Type Locality:

Calmont Leduc No. 3, in 4-14-51-21W4M, central Alberta, between 1,521 and 1,594 m (4,990 and 5,230 ft).

Distribution:

The formation extends from the southern Alberta Woodbend shelf north and west into central Albena, terminating as an effective unit roughly west of the Fifth meridian. Northeast and east of the Redwater Leduc reef the Cooking Lake incorporates increasing amounts of basinal micrites in its upper cycles until only the lower Cooking Lake remains as a correlatable carbonate unit that extends to subcrop at the pre-Cretaceous unconformity. Thickness ranges from 60 to 90 m (197 to 295 ft), with maximum thicknesses occurring beneath areas of subsequent Leduc reef growth.

Lithology:

Predominantly limestone except for a belt of dolomite up to 29 km (18 mi) wide along the western margin of the formation (Rimbey-Meadowbrook reef-chain). Limestones and their dolomitized equivalents consist of varied lithologies, including greyish brown nodular mudstones (with scattered crinoids and brachiopods), light to medium brown mudstones and wackestones with gastropods and ostracodes - some with stromatolitic carbonaceous laminae, tan, nonskeletal grainstones with pellets, intraclasts and coated grains, and light to medium brown stromatoporoid rudstones and floatstones. The stromatoporoid bearing carbonates are thickest beneath and immediately away from the overlying Leduc reef complexes.

Relationship:

Conformably overlies the Beaverhill Lake and is conformably overlain, with only minor hiatus by the Leduc Formation reefs or Duvernay Formation off-reef sediments. It clearly predates Leduc reef growth, but may have equivalents in the micritic sediments assigned to the Duvernay away from Leduc build-ups. To the west, beyond the carbonate platform margin basinal sediments of the Majeau Lake Member progressively replace the upper, and finally the greater part of the Cooking Lake carbonates in the deeper part of the Ireton Basin. Cooking Lake platform equivalents probably occur beneath Leduc Windfall reefs in west central Alberta, although they have not been distinguished. In the mountains the Flume Formation is considered to be lithostratigraphically similar to, but probably older than the suburface Cooking Lake Formation.

History:

Originally proposed as a member of the then Woodbend Formation to replace the informal term "First Fragmental". Recommended for elevation to formation status by Andrichuk and Wonfor (1954, p. 2505).

Other Citations:

Andrichuk, 1958; Andrichuk and Wonfor, 1954; Belyea, 1952, 1955, 1957, 1958; Geological Staff, Imperial Oil Limited, 1950; Kirker, 1959; Wendte, 1974.