Benk formation

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Lithostratigraphy by the Keuper group in the Germanic Basin

The Benk Formation (formerly Benker Sandstein, Estherienschichten) is a lithostratigraphic formation of the Keuper in the Germanic Triassic . The lithostratigraphic unit is underlain by the Grafenwoehr Formation and overlaid by the Stuttgart Formation . The Benk Formation is only formed on the edge of the Vindelician Land and interlocks with the Germanic Basin with the Grabfeld Formation .

definition

The lower limit of the Benk formation is the upper edge of the Grenzdolomite , the upper limit is the discordant area D2 of the Keuper. It is regionally limited to a narrow strip of approx. 20 to 80 kilometers along what was then the Vindelician country . The Benk formation consists of fine to coarse-grained sandstones in which, depending on their position in relation to the basin, red, sandy mudstones are inserted. Some of the sandstones contain sulphate tubers and crust formations. The thickness is on average about 80 to 100 meters.

The Benk formation is in Ladinian ( Langobardium to Carnian ( Cordevolium )) dated .

A type locality has not yet been determined. The type region is the area east of Bayreuth . The name is derived from the small town of Benk (now part of Bindlach ) in the Bayreuth district .

structure

A further subdivision into subformations has not yet been carried out. Four small sedimentary cycles can be distinguished.

Storage room

The deposit area is the edge of the Vindelician country. Here coarse to fine-grain sandstones were deposited in the rubble plains by episodic flooding. At the top of the four small cycles there were longer interruptions in the sedimentation , as can be seen from the soil formation (crusts).

Fossils

The Benk Formation is low in fossils and contains mussels (Bivalvia), mussel shells (Conchostraca) and silicified woods as well as a pollen and spore flora.

literature

  • Gerhard Beutler: Lithostratigraphy. In: German Stratigraphic Commission (Ed.): Stratigraphie von Deutschland IV - Keuper. Courier Forschungsinstitut Senckenberg, 253: 65-84, Stuttgart 2005 ISSN  0341-4116
  • Gerhard Beutler, Norbert Hauschke and Edgar Nitsch: Facies development of the Keuper in the Germanic Basin. In: Norbert Hauschke & Volker Wilde (Hrsg.): Trias - A whole different world of Central Europe in the early Middle Ages. Pp. 129–174, Verlag Dr. Friedrich Pfeil, Munich 1999 ISBN 3-931516-55-5
  • Edgar Nitsch: The Keuper in the Stratigraphic Table of Germany 2002: Formations and consequences. Newsletters on Stratigraphy, 41 (1-3): 159-171, Stuttgart 2005 ISSN  0078-0421

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