Constraining Displacement Magnitude on Crustal-Scale Extensional Faults Using Thermochronology Combined With Flexural-Kinematic and Thermal-Kinematic Modeling: An Example From the Teton Fault, Wyoming, USA

Abstract

Constraining the geometry and displacement of crustal-scale normal faults has historically been challenging, owing to difficulties with geophysical imaging and inability to identify precise cut-offs at depth. Using a modified workflow previously applied to contractional systems, flexural-kinematic (Move) and thermal-kinematic (Pecube) models are integrated with apatite (U-Th)/He (AHe) and apatite fission track (AFT) data from Teton footwall transects to constrain total Teton fault displacement (D_max). Models with slip onset at ∼10 Ma and flexure parameters that best match the observed Teton flexural profile require D_max > 8 km to produce young (<10 Ma) AHe ages observed at low elevation footwall positions in the Tetons. For the same slip onset, models with D_max of 11–13 km provide the best match to observed AHe data, but displacements ≥16 km are required to produce observed AFT ages (13.6–12.0 Ma) at low elevations. A more complex model with slow slip onset at ∼25 Ma followed by faster slip at ∼10 Ma yields a good match between modeled and observed AHe ages at a D_max of 13–15 km. However, this model predicts low elevation AFT ages 6–8 Ma older than observed ages, even at D_max values of 16–17 km. Based on this analysis and integration with previous studies, we propose a unified evolution wherein the Teton fault likely experienced 11–13 km of Miocene-recent displacement, with AFT data likely indicating a pre-to early Miocene cooling history. Importantly, this study highlights the utility of using integrated flexural- and thermal-kinematic models to resolve displacement histories in extensional systems.