Bronson Hill Island Arc

The Bronson Hill Island Arc is a bimodal volcanic terrane and associated sediments that are thought to have docked with Laurentia (North American) during the Ordovician, (ca 450 Ma) to create the Taconic Orogeny. These rocks are presently well exposed along the Connecticut River Valley of Vermont and New Hampshire. The arc is evidenced by plutonism and extrusive volcanics including the Ammonoosuc Formation (ca. 461 Ma from U/Pb zircon dates) and the overlying Partridge Formation (ca. 457 Ma from graptolites in the Partridge Fm.). The docked island arc has been metamorphosed and deformed during the Acadian Orogeny and the Alleghenian Orogeny.