Arctomys Formation

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.[3] 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.[4]

Arctomys Formation Stratigraphic range: Middle Cambrian ~509–500 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Formation
Underlies	Waterfowl Formation
Overlies	Pika Formation
Thickness	Up to 336 metres (1,100 ft)[1]
Lithology
Primary	Shale
Other	Dolomite, limestone
Location
Coordinates	51°57′35″N 116°55′16″W
Region	Canadian Rockies
Country	Canada
Type section
Named for	Arctomys Peak
Named by	Charles Doolittle Walcott[2]

Lithology and deposition

The Arctomys was deposited in along the western shoreline of the North American Craton during late Middle Cambrian time.[3][5] It consists primarily of red, grey, and green platy shale. Sedimentary structures include mudcracks, ripple marks, and casts of salt crystals.[1][3] Environments of deposition may have included shallow lakes, lagoons, and sheet-flood deposits on dry mud flats.[6]

Distribution and stratigraphic relationships

The Arctomys Formation is present in the Rocky Mountains of Alberta and British Columbia. It thickens northward from White Man Mountain to a maximum of 336 metres (1,100 ft) at Mount Robson.[1] It is overlies the Pika Formation and is overlain by the Waterfowl Formation.[7] Both contacts are gradational.[1]

References

1. 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. Walcott, C.D. 1920. Explorations and field work of the Smithsonian Institution in 1919. Smithsonian Institution Miscellaneous Collections, vol. 72, no. 1, p. 1-16.
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". Archived from the original on 2016-07-01. 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. 1966. Middle Cambrian to Middle Ordovician cyclic sedimentation, southern Rocky Mountains of Alberta. Bulletin of Canadian Petroleum Geology, vol. 14, no. 6, p. 405-441.
6. Spencer, R.J. and Demicco, R.V. 1993. Depositional environments of the Middle Cambrian Arctomys Formation, southern Canadian Rocky Mountains. Bulletin of Canadian Petroleum Geology, vol. 41, no. 4, p. 373-388.
7. Alberta Geological Survey. "Alberta Table of Formations, May 2019" (PDF). Alberta Energy Regulator. Retrieved 24 March 2020.