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Tethyan oceans


The Tethyan realm is a vast domain that was created during the opening of Paleotethys in the Devonian, as a consequence of the drifting of a ribbon continent, the Galatian superterrane, detached from Gondwana. The Galatian superterrane was accreted to Laurasia in the Carboniferous, soon followed by the collision of Gondwana and Laurasia in the late Carboniferous. At that time the Tethyan oceanic space extended from Sicily to China, forming a large single ocean.

Starting in the early Permian that situation was changed as the Cimmerian super terrane left Gondwana, the Paleotethys closing as the Neotethys opened. The northward subducting Paleotethys induced the opening of numerous Permian to Triassic back-arc oceanic basins in the Laurasian active margin (fig. 220 Ma). From a single ocean in the Carboniferous, the Tethyan space was now occupied by numerous oceanic basins.

When the Cimmerian terranes were accreted to Eurasia in the Triassic, many back-arc basins in Asia were closed producing the Cimmerian orogenic belt, and again a large Neotethys oceanic space occupied the Tethyan realm, however, in the western end of this realm, Triassic back-arc remained opened, creating a complex paleogeographic situation (fig. 155 Ma).

The Neotethys started subducting northward under Eurasia in the late Triassic, opening new back-arc basins in Iran and Turkey (S-Caspian and Izmir-Ankara) during the Jurassic. At the same time Pangea was split in two by the central-Atlantic Alpine Tethys fracture zone that gave birth to a very long but narrow ocean, hardly connected to the Tethyan realm through the east Mediteranean Neotethys remnant basin.

A new situation developed during the Cretaceous when intra Neotethys subduction zones appeared, at the time when west and east Gondwana started separating. This resulted in a division of Neotethys into several oceanic compartments. The new oceanic Cretaceous supra subduction oceans finally obducted onto the passive margin of Gondwana (Arabia, India), closing the older part of Neotethys at the turn of the Cretaceous (fig. 95 Ma).

By the end of the Eocene, most of the Neotethys had closed, excepted the East Mediterranean basin (fig. 57 Ma). The remnant Triassic Paleotethys basins in Greece and Turkey were also closing at that time; their accretionary fronts moving in both direction towards the north and participating into the formation of the Alpine orogeny, and southwards towards the Mediterranean area. In the present days two remnant basins of these back-arc are the Black-Sea and South-Caspian basins.