Mapping in the core of the north–central Cordillera of British Columbia has revealed a system of relatively closely spaced steeply dipping faults cutting across an earlier penetrative fabric consisting of recumbent folds and intensely cleaved sedimentary rocks. The earlier (Mid – Late Jurassic) penetrative deformation was separated from the later (Late Cretaceous – Tertiary) deformation by regional uplift, normal faulting, and initiation of intermontane deposition. The Upper Cretaceous – Lower Tertiary Sifton Formation was involved only in the later deformational pulse. Kink folding and oblique faulting are the principal mechanisms of the later pulse. The orientation of principal regional contraction changed from an early WSW–ENE direction to a late SSW–NNE direction. From this it is inferred that some of the young lineaments along and near the Rocky Mountain Trench are probably oblique–slip faults with unknown, but probably small right–lateral slip components.

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