ABSTRACT

The Muskeg Formation, as established by J. Law in 1955, is a complex of intricately interbedded and interfingering carbonate and evaporite rocks, with interspersed insoluble residual beds. The complex can be divided into several time-stratigraphic entities, which indicate a consistent upward increase in salinity. The vertical succession is consistently repeated in the horizontal dimension as normal marine sediments grade into progressively more saline sediments of an interior barred basin.

In contrast to many recent observations on supra- or intertidal deposition of evaporites, those of the Muskeg Formation are believed to have been laid down from stratified brines filling the deepest part of the basin. Physicochemical considerations permit interpretation of the evaporites of the deeps as roughly synchronous lithic equivalents of carbonate banks and reefs of the shallows.

The seaward position of a broad pre-evaporation shelf in northwestern Alberta was favored for prolific organic activity. Barrier, pinnacle, fringe, and patch reefs growing at shallow depth kept pace with subsidence. Simultaneously, much of the organic substance accumulated under anaerobic conditions in adjacent deeps. Source, reservoir, and trapping conditions thus were provided in a single environment.

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