An autochthon in
structural geology is a large block or mass of rock which is in the place of its original formation relative to its basement or foundation rock. It can be described as rooted to its basement rock as opposed to an
allochthonous block or
nappe
In geology, a nappe or thrust sheet is a large sheetlike body of rock that has been moved more than or above a thrust fault from its original position. Nappes form in compressional tectonic settings like continental collision zones or on the o ...
which has been relocated from its site of formation.
[ ]
image:thrust system en.jpg, upright=1.6, Schematic overview of a thrust system. The hanging wall block is (when it has reasonable proportions) called a
nappe
In geology, a nappe or thrust sheet is a large sheetlike body of rock that has been moved more than or above a thrust fault from its original position. Nappes form in compressional tectonic settings like continental collision zones or on the o ...
which overlays the autochthonous (unrelocated) material. A hole in the nappe which exposes the underlying autochthonous material is called a
window
A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent mat ...
. A klippe is a solitary outcrop of the nappe in the middle of autochthonous material.
While an autochthon may have experienced some minor shifting, an allochthonous block will have moved at least a few kilometres.
[Marko, F., Jacko, S., 1999]
''Structural geology (General and systematic).''
Vydavateľstvo Harlequin, Košice, p. 81 - 93 If an overlying allochthon has an opening or hole which exposes the underlying autochthonous material, the hole is called a
window
A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent mat ...
or fenster.
Autochthonous
sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...
is sediment found at or very close to its site of deposition.
The etymology of the term is from Greek: 'autos' means self, and 'chthon' means earth.
See also
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Tectonics
Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents k ...
References
External links
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Structural geology
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