Erfurt formation

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Lithostratigraphy by the Keuper group in the Germanic Basin
Exposure of the entire Unterseuper near Vellberg- Eschenau
Coal remains of plants in sandstone from the lower Lower Keuper

The Erfurt Formation (corresponds to the Unterkeuper in northern Germany ) is a lithostratigraphic formation of the Keuper in the Germanic Triassic . The lithostratigraphic unit is underlain by the Upper Muschelkalk subgroup and overlaid by the Middle Keuper group. The deposits of the Lower Keuper indicate lacustrine conditions with occasional marine influences.

definition

The lower limit of the Erfurt Formation is the base of the Lower Lettenkohlensandstein in northern Germany. In southern Germany it is the base of the Grenzbonebed. These are marine-influenced carbonates and dolomites , lacustrine limestone and claystones as well as fluvial sandstones . The thickness in northern Germany is around 60 to 80 meters on average , and over 100 meters in rift zones . In southern Germany the thickness varies from 30 to 0 meters at the basin edges towards the Vindelizisches Land . The type locality of the Erfurt formation is in Erfurt- Melchendorf ( Thuringia ). The Erfurt formation is dated to the chronostratigraphic stage of the Ladinium . In geochronology , this section can be dated between 235 and 232.5 million years (according to the STD2002).

structure

In the North German Basin , the Erfurt Formation is the only formation of the Lower Keuper. In southern Germany it meshes with the Grafenwöhr formation in the peripheral areas to the Vindelizisches Land . Further lithostratigraphic units still have to be defined in the western edge areas. A subdivision into subformations has not yet been proposed. In older works from the 1980s, a subdivision into two or three units is made, which in the future could be the basis for subformations or could be reinterpreted as subformations. In the Erfurt formation, nine small cycles can be distinguished.

Storage room

The rocks of the Erfurt formation were deposited in a wide and shallow basin. The rivers came from the Fennoscandian Shield and flowed through lakes and swamps with land in between. Here root soils and layers with sulphate tubers are found, which indicate occasional flooding and drying out under arid conditions. Occasionally the sea penetrated the basin from the southwest via the Burgundian Gate and reached the southern Lower Lusatia in the northeast and the Osnabrücker Bergland in the north .

Fossils

The Erfurt formation contains numerous remains of vertebrates (fish, amphibians and dinosaurs ). In the bonebeds it is mostly only bones and teeth, but in 1977 numerous and complete skeletons of amphibians were discovered in the upper part of the Lower Keuper near Kupferzell , such as Mastodonsaurus , Gerrothorax , Plagiosuchus and Kupferzellia .

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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