Mountain-building event that affected the Appalachian Geosyncline along the eastern coast of the U.S. Evidence for the orogeny is most pronounced in the northern Appalachian Mountains, but its effects can be noted as far away as Tennessee and Georgia.
Events ascribed to it include the development of New York's Taconic Range and Vermont's Green Mountains. Originally thought to have occurred at approximately the Ordovician-Silurian boundary ( 0441; 443 million years ago), it is now generally considered to have consisted of several pulses from the mid-Ordovician to the early Silurian Period.