The
Taconic orogeny was a mountain building period that ended 440 million years ago and affected most of modern-day
New England. A great mountain chain formed from eastern
Canada down through what is now the
Piedmont off the East coast of the United States. As the mountain chain eroded in the
Silurian and
Devonian periods, sediments from the mountain chain spread throughout the present-day
Appalachians and midcontinental North America.