Raibler layers

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Vertical Raibler layers at Zirl, the easily weatherable layers are largely eroded
Rauwacke in the Raibler layers

The Raibler Strata (also Raibler Band or Raibl Formation ) are a lithostratigraphic formation of the Upper Triassic in the Alpine region. The Raibler layers are a series of different sediments from the Carnian period , which is the oldest (lowest) chronostratigraphic level of the Upper Triassic . Characteristic for the Raibler layers is a large spectrum of different sediments and a multiple change between limestone , dolomite , marl and clastic sediments such as shale or sandstone . Additional possible evaporites and Rauwacken ago. The type locality is near Raibl in the Italian region of Friuli-Venezia Giulia . Due to their differences, the southern alpine Raibl group is differentiated from the northern alpine Raibl layers .

The change in the Raibler strata is caused by a multiple sequence of sea ​​retreat and renewed flooding . Sediments were deposited in shallow sea areas, these sea areas became increasingly shallow and ultimately more salty, limestone and dolomites with salt and gypsum inclusions formed. Then there was another rapid rise in sea level. Below adjoin the Raibler layers, the formations of the Wetterstein and the Arlberg layers in the area of Southern Alpine Schlern dolomite , above there is the formation of the main dolomite or roof stone dolomite , in the South Alps the Carnitza formation .

Occurrence

Raibler layers are found in the Southern Limestone Alps as well as in Mesozoic sediments of the Central Alps and in the Northern Limestone Alps . In the Southern Alps, the Raibler strata are not continuously developed and have very different thicknesses. In the Drauzug , which geologically belongs to the Eastern Alps, the Raibler strata consist of an alternating sequence of three carbonatic and three clastic horizons. In the Gailtal Alps, the Raibl strata show significant lead-zinc mineralization. In the Central Alpine Mesozoic Era, the Raibler strata are very differently pronounced; in the Landwasser-Ducan area in Switzerland, they are 300 or 400 meters thick. In the Tyrolean Kalkkögel, however, they reach a maximum thickness of ten meters. In the northern Limestone Alps, the Raibler layers are very widespread and also developed very differently, so they reach a thickness of 400 meters in the eastern Wetterstein Mountains , and still 350 meters north of Zirl.

In the Hallstatt Zone, however, which developed differently as a deep sea basin during this period, they are missing. Geographically, the area of ​​the Hallstatt zone affects, among other things, the area from Bad Ischl to Bad Aussee in the Salzkammergut . In the eastern part of the Northern Limestone Alps, equivalents to the marine Raibler strata are found primarily in the higher ceilings, for example in the area of ​​the Rax and the Schneeberg . Towards the foothills of the Alps, on the other hand, there are the Lunzer layers , which mainly represent terrigenous deposits, such as slate clays at the base, the Reingrabener Schiefer , named after the pure ditch between Rohr in the mountains and Gutenstein . The Lunz strata also contain Lunz sandstone and arkose , as well as coal seams that were previously mined in many places. The Carnic Opponitz strata , some dolomitic limestone and Rauwacken , appear above these Lunz strata .

Subdivision

There is a more precise subdivision of the Raibler layers in the area of ​​the Dolomites . On the eastern map sheet of the geological map of the Western Dolomites, the Raibl layers are shown as the Raibl group . In the area between the Sella and the Fanes groups in the east, they are underlain by carbonates of the Schlern group , the St. Cassian formation and the Cassian dolomite . The Raibl group itself is made up of the Holy Cross formation in the eastern part with the Fedares member , Dibona member , Lagazuoi member and the Falzarego member . The last two members are overlaid by the Travenanzes formation . In the Sella region further to the west, the group consists only of the Pordoi formation , which is interlocked with the Dibona and Lagazuoi members towards the east. The Raibl group is overlaid by the main dolomite.

Raibl event

Room Pangea , Paleo- and Neotethys , 230  mya

The deposition of the Raibl layers or the Lunz layers is related to a change in the sedimentation: The Raibl event or Reingrabener Wende (in the area of ​​the Hallstatt Basin) is one of the most drastic events in the northwestern shelf area of the Tethys . It is characterized by an abrupt beginning of a pouring of clastic- silicate sediments and a collapse of the reef systems, thus the carbonate production came to a standstill. The Raibl event was not limited locally to the northwestern edge of the Tethys, but rather likely affected the area of ​​the entire Tethys. The causes could have been warming and thus increased rainfall. In terms of time, the event can be classified in the middle Carnival , the Julium (230 million years ago).

