Nappe

Tectonic ceilings, About Schiebungs or pushing ceilings are flat or undulating body of rock in fold mountains, which are often several kilometers thick and may have a surface area of ​​up to several thousand square kilometers. If a mountain was largely built from such ceilings or pushed over wide areas from a ceiling, says the geologist from the ceiling Mountains.

Construction

The displaced rock body may from their area of ​​origin, the root ceilings, up to its front edge, the ceiling forehead, have been moved many miles and even over 100 km. Ceiling who have fallen with the participation of gravity on low-slope surfaces are referred to as Gleitdecke.

In fold mountains more separate from each other by faults ceilings are often pushed over one another and form a ceiling system. The ceilings in each thrust area is also referred to as allochthonous ( from " education center remote " ), underlying non-displaced crustal areas, however, as autochthonous ( " lying on the ground "). Parautochthone ceilings are only slightly shifted in comparison to their place of origin.

Causes of layer formation

Cause of a ceiling education is strong lateral pressure on already existing arches of the earth's crust, which dates back mostly to large-scale plate tectonics. These processes in the collision of marine or continental plates were detected on 29 August 1912 at the meeting of the Geological Association in Innsbruck and will probably go back to movement processes in the upper mantle. Now, if a piece of the earth's crust (see lithosphere ) is affected by very strong tectonic constriction may occur on a gently sloping, firmer position to a horizontal thrust on other adjacent rock or rock mass.

In detail, the mechanism of layer formation is not fully understood. The thrust of extending it very thin in comparison package of rocks, an increased pore water pressure plays a role, as it pushed through the ceiling up and their resistance to the sliding surface is greatly reduced. Also, the presence of compliant layers such as salt deposits, marls or mudstones supports the formation of ceiling tracks.

Examples

There are large parts of the mountains far from over pushed ceiling systems in the Alps. For example, the ceiling of the Northern Limestone Alps, the greywacke zone and associated rocks have been thrust over at least 150 km above its sub-camps, but probably the transport distance was more than 1000 km. The rocks of the Penninikums and the Helveticum in Switzerland, France and Austria have been transported as a ceiling over similar distances. This also applies to large areas in the Apennines, in the Carpathians and other mountain ranges such as the Himalayas of alpidischen orogeny.

Also from older mountains are ceiling is known, from the Caledonian Mountains in Scotland and Norway, or the Hercynian Mountains ( example: the Moldanubian of the Bohemian Massif or the Giessen ceiling in the Rhenish Slate Mountains).

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