| Abstract: | The Cambro-Ordovician Iapetus and Tornquist's Oceans formed a Pacific-type ocean basin rimmed by volcanic island arcs and marginal basins. By the latest Ordovician to earliest Silurian this ocean basin was beginning to close, to become a Mediterranean-type ocean basin. This was caused by the collision between a microcontinent (comprising England, Wales, much of Ireland and parts of north-west Europe), called Eastern Avalonia, and the North American super-continent, Laurentia, which resulted in no oceanic crust remaining in the region of present-day central Newfoundland. Marine basins, however, persisted into the Middle Silurian. Throughout the Silurian and early Devonian, some 40–45 million years, various terranes continued to collide with the North American margin, predominantly under major left-lateral strike-slip until the remaining seaways were eliminated in the early Middle Devonian, to be replaced by terrestrial environments of the Old Red Sandstone. |
