COMBINING APATITE (U-TH)/HE AND FISSION-TRACK DATING: IMPLICATIONS FOR DIFFERENTIAL UPLIFT OF THE TETON RANGE AND INITIATION OF THE TETON FAULT, WYOMING

Early efforts at quantifying the evolution of the Teton Range using apatite fission-track dating (AFT) revealed differential uplift rates between the northern and southern parts of the range; however, because the closure temperature for AFT is ~105°C, questions remained unanswered regarding the latest stages of exhumation. Relative to the rest of the Rocky Mountains, the Tetons experienced the majority of their uplift very recently, further substantiating the need for a more detailed thermochronological analysis. Previously, fission-track dating has been successfully integrated with other low-temperature thermochronometers to reconstruct exhumational histories and to deduce timing, rate, and slip on normal faults systems. In addition to new AFT data, we utilized apatite (U-Th)/He dating (AHe), recognized for its notably lower closure temperature, to analyze a series of transects across the Teton Range at Rendezvous Mountain, the Grand Teton, and Mount Moran, and along the range-front Teton fault. Preliminary AHe ages are consistent with previous AFT data suggesting asymmetric cooling and exhumation, particularly apparent in the northern Tetons, where the highest elevation samples yield Late Oligocene AHe ages. We also present new estimates for long-term uplift rates as well as fault initiation, which will assist in resolving controversy regarding the age and displacement of the Teton normal fault. Furthermore, data from the range-front transect helps define temporal and spatial variations in along-strike onset, and may eventually clarify ideas regarding how normal fault blocks evolve.