Costigan Member

Unit Name: Costigan Member
Unit Type: Lithostratigraphic
Rank: Member
Status: Formal
Usage: Currently in use
Age Interval: Famennian (374.5 - 359.2 ma)
Province/Territory: Alberta

Originator: de Wit and McLaren, 1950.

Type Locality:

Front ranges of the Rocky Mountains near Bow River, Alberta. Named for Mount Costigan, just north of Lake Minnewanka, Banff National Park (southeast portion of Twp. 27, Rge. 10W5M).

Distribution:

The thickness is quite variable and ranges from 18 to 125 m (59 to 410 ft) and typically varies inversely as the Morro Member thickness. The member occurs in the Rocky Mountain Front Ranges of Banff and Jasper National Parks and in the foothills to the east.

Lithology:

Upper beds of dark grey, bedded, fossiliferous limestone; lower beds of cyclic, brownish grey, platy, thin- to medium-bedded dolomite and brecciated to crenulated limestone. Occasionally beds may be quite silty or laminated or contain fragments and nodules of black chert. In the foothills subsurface white anhydrite may occur with very fine dolomite beneath the upper limestone beds from Moose Mountain (Twp. 23, Rge. 6W5) to Brazeau River (Twp. 45, Rge. 13W5M). Dissolution of these beds accounts for the breccias of the Lower Costigan (where they are not obviously of tectonic origin) in outcrop.

Relationship:

The Costigan Member rests conformably on the Morro Member of the Palliser Formation and is overlain disconformably by the Exshaw Formation. The upper limestone beds bear fossils identical in the main with those of the Big Valley Formation, a limestone in the uppermost Wabamun Group of the Alberta Plains.

References:

DeWit, R.W., and McLaren, D.J. 1950. Devonian Sections in the Rocky Mountains between Crowsnest Pass and Jasper, Alberta. Geological Survey of Canada, Paper 50-23.

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.S. Eliuk; M. T. Adamson
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 23 Dec 2008