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Edmonton Group
The Edmonton Group is a Late Cretaceous (Campanian stage) to early Paleocene stratigraphic unit of the Western Canada Sedimentary Basin in the central Alberta plains.〔 It was first described as the Edmonton Formation by Joseph Burr Tyrrell in 1887 based on outcrops along the North Saskatchewan River in and near the city of Edmonton.〔Tyrrell, J.B., 1887. Report on a part of northern Alberta and portions of adjacent Districts of Assiniboia and Saskatchewan. Geological Survey of Canada, Ann. Rept.1886, new ser., v.11, Part E, p.1-176.〕 E.J.W. Irish later elevated the formation to group status and it was subdivided into four separate formations.〔Irish, E.J.W. 1970. The Edmonton Group of south-central Alberta. Bulletin of Canadian Petroleum Geology, vol. 18, p. 125-155.〕 In ascending order, they are the Horseshoe Canyon, Whitemud, Battle and Scollard Formations.〔 The Cretaceous-Paleogene boundary occurs within the Scollard Formation, based on dinosaurian and microfloral evidence,〔Lerbekmo, J.F., Singh, C., Jarzen, D.M., and Russel, D.A. 1979. The Cretaceous-Tertiary boundary in south-central Alberta - a revision based on dinosaurian and microfloral evidence. Canadian Journal of Earth Science, 16: 325-330.〕 as well as the presence of the terminal Cretaceous iridium anomaly.〔Lerbekmo, J.F. and St. Louis, R.M. 1985. The terminal Cretaceous iridium anomaly in the Red Deer Valley, Alberta. Canadian Journal of Earth Science, 23: 120-124.〕
==Distribution and Thickness==
The Edmonton Group is present in the central plains of Alberta. It consists of sedimentary rocks that were deposited in nonmarine to brackish water environments between the Canadian Rockies in the west and the Western Interior Seaway to the east.〔 Its reaches a maximum thickness of near the foothills of the Rockies in the west, and thins eastward to zero at its erosional edge east of Edmonton.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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