Gosau Group

The Gosau Group is a lithostratigraphic group in the Northern Limestone Alps and in the Eastern Central Alps. Type locality is Gosau in Upper Austria's Salzkammergut region. The Gosau sediments were deposited unconformably on the first peak of mountain building in the central crayon over the ceiling and Faltenbau.

The Gosau sediments are the result of Transgressionszyklus that started in the Upper Cretaceous after a hiatus in the Turonian Coniacian. The sediments of the Gosau Group reach in the Paleogene to the lower Eocene. The sediments of the Gosau Group incurred during the period of orogeny in the Cretaceous period, the so-called Kreideorogenese that gripped the Eastern Alps. Large areas of the archipelago -like landscape loomed out of the sea at that time and therefore the sediment cover only parts of the Northern Limestone Alps. Gosauische or related sediments are found next to the Northern Limestone Alps and isolated in the Eastern Central Alps, according to Alexander Tollmann in the Carpathian Mountains, Southern Alps, Dinarides and still farther to the southeast in the Mediterranean area. According to the education in different basins, the thickness of the Gosau sediments varies greatly in Gosau they reach a thickness of 2600 meters, in Gams and Gruenbach the Gosau Group is up to 2200 meters thick.

History

The name Gosau as a stratigraphic term was introduced in 1782 by J. Bohadsch. The British geologist A Sedgwick and Murchison RJ 1829 created an initial rough outline of Gosau in their two papers On the Overlying deposits of the Vale of Gosau in the Salzburg Alps and On the Tertiary Formations Which range along the Flanks of the Salzburg and Bavarian Alps; being a continuation of the memoir " On the Valley of Gosau ". In the years 1930 and 1931 then followed their work A Sketch of the Structure of the Eastern Alps; with Sections through the Newer Formations on the Northern Flanks of the Chain, and through the Tertiary Deposits of Styria, & c. & c -With Supplementary Observations, Sections, and a Map. August Based on the published works of both British Emanuel von Reuss his contributions to the characteristics of the Cretaceous strata in the Eastern Alps, especially in the Gosau valley and Lake Wolfgang.

Occurrence

Gosau deposits in the Northern Limestone Alps are in the area of ​​the Lech Valley Alps west of Imst, the so-called Muttekopfgosau, in the Tyrolean lowlands in the area of ​​Brandenberger Valley in the room Wörgl and Kössen, in the space of the city of Salzburg to Bad Reichenhall and the state of Salzburg in the area of Lake Wolfgang, upper Austria in Gosau in the Salzkammergut, in space Windischgarsten, at Laussa to Großraming in Reichraminger Hintergebirge, in Styria at Wörschachwald on the southern edge of the Dead Mountains, near Mariazell and Gams. In Lower Austria, there are Gosau deposits among others Gruenbach am Schneeberg and in Gießhübl. There are also numerous small and smallest Gosau deposits. In the central alpine region there are west of Graz Kainacher Gosau and in Carinthia Krappfeld Gosau. Due to tectonic processes and erosion today Gosau deposits no longer meet their original propagation.

Subdivision

The sedimentation of the Gosau sediments in different basins difficult a lithostratigraphic classification of the different units, which were also often deposited at different times. So there are formations that are limited to one or a few Gosau deposits, other formations on the other hand, as the conglomeratic Kreuzgraben formation or the resulting slope of the pelvic Nierental lineup formed in several Gosau deposits.

The group is divided into a Lower Gosau subgroup and an Upper Gosau subgroup.

At the beginning of gosauischen transgression, usually in the Coniacian a base conglomerate, the Kreuzgraben lineup was formed. At some localities, such as in Green Brook, the first transgression took place later, in the Santonian. In this Conglomerates then most fossil -rich sandstones, marls and limestones follow a Flachwasserfazies. Partly also coal seams are found, as in the Gosau of Green Brook. After a brief period of renewed uplift and erosion, the so-called Intragosauischen phase, it came in the upper Campanian to a rapid decrease in the Alps. The sediments of the Upper Gosau as Zwieselalm formation that Gießhübl formation or the Brunnbach lineup, often are more deep-water formations, which were formed partly below the calcite compensation depth. For the upper Gosau therefore sometimes the name Flyschgosau is used frequently, the upper Gosau unconformably on the lower Gosau.

Sequence of the Gosau Group at some localities:

Type locality Gosau

• Kreuzgraben lineup
• Streiteck lineup
• Grave Brook Formation
• High moss formation
• Bibereck lineup
• Ressen lineup
• Nierental lineup
• Zwieselalm lineup

Salzburg - Bad Reichenhall

• Basal red conglomerates ( Kreuzgraben Formation)
• Sandstones and sandy marls ( Glanegger layers )
• Detritäre carbonates ( Unterberg Formation)
• Marl with Tempestiten ( grave Brook Formation)
• Deep-water sediments ( Nierental Formation)

Laussa - Großraming

• Bauxite
• Basal red conglomerates ( Kreuzgraben Formation)
• Süßwasserkalk, marl
• Limestone
• Conglomerate, sandstone and silty marl ( isolated coal leader )
• Rudistenkalk
• Gray, partly strongly silty limestone clay ( white-water formation )
• Kalkkonglomerat ( Hieselberg Formation)
• Turbiditische Karbonatbreccie, limestone (peak Brook Formation)
• Turbiditische sequence of Karbonatbreccie, sandstone, marl colorful ( Brunnbach Formation)

Fossil guide

Admits became the Gosau Group, not least through its partially extraordinary fossil richness. Thus, for according to the finding of a nearly one -meter giant ammonites Parapuzosia seppenradensis in 1971, since 1979, an ammonite, the coat of arms of Gosau.

In addition to ammonites come Actaeonellen, Nerineen and other gastropods as well as various corals especially common as fossils before. Mussels as rudists, especially Hippuritoidea, occur in a reef-building scale in part. Valuable microfossils in terms of zoning are foraminifera.

Mineral resources

Located in some places bauxite, which formed under tropical conditions in the Turonian on the basis of the Gosau Group. Best known is the bauxite deposits at Unterlaussa that has been mined until 1964.

In regression phases formed in some places in the Northern Limestone Alps but also in the Central Alps coal. The gosauische coal of Green Brook was the most important coal deposits in Austria and was mined from about 1825 to 1965.