Iapetus Ocean
The southern Iapetus Ocean opened between Laurentia and southwestern Gondwana (now South America) about 550 Ma in the Ediacaran–Cambrian transition. At the time it did so the Adamastor Ocean further east closed. The opening of the Iapetus Ocean probably postdates the opening of the Puncoviscana Ocean with the Iapetus Ocean being separated from the Puncoviscana Ocean by the ribbon-shaped Arequipa-Antofalla terrane. However, the formation of both oceans seems unrelated.