Iapetus Ocean

The Iapetus Ocean (/aɪˈæpɪtəs/; eye-AP-ih-təs)[1] existed in the late Neoproterozoic and early Paleozoic eras of the geologic timescale (between 600 and 400 million years ago).

[4] 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.

From Cambrian times (about 550 million years ago) the western Iapetus Ocean began to grow progressively narrower due to this subduction.

[12] In the west, the Iapetus Ocean closed with the Taconic orogeny (480-430 million years ago), when the volcanic island arc collided with Laurentia.

Some authors consider the oceanic basin south of the island arc also a part of the Iapetus, this branch closed during the later Acadian orogeny, when Avalonia collided with Laurentia.

[13][B] Meanwhile, the eastern parts had closed too: the Tornquist Sea between Avalonia and Baltica already during the late Ordovician,[14] the main branch between Baltica-Avalonia and Laurentia during the Grampian and Scandian phases of the Caledonian orogeny (440–420 million years ago).

Reconstruction of how the Iapetus Ocean and surrounding continents might have been arranged during the late Ediacaran period
Geological fault at Niarbyl . The narrow white diagonal line near centre of picture is where the two sides of the Iapetus Ocean met during its closure. Sutures such as these are the modern evidence for this ancient ocean.
Position of the continents after the Caledonian orogeny ( Devonian to Permian times). Differences in fossil faunas on both sides of the red line (the Iapetus Suture ) are evidence for the existence of an ocean between the two sides in the time before the continents were joined in the supercontinent Pangaea . [ 11 ]