Valais Ocean
Encyclopedia
The Valais Ocean is a disappeared piece of oceanic crust
which was situated between the continent Europe
and the microcontinent Iberia
or so called Briançonnais microcontinent
. The Valais Ocean is together with other small disappeared oceanic basins
often called the Alpine or Western Tethys Ocean
.
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 rift
ing 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.
canton
Valais
.
Oceanic crust
Oceanic crust is the part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium...
which was situated between the continent Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and the microcontinent Iberia
Iberian Peninsula
The Iberian Peninsula , sometimes called Iberia, is located in the extreme southwest of Europe and includes the modern-day sovereign states of Spain, Portugal and Andorra, as well as the British Overseas Territory of Gibraltar...
or so called Briançonnais microcontinent
Briançonnais microcontinent
The Briançonnais zone or Briançonnais terrane is a piece of continental crust found in the Penninic nappes of the Alps.According to some paleogeographic reconstructions the rocks of the Briançonnais zone were in fact a part of the microcontinent Iberia, that encompassed not only the Iberian...
. The Valais Ocean is together with other small disappeared oceanic basins
Oceanic basin
Hydrologically, an oceanic basin may be anywhere on Earth that is covered by seawater, but geologically ocean basins are large geologic basins that are below sea level...
often called the Alpine or Western Tethys Ocean
Tethys Ocean
The Tethys Ocean was an ocean that existed between the continents of Gondwana and Laurasia during the Mesozoic era before the opening of the Indian Ocean.-Modern theory:...
.
Tectonic history
After the breakup of PangaeaPangaea
Pangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....
in the early Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
age the continents Africa, South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, Europe and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
began to move away from each other. The breaking up or rift
Rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....
ing 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
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
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
Continental crust
The continental crust is the layer of igneous, sedimentary, and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial due to more felsic, or granitic, bulk composition, which lies in...
(called the Briançonnais terrane
Briançonnais microcontinent
The Briançonnais zone or Briançonnais terrane is a piece of continental crust found in the Penninic nappes of the Alps.According to some paleogeographic reconstructions the rocks of the Briançonnais zone were in fact a part of the microcontinent Iberia, that encompassed not only the Iberian...
) subducted
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
beneath the Apulian plate
Apulian Plate
The Adriatic or Apulian Plate is a small tectonic plate carrying primarily continental crust that broke away from the African plate along a large transform fault in the Cretaceous period. The name Adriatic Plate is usually used when referring to the northern part of the plate...
, a part of the African tectonic plate that had begun to move independently. This process eventually lead to the formation of the Alps
Alps
The Alps is one of the great mountain range systems of Europe, stretching from Austria and Slovenia in the east through Italy, Switzerland, Liechtenstein and Germany to France in the west....
. To the west no subduction took place, but the Iberian plate moved along and against the European plate along a large transform fault
Transform fault
A transform fault or transform boundary, also known as conservative plate boundary since these faults neither create nor destroy lithosphere, is a type of fault whose relative motion is predominantly horizontal in either sinistral or dextral direction. Furthermore, transform faults end abruptly...
, which lead to the formation of the Pyrenees
Pyrenees
The Pyrenees is a range of mountains in southwest Europe that forms a natural border between France and Spain...
.
Fragments of Valais oceanic crust have been obducted
Obduction
Obduction is the overthrusting of continental crust by oceanic crust or mantle rocks at a convergent plate boundary. It can occur during an orogeny, or mountain-building episode....
and can be found as ophiolites in the Penninic nappes
Penninic nappes
The Penninic nappes or the Penninicum are one of three nappe stacks and geological zones in which the Alps can be divided. In the western Alps the Penninic nappes are more obviously present than in the eastern Alps , where they crop out as a narrow band...
of the Alps.
Name
The Valais Ocean is named after the SwissSwitzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
canton
Cantons of Switzerland
The 26 cantons of Switzerland are the member states of the federal state of Switzerland. Each canton was a fully sovereign state with its own borders, army and currency from the Treaty of Westphalia until the establishment of the Swiss federal state in 1848...
Valais
Valais
The Valais is one of the 26 cantons of Switzerland in the southwestern part of the country, around the valley of the Rhône from its headwaters to Lake Geneva, separating the Pennine Alps from the Bernese Alps. The canton is one of the drier parts of Switzerland in its central Rhône valley...
.