Editing Flysch

{{Short description|Type of sedimentary rock sequence}}
[[File:Zumaiako_flysch-a.jpg|thumb|upright=1.02|Steeply-tilted layers of flysch on the coast of [[Bay of Biscay]], at [[Zumaia]], Basque Country, Spain]]
'''Flysch''' ({{IPAc-en|f|l|ɪ|ʃ}}) is a sequence of [[sedimentary rock]] layers that progress from deep-water and [[turbidity current|turbidity flow]] deposits to shallow-water [[shale]]s and [[sandstone]]s. It is deposited when a deep basin forms rapidly on the continental side of a mountain building episode. Examples are found near the [[North American Cordillera]], the [[Alps]], the [[Pyrenees]]<ref>{{Cite web |title=Urola Kosta: Things to do in Orio, Zarautz, Getaria and Zumaia {{!}} Bodega Katxiña |url=https://www.bodegakatxina.com/en/events/urola-kosta-que-hacer-en-orio-zarautz-getaria-y-zumaia/ |access-date=2023-07-03 |language=en-US}}</ref><ref>{{Cite web |date=2020-12-11 |title=La ruta del Flysch, un viaje distinto al País Vasco - Vipealo |url=https://www.vipealo.com/blog/la-ruta-del-flysch-un-viaje-distinto-al-pais-vasco/ |access-date=2023-07-03 |language=es}}</ref> and the [[Carpathians]].

==Sedimentological properties==

Flysch consists of repeated sedimentary cycles with upwards [[Particle size (grain size)|fining]] of the sediments. There are sometimes coarse [[conglomerate (geology)|conglomerates]] or [[breccia]]s at the bottom of each cycle, which gradually evolve upwards into [[sandstone]] and [[shale|shale/mudstone]].  Flysch typically consists of a sequence of shales rhythmically interbedded with thin, hard, [[graywacke]]-like sandstones. Typically the shales do not contain many [[fossil]]s, while the coarser sandstones often have fractions of [[mica]]s and [[glauconite]].

==Tectonics==

In a [[continental collision]], a [[subduction|subducting]] tectonic plate pushes on the plate above it, making the rock [[fold (geology)|fold]], often to the point where [[thrust fault]]s form, and a mountain chain rises. On the upper plate, the land between the mountains and the undeformed continent bends downward, forming a [[foreland basin]]. If the basin forms slowly, as in the northern [[Appalachian Mountains|Appalachians]], it fills with shallow-water sediments.<ref name=Twiss>{{cite book| last1 = Moores | first1 = Eldridge M. |last2=Twiss|first2=Robert J. |title=Tectonics|date=2000|publisher=Freeman|location=New York|isbn=0716724375|pages=265&ndash;266|edition=3rd print}}</ref> If it forms rapidly, as in the east side of the [[North American Cordillera]], then sea water may rush in, and the first sedimentary deposits are deep water deposits. If the mountain slope is steep enough at the edge of the basin, it will shed material in rapidly moving sedimentary flows called [[turbidity current]]s, resulting in [[turbidite]] deposits. As the basin fills up, shallow-water sandstones and continental deposits form.<ref name=Twiss/><ref name=Einsele>{{cite book|last1=Einsele|first1=Gerhard|title=Sedimentary Basins : Evolution, Facies, and Sediment Budget|url=https://archive.org/details/sedimentarybasin00eins|url-access=limited|date=2000|publisher=Springer|location=Berlin|isbn=9783540661931|edition=2nd|pages=[https://archive.org/details/sedimentarybasin00eins/page/n217 210]&ndash;211}}</ref> Most of the resulting rocks have little deformation, but near the edge of the mountain chain they can be subject to folding and thrusting.<ref name=Twiss/> After the basin fills up, continental sediments ([[molasse]]) are deposited on top of the flysch.<ref name=Einsele/>

==Name and use==

[[Image:Carpathian flysch cm03.jpg|thumb|[[Carpathian Flysch Belt|Carpathian flysch]]]]
The name flysch was introduced in geologic literature by the [[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 name="Labhart">{{cite book|last1=Labhart|first1=Toni P.|title=Geologie der Schweiz|language=German|trans-title=Geology of Switzerland|date=2005|publisher=Ott Verlag|location=Bern|isbn=3-7225-0007-9|page=64|edition=7th}}</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 basin|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==
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==Further reading==
{{Refbegin}}
*{{Cite EB1911|wstitle=Flysch|volume=10|page=586}}<!-- DO NOT cut and paste any text from this source, unless you personally know that it comes from a non-copyrighted source! -->
*{{cite book|last1=Stanley|first1=Steven M.|title=Earth System History|date=2005|publisher=Freeman|location=New York|isbn=9780716739074|edition=2nd}}
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{{Commons}}

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[[Category:Sedimentary rocks]]
[[Category:Sedimentology]]