Folded Faults in Rocky Mountain Foothills of Alberta, Canada

Abstract

A series of thin fault plates, lying in the Brazeau area of the central foothills of Alberta, are described. Developed at the surface in beds of the Upper Cretaceous Alberta group and Brazeau formation, they are folded as a group into several anticlines and synclines. This structure is attributed to two distinct periods of movement. It is shown that the disturbance causing the folding of the fault plates also formed Chungo anticline, the major structure of the Brazeau area. The folded fault system is found to extend throughout a large part of the adjoining foothills, indicating a widespread influence of the two episodes of movement. Many folded faults are found in other parts of the foothills and mountains and a similar tectonic history throughout is suggested. It is post lated that the entire foothill belt and at least the outer ranges of the Rocky Mountains were subjected to low-angle thrust faulting followed by large-scale folding with attendant thrust faulting. It is not suggested that these movements each occurred uniformly throughout the foothills and mountains; in the southern foothills there is some evidence of two periods of faulting prior to the major folding.