Wapiti Formation

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Wapiti Formation
Stratigraphic range: Late Cretaceous to Early Paleocene
Type Geological formation
Lithology
Primary Sandstone, siltstone, mudstone
Other conglomerate, coal
Location
Region  Alberta
Country  Canada
Type section
Named for Lower part of Wapiti River
Named by G.M. Dawson, 1881.[1]

The Wapiti Formation is a geological formation of the Western Canada Sedimentary Basin in northwestern Alberta, Canada. Its deposition spanned the time interval from Late Cretaceous (Campanian stage) to early Paleocene, and it includes sediments that were deposited before, during, and after the Cretaceous-Paleogene (K-Pg) extinction event.[2] It was named by G.M. Dawson in 1881,[1] presumably for exposures along the lower part of the Wapiti River and downstream along the Smoky River in Alberta.[3]

Dinosaur remains are among the fossils that have been recovered from the Cretaceous portion of the formation.[4] The Wapiti Formation does not produce many fossils due to its limited surface exposure and accessibility, although two Pachyrhinosaurus bone beds have been productive.[5]

Lithology[edit]

The Wapiti Formation consists of interbedded sandstones, siltstones, shales and mudstones, with thin conglomerates, coal seams and bentonite beds. The sandstones are typically thick, pale grey, crossbedded and bentonitic. The middle part contains less sandstones, more mudstones, and fewer and thinner coals. The upper part contains thicker lenticular sandstones and more coals.[3]

Environment of Deposition[edit]

The Wapiti Formation was deposited in inland fluvial and floodplain environments, with local areas of lacustrine sediments.[2] The sandstones were deposited mainly in fluvial channel environments, with siltstones, carbonaceous shales and coals accumulating in overbank settings.

Thickness and Distribution[edit]

The Wapiti Formation rests conformably on the marine shales of the Smoky Group. It is more than 1,300 m (4,300 ft) thick in the foothills of the Canadian Rockies in the west,[2] and it thins eastward to its erosional edge.[6] It is correlative with the entire sequence of the Belly River Group, Bearpaw Formation, Edmonton Group and Scollard Formation in south-central Alberta.[2] In most areas it is unconformably overlain by glacial and post-glacial sediments of Quaternary age, or exposed at surface. In a few upland areas it is unconformably overlain by Paleogene gravel deposits.[3]

Vertebrate paleofauna[edit]

Dinosaurs of the Wapiti Formation
Genus Species Location Stratigraphic position Abundance Description Images

Albertosaurus[4]

Indeterminate[4]

Pachyrhinosaurus[4]

Indeterminate[4]

Saurornitholestes[4]

Indeterminate[4]

Troodon[4]

Indeterminate[4]

See also[edit]

References[edit]

  1. ^ a b Dawson, G.M. 1881. Report on the exploration from Simpson on the Pacific coast to Edmonton on the Saskatchewan River, embracing a portion of the northern part of Brisish Columbia and the Peace River country. Geological Survey of Canada, Report of Progress 1879-1880, Part B, p. 1-77.
  2. ^ a b c d Mossop, G.D. and Shetsen, I., (compilers), Canadian Society of Petroleum Geologists (1994). "The Geological Atlas of the Western Canada Sedimentary Basin, Chapter 24: Upper Cretaceous and Tertiary strata of the Western Canada Sedimentary Basin". Retrieved 2013-08-01. 
  3. ^ a b c 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.
  4. ^ a b c d e f g h i Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 574-588. ISBN 0-520-24209-2.
  5. ^ Ryan, M. J., and A. P. Russell, 2001, Dinosaurs of Alberta (exclusive of Aves), in: Mesozoic Vertebrate Life, edited by Tanke, D. H., and K. Carpenter, Indiana University Press, pp. 279–297 ISBN 978-0253339072
  6. ^ Prior, G. J., Hathaway, B., Glombick, P.M., Pana, D.I., Banks, C.J., Hay, D.C., Schneider, C.L., Grobe, M., Elgr, R., and Weiss, J.A. (2013). "Bedrock Geology of Alberta. Alberta Geological Survey, Map 600". Retrieved 2013-08-13.