An integrated regional scheme of lithostratigraphic nomenclature is proposed to encompass the Lower Cretaceous strata on both sides of the international border. The Blairmore Group, defined in the southern Alberta Foothills, is extended to encompass the entire Sweetgrass arch area. The informal Cut Bank sandstone member of northern Montana is raised to formation status and extended into southern Alberta. The Cut Bank Formation is correlated with the Cadomin Conglomerate of the Alberta Foothills.
The Mannville Group formerly was extended to the Lower Cretaceous continental strata of the southern Alberta plains. This name is now restricted to strata occurring north and east of the Sweetgrass arch area which resemble the type Mannville. The Kootenai Formation (Group?) nomenclature, formerly used in Montana, is discarded because of continued confusion with the older, formally defined Kootenay Group of the Alberta Foothills. Most of the informal members defined in various oil fields should be confined strictly to the areas in which they are defined.
The present configuration of the Sweetgrass arch is the product of Late Cretaceous-Early Tertiary Laramide deformation, but the presence of a paleotectonic high coinciding with the present arch trend can be documented from the early Paleozoic. Sedimentation and erosional patterns were greatly affected by the ancestral arch and produced marked stratigraphic variations around it resulting in independent Canadian and American schemes of stratigraphic nomenclature being proposed.