Iapetus Suture

The geological fault zone resulting from the continental collision is known as the Iapetus Suture, named after the ocean it replaced.

The closure of Iapetus involved a complex and protracted collisional history of numerous continental fragments, volcanic arcs and back-arc basins that were accreted to Laurentia and Avalonia between the Early Ordovician and Late Silurian.

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.

The Middle Ordovician Red Indian Line is considered the main Iapetan suture zone in that it separates peri-Laurentian and peri-Gondwanan oceanic elements.

The Dog Bay Line is a younger feature in the Appalachians and delineates the terminal Iapetan suture in Newfoundland as it marks the Early Silurian (Salinic) collisional zone between Ganderia and Laurentia.

Reconstruction showing the collision of three paleocontinents during Caledonian orogeny approximately 390 million years ago. The red line shows where the Iapetus Suture extends through present-day Ireland and Great Britain . A related suture through Denmark, Poland and Ukraine is the Trans-European Suture Zone .
Photograph of the Kilkee Cliffs on the Loop Head Peninsula. These are folds from the closure of the Iapetus Ocean at the end of the Silurian period. [ 3 ]
The Niarbyl Fault marks the Iapetus Suture on the Isle of Man. The rocks at top and left formed in Laurentia but the rocks at lower right formed in Gondwana