The Devonian system in Manitoba, Saskatchewan, North Dakota, and eastern Montana comprises four major lithologic units of group rank that are named in ascending order: Elk Point, Manitoba, Saskatchewan, and Qu'Appelle. Isopach, lithofacies, tectonic, and environmental maps are employed to present the gross lithologic character and depositional history of each group.

The Elk Point group consists principally of carbonate and evaporite strata and exhibits marked tectonic differentiation into shelf and basin areas. The shelf areas are characterized by normal marine carbonate deposition that includes biohermal-type reefs. The basin area, sharply delineated by isopach and lithofacies patterns, consists of strata that include salt and anhydrite (Prairie evaporite) as much as 600 feet thick. The thickness of the Elk Point group exceeds 700 feet in the basin and thins to a few feet in peripheral areas on the south where near-shore and transitional deposits are recognized.

The Manitoba group consists predominantly of normal marine carbonate strata with several thin persistent argillaceous zones and beds of anhydrite. A basin of limited areal extent contains as much as 300 feet of salt and anhydrite (Davidson evaporite) in central Saskatchewan. Repetitive lithologic sequences suggest a cyclical type of deposition and rhythmic environmental changes. The lowest complete cycle is named the Dawson Bay formation. The group ranges in thickness from 200 to 800 feet.

The Saskatchewan group consists of shelf-type carbonate strata as much as 1,000 feet thick. Two fragmental and reefoid units exhibit marked lateral persistence throughout the area. The upper reefoid unit is correlated with the Nisku member of the Winterburn formation of central Alberta.

The Qu'Appelle group consists of an assemblage of red argillaceous siltstone and dolomitic shales in the east and becomes anhydritic in the west. A persistent silt zone marks the base of the unit. The upper contact is placed at the base of a widespread black bituminous shale that constitutes the lowest black shale zone of the Exshaw formation.

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