Obtus tone formation

from Wikipedia, the free encyclopedia
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
    • Obtus clay from a construction pit in Hüttlingen

    The Obtususton Formation is a lithostratigraphic formation of the southern German Jura. It is underlain by the Arietenkalk Formation and overlaid by the Numismalis Marl Formation . In Franconia , it meshes with the Gryphae sandstone formation . It reaches a thickness of about 60 m and is dated to the Upper Sinemurium .

    history

    FA Quenstedt called these layers in 1856/57 Oxynotelager and placed them in his stratigraphic unit Lias beta. The Obtus Clay is named after the ammonite Asteroceras obtusum , which was previously called Ammonites obtusus . A type locality, as it is actually required to define a lithostratigraphic unit, has not yet been defined.

    definition

    The Obtus Clay Formation consists mainly of pyrite-rich claystones with some embedded limestone banks. The thickness is up to about 40 m in the Swabian Alb area and decreases to 0 m in eastern Württemberg. In the southern Upper Rhine area, the thickness can increase up to 60 m. The base of the formation is formed by a Schilllage, the so-called "Capricornenlager". The upper limit is the lower edge of the "cymbium bank", which already belongs to the numismatic marl formation above it .

    Temporal scope and distribution area

    Sediments from the Obtus Clay Formation were deposited during the Upper Sinemurian . It includes max. the ammonite zones of Caenisites turneri , Asteroceras obtusum , Oxynoticeras oxynotum and Echioceras raricostatum . The formation is widespread in the Swabian Alb and extends to the Upper Rhine Valley Trench, where it becomes very powerful. It interlocks with the Gryphaeensandstein Formation in Eastern Wuerttemberg and Franconia . There is a small layer gap between the Obtus Clay Formation and the overlying Numismalis Marl Formation.

    Breakdown

    The obtuse tone formation is subdivided into the basal "capricorn camp", the lower and the upper obtuse tone. The boundary between the Lower and Upper Obtus Clay Formations is the Beta Lime Bank. In the Wutach area, the formation is completed by the obliquabank. Above the beta limestone bank in the upper Obtus Clay, some shill limestone banks are still regionally formed ("Söllsche Lagen").

    literature

    • 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
    • Eckhard Mönnig: The Jura of Northern Germany in the Stratigraphic Table of Germany 2002. Newsletters on Stratigraphy, 41 (1-3): 253-261, Stuttgart 2005 ISSN  0078-0421
    • Friedrich August Quenstedt: The Flözgebirge Wuerttemberg. Laupp Publishing House, Tübingen 1843.
    • Friedrich August Quenstedt: The Jura. Laupp Publishing House, Tübingen 1856–57.

    Web links