The widespread Meramecian Mount Head Formation (Rundle Group) consists of approximately 500 to 1000 ft of limestones and dolomites, with local shales, sandstones, siltstones, and solution breccias, all of shallow marine origin. In the eastern ranges the formation contains six members -- the Wileman, Baril, Salter, Loomis, Marston, and Carnarvon (Douglas, 1958) -- which are clearly recognizable from the southern Livingstone Range near Crowsnest Pass to the eastern Fairholme Range in the Bow Valley, north of which they lose their distinctive character.
The non-skeletal limestone, solution breccia, and dolomite of the lower four members, which accumulated in shallow shoals, lagoons, and supratidal sabkhas, change facies westward into skeletal limestones of the Livingstone Formation, which were derived from widespread echinoderm-bryozoan shoals. This facies change begins with the Wileman and Baril to the east and progresses westward through the overlying Salter and Loomis. The dolomites and micritic limestones of the overlying Marston and Carnarvon Members, which originated in lagoons and sabkhas, pass westward into the barrier shoal and open marine skeletal and micritic limestones and calcareous shales of the Opal Member (new name). Only the upper part of the Carnarvon Member extends to the west where it overlies the Opal, and represents a return to widespread lagoonal conditions. Correlations across these facies changes are supported by the stratigraphic distribution of four assemblages of corals and brachiopods.