Ostreenkalk formation

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Lithostratigraphy of the South German Jura .
Abbreviations:
  • Humph.-Fm. = Humphriesioolite Formation
  • L.Bk-Fm = Lying bench lime formation
  • H.Bk-Fm = hanging bank lime formation
  • Zm-Fm = cement marl formation
  • S.-Fm = Solnhofen formation
  • Rö.-Fm = Rögling formation
  • U.-Fm = Usseltal formation
  • Mö.-Fm = Mörnshein formation
  • N.-Fm = Neuburg formation
  • R.-Fm = Rennertshofen formation

    • The Ostreenkalk Formation is a lithostratigraphic (the rock layers concerned) formation of the southern German Jura . It is underlain by the Wedelsandstone Formation , and regionally differently overlaid by the Hauptrogenstein Formation or Hamitenton Formation . It interlocks regionally with the Humphriesioolite Formation or the Sengenthal Formation and reaches a thickness of up to about 20 m. It is dated to the higher sub-bajocium .

    history

    The term Ostreenkalk was already used by FA Quenstedt 1856-57 and equated with its stratigraphic unit Braunjura delta. It is named after the oyster- like "Ostreen" (today Lopha marshi , Ctenostreon pectiniformis and Ctenostreon proboscideum ), which are found in large numbers in some banks . A type locality, as it is actually required to define a lithostratigraphic unit, has not yet been determined.

    Definition and distribution area

    The Ostreenkalk formation consists of alternating layers of shill limestone and marl. The thickness varies in the area of ​​the Swabian Alb between 25 and 40 m. The lower limit forms the basis of the so-called giganteus tone. The upper limit (and thus the limit to the Hamitenton Formation ) is formed by the upper edge of the "Subfurcatenoolith", which is not formed everywhere. The upper limit of the Ostreenkalk formation is diachronous, i.e. H. has a different age. The key abbreviation of the State Office for Geology, Raw Materials and Mining (Baden-Württemberg) for the Ostreenkalk formation in geological maps is bj2.

    Temporal scope and breakdown

    The sediments of the Ostreenkalk Formation were deposited during the higher sub- Bajocian. The Ostreenkalk formation comprises at most the ammonite zones of Stephanoceras humphresianum and Strenoceras niortense . The formation is widespread in the Swabian Alb . It meshes with the Humphresioolite Formation on the southern West Alb, the Kraichgau and the Upper Rhine Graben . In the Aalen area, it changes into the Sengenthal formation . The upper limit is strongly diacron, that is, has a different age. The area of ​​the subfurcatenoolith is probably eliminated as a separate subformation.

    Breakdown

    The Ostreenkalk formation contains the so-called Giganteuston at the base, which got its name from the Belemnite species Belemnites giganteus (today Megateuthis suevica (Klein, 1773)).

    Fossil guide

    Macrofossils in the Ostreenkalk Formation are mainly ammonites , belemnites and mussels . Serpulids that crust over the mussels are also quite common .

    literature

    • Friedrich August Quenstedt: The Flözgebirge Wuerttemberg. Laupp Publishing House, Tübingen 1843.
    • Friedrich August Quenstedt: The Jura. Laupp Publishing House, Tübingen 1856–1857.
    • Gert Bloos, Gerd Dietl & Günter Schweigert: The Jura of Southern Germany in the Stratigraphic Table of Germany 2002. Newsletter on Stratigraphy, 41 (1-3): 263-277, Stuttgart 2005 ISSN  0078-0421

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