EXHUMATION OF THE WESTERN CHUGACH OROGENIC WEDGE: A LOW-TEMPERATURE THERMOCHRONOMETER PERSPECTIVE

The southwest Alaska syntaxial region is a critical area for understanding exhumation processes related to active forearc deformation of a convergent accretionary wedge. The Cenozoic exhumation within and around this syntaxis has been driven by dynamic tectonic and climatic variations, though exhumation has remained focused in the core of the syntaxial bend since at least the mid-Tertiary. Here we review the application of low-temperature thermochronology data and their constraints on exhumational processes in the western Chugach Mountains, Prince William Sound, and surrounding region. The thermochronology ages place constraints on the spatial and temporal patterns of exhumation, which highlight distinct forearc domains across the wedge and also allow us to: (1) quantify the magnitude of rock uplift and exhumation; (2) provide estimates of the long-term exhumation rates; (3) place additional constraints on the timing of transition from steep to flat-slab subduction in this region; and (4) interpret the styles and causes of western Chugach Mountain deformation and uplift. These data and interpretations are put in context with numerical, physical, and theoretical models of convergent wedge deformation and exhumation during orogenesis. Regionally, these findings provide insight into the understanding and timing of the near- and far-field effects of flat-slab subduction in south-central Alaska. This area may serve as a key empirical example of forearc deformation along a major active subduction zone, which may have important implications for understanding the processes and potential imprints of exhumation recorded in ancient orogens.