| The Skeena Fold Belt in northwest British Columbia encompasses the Jurassic-Cretaceous Bowser Basin. Structural mapping indicates that northeast-trending folds, dominant in the west, formed first; these were overprinted by northwest-trending folds, recognized. En echelon vein arrays and brittle faults associated with F2 folds indicate relatively brittle conditions. A local brittle D3 deformation, represented by predominantly strike-slip conjugate faults resulted from north-south shortening. Cleavage is most strongly developed along the west of the fold belt and resulted from pressure solution. Strain shadows represent new mineral growth during deformation. Preliminary whole rock argon geochronology from the western basin margin yields partial plateau ages between 128 and 146 Ma, interpreted as the ages of cleavage development. Deformation probably began in earliest Cretaceous time, coeval with late sedimentation in the Bowser Basin. Structural relationships are consistent with hypothesized sinistral transpression along the paleo-Pacific margin followed by convergence and late strike-slip deformation. |
