Geologic Evolution of the Denali Fault System and Associated Crustal Structure

The active right-lateral Denali Fault spans the North American Cordillera from British Columbia through Alaska. The fault intersects diverse and complex geology, which manifests as variable geophysical properties of crust along the fault. Here, we use new P-receiver functions and compiled geologic maps to review how the geologic evolution of the fault is expressed in the seismological data sets. Outcomes from our analysis include the following: (1) the eastern Denali Fault is a profound geologic and geophysical boundary, whereas the western Denali Fault is not; (2) the active strand of the Denali Fault is localized in the east and multistranded in the west; and (3) the Denali Fault is a composite feature wherein the eastern section of the fault formed since 50 Ma and the western section formed during the Cretaceous. Along-strike variability in the geology associated with the Denali Fault results in variable geophysical character of the fault ranging from a discrete boundary that penetrates the lithosphere in the east to nearly undetectable in the west. Altogether, the geologic and geophysical signature of the Denali Fault highlights its importance in the Cordilleran geologic framework and emphasizes the intrinsic variability that arises from the development of >1,000-km-long continental fault systems.