A THERMOCHRONOLOGICAL PERSPECTIVE ON CENOZOIC TECTONICS ALONG THE DENALI FAULT SYSTEM ACROSS ALASKA

The integrated application of a broad range of thermochronometers to samples collected along and across the strike of a strike-slip fault system allows: a) insight into the long-term slip history of the fault system, b) the relationship between geometric complexities and regions of focused exhumation c) delineation of block rotation boundaries, d) constraints on slip-partitioning onto linked fold and thrust belts, and ultimately e) insight into the history of convergent margin processes.

In this synthesis we compile thermochronometers from ⁴⁰Ar/³⁹Ar hornblende through (U-Th)/He apatite to capture the Cenozoic thermal history along a ~800 km transect of the Denali Fault system. We contour new and published data by radiometric system to emphasize regions of deep exhumation (>~10 km) and changes in material flux through time. Highlights include: 1) the identification of two regions of deep Neogene exhumation (Cottonwood Complex Nutzotin Mountains; Mount Hayes region of the eastern Alaska Range), 2) significant late-Miocene to present vertical tectonics (~ 5 km) on fold and thrust belts on both sides of the Denali Fault system (Northern Alaska Range Fold and Thrust Belt Kansas Creek Fault; Southern Alaska Range Fold and Thrust Belt, Susitna Glacier Thrust Fault and McCallum Thrust Fault), 3) the identification of a previously unmapped high angle fault near Mount Nenana, 4) the interpretation that the Totschunda Fault system has experienced limited vertical tectonics since the Cretaceous (~ 5 km), 5) the delineation of significant Neogene deformation in the Revelation Mountains related to the block boundary between the southern Alaska Block and the Bering Block, and 6) identification of episodes of exhumation along the DFS that vary in space and time but can be correlated with regional tectonic events including a regional Eocene thermal perturbation, late Oligocene to Present flat slab subduction of the Yakutat microplate, Pacific Plate vector changes, and variations in both the geometry of the southern Alaska Block and orientation to the trench of the Totschunda Fault, as the Totschunda Fault is translated along the arc of the Denali Fault system.