The climate event itself is global, and is referred to as Carnian Pluvial Event  (CPE), Carnian Wet Intermezzo and the like. called.

Dating

The northern Alpine Raibler strata are dated to the Middle and Upper Carnian, i.e. the Julium and Tuvalian . In the Southern Alps, the Raibler layers still reach down into the Cordevolium .

The Raibler layers (here the Pordoi formation) divide the Sella in the Dolomites into two floors

geomorphology

Parts of the Raibler layers can easily be eroded . This has an influence on the geomorphology, so the Sella in the Dolomites owes its characteristic storey structure to the Raibler layers, which form the separating layer between the lower and upper floors.

Hydrogeology

Due to the water-retaining property of part of the Raibler strata, spring horizons often form along the Raibler strata.

Web links

Commons : Raibl beds  - Collection of pictures, videos and audio files

Individual evidence

  1. ↑ Karl Krainer: Contribution to the microfaces, geochemistry and paleogeography of the Raibler strata of the eastern Gailtal Alps (Bleiberg area - Rubland) and the Karwendel (Lafatsch area / Tyrol) , Arch. F. Lagerst.forsch., Vol. 6, Geol. B.-A., Vienna 1985, pp. 130-133. PDF file , accessed on June 16, 2009.
  2. ↑ Hermann Jerz , Investigations into the material inventory , formation conditions and palaeogeography of the Raibler layers between Lech and Inn (Northern Limestone Alps), Geologica Bavarica, Volume 56, published by Bayer. Geological State Office, Munich 1966, p. 7.
  3. ^ Rainer Brandner : Sea level fluctuations and tectonics in the triad of the NW-Tethys , habilitation thesis, Innsbruck 1983, p. 32f.
  4. ^ Otto F. Geyer: The Southern Alps between Lake Garda and Friuli. Collection of geological guides , Volume 86, Verlag Borntraeger, Berlin-Stuttgart 1993, ISBN 3-443-15060-8 , p. 112.
  5. ↑ O. Kraus: The Raibler layers of the Drauzuges (Southern Limestone Alps). Lithofacial, sediment petrographic and palaeogeographic investigations , Jb.Geol. BA, Vol. 112, Vienna 1969, p. 82. PDF file , accessed on June 16, 2009.
  6. ↑ Karl Krainer: Contribution to the microfaces, geochemistry and paleogeography of the Raibler strata of the eastern Gailtal Alps (Bleiberg area - Rubland) and the Karwendel (Lafatsch area / Tyrol) , Arch. F. Lagerst.forsch., Vol. 6, Geol.B.-A., Vienna 1985, p. 129. PDF file , accessed on June 16, 2009.
  7. ↑ Wolfgang Harsch: Lithofacial, sedimentological and palaeogeographic investigations in the Raibler strata of the Northern Limestone Alps between Fernpass and Rhine as well as various deposits in Graubünden. Dissertation, Munich 1968, p. 46.
  8. ^ Fridolin Purtscheller, Ötztaler and Stubai Alps , Geological Guide Collection, Volume 53, 2nd edition, Verlag Gebrüder Borntraeger, Berlin-Stuttgart 1978, ISBN 3-443-15022-5 , p. 31.
  9. ↑ Hermann Jerz, Investigations into the material inventory, formation conditions and palaeogeography of the Raibler layers between Lech and Inn (Northern Limestone Alps), Geologica Bavarica, Volume 56, published by Bayer. Geological State Office, Munich 1966, p. 9.
  10. ^ Rainer Brandner : Sea level fluctuations and tectonics in the triad of the NW-Tethys, habilitation thesis, Innsbruck 1983, p. 25.
  11. ^ Erich Thenius: Lower Austria. Geology of the Austrian federal states in brief individual representations. 2nd expanded edition, Vienna 1974, p. 118 f.
  12. ↑ Autonomous Province of Bolzano-South Tyrol, Office for Geology & Building Materials Testing: Geological map of the Western Dolomites . Scale 1: 25,000, taken from 1992 - 2007
  13. ↑ Thomas Hornung: The 'Carnian Crisis' in the Tethys realm: multistratigraphic studies and paleoclimate constraints, Dissertation , Innsbruck 2007, p. 26.
  14. ↑ ops. cit. Hornung 2007, p. 4.
  15. ↑ Alfonso Bosellini: Geologia delle Dolomiti , Athesia, Bozen 1996, ISBN 88-7014-889-0 , p. 179.
  16. ↑ See under other water balance in the Puez-Geisler Group or the Trudner Horn Nature Park , both accessed on June 17, 2009.