Tectonic models have focused on explaining how orogenic belts initiate and develop in terms of plate interactions, but the related problem of how orogenies end has received relatively little attention. This project will address this issue by a detailed study of the circumstances of the ending of the Taconic orogeny in New England, and will involve extensive radiometric age dating. These and extensive existing geological data for this area will be utilized in testing several models of how orogeny terminates. Results are expected to applicable to the general problem.