Author ORCID Identifier

https://orcid.org/0000-0002-8288-7236

Year of Publication

2020

Degree Name

Master of Science (MS)

Document Type

Master's Thesis

College

Arts and Sciences

Department/School/Program

Earth and Environmental Sciences (Geology)

First Advisor

Dr. J. Ryan Thigpen

Abstract

The Teton fault is a range-front normal fault in northwestern Wyoming. Previous estimates of the maximum displacement (Dmax) on the Teton fault cover a wide range (2 - 11 km). Discrepancies also exist regarding the slip onset timing, which spans 2 - 13 Ma. To address these discrepancies, the exhumation history of the Teton Range is here investigated using forward flexural-kinematic (Move) and thermal-kinematic (Pecube) models that can be compared with previously reported apatite fission track (AFT) and apatite (U-Th)/He (AHe) ages from Mount Moran, which has been previously hypothesized to represent the paleo-center of the Teton fault.

In this study, kinematic models that include flexural isostasy and erosion were constructed to test possible structural solutions for Teton fault evolution. Free parameters include fault dip angle, elastic thickness (Te), depth of detachment (Zd) and magnitude (Dmax) and duration of slip. Flexural parameters and the fault subsurface geometry were constrained by comparing model results with the present-day wavelength of footwall uplift and structural configuration of the Jackson Hole basin. This led to the identification of a reference model that includes a surface fault dip of 70°, Te of 5 km, and Zd of 15 km. This reference model structural evolution is then used to create velocity fields for the thermalkinematic models, which produces a 2D thermal history that includes predicted AFT and AHe ages, to be compared with the observed ages.

The flexural-kinematic models yield predictions of the footwall uplift contribution to total fault slip, which can then be compared to the range of Dmax estimates. Using these model results, previous estimates for Dmax (2 - 9 km) correspond to footwall uplifts of 0.7- 2.4 km. For comparison, the modern footwall relief at Mount Moran (~1.8 km) and Grand Teton (~2.2 km) would yield modeled Dmax estimates of 6 - 8 km, which is a minimum estimate, as these values do not account for an estimated ~2 km of overburden erosion. Thus, these model results indicate that the Dmax for the Teton fault is likely >9 km. To produce the footwall uplift necessary to exhume reset AFT ages observed at the base of the Moran transect (~4.2 km), flexural-kinematic models require Dmax estimates of 13 - 17 km. Results from the thermal-kinematic history that best match observed AHe and AFT data include Dmax estimates of 15 - 17 km. These preferred models also suggest that the onset Teton fault motion and footwall exhumation began ~12 Ma.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2020.487

Funding Information

National Science Foundation, Award # 1932808, 2020

Geological Society of America, Graduate Student Research Grant, 2019

Earth and Environmental Sciences Ferm Fund, 2019

Earth and Environmental Sciences Brown-McFarlan Fund, 2019

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