The dramatic relief of the Teton Range in northwestern Wyoming results from motion along the Teton normal fault. New apatite (U-Th)/He (AHe) and fission track (AFT) ages of samples collected in the footwall yield fundamental constraints on contrasting models of Teton fault activity and consequent relative footwall uplift. Low-elevation samples in the immediate footwall of the fault range from 12.5 to 6.5 Ma. AHe ages of samples from subvertical transects range from 57.8 to 6.5 Ma (Rendezvous), 54.0 to 6.8 Ma (Grand), and 20.5 to 7.1 Ma (Moran), with all three transects yielding an expected trend of decreasing age with decreasing elevation. AFT ages obtained from the three transects range from 55.4 to 45.7 Ma (Rendezvous), 43.2 to 13.3 Ma (Grand), and 38.0 to 11.7 Ma (Moran). Inverse thermal history modeling indicates that the onset of relatively rapid cooling, as a proxy for relative footwall uplift, initiated first in the northern part of the range (15–13 Ma) and then migrated south as fault displacement continued (7 Ma to present at Rendezvous). Thus, this work suggests that although the Teton fault likely initiated due to Basin and Range extension, this structure remains active. Normal fault displacement models also suggest a minimum of ~6 km displacement for footwall uplift of ~2 km. If evaluated in the context of established normal fault length-displacement relationships, this yields a length of ~180 km, substantially longer than current estimates of Teton fault length and putting the northern end of the fault well into, and potentially beyond, the bounds of Yellowstone National Park.
|Number of pages||24|
|State||Published - Nov 2017|
Bibliographical noteFunding Information:
The authors thank Jeff Rahl and Rick Law for numerous discussions in the early stages of this research. Philip Mothena provided invaluable assistance in the field. Barbara Carrapa is recognized for providing the equipment and guidance necessary for fission track analysis. Midland Valley generously provided the academic license of Move used for the structural and geomorphic calculations. This research was funded by The Geological Society of America Graduate Student Research Grant program, the Sigma Xi Grants-in-Aid of Research program, and the VT Geosciences Heath Robinson- Roy J. Holden Fund grants to S. J. B. Critical reviews by Andrew Carter, Ryan McKeon, two anonymous reviewers, and Editor John Geissman helped to substantially improve earlier versions of this work. Data used in this study are available in the tables, figures, and supporting information.
©2017. American Geophysical Union. All Rights Reserved.
- Teton Range
- fission track
- normal fault
ASJC Scopus subject areas
- Geochemistry and Petrology