TETON FAULT EVOLUTION PART 2: FAULT GROWTH MODELS AND LENGTH-DISPLACEMENT SCALING RELATIONSHIPS

The Teton fault system in northwest Wyoming separates the Teton Range in the footwall from the Jackson Hole valley in the hanging wall. Although offset across this structure is responsible for uplift of the Tetons, disputes remain regarding the timing of movement, with estimates of onset ranging from 16-2 Ma. These discrepancies in onset timing combined with inconclusive subsurface seismic imaging across the fault lead to disparity in interpreted long- and short-term slip rates and total displacement magnitude. Such variations result in disagreements regarding the accuracy of seismic hazard assessments within this seismically active region. To constrain uplift and cooling history in the Teton Range, Brown et al. (in review) used inverse thermal history models (QTQt) of apatite (U-Th)/He (AHe) ages from three subvertical transects in the immediate footwall from the northern, central, and southern parts of the range-front. In the Brown et al. (in review) study, models from the northern (Moran), central (Grand Teton), and southern (Rendezvous) transects yield rapid uplift timing of 13-8 Ma, 10 Ma-present, and 7 Ma-present, respectively. This southward younging of Teton fault activity indicates a need for additional cooling data to be generated in the southernmost regions of the Teton fault. This data is particularly critical as the southern region is the most heavily populated zone along the fault (Jackson Hole, Wilson, Teton Village). In addition to fault timing, the inverse thermal history models indicate that the Teton fault has accumulated a minimum throw of ~6 km. Length-displacement scaling relationships for normal faults generally range from 10:1 to 100:1, with most faults having L:D of 20:1 to 50:1. If correct, this would indicate that the Teton fault should have a surface length of 120-300 km. Such lengths cause the original Teton fault to extend beneath and/or north of the Yellowstone Caldera system, with the southern Gallatin Range of Montana potentially representing the vestigial fault tip. In this scenario, the Yellowstone segment of the fault would have been obliterated during encroachment of the hotspot. To test this, we will collect AHe subvertical transects in the Gallatin Range in the upcoming field season.