The Relations Between Folds and Late-Formed Joints in South Pembrokeshire

Abstract

AbstractThe late-formed joint sets in the Armorican belt of south Pembrokeshire are younger than both the folds and wrench faults of the region. On fold limbs these joint sets are oriented normal to bedding surface and symmetrically about axial-traces. Lens-belts and joint-drags parallel to the joint sets indicate a shearing pattern parallel to stratification planes. The orientations of fractures in collapsed blocks of Carboniferous Limestone, in Triassic breccias, show that the late joints were formed before the end of the Triassic. The term kathetal-joints is used for those which always remain normal to bedding surfaces.