Graduation Date
Fall 2025
Document Type
Thesis
Program
Master of Science degree with a major in Environmental Systems, option Geology
Committee Chair Name
Laura Levy
Committee Chair Affiliation
Cal Poly Humboldt Faculty or Staff
Second Committee Member Name
Jacky Baughman
Second Committee Member Affiliation
Cal Poly Humboldt Faculty or Staff
Third Committee Member Name
Brandon Browne
Third Committee Member Affiliation
Cal Poly Humboldt Faculty or Staff
Fourth Committee Member Name
Andrew Malone
Fourth Committee Member Affiliation
Community Member or Outside Professional
Keywords
Northern California, Klamath Mountains, Last glacial maximum, Mt. Eddy, Thompson Peak, Paleoclimate, Equilibrium line altitude, Glaciers, PalaeoIce, Sediment provenance, Red Banks Tephra, Radiocarbon, Core chronology, X-ray fluorescence
Subject Categories
Geology
Abstract
This study reconstructs the timing, extent, and paleoclimate conditions associated with late Pleistocene glaciation in the Mount Eddy region of the eastern Klamath Mountains, northern California and investigates the provenance of clastic sedimentation in Middle Deadfall Lake, just east of Mt Eddy. Using a multi-pronged approach that combines geomorphic mapping, sediment core analysis, X-ray fluorescence (XRF) geochemistry, tephrochronology, and glacier modeling using PalaeoIce 2.0, this research provides new insights into glacial dynamics and climate variability in a region with limited glacially derived paleoclimate datasets, as well as past volcanic eruption deposits.
Field and GIS-based geomorphic mapping identified three generations of moraines, interpreted as distinct stages of glacial advance and retreat Deadfall Basin. Paleoglacier reconstructions in Deadfall Basin, along with Stuart Fork Valley, and Sugar Pine Valley of the Trinity Alps indicate that the Last Glacial Maximum (LGM) equilibrium-line altitudes (ELAs) in the Klamath Mountains range from 2200 – 1920 m.
Sediment cores from Middle Deadfall Lake contain multiple tephra layers, including a deposit that is geochemically correlated to the Red Banks Plinian eruption from Mount Shasta, which provides a stratigraphic age marker of 10,900 ± 200 cal yr BP. Radiocarbon dating and Bayesian age-depth modeling constrain the timing of final glacier retreat from the basin to 11,390 ± 490 cal yr BP, synchronous with regional deglaciation in northern California.
Paleoclimate modeling based on reconstructed ELAs suggests temperature depressions of approximately 4 –7.5 °C and precipitation rates between 50–110% of modern values during the LGM in the Klamath Mountains. These results indicate that glaciation in the Klamath Mountains occurred under cooler and drier to marginally wetter conditions relative to the present. The persistence of a west-to-east precipitation gradient in the Klamath Mountains inferred from differences in LGM ELAs and modern ELAs between Mount Eddy and the Trinity Alps, emphasizes the role of proximity to moisture source on regional glaciation.
This research provides the first reconstruction of LGM glacier extent and paleoclimate conditions in the Mount Eddy region and the first to correlate LGM glacier extent from Mt Eddy to the Trinity Alps, contributing a critical dataset to the limited paleoglacial record in the Klamath Mountains. These results emphasize the sensitivity of valley glaciers to changes in temperature and precipitation and highlight the need for continued research in the glacial variability and climate dynamics of the Klamath Mountains.
Citation Style
APA
Recommended Citation
Stebbins, Emily, "Provenance of clastic sedimentation in Middle Deadfall Lake and paleoclimate modelling of glacier fluctuations at Mount Eddy, eastern Klamath Mountains, California, USA" (2025). Cal Poly Humboldt theses and projects. 2531.
https://digitalcommons.humboldt.edu/etd/2531