Unit Name: Pika Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Middle Cambrian (513 - 499 ma)
Province/Territory: Alberta
Originator: Deiss, 1939a
Type Locality:
Helena Ridge, Alberta at 51 deg 18'30"N, 115 deg 54'W, part of the Castle Mountain massif. The type section is continuous with that of the Eldon Formation.
Distribution:
Like most Middle Cambrian formations the Pika thickens from east to west; it is 159 m (522 ft) at the type section. On the Bow River transect the formation thickens from slightly more than 90 m (295 ft) at the mountain front to 237 m (777 ft) at Mount Bosworth. The greatest measured thickness is 361 m (1,184 ft), at Chaba River. Eastward, the Pika thins to extinction in the subsurface of the plains. The Pika is the most extensive of the Middle Cambrian carbonate formations. It extends northward from south of Mount Assiniboine to Kakwa Lake, and from the main ranges eastward to Rge. 8W4M (111 deg N) (Pugh, 1971).
Locality Data:
Thickness(m): Minimum 90, Maximum 361, Typical 159.
Lithology:
The Pika Formation is dominated by thin-bedded lime mudstone with burrowed, dolomitized partings. In the lower part westward pinching tongues of shale form the basal units of limestone dominated, shallowing-upward small scale cycles, with some flat pebble conglomerate in the upper units. In the main ranges dolomitization is erratic; in the front ranges the upper third is a consistently dolomitized member with many beds of oolite and flat pebble conglomerate.
Relationship:
The Pika is in gradational contact with the underlying Eldon and Titkana formations in the west, and with the shady Earlie Formation in the eastern subsurface. Its contact with the overlying Arctomys Formation is abrupt and may be disconformable; beneath the plains its contact with the overlying Sullivan Formation is unconformable. The Pika passes westward into basinal shaly limestone of the upper middle Chancellor Formation (McIlreath, 1977a). Along the Kicking Horse Rim the Pika merges with the underlying Eldon and overlying Waterfowl carbonates into a single multistorey carbonate unit.
History:
Deiss recognized as the Pika Formation the upper, shale more prominently bedded and lithologically varied part of Walcott's (1908a, b) type Eldon.
References:
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.
Pugh, D.C., 1971. Subsurface Cambrian stratigraphy in southern and central Alberta. Geological Survey of Canada, Paper 70-10.
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