Hamitenton 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 Hamitenton Formation (formerly Hamitenton) is a lithostratigraphic formation of the southern German Jura . It is overlaid by the Dentalienton Formation and underlain by the Humphriesioolite and Ostreenkalk Formations . To the east it is laterally replaced by the Sengenthal Formation . In the Upper Rhine area it is represented by the main roe rock formation . It has a thickness of 0.6 to 45 m. It is dated to the Upper Bajocium .

    history

    The term was proposed by Gert Bloos, Gerd Dietl and Günter Schweigert in 2005 for a lithostratigraphic rock formation that Friedrich August Quenstedt had already called "Hamitenthon" in 1857. The name comes from the heteromorphic ammonites found in it, which earlier was mistakenly placed in the chalk genus Hamites .

    Definition and distribution area

    The Hamitenton Formation consists mainly of clay stones. The upper edge of the so-called Subfurcaten-Ooliths (Subfurcaten-Subformation der Ostreenkalk-Formation) was defined as the basis of the formation. The upper limit is formed by the top of the "Parkinsoni Oolite" or the Upper Parkinsonia Oolite in the western Swabian Alb. In the area of ​​the eastern Alb, the Hamitenton Formation meshes with the Sengenthal Formation. It reaches its greatest thickness in the Wutach area at 52 m. Here, in the top of the formation, a powerful claystone package has been developed, the Parkinsonian tone.

    Type region and type profile

    The type region extends from Donzdorf to the Wutach region west of Blumberg . Dietl (2006) defined the bed of the Wettbach creek on the north side of the Plettenberg above Rosswangen as the type profile . Two further reference profiles were selected by Dietl: a reference profile on the western slope of the Eichberg in the Wutach area and a reference profile in the construction site of the A 8 near Gruibingen , which was recorded in great detail by Gerd Dietl in 1988.

    Temporal scope and breakdown

    The Hamitenton Formation is stratigraphically dated to the Upper Bajocium. It includes the upper niortense biozone, the Garantiana biozone, the Parkinsoni biozone and the base of the Zigzag biozone.

    In Central Wuerttemberg, the Hamitenton formation is divided into the Lower Hamitenton and the Upper Hamitenton by the Hamitenbank. The Parkinsonienoolith at the top of the formation consists initially of a bank, which is divided into two banks to the west. Between the two oolite banks, the increasingly powerful Parkinsonian tone turns on towards the southwest, reaching a thickness of 45 m in the Wutach area. At the same time, however, the thickness of the actual Hamitentons decreases more and more (to approx. 8 m).

    In the Wutach area, Parkinson’s is structured as a separate subformation. The actual Hamitenton, on the other hand, is also called the Hamitenton subformation.

    Fossil content

    The Hamitenton Formation is best known for its ammonite fauna (genus Spiroceras , formerly Hamites ). In part it contains extremely variable species; the casings vary from loosely rolled up to loosely rolled up trochospirally to straight. However, there are also “normally” rolled-up ammonite genera such as Garantiana , Strenoceras and Parkinsonia (e.g. Parkinsonia parkinsoni ).

    literature

    • Gert Bloos, Gerd Dietl, Günter Schweigert: The Jura of Southern Germany in the Stratigraphic Table of Germany 2002. In: Newsletters on Stratigraphy. Vol. 41, No. 1/3, 2005, ISSN  0078-0421 , pp. 263-277.
    • Gerd Dietl: The Hamitenton formation (bj3) of the Swabian Jura - description and structure. Annual books of the Society for Natural History in Württemberg, 162: 25–45, Stuttgart 2006 ZDB -ID 219059-x

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