Denali fault slip rates and Holocene–late Pleistocene kinematics of central Alaska

The Denali fault is the principal intracontinental strike-slip fault accommodating deformation of interior Alaska associated with the Yakutat plate convergence. We obtained the first quantitative late Pleistocene–Holocene slip rates on the Denali fault system from dating offset geomorphic features. Analysis of cosmogenic 10Be concentrations in boulders ( n = 27) and sediment ( n = 13) collected at seven sites, offset 25–170 m by the Denali and Totschunda faults, gives average ages that range from 2.4 ± 0.3 ka to 17.0 ± 1.8 ka. These offsets and ages yield late Pleistocene– Holocene average slip rates of 9.4 ± 1.6, 12.1 ± 1.7, and 8.4 ± 2.2 mm/yr−1 along the western, central, and eastern Denali fault, respectively, and 6.0 ± 1.2 mm/yr−1 along the Totschunda fault. Our results suggest a westward decrease in the mean Pleistocene– Holocene slip rate. This westward decrease likely results from partitioning of slip from the Denali fault system to thrust faults to the north and west.