Transverse faulting in the Paradox Basin, Colorado Plateau, USA: Active, intermittent faulting over a 300 million year history of strain accommodation and fluid flow

Abstract The Paradox Basin (Colorado Plateau, USA) is dominated by major, first-order northwest-trending structures commonly 40 km or more in trace length, including (1) regional salt wall corridors related to passive diapirism during Pennsylvanian to Jurassic time, (2) gentle upright folds produced by Laramide shortening during the Late Cretaceous through early Cenozoic, (3) late Laramide normal faults, and (4) normal faults representing Neogene salt dissolution collapse. Less obvious at a regional scale are the fault zones aligned perpendicular (northeast-trending) to the dominant structural grain. There are 16 such faults zones, marked by short trace lengths (3–12 km), small offsets (10–100 m), and predominantly extensional kinematics. Based on published geological maps, field observations of fault zone properties (including fluid flow indicators), and kinematic analysis, we interpret these structures as transverse accommodation faults. Co-spatial structural associations reveal the transverse fault zones were active intermittently, likely as a means of minimizing along-strike strain incompatibility that accrued along the first-order structures as they evolved during late Paleozoic to Late Jurassic halokinesis, (mild) Late Cretaceous to Eocene folding, late Laramide normal faulting, and Neogene to recent collapse faulting. Locally, transverse faulting was influenced by reactivation of northeast-striking faults that offset sub-salt formations, including basement. Active, intermittent transverse faulting over the past ~300 m.y. is consistent with the synthesis of published interpretations and age determinations focusing on the timing of diverse fluids that exploited the permeability of the transverse fault zones. The Paradox Basin, with its enormous subsurface salt volume and enduring fluid flow, has been an ideal dynamic environment for producing intermittently active transverse accommodation faulting.