Terranes are geologic regions reflecting the role of plate tectonics in Connecticut’s history. The name of each plate reflects its ancestral origins. There are four major terranes in Connecticut. (DEP, 1990)
Proto—North America Terrane consists of the original edge of North America before the formation of Pangaea. This matches the northwest highlands of Connecticut and contains the aforementioned carbonate shelf. (Bell, 1985)
Iapetos Terrane is split into two due to the Newark terrane (formed from the great crack or the splitting apart of Pangaea. It underlies the southwest hills of the western uplands and the Windham hills of the eastern uplands. It is comprised of the remnants of the Iapetos Ocean. (Bell, 1985)
The Avalonian Terrane is a remnant left over when the African continent collided with us during the formation of Pangaea. This corresponds to the Mohegan Range of the eastern uplands of our state. (Bell, 1985)
The above three terranes are called collision terranes because they formed due to the formation of Pangaea.. The fourth terrane called the Newark Terrane formed due to the splitting up of Pangaea. The formation of this terrane was similar to a door opening up into the Earth. Due to this “crack,” the region was put under alot of stress. This is where the central valley of Connecticut is located. (Bell, 1985)
From west to east in Connecticut, our terranes go as follows: Proto-North America, Iapetos, Newark, Iapetos, Avalonia. Though today these terranes are hard to recognize from the surface due to erosion and glaciation changing our landscape. Evidence of our geologic past can still be found in the stone walls that abound in Connecticut. (Bell, 1985)
