Varian marl 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 Variansmergel Formation is a lithostratigraphic formation of the southern German Jura . It is subordinated to different regions by the main roe stone formation and dental clay formation and superimposed by the ornate clay formation . It interlocks regionally with the Sengenthal formation and reaches a thickness of up to about 6 m, making it the thinnest formation in the southern German Jura. It can also be completely absent regionally; instead, a layer gap is formed. It is dated to the middle and upper bajocium .

    History and naming

    The Varian marl formation was proposed by Gert Bloos, Gerd Dietl and Günter Schweigert in 2005. It is named after the armwort Terebratula varians . A type locality, as it is actually required to define a lithostratigraphic unit, has not yet been determined.

    Definition and distribution area

    The Varians marl formation consists of alternating layers of fine sandy limestone and clay marls . It is developed in the Rhine Valley, the Wutach region and in the West Alb. It is completely absent in the area around Gosheim ; instead, a layer gap can be observed here, which comprises up to three ammonite zones. In the Wutach area it reaches its maximum thickness of 6 m. In the Eastern Alb it is represented by the Sengenthal formation . The lower limit is defined by the onset of the fine sandy limestone marl and clay marl, regionally just below the limit an ironoolite bank is formed, which still belongs to the main roe rock formation below . The upper limit is formed by the lower edge of the macrocephalic oolite, which already belongs to the regalia formation .

    Temporal scope and breakdown

    The sediments of the Varians Marl Formation were deposited during the Middle Bajoc and probably still in the deeper Upper Bajoc. The Varian marl formation includes the ammonite zones of the Procerites progracilis , Tulites subcontractus , Morrisiceras morrisi and Prohecticoceras blanazense . The Varian marl formation is not subdivided into sub-formations.

    literature

    • Volker Dietze and Gerd Dietl: Fine stratigraphy and ammonite fauna horizons in the Upper Bajocian and Bathonian of the Ipf area (Swabian Alb, south-west Germany). Stuttgart Contributions to Natural History, Series B, 360: 51 S., Stuttgart 2006 ( online ; PDF; 2.3 MB)
    • 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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