Paleontology and geology

During much of the Quaternary, a thick sheet of ice covered Vermont. The weight of that ice depressed the surface of the land, allowing ocean waters to infiltrate the lakes of this region. In westernmost Vermont, fossils in lake deposits indicate that the salinity fluctuated as lake waters mingled with ocean water entering through the St. Lawrence River to the north. As the glaciers melted, the land was able to rebound in elevation, building a barrier to the ocean waters and freshwater lake conditions returned.