Deformation within a strike-slip fault network at Westward Ho!, Devon U.K.: Domino vs conjugate faulting

Abstract

A system of NE trending left-lateral faults and NW-trending right-lateral faults at Westward Ho! (north Devon, U.K.) cut steeply dipping (∼60°) strata. Faults were accurately mapped in the field and from aerial photography, and lateral separations of marker beds measured along the fault traces. These data are used to examine the displacements within the network of interacting faults and to calculate variations in the density and relative proportions of the fault sets. The displacements are also used in a tensor analysis of the strain and, together with block rotations, used to restore the deformation. The results show a range of heterogeneity within the fault network, both in terms of the fault patterns and strain. Some sub areas show a dominance of one fault set, with regularly spaced larger displacements, separating relatively weakly deformed blocks with smaller antithetic faults. Within these areas up to 20° rotation of the faults and bedding produces a domino style deformation that accommodates up to ∼15% extension. The domino regions are separated by areas of conjugate faulting, in which both sets of faults are equally developed and have similar displacement ranges. Conjugate areas have little or no rotation of the bedding and generally lower strains than domino regions.