Flysch

Flysch [ fli ː ʃ ] called in the geology of sedimentary facies, a navy, which is usually represented by an alternation of shales and coarse-grained rocks ( typically sandstones ). These sediments are often subsequently deformed (folded), partly even so intense that it then is metamorphic rocks. Flyschserien occur during mountain -building processes and the coarse-grained rocks represent the eroded material of the forming mountain range dar. Since this material usually in the form of suspension flows entering the deposition chamber, is in geology in connection with flysch often talk of turbidites.

Etymology

For the first time in the geological literature, the term 1827 is used by Bernhard Studer, the resulting rock formations in the Simmental and in the valley of the Sarine in the Swiss Alps called the calcareous from " predominantly sandy or marly black or gray shales and very hard and tight sandstones with and dark gray cement "passed. The term flysch "is derived from the local dialect here in the Simmental and called slate-like, slightly fissile, efflorescent into platelets, easily erodible rock material. Studer even brought the word using the original Low German word seam ' in connection, in turn, is related to various ancient words of the Germanic language family, as much as the flat all ' or ' mean level '. Thus, should the term flysch ' probably go back to the schistose nature of the rocks so designated in the Simmental Swiss German.

Formation

As flysch sequences of marine clastic sediments are referred to in modern geology, among other things, caused by slipping of previously deposited on the continental shelf sediments output over the continental slope into the deep sea. This slide is usually in the form of an avalanche -like slurry or suspension flows. Since such landslides during an orogeny that takes millions of years, quite often repeat, leads to characteristic sequences in which alternating layers of mudstone with layers of coarse-grained material. The latter often have a very mixed mineral composition. Although they exist, such as a sandstone, predominantly of quartz grains, but usually contain larger quantities of lime or clay. Furthermore, a variety of minerals, among others, Glauconite, mica and / or feldspar be included.

The layers of coarser material that are deposited by the streams of suspension within a few hours or days, is referred to in terms of their emergence as turbidites. The Tonsteinlagen between are the result of an extremely slow running, continuous sedimentation of clay particles ( the so-called Hintergrundsedimentation ) in the deep sea.

The term flysch thus refers to a special sedimentary facies and you can here a distal and a proximal facies differ, the transition between the two facies is fluid. In typical distal flysch turbidites which are represented by thin Siltbänder, which are distinguished in the rock rather by a different color than weathering by a naked- eye grain size difference. In typical proximal flysch turbidites are represented by the partly more than 1 meter thick sandstone banks that can even contain remains of plants. Another indicator for proximal flysch are unstratified brecciated sediment masses ( Olisthostrome ). A Flyschlage with such a chaotic structure is referred to as Wildflysch.

The output of the Flysch sediments may be unconsolidated muds or sands, but it is also already solidified rocks be included in a landslide with and turned on Wildflysch in a sandstone - mudstone sequence. The ( Olistholithe ) contained in Wildflysch from the Flyschsedimenten facies usually significantly different rocks may partly house size and more reach ( Olisthoplaka ), and in some areas can be kilometers in size has slid plaice ( Olisthothrymmata ) prove. The transport of such other rocks may be more than 100 kilometers long, even with the Olisthothrymmata.

The composition of the flysch turbidites is very different, because the starting material from a variety of resources which is strongly mixed. As a result of deposition in the foreland of a nascent emergence in the mountains, can be in many cases the composition of the Flysch the sequence of deformation processes reconstruct, which drain into the areas of origin of the parent rocks. There advised over time again and again other rocks under the influence of orogenic processes, are eroded and rearranged so that they ultimately find in the flysch deposits. Due to its position close to orogenic processes Flyschgesteine ​​are often included after the deposition in this with and are then strongly tectonically deformed today.

Occurrence

Flysch is found in almost all mountain ranges of the world, such rock sequences occur in almost all open fold mountains to light. Geologically young deposits are:

• Rhenodanubische the flysch of the flysch zone, upstream of the Eastern Alps as a range of hills on the northern edge, and its eastern continuation, the Carpathian flysch on the north and east of the Carpathians,
• The Flyschvorkommen in the Apennines, the Pyrenees, the Caucasus and the Himalaya
• The flysch on the west coast of the U.S.

In Germany there is variszischer flysch as part of the Kulm facies with their typical greywacke in the Rhenish Slate Mountains, in the Harz Mountains and the Thuringian- Franconian - Vogtländische Slate Mountains.