Flysch
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Vsmith
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[[Image:Carpathian flysch cm03.jpg|thumb|right|200px|Carpathian flysch]]
'''Flysch''' is a sequence of [[sedimentary rock]]s that is deposited in a deep [[marine]] [[sedimentary facies|facies]] in the [[foreland basin]] of a developing [[orogen]]. Flysch is typically deposited during an early stage of the [[orogenesis]], when the orogen evolves the foreland basin will become shallower and [[molasse]] will be deposited on top of the flysch. It is therefore called a [[Orogeny|syn-orogenic]] sediment (deposited contemporaneously with mountain building).
==Sedimentological properties==
Flysch consists of repeated sedimentary cycles with upwards [[Particle size (grain size)|fining]] of the sediments. At the bottom of each cycle are sometimes coarse [[conglomerate (geology)|conglomerates]] or [[breccia]]s, which gradually evolve upwards into [[sandstone]] and [[shale|shale/claystone]]. Typically the shales don't contain many [[fossil]]s, the coarser sandstones often have fractions of [[mica]]s ans [[glauconite]].
Flysch is formed under deep marine circumstances, in a quite and low-energetic depostional environment. The coarser layers (which require higher energy) are disruptions in these circumatsnces, caused by pulsewise flows of [[mass transport]] from the forming orogenic [[accretionary wedge|wedge]]. In many cases the mass transports are represented in the record by [[turbidite]]s.
==Tectonics==
Flysch deposits form at [[Convergent boundary|convergent plate boundaries]] at the stage of [[continental collision]], often in remnant ocean basins that exist along the same boundary. The sedimental material in the flysch is derived from the forming [[mountain]]s and deposited along the axis of the new mountain chain into remnant ocean basin. The same ocean basin is in the process of [[Subduction|subducting]] under the orogenic wedge. As subduction continues, the flysch sediments are scraped off the down-going oceanic plate and are [[accretion (geology)|accreted]] onto the orogenic wedge. As a result, flysch deposits are often highly deformed by [[thrust fault]]ing and [[fold (geology)|folding]].
==Name and use==
The name flysch was introduced in geologic literature by [[Switzerland|Swiss]] geologist [[Bernhard Studer]] in 1827. Studer used the term for the typical alternations of sandstone and shale in the foreland of the [[Alps]]. The name comes from the [[German language|German]] word ''fliessen'', which means ''to flow'', because Studer thought flysch was deposited by rivers. The insight that flysch is actually a deep marine sediment typical for a particular [[plate tectonic]] setting came only much later.<ref>{{aut|Laphart, T.}}; '''2005''': ''Geologie der Schweiz'', Ott Verlag, ISBN 3-7225-0007-9. (in German), see p. 64</ref>
The name flysch is currently used in many mountain chains belonging to the Alpine belt. Well-known flysch deposits are found in the [[foreland]]s of the [[Pyrenees]] and [[Carpathians]] and in tectonically similar regions in [[Italy]], the [[Balkans]] and on [[Cyprus]]. In the northern Alps, the Flysch is also a [[lithostratigraphy|lithostratigraphic]] unit.
==References==
<references/>
===Literature===
*{{aut|Stanley, S.M.}}; '''1999''': ''Earth System History'', W.H. Freeman and Company, New York, ISBN 0-7167-2882-6. See p. 243.
*{{aut|Einsele, G.}}; '''2000''' (2<sup>nd</sup> ed.): ''Sedimentary Basins, Evolution, Facies, and Sediment Budget'', Springer, ISBN 3-540-66193-X. See p. 606-610.
{{Commons|Flysch}}
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===External links===
*[http://5.1911encyclopedia.org/F/FL/FLYSCH.htm Flysch] at ''1911encyclopedia.org''
[[Category:German loanwords]]
[[Category:Sedimentary rocks]]
[[Category:Sedimentology]]
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[[pl:Flisz (geologia)]]
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