Abrupt changes in structural style and associated stratigraphic thickness across cross-strike lineaments, Rocky Mountain Foothills, northeastern British Columbia

摘要

Abrupt changes in structural style across cross-strike valleys have been mapped in the Foothills of northeastern British Columbia. These changes, which can be characterized as differing degrees of structural disharmony, appear to correspond with changes in thickness of the mechanically weak Triassic Toad-Grayling Formation. The pattern of inferred thickness changes is interpreted to reflect a pre-contractional configuration of small-offset normal faults, linked by minor, cross-strike, oblique-slip faults. Subsequent Laramide contractional deformation resulted in a combination of "thin-skinned" detachment folding and relatively "thick-skinned" reactivation of the pre-existing normal faults (per- haps involving thick Proterozoic units).