Molasse

Molasses is the name of sediments and sedimentary rocks, which in the removal of a fold mountain range (→ Orogen ) between the last phase of his training ( lifting phase) and its extensive leveling result to a mountain hull. Molasses is distinguished from flysch, which comes in effect only during the orogeny in the deposition.

Word origin and concept development

The term molasses was introduced in 1779 by Horace - Bénédict de Saussure in the scientific literature; he derives perhaps from the homonymous French-Swiss word for very soft off ( this was used in the 14th century and is in turn derived from the Latin mollis back ). The term was then applied in 1789 by Gregory de Razumowski on fine-grained soft sandstone in the foothills of the Alps, which harden quickly in the open air during the drying process. In western Switzerland and sandstones were designated as molasses, from which millstones you (Latin mola ) could produce.

Later the name was extended to similar rocks throughout northern foothills of the Alps. Today the term is used worldwide for sediments which deposit mainly in the foothills of in the course of his orogeny ( orogeny ) lifted Mountains ( Orogen ) and result from the erosion of the heaving rock mass.

Formation and rocks

Be Molassesedimente, in contrast to the predominantly deep marine flysch, mainly sedimented in terrestrial or shallow marine deposition environments, in the foothills of a mountain range ( Außenmolasse ) or in its interior ( Innenmolasse ). Gravel, sand, silt and clays are transported by the rivers from the mountains to the forward and backward country and deposited there. Near the edge of the mountain prevail sandstones and conglomerates before (the latter in the Alps known as the conglomerate ), at a greater distance from the mountains, however, finer sediments such as fine sand or silt. Appropriate, the parent rocks lime, deposits of marl rocks form.

In the region of Außenmolasse change through temporary marine incursions from many marine and terrestrial sediments. Thus were formed in the foothills of the Alps, Freshwater with fluvial and lacustrine sediments and the Meeresmolasse with more marine facies, which are divided into a Lower and Upper Marine Molasse due to large-scale marine incursions and return trains, which are replaced each of the Lower and Upper Freshwater. The deposits of the Marine Molasse are characterized in part by fossil wealth of, as is the case for example with the Erminger Turritellenplatte at Ulm.

Rocks are predominantly reddish colored a Innenmolasse and associated with volcanic deposits.

Molassesedimente often contain remains of plants and other fossils. Therefore, especially in sediments of a Außenmolasse led to the formation of coal ( Ruhr area) and biogenic natural gas ( approximately in the foothills of Upper Bavaria and Upper Austria ). The deeper oil and gas reserves in southern Bavaria and Upper Austria, on the other hand come from the lower-than- Alps fish shales of the Oligocene and reached only by migration into the lowest, dating from the Upper Eocene sandstone layers of the Molasse Basin.

Depositional environments of the Außenmolasse usually arise by the sinking of the earth's crust in the foreland of a ceiling stack by its high weight - hence the corresponding sink is also called sink or foreland foreland basin. Due to continuous reduction, a foreland basin sedimentary pile record with several thousand meters thick. Innenmolassen deposited in smaller-scale basins, sink down directly into the ceiling stack. The formation of these basins results as a rule of expansion processes, which can have different causes. The elongation processes are often the cause of the volcanism that accompanies the Innenmolassesedimentation.

Occurrence

It is known that tertiary molasse basin in the foothills of the Alps, a Außenmolasse. The Molassesedimente the Alps are used in the French Alps, the Swiss Plateau and in the German and Austrian Alpine foothills. You put yourself in the Carpathian foredeep to the east and continue to follow the Carpathian arc. In the Alps, but also numerous Innenmolasse deposits are preserved, such as the Plateau de Valensole, the Plateau de Cham cash or in Klagenfurt basin. The Po Valley contains the Innenmolasse the Alps, at the same time it is the Außenmolasse of the Apennines.

Although the Pannonian plain is enclosed by alpidischen mountain ranges, their deposits because of the size and the evolution of the Pannonian Basin need to be addressed not as internal rather than Außenmolasse.

The mountains of the southern Balkans and the mountainous islands in the Aegean have their Molassesedimente.

Außenmolasse the Pyrenees can be found in the Aquitaine basin in southwestern France and in the Ebro Basin in northern Spain. It also emerged in the Tertiary ( the sedimentary history of the Aquitaine basin, however starts well before the emergence of the Pyrenees).

An example of a molasse basin outside Europe are the Muree -and Siwaliks formation of Subhimalayas that are already being run over as Außenmolasse the Himalayas and pushed onto the Quaternary sediments, which Ganges, Indus and Brahmaputra deposited as youngest molasse of the Himalayas ..

Examples of Molassesedimente older age are the removal of remnants of the Variscan Mountains from the younger Upper Carboniferous and Permian ( Rotliegend ) in France, Belgium and Germany, such as the Saar-Nahe Basin ( Innenmolasse ) and the across the lap of Namur, the Aachen area and the Ruhr coal basin extending ( Außenmolasse ). Similar sediments are found on and also in the Appalachian Mountains in the United States.