Unit Name: Brazeau Formation
Unit Type: Lithostratigraphic
Usage: Currently in use
Age Interval: Late Cretaceous (99.6 - 65.5 ma)
Province/Territory: Alberta; British Columbia
Originator: Malloch, 1911.
Section measured on the southernmost branch of Wapiabi Creek in the Bighorn Basin of the central Foothills, Alberta (52°27'N, 116°35'W).
Malloch (1911) indicated the type section to be about 520 m (1,706 ft) thick in the Bighorn Coal Basin. However, the section there is not a true thickness because the top has been erosionally truncated. Recently a complete, 950 m (3116 ft) thick section of the Brazeau Formation was measured and described by Jerzykiewicz (1985) and Jerzykiewicz and Sweet (1988) along Blackstone River between 52 deg 44'N, 116 deg 15'W and 52°42'40"N, 116°19'W, which now serves as a supplemental reference section. The Brazeau Formation occurs within the Foothills between the Kakwa River valley in the northwest to the Bow River valley in the southeast.
A nonmarine succession of interbedded mudstone, siltstone and fine-grained sandstone with subordinate, but prominent coarser grained sandstone layers. Chert-pebble conglomerate occurs in the lower part of the formation. Thin coal beds, coaly shale and numerous thin bentonites occur in the upper part of the formation. The sandstone is grey to greenish grey, and usually has a salt-and-pepper appearance due to chert and lignitic fragments. The mudstone is greenish grey to dark grey; some organic-rich mudstones are almost black. Fluvial fining-upward cycles are most common, but a variety of lacustrine facies, including offshore rhythmites are also present.
The Brazeau Formation overlies the marine Wapiabi Formation and is overlain by the nonmarine Entrance Conglomerate, which occurs at the base of the Coalspur Formation. The Brazeau is correlative to the Belly River, Bearpaw and St. Mary River formations of the southern foothills.
The name Brazeau was first introduced by Malloch (1911) for 520 m (1716 ft) of "...alternating beds of black and brown shales, with greenish grey sandstones containing pebbles of chert..." which he observed above the marine Wapiabi Formation in the Bighorn Basin. The formation was included in the Saunders Group by Allan and Rutherford (1923). MacKay (1930, p. 486) later extended the name Brazeau to the Coal Valley area, where he applied it to the entire estimated thickness of 3330 m (9812 ft) of post-Wapiabi strata including the coal beds. Later MacKay (1943, p. 3) modified his ideas on the Brazeau Formation and limited it to an interval of about 1425 m (4674 ft) of strata above the Wapiabi Formation and below a quartzite cobblestone conglomerate at the base of the Edmonton Formation which he observed about 275 m (902 ft) below the lowest coal seam. Lang (1947, p. 32) used the name Brazeau for the interval from the top of the Wapiabi Formation up to the base of a prominent conglomerate bed which he named the Entrance Conglomerate. The Brazeau Formation has subsequently been utilized in mapping by Douglas (1958b), Irish (1965b), Ollerenshaw (1966), and in regional stratigraphic studies (Jerzykiewicz and McLean, 1980).
Allan, John Andrew and Rutherford, Ralph L., 1923. Saunders Creek and Nordegg coal basins, Alberta, Canada; Research Council of Alberta, Geological Survey Division, Report No. 6.
Douglas, R.J.W., 1958b. Chungo Creek map-area, Alberta (report and geologic map 6-1958) (Scale: 1 in. to 1 mile); Geological Survey of Canada, Paper No. 58-3, 45 p.
Irish, E.J.W., 1965b. Geology of the Rocky Mountain Foothills, Alberta; Geological Survey of Canada, Memoir 334.
Jerzykiewicz, T. and McLean, J.R., 1980. Lithostratigraphic and sedimentological framework of coal-bearing Upper Cretaceous-lower Tertiary strata, Coal Valley area, central Alberta Foothills; Geological Survey of Canada, Paper 79-12.
Jerzykiewicz, T. and Sweet, A.R., 1988. Sedimentological and palynological evidence of regional climatic changes in the Campanian to Paleocene sediments of the Rocky Mountain Foothills, Canada. Sed. Geol., vol. 59, pp. 29-76.
Jerzykiewicz, T., 1985. Stratigraphy of the Saunders Group in the central Alberta Foothills - a progress report; Geological Survey of Canada, Paper 85-1B, pp. 247- 258.
Lang, A.H., 1947. Brule and Entrance map-areas, Alberta; Geological Survey of Canada, Memoir 244.
Mackay, B.R., 1930. Stratigraphy and structure of bituminous coal fields in the vicinity of Jasper Park, Alberta. Can. Inst. Min. and Metall., Trans., v. 33, p. 473-509.
Mackay, B.R., 1943. Wawa Creek, Alberta. Geological Survey of Canada, Paper 43-10.
Malloch, G.S., 1911. Bighorn Coal Basin, Alberta; Geological Survey of Canada, Memoir 9, 78 p.
Ollerenshaw, N.C., 1966. Geology, Burnt Timber Creek, West of Fifth Meridian, Alberta; Geological Survey of Canada, Preliminary Map 11-1965, Scale: 1:63 360 = 1 inch to 1 mile, NTS 82O/11.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: T.T.Z. Jerzykiewicz
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 20 Jul 2009