The Arctomys Formation is a

stratigraphic 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 three related subfields: lithostr ...

unit of late

Middle Cambrian Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek ...

age. It is present on the western edge of the

Western Canada Sedimentary Basin The Western Canadian Sedimentary Basin (WCSB) underlies of Western Canada including southwestern Manitoba, southern Saskatchewan, Alberta, northeastern British Columbia and the southwest corner of the Northwest Territories. This vast sedimentary ...

in the

Canadian Rockies The Canadian Rockies (french: Rocheuses canadiennes) or Canadian Rocky Mountains, comprising both the Alberta Rockies and the British Columbian Rockies, is the Canadian segment of the North American Rocky Mountains. It is the easternmost par ...

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

and

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost Provinces and territories of Canada, province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include ...

. It was named for Arctomys Peak near

Mount Erasmus Mount Erasmus is a mountain summit located in the North Saskatchewan River valley of Banff National Park, in the Canadian Rockies of Alberta, Canada. Its nearest higher peak is Mount Amery, to the north-northwest. Mount Erasmus can be seen from ...

Banff National Park Banff National Park is Canada's oldest national park, established in 1885 as Rocky Mountains Park. Located in Alberta's Rocky Mountains, west of Calgary, Banff encompasses of mountainous terrain, with many glaciers and ice fields, dense conif ...

Charles Doolittle Walcott Charles Doolittle Walcott (March 31, 1850February 9, 1927) was an American paleontologist, administrator of the Smithsonian Institution from 1907 to 1927, and director of the United States Geological Survey.Wonderful Life (book) by Stephen Jay G ...

in 1920.

Outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficia ...

s of the Arctomys can be seen in Banff and

Jasper National Park Jasper National Park is a national park in Alberta, Canada. It is the largest national park within Alberta's Rocky Mountains spanning . It was established as a national park in 1930 and declared a UNESCO World Heritage Site in 1984. Its locatio ...

Lithology and deposition

The Arctomys was deposited along the western shoreline of the

North American Craton North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating direction or geography. Etymology The word ''north'' is ...

during late

time.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. It consists primarily of red, grey, and green platy

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especia ...

Sedimentary structure Sedimentary structures include all kinds of features in sediments and sedimentary rocks, formed at the time of deposition. Sediments and sedimentary rocks are characterized by bedding, which occurs when layers of sediment, with different partic ...

s include

mudcrack Mudcracks (also known as mud cracks, desiccation cracks or cracked mud) are sedimentary structures formed as muddy sediment dries and contracts.Jackson, J.A., 1997, ''Glossary of Geology'' (4th ed.), American Geological Institute, Alexandria, VA, ...

ripple marks In geology, ripple marks are sedimentary structures (i.e., bedforms of the lower flow regime) and indicate agitation by water ( current or waves) or wind. Defining ripple cross-laminae and asymmetric ripples * ''Current ripple marks'', ' ...

, and casts of

salt crystals Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

. Environments of deposition may have included shallow lakes, lagoons, and sheet-flood deposits on dry mud flats.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.

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 White Man Mountain is located on the Continental Divide between Alberta and British Columbia. It was named by George Mercer Dawson in 1884 and is Alberta's 92nd most prominent mountain. See also * List of peaks on the Alberta–British Columbia ...

to a maximum of 336 metres (1,100 ft) at

Mount Robson Mount Robson is the most prominent mountain in North America's Rocky Mountain range; it is also the highest point in the Canadian Rockies. The mountain is located entirely within Mount Robson Provincial Park of British Columbia, and is part ...

. It is overlies the

Pika Formation The Pika Formation is a stratigraphy, stratigraphic unit of Middle Cambrian age that is present on the western edge of the Western Canadian Sedimentary Basin, Western Canada Sedimentary Basin in the Canadian Rockies of Alberta and British Columbi ...

and is overlain by the Waterfowl Formation. Both contacts are gradational.

References

{{Western Canadian Sedimentary Basin, Canadian Rockies=yes Cambrian Alberta Cambrian British Columbia Cambrian System of North America Western Canadian Sedimentary Basin Geologic formations of Alberta Geologic formations of British Columbia