Stephanian (stage)
The Stefanium, often shortened ( also used in the French form Stéphanien ) to Stefan, is in the Earth's history, a period of the Carboniferous ( Paleozoic ). It is the top regional or supra- regional level of the carbon or the subsystem Silesium. It is underlain by the regional stage of the Westfalium and from the regional stage of the Autunium, the lowest level of the Permian of Central Europe ( Dyas ) superimposed. The term could be in international use not enforce and comply with the global chronostratigraphic stages of Kasimovian and the lower Gzhelium. More recent studies it was found that the boundary Stefanium / Autunium diachronically runs or is faziesabhängig and within the global carbon. In absolute terms, the Stefanium starts at about 305 million years ago and ends regional and facies vary at about 302 to about 300 million, well before the global Carboniferous / Permian boundary, which is now dated geochronological 299 million years.
History and naming
The term Stefanium or Stéphanien was introduced by Ernest Munier - Chalmas and Albert de Lapparent 1894 in the literature. It is named after the city of Saint -Étienne (Dept. Loire, France) named. The Latin name of the city is " Stephen ".
Definition and correlation
The base of Stefanium was defined lithological - facies in the first place. About an unconformity with likely significant hiatus put a limnic - terrestrial layers containing plant fossils ( Bowmanites verticillata ( Schlotheim ) Hoskins & Crosse, 1943 Annularia stellata and Pecopteris polymorpha ). In the marine area, the foraminiferal genus is a Triticites. Meanwhile, the Westfalium / Stefanium boundary is correlated with the Moscovian / Kasimovian limit. The controversial Cantabrium sub-stage is expected to Stefanium. However, it is outside of northern Spain not prove. Therefore, the current Westfalium / Stefanium limit is still subject to certain uncertainties ..
The upper limit of Stefanium (and thus of the Central European Carboniferous) and the lower limit of Autuniums (and thus the limit of the Central European Permian ) was developed by Bertrand (1918 ) with the first appearances of " Callipteris " conferta (now Autunia conferta from the group of Peltaspermales ) defined. This definition of the beginning of Autuniums ( and the Permian in Central Europe), however, is extremely problematic. Later it turned out namely that deposits with reputable than stefanisch plant fossils exchange store with deposits or represented laterally containing autunische plant fossils. This is because Autunia was meso- or xerophilic and wet locations did not occur. Autunia fossils are also less likely to receive as a plant in the vicinity of water. These have in the aquatic better conservation and tradition chances than Autunia on dry sites. The Callipteriden are relatively difficult to determine; many provisions of Autunia conferta are misidentifications and must be corrected. According to current knowledge Autunia conferta already starts in Stefan B Blanzy, so starts still significantly higher in the Carboniferous. The Rotliegend of the Saar-Nahe Basin, however Autunia conferta does not begin until well above the base of the Permian. The beginning of the Stefanium B of the European Upper Carboniferous is now correlated with the highest part of the international chronostratigraphic Kasimovian stage; it extends into the lower Gzhelium stage. Thus, there is a clear discrepancy between the biostratigraphically defined the beginning of the Autuniums and the beginning of lithostratigraphically defined Unterrotliegend with which the Autunium was correlated earlier.
According uncertain are the absolute age of the Stefanium. Following the Stratigraphic Table of Germany 2002 (STD2002) it ranges from 305 to about 302 / 300 million years with strong diachronic ceiling. After the calibrated time scale of Menning et al. (2006 ) of about 306 and 300 million years, or about 307-301 million years ago in the International Stratigraphic Chart 2009, which was calculated from the global Moscovian / Kasimovian limit by mid- Gzhelium.
Subdivision of Stefanium
Regional level of Stefanium was traditionally divided into three stages which are known as Stefanium A, B and C. Some writers were still trying to establish a Stefanium D, which proved to be untenable. The Stefanium located in Central Europe unconformably on the Westfalium D with a hiatus of unknown duration. RH Wagner (1969 ) described from Cantabria, where the transition is complete at the base of Stefanium nor the Cantabrium (also Kantabrium ). Later, the Stefanium A was renamed the Barruelium. For the Stefanium B / C beat Doubinger et al. (1995 ) a new level Forezium ( Forezien ) before, after, Forez, a landscape in France, which has so far received little attention.
- Stefanium C ( Forezium )
- Stefanium B ( Forezium )
- Stefanium A ( Barruelium )
- Cantabrium (also Kantabrium )