MAPPING AND INTERPRETING THE GLACIAL HISTORY OF THE STOWE QUADRANGLE, NORTHERN VERMONT

Glacial history is an important factor in the evolution of the New England landscape. Ice movement and associated sediment deposition have left behind a record that can be used as a tool to reconstruct the geologic past and understand the current layout of surficial materials. This project focuses on the Stowe Quadrangle in northern Vermont, an area that extends across the Little River Valley from the Green Mountains to the west and the Worcester Mountains to the east. We recorded evidence for glacial movement and mapped the different glacial materials in the area. Our findings are presented as a geologic map of surficial materials, geologic cross sections that illustrate the 3-D distribution of those materials, and an interpretation of the glacial history of the area. Field work was conducted in June 2019 using the mobile app Fulcrum to record observations at over 2,500 sites. Traditional topographic maps, aerial imagery, and LiDAR shaded-relief imagery were used in conjunction with our field observations in QGIS software to create a surficial geologic map of our field area.

Glacial striations in the quadrangle are dominated by two distinct sets, one striking NW-SE, which can be found particularly at higher elevations, and another striking N-S, which are most common at lower elevations in the valley. Using these data we determined that the Laurentide Ice Sheet had originally flowed NW-SE obliquely across the mountains. As the ice thinned and became confined by the topography, it flowed N-S, parallel to the Little River valley. A brief overview of our data shows that glacial till is the most wide spread surficial material deposited across the mapping area. The retreating ice sheet dammed the Winooski River valley, leading to the formation of a series of glacial lakes. The two lakes that formed in this area were Glacial Lakes Winooski, which rose to approximately 315 m, and Mansfield, which reached a lower elevation of approximately 225 m. These glacial lakes deposited the widespread fine-grained lacustrine sediments observed at lower elevations. Following the Laurentide Ice Sheet’s retreat from the Winooski River Valley and the draining of the glacial lakes, the Little River and its tributaries have been incising through the lacustrine sediments, forming the abandoned terraces and eroded deltas that we observed.