New England Karst Aquifers
From Tobin and Weary (2004):
In the New England States, solution terrain is confined to crystalline limestones and marbles mainly in northeastern Maine, western Vermont, and western Massachusetts. Solution features in these areas are primarily narrow fissures generally less than 200 ft (60 m) long and less than 30 ft (10 m) deep. A few small caves are known in western Vermont and in the Berkshire Mountains of western Massachusetts. In eastern Vermont and much of Maine, carbonate rocks high in silica and other impurities' are commonly, yet incorrectly, referred to as limestone. Solution features are generally absent in these rocks.