Deformation bands record oblique-slip faulting in the Cañon City Embayment, Colorado

The Caon City Embayment (CCE) in south-central Colorado is a large-scale syncline comprised of Ordovician to Tertiary sedimentary rocks overlying Proterozoic basement that was affected by several major faults during the Laramide orogeny. Such faulting may be accompanied by a damage zone that, when within highly porous rocks, manifests itself as arrays of deformation bands that increase in density towards the fault. As such, the deformation bands are precursors to the faults, with geometric and kinematic properties related to the fault that they are associated with. Three field areas were studied and measurements were collected on 1131 deformation bands. The orientation and kinematics of the deformation bands indicate that they are part of oblique-slip fault damage zones. The field area with the highest deformation band density describes a contractional horsetail splay that may have developed from pre-existing weaknesses from older faults attributed to the Ancestral Rocky Mountain orogeny.