80-8 Testing Three Luminescence Dating Methods on Glacial Moraines in the Beartooth Mountains, Montana, USA

Session: Recent Advances in Glacial Geology, Geomorphology, and Chronology

Presenting Author:

Authors:

Abstract:

Cirque glaciers are highly sensitive to changes in terrestrial climate. Dating glacial moraines is one way to reconstruct the history of a glacier’s advance and retreat, thereby building an indirect record of local climate conditions. In this study, we visited two cirque glaciers in the Beartooth Mountains of southern Montana and northern Wyoming. These glaciers were previously constrained as readvancing in the late Holocene using in situ cosmogenic Be-10 surface exposure dating of moraine boulders. We collected samples from some of those previously dated glacial moraine boulders and sand samples from nearby morainal till. The till samples were collected in transects, from the crest of the lateral moraines to the modern ice margin. We measured the luminescence rock surface exposure ages for the boulder samples, burial ages from some of the till samples, and portable luminescence reader signals from still other till samples. Initial results suggest moderate agreement between Be-10 and luminescence rock surface exposure ages, with a high degree of scatter and no systematic offset between techniques. Sediment burial ages are in proper stratigraphic (e.g., recessional) order, with burial ages comparable to Be-10 results. Portable luminescence reader measurements show some systematic relationship with position along the transect. We discuss possible interpretations for the observed scatter between methods and potential for developing luminescence methods for moraine deposition, especially on Holocene timescales.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-11114

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