Although well documented from both the Appalachian and Rocky Mountains, an actual mechanism for formation of faults oriented at high angles to the predominant structural trend appears somewhat enigmatic. A system of transverse faults contained within the major Rundle and Sulphur Mountain thrust sheets has been mapped in detail at a scale of 1:12,000. Mesoscopic fractures, minor folds, and lineations have been analyzed in terms of their interrelation with the major structural features to more accurately delineate the relative timing and actual deformation mechanisms. Analysis of available field data indicates progressive eastward-advancing deformation characterized by large-scale folding followed by thrusting. Specifically, the transverse fault system consists of a major f ult which offsets the Sulphur Mountain thrust and terminates within the Rundle thrust sheet and several minor transverse offsets which are restricted to the Sulphur Mountain thrust sheet. Actual translation along transverse faults is thought to coincide with motion along a major hanging wall of an imbricate slice in the Rundle thrust sheet, while post-dating both motion along the Sulphur Mountain sheet and folding of foreland sediments. Calculated values for net slips are approximately parallel to associated lineations and range from a few centimeters to slightly greater than 300 m oriented at high angles to bedding. Analysis of mesocopic fractures indicates a predominance of planes striking roughly normal to the "b" tectonic axis with dips ranging between 60 and 90° in either direc ion. The observed displacements are thought to have occurred predominantly

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along these preexisting fracture planes in response to extensional forces imposed by the Rundle thrust stepping up-section.

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