LOW TEMPERATURE THERMOCHRONOLOGY CONSTRAINTS ON EXHUMATION ALONG AND ACROSS THE EAST-CENTRAL DENALI FAULT, ALASKA

The intracontinental Denali Fault is a ~2000 km long obliquely transpressional curvilinear structure in south-central Alaska. The arcuate shape of the fault results in partitioning of strain and a gradual decrease in Quaternary dextral slip rate from east to west. The central segment of the Denali Fault curves through the Alaska Range Suture Zone, while the relatively linear east-central segment marks the boundary between lithotectonic terranes of contrasting rheologic strength. The rheologically weaker Yukon Composite Terrane lies north of the Denali Fault while the rheologically stronger Wrangellia Composite Terrane lies to the south. Our area of interest is the linear east-central segment of the Denali Fault that is located between the Alaska Range Suture Zone and the Denali-Totschunda fault junction. This study is apart of a collaborative NSF project that seeks to determine the competing inputs of fault geometry and rheologic strength in controlling deformation patterns along strike-slip faults. We contribute to this end by considering vertical tectonics on the east-central Denali Fault and on subsidiary thrusts by constraining spatial-temporal patterns of exhumation using low temperature thermochronology. We present preliminary apatite fission track thermochronologic data and apatite (U-Th)/He dates from basement samples in thrust sheets on the south side of the east-central Denali Fault. The east-central Denali Fault represents a natural opportunity to test the relative contributions of fault geometry and rheologic strength because it is linear in trace, proximal to a restraining bend, and marks the boundary between two accretionary tectonic terranes of varied rheologic strength.