Unit Name: Birdbear Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Frasnian (385.3 - 374.5 ma)
Province/Territory: Saskatchewan; Idaho; Montana; North Dakota; Wyoming
Originator: Sandberg and Hammond, 1958.
Type Locality:
Mobil Oil Producing Co. No. 1 Birdbear (C SENW-22-149N-91W), in Dunn County, North Dakota, between 3,142.5 and 3,169.9 m (10,310 and 10,400 ft). A characteristic reference section in southwestern Saskatchewan (Kent, 1963) is in the Mobil Oil Woodley Sinclair Cantuar X-2-21 well, in Lsd. 2-21-16-17W3M, between 1,377.1 and 1,396.9 m (4,518 and 4,583 ft).
Distribution:
On average the Birdbear Formation is about 30 to 45 m (98 to 148 ft) thick, with the thickest sections occurring in west-central Saskatchewan. The lower member ranges in thickness from 5 to 33 m (16 to 108 ft), the upper member range is from 6 to 42 m (20 to 138 ft). The thickest development of the lower member is in the Kindersley-Rosetown area of western Saskatchewan. The upper member is thickest in the Maple Creek area of southwestern Saskatchewan. The formation is present south of a line running approximately east-west near Saskatoon, throughout the Williston Basin.
Lithology:
The lower member is composed predominantly of nonargillaceous limestones and dolomites, the upper member is mainly dolomite with interbedded evaporites. Near the Saskatchewan-Alberta border the lower Birdbear is composed of argillaceous carbonates. Generally the carbonates are yellowish brown and crypto to microcrystalline, with sparse faunal content except for the upper part of the lower member, and local concentrations. Faunal descriptions are given in Warren and Stelck, 1956, 1968a; Nichols, 1970.
Relationship:
The lower contact with argillaceous carbonates of the Duperow Formation is generally conformable, though locally disconformable (Kent, 1968a, p. 35; Dunn, 1975, p. 26). The upper contact with carbonates of the Torquay Formation is irregular and gradational. The local absence of some Torquay strata in western Saskatchewan gives rise to a disconformable contact. The Birdbear is equivalent to the upper Southesk Formation of the Rockies and eastern Alberta, and the upper Ireton and lower Nisku formations of central Alberta.
Other Citations:
Halabura, 1982; Kent, 1963, 1968a; Nichols, 1970; Sandberg and Hammond, 1958; Warren and Stelck, 1956; 1968a.
References:
Dunn, Colin E., 1975. The Upper Devonian Duperow Formation in Southeastern Saskatchewan; Province of Saskatchewan, Department of Mineral Resources, Saskatchewan Geological Survey, Sedimentary Geology Division, Saskatchewan Industry and Resources (SIR) Report No. 179, 149 p., 4 tables, 19 plates, 26 figures (7 in pocket).
Kent, D.M., 1968a. The geology of the Upper Devonian Saskatchewan Group and equivalent rocks in western Saskatchewan and adjacent areas; Saskatchewan Department of Mineral Resources, Saskatchewan Industry and Resources (SIR) Report No. 99, 221 p., 8 tables, 21 plates, 3 figures. 9 maps, 2 panel diagrams, 14 cross sections, in pocket.
Nichols, R.A.H., 1970. "The petrology and economic geology of the Upper Devonian Birdbear Fonmation in southeastern Saskatchewan"; Sask. Dept. Min. Res., Rept. 125.
Sandberg, C.A. and Hammond, C.R., 1958. "Devonian System in Williston Basin and central Montana"; American Association of Petroleum Geologists (AAPG), AAPG Bulletin, vol. 42, pp. 2293-2334.
Warren, Percival Sidney and Stelck, Charles Richard, 1956. "Devonian faunas of Western Canada, Part 1 of Reference fossils of Canada"; Geological Association of Canada, Special Paper no. 1, 15 p.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: K.R. Milner; C.E. Dunn
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 30 Mar 2009