Iapetus Suture

The Iapetus Suture is a major geological boundary tracing the collision of ancient landmasses across the northeastern United States (Maine, New Hampshire, Massachusetts and Connecticut), Newfoundland and Quebec in Canada, Ireland (following the River Shannon estuary to Clogherhead), the Isle of Man (exposed at the Niarbyl Fault) and Great Britain (from the Solway Firth to Lindisfarne). It formed as the ancient Iapetus Ocean closed, during the Salinic and Caledonian orogenies, when the paleocontinents Laurentia, Ganderia, Carolinia, Avalonia and Baltica gradually converged, subducting the intervening oceanic crust until the ocean disappeared by about 420 million years ago, near the end of the Silurian. Its closure involved complex accretion of continental fragments, volcanic island arcs and back-arc basins, and across the regions it crosses the suture marks the boundary between Laurentian rock to the northwest and Avalonian rock to the southeast. This entity documents the Iapetus Suture specifically as a geological formation, the tectonic boundary itself, distinct from Iapetus the Titan of Greek mythology and from Iapetus, the moon of Saturn, both of which take their name from the same mythological figure the suture is named after.