ABSTRACT

This stratigraphic package corresponds to the Tippecanoe Sequence but includes older and younger rocks in the mountains. Its present distribution is severely constrained by erosion prior to the sub-Devonian Unconformity. The entire package is missing from virtually all of the basin north of the Meadow Lake Escarpment, and locally the Devonian rests directly on Precambrian. The base of the package is a regional unconformity (on Deadwood, Franklin Mountain and Precambrian units) except in the Rocky Mountains, where it is conformable with the McKay and Kechika groups. Unconformities are also present within the package, with significant downcutting in the extreme northwest.

The outcrop sequences of British Columbia, Mackenzie and Alberta disappear abruptly eastward in the subsurface below the sub-Devonian Unconformity. Nonda carbonates (up to 270 m) are the only rocks with any significant subsurface distribution. Preserved in the subsurface of southern Saskatchewan and Manitoba are a basal arenaceous unit

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(Winnipeg) and a sequence of platform carbonates that essentially was depostionally continuous with similar rocks in northeastern Manitoba and the Rocky Mountains. The eastern feather-edge (Winnipeg) is in outcrop at Lake Winnipeg; the western feather-edge (basal Red River; sub-surface) is 150 km west of the Alberta-Saskatchewan border.

The stratigraphic package is thickest (about 500 m) in southeastern Saskatchewan adjacent to thicker developments in Montana and North Dakota. Above the Winnipeg (up to 75 m), the Red River, Stony Mountain, Stonewall and Interlake units represent subtidal to supratidal environments with deposition of shallow water carbonates. Thin evaporitic, argillaceous and sandy intervals provide stratigraphic marker horizons that can be traced for considerable distances in the subsurface.

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