 The closure of Iapetus involved a complex and protracted collisional history of numerous micro-continents, volcanic arcs and back-arc basins that were accreted to Laurentia and Avalonia between the Early Ordovician and Late Silurian.The notion of a single suture zone in a complex orogen such as the Appalachian/Caledonian is unrealistic as several temporal and spatial distinct suture zones are present.The Early Ordovician (Taconic) Baie Verte Line in Quebec and Newfoundland marks the boundary between the continental margin of Laurentia and Iapetan oceanic rocks, while the Early Ordovician (Penobscot) GRUB Line defines the contact between the vestiges of Iapetus and Ganderia.