19 Ice sheets, glaciers, and landscapes, oh my!

Glaciers and ice sheets shaped the landscape of the Northeast. Ice continues to shape the landscape of alpine and polar regions. We welcome submissions on glaciers &  ice sheets of any size, shape, age, and location.

Monday, 23 March 2026
8:00 AM - 12:00 PM
CCC, Room 26

Long-lived glacial and post-glacial lake history in the Clyde River valley, Northern Vermont

Paper number: 19-4
Program: Technical Sessions
Time: 9:05 AM – 9:25 AM

Authors

Abstract

The Clyde River drainage basin is the easternmost of three major generally north-flowing drainages feeding Lake Memphremagog along Vermont’s northern border with Québec. Recent mapping in the area reveals a complex and unusual deglacial lake history, one that extends throughout most of the Holocene.

 

A series of glacial lakes flooded the Clyde River valley as the ice sheet retreated NW, down the valley. The oldest and highest of these lakes was dammed by dead ice in the Nulhegan Basin that drained via successively lower-elevation drainage channels into the adjacent Willoughby River valley. Further retreat of the ice sheet past a natural dam (“Great Falls” near West Charleston) left a relatively small, shallow lake in the Clyde River valley. An abandoned outlet channel at the NW end of the lake indicates this lake persisted after the ice sheet retreated farther NW, continuing to dam other lower-elevation lakes in the valley that eventually merged with Glacial Lake Memphremagog.

 

Organic sediments dominate the ~14 km long, broad, low-gradient valley bottom marking the extent of the Holocene lake. Historic records indicate this lake existed until the late 1700’s when the lake drained, possibly catastrophically, as glacial till filling the narrow bedrock outlet eroded. Sediment collected from two in-stream lakes along the course of the Clyde River provide further insight into the history of the Holocene lake in the Clyde River valley. Pensioner Pond is located just upstream from the site of the natural dam and was a bathymetric depression within the larger Holocene lake. Salem Lake, located ~4.5 km downstream from the natural dam, would have received sediment eroded following the dam failure. The stratigraphy in both lakes show a marked increase in clastic sediment consistent with the suspected timing of lake drainage. This pattern is consistent with (1) enhanced focusing of sediment in Pensioner Pond and (2) increased input of sediment into the downstream Salem Lake as the upstream trapping efficiency and storage capacity is reduced following the drainage of the paleolake. Tromino passive seismic profiles indicate that the preglacial Clyde River drained west and was a tributary to the Barton River, another major river flowing north into the modern Lake Memphremagog.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411328

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