The Ishbel Group is a stratigraphic unit of Permian age in the Western Canadian Sedimentary Basin. It is present in the Canadian Rockies of Alberta and British Columbia. First defined by A. McGugan in 1963,McGugan, A., 1963. A Permian brachiopod and fusulinid fauna from Elk Valley, British Columbia, Canada. Journal of Paleontology, v. 37, p. 621-627. it is named for Mount Ishbel of the Sawback Range in Banff National Park, and parts of the group were first described in the vicinity of the mountain at Ranger Canyon and Johnston Canyon.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. .
Lithology The Ishbel Group is composed of carbonate rocks (limestone and dolomite) and sandstone, with minor chert and siltstone. Depositional conditions were similar to those of the Phosphoria Formation to the south in United States.
Paleontology Among the fossils that have been found in the Ishbel Group are corals, bryozoa, crinoids, and conodonts, as well as productid, chonetid and spiriferid brachiopods, omphalotrochid gastropods, and edestid elasmobranch fish.
Distribution The Ishbel Group reaches a maximum thickness of up to about 425 metres (1400 ft). It is present in the front ranges of the Canadian Rockies as far north as the Peace River.
Subdivisions
Sub-unit Age Lithology Max.thickness ReferenceKindle Formation Asselian to early Artinskian siltstone, shale Belloy Formation Permian limestone, dolomite, and sandstone Fantasque Formation Permian spicular chert, shale, and siltstone Mowitch Formation Roadian to Wordian sandstone with gypsum Ranger Canyon Formation Roadian to Wordian dark chert, silicified sandstone, evaporite minerals Ross Creek Formation late Sakmarian to Artinskian shaly siltstone, calcareous siltstone, silty carbonate, phosphatic coquinas Telford Formation Asselian to Sakmarian sandy limestone and dolomite Johnston Canyon Formation late Sakmarian to Artinskian phosphatic siltstone, calcareous siltstone, and silty limestone and dolomite Belcourt Formation Asselian to Sakmarian silty dolomite with chert
Relationship to other units The Ishbel Group is disconformably overlain by the Spray River Group and unconformably overlies the Tunnel Mountain Formation and the Kananaskis Formation. It is partly equivalent to the Phosphoria Formation of Montana, Idaho, Wyoming, and Utah.
References