Lunz formation

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The Lunz Formation , also Lunzer layers or Lunzer sandstone, is a lithostratigraphic formation of the Triassic in the Northern Limestone Alps . The type locality is near Lunz am See in the Lower Austrian Ybbstal . The formation is best known for the former coal mines and their rich flora .

Research history

The term Lunzer layers was first used in 1863 by Marko Vincenc Lipold . The delimitation of the formation was not clear in the literature for a long time, in some cases the Reingraben formation and the Opponitz formation were also included in the Lunz strata.

Definition and distribution area

The lower limit of the Lunz Formation is defined with the onset of sandstone above the Reingraben Formation . The upper limit with the re-establishment of the carbonate sedimentation of the Opponitz Formation . The paleographical deposit area of ​​the Lunz Formation was in the south-east of the Bohemian-Vindelician Land . Their current distribution area is the northern part of the eastern Northern Limestone Alps , where they represent part of the Raibler strata , which were largely formed under marine conditions (these appear southwards in the Göstling Alps and the Dead Mountains ). The formation reaches a thickness of up to 500 meters (Saggraben on the Salza).

The main distribution area is in the Lower Austrian Pre-Alps around Lunz , and for example around Opponitz , Lilienfeld , Gaming . Here they belong to the Bajuwarikum .

In the Upper Austrian Prealps they appear in the Weyrer Bögen , and to the west they form important leading horizons of the also Bavarian tectonic nappes around Wettersteinkalk , for example on the Ennsberg , on the Sengsengebirge , and south of the Steyrling , and south in the border area of ​​the Reichraminger Hintergebirge and Haller Walls of the Ennstal Alps.

According to the stratigraphic table of Austria from 2004, there is also an occurrence in the central Alpine Semmering area. The formation is underlain here by Kapellener Schiefer and overlaid by a unit, which there is possibly called Bunter Keuper .

The term is also used in the Carpathian stratigraphy .

The profile of the type locality

At the type locality Lunz am See, the formation is not quite 120 meters thick. The lying part is formed by the 50 meter thick main sandstone . The gray sandstone, which is up to 150 meters thick in other places, consists of small to medium-sized quartz grains and well-preserved feldspar grains , which are consolidated by silicate binders. The hanging part is formed by the slate complex . It consists of dark gray slate, which is interrupted several times by silty layers, fine-grain sandstone and coal seams up to a few meters thick. In contrast to the main sandstone, the sandstone in the slate complex is rich in fossils and the binder here is calcitic . In the Lunz profile, a distinction is made between several coal seams: the first and second lying seam, followed by a slate and a total of two silt and three sandstone layers, the middle seam . Above this follows slate and a sandstone surrounded by silt above and below. Above that is the hanging seam . The slates above this hanging seam are known as the treasury because of their wealth of plant fossils . Above the treasure chamber, three more sandstone banks follow in the Lunz profile, in between silty slate, some of which also contain thin layers of coal.

From the point of view of its origin, the cross-layered main sandstone is interpreted as the formation of a delta, which over the course of time has filled the Reifling basin, which is at least 150 meters deep. The slate complex was created in coastal lowlands and swamps, the sandstone banks in this complex are partly interpreted as terrigenous deposits, partly as deposits in a very shallow marine or brackish environment.

Chronological order

Due to strong similarities to the Germanic sandstone reed , which is confirmed by heavy mineral investigations and the identity of numerous megaspores , the Lunz Formation is also dated to the late section of the early Carnian . It is placed in the context of the Raibl event  (Carnian Pluvial Event), a climatic event in the Central Carnation ( Julium , around 230 million years ago).

Fossil guide

Plant fossil from the hanging wall of the Lunz Formation

While only a few plant fossils are found in the main sandstone, the slate complex in the hanging wall offers a rich flora, especially in the area of ​​the treasury . This technical Lunz flora called fossils group includes, among other ferns , seed ferns , giant horsetails , Ginkgo plants , Bennettitales and cycads (cycads). Conifers are also rare . Elements of the fauna are mussels , brackish snails , leaf crabs and rarely also vertebrates like the mastodonsaurus or the nothosaurus . Found in the main rock fossil resins ( Schlierseerit ) of the same age contain organic inclusions of various microfossils ( ciliates , scarf amoeba , cyanobacteria and green algae ). Some of these inclusions are preserved in soft tissue and are among the oldest representatives of their group of forms.

Due to the closure of all mines, the possibilities for finding fossils are now limited.

Coal mining

Miners in the 19th century in Hollenstein an der Ybbs

The Lunz hard coal was mined as forged coal in many places in Lower Austria mainly in the 19th century, but partly also in the 20th century. The coal, which often crumbled into fine grains, was mainly used as forge coal. The Schrambach -Lilienfeld mining district has been in continuous operation for the longest time. There were also major downsizing at Gaming and at Sulzbach near Lunz am See. In 1962 the last mine in the Lunzer Kohlen in Gaming was shut down.

literature

  • Alexander Bittner: About the stratigraphic position of the Lunzer sandstone in the Triassic formation. In: Yearbook of the Imperial Geological Institute. 47, 1897, pp. 429-454 ( PDF on ZOBODAT ).
  • Manfred Behrens: Heavy mineral distributions and sediment structures in the Lunz strata (Kam, Triassic, Austria). In: Jahrbuch der Geologische Bundesanstalt 116 (1972), pp. 51–83 ( pdf , geologie.ac.at).

Web links

Commons : Lunz-Formation  - Collection of pictures, videos and audio files

Individual evidence

  1. ↑ Alexander Tollmann: Analysis of the classical North Alpine Mesozoic. Stratigraphy, fauna and facies of the Northern Limestone Alps. (= Monograph of the Northern Limestone Alps. Part II). Verlag Deuticke, Vienna 1976, ISBN 3-7005-4412-X , p. 145.
  2. ^ Thomas Hornung, The 'Carnian Crisis' in the Tethys realm: multistratigraphic studies and paleoclimate constraints. Dissertation. Innsbruck 2007, p. 146.
  3. ↑ a b Lit. Behrens 1972, p. 54 ff (pdf p. 4 ff).
  4. ↑ Geological Federal Institute: Stratigraphic Table of Austria. Edition 2004 ( pdf ( memento of the original from April 24, 2018 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this note. , Geology-is-everything. at). @1@ 2Template: Webachiv / IABot / www.geologie-ist-alles.at
  5. ↑ R. Aubrecht et al .: provenance of the Lunz Formation (Carnian) in the Western Carpathians, Slovakia. In: Palaeogeography, Palaeoclimatology, Palaeoecology Vol. 471, 2017, pp. 233-253, doi: 10.1016 / j.palaeo.2017.02.004 .
  6. ↑ a b ops cit. Hornung 2007, p. 146 ff.
  7. ↑ ops cit. Hornung 2007, p. 149.
  8. ↑ N. Vávra: Fossil resins from the Alpine Mesozoic. In. Amber - tears of the gods. Bochum 1996, pp. 351-356.
  9. ↑ ops cit. Tollmann 1976, p. 148.
  10. ↑ ops cit. Hornung 2007, p. 148.
  11. ↑ a b Erich Thenius: Lower Austria. Geology of the Austrian federal states in brief individual representations. 2nd, expanded edition. Vienna 1974, p. 118 f.
  12. ↑ ops cit. Tollmann 1976, p. 149.
  13. ^ R. Oberhauser, FK Bauer: The geological structure of Austria. Springer-Verlag, Vienna 1980, ISBN 3-211-81556-2 , p. 549.