ABSTRACT

Evaporite components of the Elk Point Group, primarily consisting of salt, comprise in ascending order, the Lower and Upper Lotsberg units, and the Cold Lake and Prairie formations. The Lotsberg salts are restricted to the central Alberta sub-basin. The Cold Lake salt occurs in both the central and northern Alberta sub-basins. The Prairie salt extends from North Dakota to northern Alberta. Dissolution occurred along the updip limit of only the upper three salts, generating narrow, linear, north-northwest-trending salt scarps. Successive salt scarps are offset farther and farther to the west.

The updip limit of bitumen deposits in the Lower Cretaceous Mannville Group coincides with the crest of the asymmetrical Athabasca Anticline, which was produced primarily by post-Early Cretaceous dissolution along the Prairie salt scarp. Prior to Mannville deposition, the present location of the Prairie salt scarp had been established and salt removal was nearly complete to the east of the salt scarp in the Fort McMurray area and the area southeast of the Meadow Lake Escarpment in Saskatchewan. The bulk of post-Early Cretaceous salt removal occurred post-Second White Specks and was primarily removed from along the toe of the salt scarps. Up to 75 m thick intervals of salt were removed from along the Prairie salt scarp. Maximum removal (100 m) occurred over the Cold Lake and Upper Lotsberg salt scarps, adjacent to the Meadow Lake Escarpment. Bitumen migrated across the crest of the Athabasca Anticline north of Township 86, where there was less than 50 m of post-Mannville collapse.

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Pre-Mannville salt dissolution was related to groundwater flowing from the Canadian Shield, whereas later dissolution is suggested to have been primarily a function of gravity driven, west-to-east meteoric flow in the Western Canada Sedimentary Basin.

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