Autochthonous (geology)

Autochthonous (from ancient Greek αὐτός autós "self" and χθών chthōn "earth", so for example "indigenous", "stationary" or "long-established") is an attribute in geology for rocks or rock packages that were created or remained on the spot are. The term parautochthon is used for rocks or rock groups that are only marginally transported and still have a certain connection to their place of formation . On the other hand, allochthonous rocks or rock groups or their substance have been moved to their current position.

What the name means exactly depends on the context. Sedimentary rocks are autochthonous if the vast majority of the material they are made of was formed in the deposition area before the actual sedimentation . This applies to most limestones , but never to e.g. B. sandstones or silt stones . Such allochthonous sediments are also called detritic .

In structural geology , autochthonous means that a rock formation has remained stationary during a mountain formation . Autochthonous rock units in this sense (also referred to as the autochthonous ) are always at the base of stacks of tectonic nappes . A tectonic blanket is by definition never autochthonous.

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• Collective of authors: Lexicon of Geosciences. Volume I. Spectrum Academic Publishing House, Heidelberg / Berlin 2000, ISBN 3-8274-0299-9 , p. 171