1. Introduction

Convergent margins often accumulate long-lived lithospheric-scale crustal weaknesses that result from the accretion and dismemberment of terranes (e.g., Wilson, 1965). These mechanical weaknesses frequently manifest as strike-slip faults in oblique convergent settings and slip in response to changing plate boundary conditions (e.g., Powell, 1993; Storti et al., 2003; Najman et al., 2022). The evolution of transform-fault systems is a response, in part, to the orientation of pre-existing faults with respect to variations in plate convergence (e.g., Walcott 1998; McCaffrey et al., 2000). Thus, changes in the orientation of convergence during major plate reconfigurations may modify which faults accumulate strain through geologic time. As fault splays are translated and rotated along a master strike-slip system they can also become preferentially aligned for increased slip accommodation (e.g., Riccio et al. 2014).
Strike slip faults typically have a dip slip component in transpressional settings and thus, thermochronology is often used to document rock cooling along strike slip systems (e.g., Fitzgerald et al., 1995; Benowitz et al., 2014) which can be inferred to reflect periods of partitioned horizontal slip. Exhumation related rapid cooling can also be inferred from kinetic modelling of thermochronology data from strike slip fault corridor sampling transects. Therefore, applying geochronology and thermochronology to rock samples collected along the Totschunda fault integrated with regional geologic constraints presents an opportunity to improve our understanding of the slip distribution on the Denali fault strike-slip fault system and also the mechanisms responsible for slip distribution between the Totschunda and Eastern Denali faults since ca. 52 Ma.
The intersecting Totschunda and Denali faults of Alaska are both interpreted as Cretaceous strike-slip faults that developed across a Mesozoic collisional suture zone with strike-slip reactivation of the suture zone structures (e.g., Churkin et al., 1982; Ridgway et al. 2002; Fitzgerald et al., 2014; Trop et al., 2019, 2020). While plate convergence along the southern Alaska boundary continues, Late Miocene clockwise rotation of the Pacific plate and attached Yakutat microplate relative to North America has influenced tectonics extensively in interior Alaska (e.g., Fitzgerald et al. 1993, 1995; Waldien et al., 2019) and may have drastically modified which faults transfer stress from the plate boundary into interior Alaska. Numerous studies suggest that in response to the Late Miocene Pacific-Yakutat plate motion change, the Eastern Denali fault (Figure 1) has played a diminished role in the transfer of slip from the plate boundary to the continental interior (Waldien et al., 2018; Choi et al., 2021; Allen et al., 2022; Trop et al., 2022; Benowitz et al. 2022a, b). Herein we refer to the Pacific and neighboring Yakutat microplate as the Pacific-Yakutat plate when referencing how the Late Miocene Pacific plate vector change affected Alaska plate boundary conditions.