandovery) age. ^[3] It is present on the western edge of the Western Canada Sedimentary Basin in the Rocky Mountains of British Columbia and Alberta, and the Purcell Mountains of British Columbia. It consists of carbonate rocks, and was named for the Beaverfoot Range at Pedley Pass southeast of Golden, British Columbia by L.D. Burling in 1922. ^{[1] [2]}

The formation is fossiliferous and is known for its brachiopod faunas. It also contains rugose corals and conodonts. ^[3]

Thickness and lithology

The Beaverfoot Formation is about 500 m (1640 ft) thick at its type section in Pedley Pass. ^{[1] [2]} It was deposited in shallow tropical waters on the western edge of a carbonate platform as limestone, much of which has been altered to dolomite. ^[3] Chert nodules are present in some beds. ^[1]

Distribution and relationship to other units

The Beaverfoot Formation is present in the western ranges of the Rocky Mountains of British Columbia and forms cliffs along the eastern wall of the Rocky Mountain Trench. It is also present in the Purcell Range west of Radium, British Columbia, and in the main ranges of the Alberta Rockies between the Clearwater and North Saskatchewan Rivers. It disconformably overlies the Mount Wilson Formation or older rocks. It is conformably overlain by the Tegart Formation in the western ranges, and unconformably overlain by the Late Devonian Cairn Formation to the east in Alberta. ^{[1] [4]}

Paleontology

The Beaverfoot Formation spans the Ordovician-Silurian boundary and records faunal changes that occurred during the Ordovician-Silurian extinction events. It is known for fossil rhynchonellid, atrypid, and pentamerid brachiopods, most of which have undergone silicification and can be separated from the dolomite matrix by treatment with acid. It also contains conodonts and rugose corals ( Deiracorallium prolongatum , Salvadorea distincta , Bighornia patella , Bighornia cf. bottei ). ^{[3] [5]}

See also

• List of fossiliferous stratigraphic units in Alberta

References

1. Glass, D.J. (editor) 1997. Lexicon of Canadian Stratigraphy, vol. 4, Western Canada including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba, p. 118. Canadian Society of Petroleum Geologists, Calgary, 1423 p. on CD-ROM. ISBN   0-920230-23-7.
2. Burling, L.D. 1922. A Cambro-Ordovician section near Mount Robson, British Columbia. Geological Magazine, vo. 49, p. 452-461.
3. Jin, J., Caldwell, W.G.E. and Norford, B.S. 1989. Rhynchonellid brachiopods from the Upper Ordovician Lower Silurian Beaverfoot and Nonda formations of the Rocky Mountains of British Columbia. Geological Survey of Canada, Bulletin 396, p. 21-59.
4. Norford, B.S. 1969. Ordovician and Silurian stratigraphy of the southern Rocky Mountains. Geological Survey of Canada, Bulletin 176.
5. Beaverfoot Formation at Fossilworks.org