Tethys Ocean
The Tethys Ocean (/ˈtiːθɪs, ˈtɛ-/ TEETH-iss, TETH-; Greek: Τηθύς Tēthús), also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean during much of the Mesozoic Era and early-mid Cenozoic Era. It was the predecessor to the modern Indian Ocean, the Mediterranean Sea, and the Eurasian inland marine basins (primarily represented today by the Black Sea and Caspian Sea).[1][2]
During the Early Mesozoic era, as Pangaea broke up, the Tethys Ocean was defined as the ocean located between the ancient continents of Gondwana and Laurasia. After the opening of the Indian and Atlantic oceans during the Cretaceous Period and the breakup of these continents over the same period, it came to be defined as the ocean bordered by the continents of Africa, Eurasia, India, and Australasia. During the early-mid Cenozoic, the Indian, African, Australian and Arabian plates moved north and collided with the Eurasian plate, which created new borders to the ocean, a land barrier to the flow of currents between the Indian and Mediterranean basins, and the orogenies of the Alpide belt (including the Alps, Himalayas, Zagros, Caucasian and Ural Mountains). All of these geological events, in addition to a drop in sea level rise from Antarctic glaciation, brought an end to the Tethys as it previously existed, fragmenting it into the Indian Ocean, the Mediterranean Sea, and the Paratethys.[1][2]
It was preceded by the Paleo-Tethys Ocean, which lasted between the Cambrian and the Early Triassic, while the Neotethys formed during the Late Triassic and lasted in some form up to the Oligocene–Miocene boundary (about 24–21 million years ago) when it completely closed.[1][3] A portion known as the Paratethys was isolated during the Oligocene (34 million years ago) and lasted up to the Pliocene (about 5 million years ago), when it largely dried out.[4] The modern inland seas of Europe and Western Asia, namely the Black Sea and Caspian Sea, are remnants of the Paratethys Sea.[1]
Terminology and subdivisions[edit]
The eastern part of the Tethys Ocean is sometimes referred to as Eastern Tethys. The western part of the Tethys Ocean is called Tethys Sea, Western Tethys Ocean, or Paratethys or Alpine Tethys Ocean. The Black, Caspian, and Aral seas are thought to be its crustal remains, though the Black Sea may, in fact, be a remnant of the older Paleo-Tethys Ocean.[5]
The Western Tethys was not simply a single open ocean. It covered many small plates, Cretaceous island arcs, and microcontinents. Many small oceanic basins (Valais Ocean, Piemont-Liguria Ocean, Meliata Ocean) were separated from each other by continental terranes on the Alboran, Iberian, and Apulian plates. The high sea level in the Mesozoic flooded most of these continental domains, forming shallow seas.
During the early Cenozoic, the Tethys Ocean could be divided into three sections: the Mediterranean Tethys (the direct predecessor to the Mediterranean Sea), the Peri-Tethys (a vast inland sea that covered much of eastern Europe and central Asia, and the direct predecessor to the Paratethys Sea), and the Indian Tethys (the direct predecessor to the Indian Ocean).[6] The Turgai Strait extended out of the Peri-Tethys, connecting the Tethys with the Arctic Ocean.[7]
As theories have improved, scientists have extended the "Tethys" name to refer to three similar oceans that preceded it, separating the continental terranes: in Asia, the Paleo-Tethys (Devonian–Triassic), Meso-Tethys (late Early Permian–Late Cretaceous), and Ceno-Tethys (Late-Triassic–Cenozoic) are recognized.[8] None of the Tethys oceans should be confused with the Rheic Ocean, which existed to the west of them in the Silurian Period.[9] To the north of the Tethys, the then-land mass is called Angaraland and to the south of it, it is called Gondwanaland.[10]
