Along-fault migration of the Mount McKinley restraining bend of the Denali fault defined by late Quaternary fault patterns and seismicity, Denali National Park & Preserve, Alaska

Abstract

The tallest mountain in North America, Denali (formerly Mount McKinley, 6,190 m), is situated inside an abrupt bend in the right-lateral strike-slip Denali fault. This anomalous topography is clearly associated with the complex geometry of the Denali fault, but how this restraining bend has evolved in conjunction with the regional topography is unknown. To constrain how this bend in the Denali fault is deforming, we document the Quaternary fault-related deformation north of the Denali fault through combined geologic mapping, active fault characterization, and analysis of background seismicity. Our mapping illustrates an east–west change in faulting style where normal faults occur east of the fault bend and thrust faults predominate to the west. The complex and elevated regional seismicity corroborates the style of faulting adjacent to the fault bend and provides additional insight into the change in local stress field in the crust adjacent to the bend. The style of active faulting and seismicity patterns define a deforming zone that accommodates the southwestward migration of this restraining bend. Fault slip rates for the active faults north of the Denali fault, derived from offset glacial outwash surfaces, indicate that the Mount McKinley restraining bend is migrating along the Denali fault at a late Pleistocene/Holocene rate of ~ 2–6 mm/yr. Ongoing thermochronologic and structural studies of the Mount McKinley restraining bend will extend these constraints on the migration and evolution of the restraining bend deeper in time and to the south of the Denali fault.