ABSTRACT

The area, situated within the Front Ranges sub-province of the Rocky Mountains between Calgary and Banff, includes parts of the Mount Rundle, Inglismaldie, Aylmer, Lac des Arcs, Exshaw, Costigan and Orient thrust sheets, all of which are considered to be parts of the major McConnell thrust sheet and to be underlain by the McConnell fault at depth. The thrust faults from which the respective sheets are named are similarly thought to be branches of the master fault.

Strata comprising the thrust sheets, ranging in age from Middle Cambrian to Lower Cretaceous, have been folded on different scales, possibly as a consequence of lateral variations in competency of rock units in the area. Axial trends of the larger folds are not constant across the thrust faults, and the convergence of fold trends is considered to be a function of rotation of the thrust sheets in a horizontal plane resulting from changes in throw along the bounding faults.

Examples of motion transfer present in the area include the Mount Rundle-Inglismaldie-Lac des Arcs and Aylmer-Exshaw-Costigan families of thrusts, the latter modified by the Ghost River oblique fault. Widespread exposure of the folded McConnell fault resulting from relatively late flexing of the Orient block shows this thrust to have little tendency to follow preferred bedding zones and the other faults of the area appear to have similar stratigraphic relationships.