Date of Award

Winter 2022

Project Type

Thesis

Program or Major

Earth Sciences

Degree Name

Master of Science

First Advisor

Joseph Licciardi

Second Advisor

Alia Lesnek

Third Advisor

Michael Palace

Abstract

During the Last Glacial Maximum, major drainages along the east side of the Teton Range were occupied by alpine glaciers that extended to the floor of Jackson Hole. Chronologies of glaciation in the central and northern parts of the range have been developed via 10Be exposure dating of well-preserved terminal and lateral moraine complexes. However, few glacial records have been developed in the southern portion of the range. The metamorphic and sedimentary bedrock and shallow hypsometry of Granite Canyon stand in contrast to the crystalline lithology and steeper hypsometry of glaciated valleys further north along the eastern range front. Granite Canyon offers an opportunity to evaluate how these geologic factors impact the timing and style of glacial fluctuations and the resulting geomorphic expression of moraines. In this study, we report 36Cl and 10Be exposure ages for the Granite Canyon latero-terminal moraine complex, analyze the Granite Canyon glacier hypsometry and moraine morphology relative to adjacent valleys further north, and calculate vertical separation of fault scarps on the lateral moraines to determine cumulative vertical offset rates for the Teton Fault at Granite Canyon since deglaciation. Our results indicate mean ages of 16.5 ± 0.6 ka from 36Cl and 16.9 ± 0.8 ka from 10Be for the terminal, recessional, and right lateral loop moraines and 14.4 ± 0.3 ka from 36Cl for the left lateral moraine. The moraine ages at Granite Canyon record an earlier timing of glacier retreat from its terminus compared with the valleys in the central and northern parts of the range and other western U.S. ranges, and the left lateral moraine suggests upvalley glacier retreat around the same time as the rest of the Teton Range. The early retreat and subtle expression of moraines can likely be attributed to the shallower valley and glacier hypsometry of Granite Canyon. We calculate approximately 11 m of vertical separation on the fault at Granite Canyon, which implies a vertical offset rate of ~0.8 m/ky since deglaciation. This study provides the first Teton Fault vertical offset rate estimates based on direct age control for the Granite Canyon moraines and yields values that are consistent with offset rates from previous studies in the Teton Range. These results improve our understanding of geomorphic controls on glacier behavior, expand on knowledge of the paleoseismic history of the Teton Fault, and inform cosmogenic isotope production rate calibration efforts with the use of multiple isotopes on the same samples.

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