Valais Ocean
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The Valais Ocean is a disappeared piece of oceanic crust which was situated between the continent Europe and the microcontinent Iberia. The Valais Ocean is together with other small disappeared oceanic basins often called the Alpine or Western Tethys Ocean.
Tectonic history
After the breakup of Pangaea in the early Mesozoic age the continents Africa, South America, Europe and North America began to move away from each other. The breaking up or rifting was not a process that happened along one clear line. At the southern edge of the European plate the microcontinent Iberia began also to break away from Europe. In the western part of the rift that separated the two landmasses oceanic crust was formed in what is at present the Gulf of Biscay, while in the eastern part the Valais Ocean was formed.
When in the Cretaceous period Africa began to move towards Europe again the Valais Ocean was sandwiched between the two continents. To the east the Valais oceanic crust, together with a piece of Iberian continental crust (called the Briançonnais terrane) subducted beneath the Apulian plate, a part of the African tectonic plate that had begun to move independently. This process eventually lead to the formation of the Alps. To the west no subduction took place, but the Iberian plate moved along and against the European plate along a large transform fault, which lead to the formation of the Pyrenees.
Fragments of Valais oceanic crust have been obducted and can be found as ophiolites in the Penninic nappes of the Alps.
Name
The Valais Ocean is named after the Swiss canton Valais.