Erfurt-Formation

The Erfurt Formation (equivalent in Northern Germany the Lower Keuper ) is a lithostratigraphic formation of the Keuper in the Germanic Triassic. The lithostratigraphic unit is underlain by the Upper Muschelkalk subgroup and overlain by the Middle Keuper Group. The deposits of the Lower Keuper indicate lacustrine conditions with occasional marine influences.

Definition

The lower limit of Erfurt Formation is in northern Germany, the base of the Lower Latvians carbon sandstone. In southern Germany, it is the basis of Grenzbonebeds. It is marine -influenced carbonates and dolomites, lacustrine limestone and mudstones and fluvial sandstones. The thickness is in northern Germany on average about 60 to 80 meters, in grave zones over 100 meters can be achieved. In southern Germany, the cardinality of 30-0 meters on the pool edges for Vindelician country varies out. The type locality of the formation is situated in Erfurt Erfurt Melchendorf ( Thuringia). The Erfurt- formation is dated in the stratigraphic level of the Ladinian. In geochronology this section can be dated with about 235 to 232.5 million years ago (after the STD2002 ).

Structure

In the North German Basin, the Erfurt Formation is the only formation of the Lower Keuper. In southern Germany it dovetails in the peripheral areas to Vindelician country with the Grafenwoehr lineup. More lithostratigraphic units have yet to be defined in the western border areas. A breakdown in Subformationen has not yet been proposed. In earlier work of the 1980s, a subdivision is made in two or three units, which could be the basis for Subformationen in the future or could be reinterpreted as Subformationen. In the Erfurt lineup nine small cycles can be distinguished.

Depositional environment

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 intervening with land. Here root and soil layers are found with sulfate nodules suggestive of occasional flooding and drying under arid conditions. From the southwest sea of the Belfort Gap occasionally penetrated into the basin, reaching in the north- east, the southern part of Lower Lusatia and in the north the Osnabrück Bergland.

Fossils

The Erfurt Formation contains numerous remains of vertebrates (fish, amphibians and dinosaurs ). In the bonebeds there are mostly just bones and teeth, but in 1977 and numerous complete skeletons were in the upper part of the Lower Keuper in copper cell discovered amphibians such as Mastodonsaurus, Gerrothorax, Plagiosuchus and Kupferzellia.