Date of Award

Spring 5-11-2025

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Earth Sciences

First Committee Advisor

Brenda Hall

Second Committee Member

Thomas Lowell

Third Committee Member

Aaron Putnam

Additional Committee Members

George Denton, Katherine Allen, Karl Kreutz

Abstract

The end of the last ice age provides to most recent geologic analog to the speed and magnitude of modern climate change. By understanding how the earth’s climate systems interacted during the termination of the last ice age, we can better inform models of future climate change. Here, I investigate the end of the last ice age through the glacial-geologic record to further develop our understanding of the mechanisms at play during times of abrupt climate change. Using cosmogenic nuclide exposure age dating, I developed a chronology of past ice extents in Antarctica and Maine. To begin, I investigated the mechanisms controlling ice-sheet extent in the Royal Society Range, Antarctica (Miles et al., 2024). There, I found that while marine mechanisms, such as sea-level and sea-temperature, play a defining role in the extent of marine terminating glaciers, glaciers which do not meet the ocean expand and retreat out of phase with marine terminating glaciers. The extent of these glaciers is primarily controlled by accumulation. Thus, during climatic warming, they expand slightly due to increased accumulation. This work bears on predicting the future of the East Antarctic ice sheet, where marine-terminating portions will continue to retreat while land-terminating portions may thicken. In Maine, my work focused on using the cosmogenic nuclide record to track past changes in ice sheet thickness in the area around Katahdin. There, I found evidence of a stillstand or readvance an ice mass in the valley south of Katahdin. Ages on the iv moraine indicate that this event occurred at 14.5 ka at the beginning of the Bølling–Allerød (14.6 – 12.8 ka). I also developed a thinning history from ages of boulders along Keep Ridge and the Basin Ponds moraine. These ages indicate that ice retreated from the summit before 16.1 ka, when the Basin Ponds moraine was formed. The Basin Ponds moraine has a bimodal age distribution, with ages clustering at 16.1 ka and 14.5 ka. Ages below the moraine show that ice retreated rapidly from the area after 14.5 ka. Together, this work in Maine provides information about the timing of climatic warming during the termination of the last ice age in Maine. This dissertation uses the past history of ice sheets to further our understanding of the end of the last ice age.

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