Unit Name: Duvernay Formation
Unit Type: Lithostratigraphic
Usage: Currently in use
Age Interval: Frasnian (385.3 - 374.5 ma)
Age Justification: Sparse pelagic fauna of tentaculitids, ostracods, conodonts and embroyonie brachiopods. Also contains specialized forms such as Leiorhyncus walcotti. Bioturbation generally absent.
Originator: Geological Staff, Imperial Oil, 1950.
Type well Anglo Canadian Beaverhill Lake No. 2 in 11-11-50-17W4M, in Alberta, between 1,178 and 1,231 m (3,863 and 4,038 ft); continuous wireline core.
Distributed over most of central Alberta and absent in areas of Leduc reef growth, except beneath the Duhamel reef, where it may be represented by a thin development of calcilutite. At its type section in the East Shale Basin it is 53 m (174 ft) thick; it thickens to 75 m (246 ft) east and southeastward towards the Southern Alberta Shelf. Northeastward it reaches 120 m (394 ft) at its truncation in the subsurface at the pre-Cretaceous unconformity. In the West Shale Basin it averages 60 m (197 ft) thick and thickens northward, attaining over 250 m (820 ft) to the east of Lesser Slave Lake.
Interbedded dark brown bituminous shales, dark brown, black and occasionally grey-green calcareous shales and dense argillaceous limestones. Sediments are characteristically petroliferous and exhibit plane parallel millimetre lamination. Rarely is composed of thin calcarenitic beds and coral rich lime mud accumulations. Disseminated pyrite common within some thin stringers.
Conformably overlies platform carbonates of the Cooking Lake Formation and is the basinal equivalent of surrounding Leduc reef growth peripheral to the East Shale Basin. Thickens, up a depositional slope towards Leduc buildups, passing into lithologies more typical of the lower Ireton Formation which conformably overlie it elsewhere. The top of the Duvernay may therefore be considered partially facies controlled. Northward thick developments previously assigned to this formation may include basinal equivalents of the Cooking Lake, Leduc and Ireton formations and are conformably overlain by the Grosmont Formation. Further westward in the West Shale Basin it overlies shales of a similar lithology which have been assigned to the Majeau Lake Member of the Cooking Lake Formation. It is the lateral equivalent of dark euxinic shales of the Perdrix Formation of the Rocky Mountains. South of the Peace River Arch it may be equated to a thin development overlying the Waterways Formation.
The name was first applied by well-site geologists to describe the brown bituminous shales found in wells drilled in the Duvernay area of east-central Alberta. Originally proposed in 1950 as a member of the Woodbend Formation. Recommended to the geologic names and correlations committee of the Alberta Society of Petroleum Geologists for elevation to formation status by Andrichuk and Wonfor (1954, p. 2505).
Andrichuk, 1961; Andrichuk and Wonfor, 1954; Belyea, 1964; Geological Staff, Imperial Oil Ltd., 1950; Kirker, 1959; Loranger, 1965; Oliver and Cowper, 1963; Stoakes, 1979.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 4, western Canada, including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba; D.J. Glass (editor)
Contributor: F.A. Stoakes
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 21 Mar 2011