Iapetus Ocean

The Iapetus Ocean (/aɪˈæpɪtəs/; eye-AP-ih-təs) existed in the late Neoproterozoic and early Paleozoic eras of the geologic timescale (between 600 and 425 million years ago). It was in the Southern Hemisphere, between the paleocontinents of Laurentia, Baltica and Avalonia. The ocean disappeared with the Acadian, Caledonian and Taconic orogenies, when these three continents joined to form one big landmass called Euramerica. The "southern" Iapetus Ocean has been proposed to have closed with the Famatinian and Taconic orogenies, meaning a collision between western Gondwana and Laurentia. Because the Iapetus Ocean was positioned between continental masses that would at a much later time roughly form the opposite shores of the Atlantic Ocean, it can be seen as a sort of precursor of the Atlantic, and the process by which it opened shares many similarities with that of the Atlantic's initial opening in the Jurassic. The Iapetus Ocean was therefore named for the titan Iapetus, who in Greek mythology was the father of Atlas, after whom the Atlantic Ocean was named. At the start of the 20th century, American paleontologist Charles Walcott noticed differences in early Paleozoic benthic trilobites of Laurentia (such as Olenellidae, the so-called "Pacific fauna"), as found in Scotland and western Newfoundland, and those of Baltica (such as Paradoxididae, often called the "Atlantic fauna"), as found in the southern parts of the British Isles and eastern Newfoundland. Geologists of the early 20th century presumed that a large trough, a so-called geosyncline, had existed between Scotland and England in the early Paleozoic, keeping the two sides separated. With the development of plate tectonics in the 1960s, geologists such as Arthur Holmes and John Tuzo Wilson concluded that the Atlantic Ocean must have had a precursor before the time of Pangaea. Wilson also noticed that the Atlantic had opened at roughly the same place where its precursor ocean had closed.