The Proto-Tethys or Theic Ocean was an ancient

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wor ...

that existed from the latest

Ediacaran The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and t ...

to the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferou ...

(550–330 Ma).

History of concept

The name "Proto-Tethys" has been used inconsistently for several concepts for a supposed predecessor of the Paleo-Tethys Ocean, a palaeocean that separated the margins of

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final sta ...

, often referred to as peri-Gondwana, from various continents and Gondwana-derived continental fragments from Precambrian times and onwards. According to , after the Cadomian orogenic events 550 Ma, the Proto-Tethys Ocean formed the eastern part of an oceanic domain (of which the

Iapetus In Greek mythology, Iapetus (; ; grc, Ἰαπετός, Iapetós), also Japetus, is a Titan, the son of Uranus and Gaia and father of Atlas (mythology), Atlas, Prometheus, Epimetheus (mythology), Epimetheus, and Menoetius (mythology), Menoetius. ...

and Tornquist oceans formed the western parts) which subducted under the northern margins of

. In this model the Proto-Tethys separated the

North China North China, or Huabei () is a geographical region of China, consisting of the provinces of Beijing, Tianjin, Hebei, Shanxi and Inner Mongolia. Part of the larger region of Northern China (''Beifang''), it lies north of the Qinling–Hu ...

and Baltica continents from Gondwana. In the Early Ordovician 500-480 Ma, the Proto-Tethys was subducted under Cadomia as a result of the Chamrousse

back-arc basin A back-arc basin is a type of geologic basin, found at some convergent plate boundaries. Presently all back-arc basins are submarine features associated with island arcs and subduction zones, with many found in the western Pacific Ocean. Most o ...

. used the name 'Ran Ocean' for a similar concept, the Cambrian-Ordovician ocean that separated Baltica from Gondwana. Other geologists dispute the existence of such an ocean.

Palaeozoic evolution

The ocean formed when

Pannotia Pannotia (from Greek: '' pan-'', "all", '' -nótos'', "south"; meaning "all southern land"), also known as the Vendian supercontinent, Greater Gondwana, and the Pan-African supercontinent, was a relatively short-lived Neoproterozoic supercontine ...

disintegrated, Proto-Laurasia (Laurentia, Baltica, and Siberia) rifted away from a supercontinent that would become

. Proto-Tethys formed between these two supercontinents. The ocean was bordered by

Panthalassic Ocean Panthalassa, also known as the Panthalassic Ocean or Panthalassan Ocean (from Greek "all" and "sea"), was the superocean that surrounded the supercontinent Pangaea, the latest in a series of supercontinents in the history of Earth. During the ...

to the north, separating it from Panthalassa by

island arcs Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries. Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle alon ...

and

Kazakhstania Kazakhstania ( kk, Qazaqstaniya), the Kazakh terranes, or the Kazakhstan Block, is a geological region in Central Asia which consists of the area roughly centered on Lake Balkhash, north and east of the Aral Sea, south of the Siberian craton and ...

. The Proto-Tethys expanded during the

Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago ...

. The ocean was at its widest during the Late

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. T ...

to Middle

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleoz ...

. The ocean was situated between the

Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part ...

to the west, and

to the east. The ocean began to shrink during the Late Silurian, when

, and

South China South China () is a geographical and cultural region that covers the southernmost part of China. Its precise meaning varies with context. A notable feature of South China in comparison to the rest of China is that most of its citizens are not n ...

moved away from Gondwana and headed north. In the late

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wh ...

, the microcontinent of

collided with Siberia, shrinking the ocean even more. The ocean closed when the North China

craton A craton (, , or ; from grc-gre, κράτος "strength") is an old and stable part of the continental lithosphere, which consists of Earth's two topmost layers, the crust and the uppermost mantle. Having often survived cycles of merging and ...

collided with Siberia-Kazakstania continent in the

, while the Paleo-Tethys Ocean expanded.

References

Notes

Sources

* * * * {{Refend

External links