Unit Name: Eldon Formation
Unit Type: Lithostratigraphic
Usage: Currently in use
Age Interval: Middle Cambrian (513 - 499 ma)
Province/Territory: Alberta; British Columbia
Originator: Walcott, 1908a, b
Indicated by Walcott to be some part of Castle Mountain overlooking Eldon Switch, Alberta, on the Canadian Pacific Railway. Walcott measured the type section on Helena Ridge behind Castle Mountain, as did Deiss (1939a).
At the faulted type section the Eldon is about 340 m (1,115 ft) thick. It thickens westward to 500.5 m (1642 ft) at Mount Bosworth, and in the most westerly sections ranges between 410 and 490 m (1,345 and 1,607 ft). It thins eastward to 258 to 303 m (846 to 994 ft) along the mountain front, and to ultimate disappearance in the subsurface of the Plains approximately along a line joining Red Deer, Strathmore and Claresholm.
Thickness(m): Minimum 258, Maximum 500.5, Typical 340.
Limestone and dolomite. The primary depositional facies is mainly burrow-mottled lime mudstone, with minor beds of pellet grainstone and oolite. Along the Kicking Horse Rim peritidal facies are prominent (cryptalgal laminites, oolites and stromatolites) (Aitken, 1971). Immediately west of the Rim, before the westward dip carries the Eldon from view, it has changed to a regularly thin bedded, dolomitic lime mudstone with many slides and penecontemporaneous folds (slope or ramp facies). In the main ranges the Eldon is extensively altered to pale colored, fine- to coarse-crystalline dolomite. It is a major cliff forming unit. A single eastward-pinching tongue of outer detrital fossiliferous argillite, the informal Field Member or unit interrupts the Eldon carbonates at Mount Field, Mount Stephen and Vermilion Pass.
The Eldon is in conformable, gradational contact with the Stephen Formation below and the Pika Formation above. Westward, with facies changes to argillaceous basinal limestone and shale it passes into the lower and part of the middle units of the Chancellor Formation (McIlreath, 1977a). With eastward shale-out the Eldon passes into part of the subsurface Earlie Formation. Northward the Eldon becomes the Titkana Formation, traceable in essentially the same carbonate facies to at least Pine Pass (Slind and Perkins, 1966). The Eldon is readily identifiable southward to the Mount Assiniboine area, south of which it plunges from view. It probably reappears as the Windsor Mountain Formation in the Castle River area in southwestern Alberta (Norris and Price, 1966), but present faunal control does not conclusively prove this. Along the Kicking Horse Rim the Eldon merges with Pika and Waterfowl equivalents in a thick, rather local multi-storey carbonate mass.
The Eldon, as defined by Walcott was emended by Deiss (1939a, p. 1008), who recognized as the Pika Formation the upper, shady more prominently bedded and lithologically varied part of the type Eldon.
Deiss, C. F., 1939a. Cambrian formations of southwestern Alberta and southeastern British Columbia; The Geological Society of America (GSA), GSA Bulletin, vol. 50, no. 6 (June), pp. 951-1019.
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.
Norris, D.K. and Price, R A., 1966. Middle Cambrian lithostratigraphy of southeastern Canadian Cordillera. Bull. Can. Petrol. Geol., v. 14, p. 385-404.
Slind, O.L. and Perkins, G.D., 1966. Lower Paleozoic and Proterozoic sediments of the Rocky Mountains between Jasper, Alberta and Pine River, British Columbia; Canadian Society of Petroleum Geologists (CSPG), Bulletin of Canadian Petroleum Geology, vol. 14, no. 4 (December), pp. 442-468.
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.
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