227-3 Chronology and Paleoclimate Modelling of Glacier Fluctuations at Mount Eddy, Eastern Klamath Mountains, California, USA

Session: Recent Advances in Glacial Geology, Geomorphology, and Chronology (Posters)

Presenting Author:

Authors:

Abstract:

During the Quaternary, the Klamath Mountains of northern California were glaciated numerous times, as evidenced by moraines and glacial erosional features, such as striations on bedrock and roche moutonnées. Until 2022, when modern glaciers melted completely, the Klamath Mountains had some of the lowest elevation glaciers in the continental United States. This was potentially due to the proximity of the region to the moisture source of the Pacific Ocean. This study focuses on reconstructing past climate change in the region by determining the timing and extent of glacier fluctuations in the Deadfall Lakes basin, located on the western side of the highest peak in the Klamath Mountains, Mount Eddy (2752 masl). Our methods include mapping of glacial features, modelling paleoglacier extent, and constraining the chronology of glacier retreat and advance using analyses of sediments from Middle Deadfall Lake (e.g., bulk density, percent organic matter, x-ray fluorescence, radiocarbon dating and tephra geochemistry). We determined that glaciers retreated from Middle Deadfall Lake basin by ~12,000 cal yr BP. Additionally, we identified several tephra deposits in the lake sediments from volcanic eruptions in the region. Through geomorphic mapping (in field and by satellite imagery), and the use of the PalaeoIce 2.0 Python package for ArcGIS, we determined the Last Glacial Maximum (LGM) Elevation Line Altitude (ELA) was ~2200 masl. (In the absence of modern glaciers in the Mt Eddy watershed, we assumed that the modern ELA is at or above the headwall height.) These values are comparable to that of the northern Sierra Nevada (~300 km to the southeast) which exhibits LGM ELAs of ~2000 - 2400 m and ~200 m higher than those of the Trinity Alps (~30 km to the southwest). Further paleoglacier modeling of these locations using the same methodology (e.g., PalaeoIce 2.0) may offer more insight into differences in LGM ELAs and therefore past climate changes.

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

doi: 10.1130/abs/2025AM-7680

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.