Unit Name: Cathedral Formation
Unit Type: Lithostratigraphic
Usage: Currently in use
Age Interval: Middle Cambrian (513 - 499 ma)
Province/Territory: Alberta; British Columbia
Originator: Walcott, 1908a,b
South slopes of Mount Bosworth, 8.3 km (5 2 mi) northwest of Lake Louise Alberta, at 51 deg 28'N, 116 deg 19'W (following Rasetti, 1951).
At Ross Lake, the nearest complete section to the faulted type section the Cathedral is 375.4 m (1,231 ft) thick. The thickest section known, at Mount Stephen reaches about 610 m (2,000 ft). Immediately west of this maximum the upper third, more or less, of the Cathedral terminates in the Cathedral Escarpment (McIlreath, 1977a, 1977b), while the lower third persists westward as a rapidly thinning tongue of deep water limestones (ibid.). The Cathedral thins eastward to 159.1 m (522 ft) at the mountain front at Ghost River, and disappears in the subsurface of the plains.
Thickness(m): Minimum 159, Maximum 610.
Limestone, mainly burrow-mottled dolomitic lime-mudstone with minor beds of pellet grainstone and, near the base, a few oolite beds. In the Main Ranges this facies is extensively altered to fine- to coarse-crystalline dolomite. It is a major cliff forming unit. Along the Kicking Horse Rim (Aitken, 1971; McIlreath, 1977a) limestone and dolomite of peritidal origin (oolites, stromatolites and cryptalgal laminite) are prominent; tongues of cryptalgal laminite extend some distance eastward. A tongue of grey-green shale with Albertella, the Ross Lake Member, that may be considered a tongue of the Mount Whyte Formation extends westward almost to the crest of the Rim. A higher, lithologically similar unnamed tongue with Glossopleura is less extensive.
The Cathedral is in gradational contact with the underlying Mount Whyte and Naiset formations, and with the overlying Stephen Formation. Locally, along the Kicking Horse Rim it is in disconformable contact with underlying Gog Group (Precambrian) beds. The Cathedral thins eastward, in part by facies change to the Mount Whyte and Earlie formations. Westward the upper part of the Cathedral terminates along a line through Mount Stephen in a near-vertical reef, the Cathedral Escarpment, buried in shaly rocks of the Stephen Formation (McIlreath, 1977a); the lower part persists a few kilometres further westward in a thinning wedge of slope facies. (ibid.) Southward, along the structural grain the Cathedral plunges from view south of Mount Assiniboine; when coeval rocks next appear, shale-out of the Cathedral (Gordon Shale) has occurred. The considerably thinned carbonate unit remaining is either the Elko Formation or, less likely the Elko plus Windsor Mountain formations. Northward the Ross Lake Shale (with Albertella) and the higher shales (with Glossopleura) thicken, other shaly tongues appear, and the Cathedral passes into the mid-part of the Snake Indian Formation.
Walcott (1917a) amended his original definition of the Cathedral Formation by transferring the lower part to the Ptarmigan Formation (abandoned). Present usage follows that original definition.
McIlreath, I.A., 1977b. Accumulation of a Middle Cambrian deep water limestone debris apron adjacent to a vertical submarine carbonate escarpment, southern Rocky Mountains, Canada. In- Deep-water carbonate environments; Cook, H.E. and Enos, P. (Eds.). SEPM Spec. Pub. 25, p 113-124.
McIlreath, Ian A., 1977a. Stratigraphic and sedimentary relationships at the western edge of the middle Cambrian carbonate facies belt, Field, British Columbia; University of Calgary, Calgary, AB, Unpublished Ph.D. thesis, 269 p.
Rasetti, F., 1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains. Smithsonian Inst., Misc. Coll., v. 116, no. 5.
Walcott, C.D., 1908a. Nomenclature of some Cambrian Cordilleran formations; Smithsonian Miscellaneous Collections, vol. 35, no. 1.
Walcott, C.D., 1908b. Cambrian geology and paleontology: Cambrian sections of the Condilleran area. Smithsonian Miscellaneous Collections, vol. 53, no. 5, pp. 204-208.
Walcott, C.D., 1917a. Cambrian geology and paleontology, Part 4, No. 1. Nomenclature of some Cambrian Cordilleran formations. Smithsonian Miscellaneous Collections, vol. 67, no. 1, pp. 1-8.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: L.V. Hills; J.D. Aitken
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 28 Mar 2014