Date of Award
Summer 7-21-2025
Document Type
Thesis (Master's)
Department or Program
Earth Sciences
First Advisor
Meredith Kelly
Abstract
The collapse of the Northern Hemisphere ice sheets subsequent to the Last Glacial Maximum (~26-19 ka) marked one of the largest natural climate change events in recent time. In response to global warming, the Laurentide Ice Sheet (LIS), the ice sheet that covered much of northern North America, receded almost completely during a time known as “Termination 1” (~19-11 ka). The climate changes during this time also caused significant changes in landscape morphology, ecology, and the lifeways of indigenous peoples. This project characterizes the timing of deglaciation and major post-glacial landscape changes across New Hampshire using lake sediment cores. I developed new sediment records from three lakes in central New Hampshire using proxies including visual stratigraphy, radiocarbon dating, loss on ignition, and magnetic susceptibility. I also compiled stratigraphic, radiocarbon, and lithologic proxy data from 19 previously studied lakes across New Hampshire and eastern Vermont. From these data, I generated age-depth models for the new and previously studied lakes and used these to determine the timing of deglaciation of the LIS in New Hampshire and the transition from basal clastic sediment to overlying organic sediment, which marks a significant landscape change.
To assess the broader pattern of deglaciation, I compared the lake-based ages of deglaciation with chronologies of deglaciation based on glacial varves (annually laminated pro-glacial lake sediments) and surface exposure dating. The lake-based ages of regional deglaciation range from ~20 to 13 cal ka BP and show a trend indicative of consistent northward retreat of the LIS, similar to that indicated using varve chronology. I determined the timing of clastic-to-organic sedimentation in the three new lakes and 12 previously studied lakes. The age of the sedimentological transition in the lakes has no clear spatial trend, and dates to ~13.8-11.0 cal ka BP. My results provide a better understanding of regional deglaciation and provide insight into the environmental changes associated with the transition from clastic-to-organic sediment.
Recommended Citation
Randall, Anne Hannah, "A multi-proxy reconstruction of environmental conditions during Termination 1 in central New Hampshire" (2025). Dartmouth College Master’s Theses. 248.
https://digitalcommons.dartmouth.edu/masters_theses/248
Compilation of Lake Record Data
