Namurium
The Namurium , also shortened to Namur , is a time interval of the Carboniferous ( Paleozoic ) in the history of the earth . It is the lower regional and supra-regional level of Silesium or the earlier Upper Carboniferous in Central and Western Europe. The boundaries of the European Upper Carboniferous or Silesium do not coincide with the boundaries of the global Pennsylvania subsystem, which is roughly the equivalent of Upper Carboniferous. Expressed in absolute numbers ( geochronologically ), the Namurium ranges from around 326.5 million to 316.5 million years ago. It follows the Viseum stage and managed by the Westfalium superseded stage.
History and naming
The stage is named after the Belgian city of Namur . J.-C. In 1881 Purves eliminated a step that lay between the layers with the coal seams and the coal lime. In 1883 he named this stage Namurium ("Namuria"). The Namurium stage was ratified by the 1st Carboniferous Congress in Heerlen in 1927, but the stratigraphic scope was expanded upwards and now included all Upper Carboniferous layers that did not belong to the productive Upper Carboniferous. However, the Namurium was not adopted as a global level by the International Commission on Stratigraphy . However, it is still available as a regional and supra-regional level in Central and Western Europe.
Definition and correlation
The lower limit of the Namurium and also of the Silesium is defined by the first onset of the ammonite type "Cravenoceras" leion (= Emstites leion ). The upper limit was originally marked by the onset of the first coal seams. In the meantime, the Namurium / Westfalium boundary is defined with the first onset of the ammonite species Gastrioceras subcrenatum (Schlotheim). In the global level structure, this corresponds to the middle Bashkirium . Expressed in absolute numbers, the Namurium ranges from 328.3 to about 315 million years or 326.5 to 316.5 million years, depending on the stratigraphic table used.
Breakdown
Traditionally, the Namurium is divided into three sub-levels, which were designated with the capital letters A, B and C. However, it turned out that these three sub-levels represent periods of time of very different length, with Namurium A taking up the vast majority of the time, more than Namurium B and C combined. In England a different sub-school structure was established. Biostratigraphically, the Namurium was also divided into E1,2, H1,2, R1,2 and G1. E = Eumorphoceras , H = Homoceras , R = Reticuloceras and G = Gastrioceras ; all four genera are ammonoids .
- Namurium C, corresponds to the Yeadonium (or G1)
- Namurium B and R2, corresponds to the children's scoutium (or R1) and Marsdenium (or R2)
- Namurium A, corresponds to Pendleium (or E1), Arnsbergium (or E2), Chokierium (or H1) and Alportium (or H2)
swell
literature
- Michiel Dusar: Namurian. In: Geologica Belgica. 9 (1-2), Brussels 2006, pp. 163-175. (PDF)
- Manfred Menning, Dieter Weyer, Immo Wendt, Günther Drozdzewski: A numerical time scale for the Pennsylvania in Central Europe. (= Courier Research Institute Senckenberg. 254). Frankfurt am Main 2005, ISBN 3-510-61380-5 , pp. 181-198.
- Hans-Georg Herbig: The international Mississippium-Pennsylvania border - development of the concept, definition and application in Germany. (= Courier Research Institute Senckenberg. 254). Frankfurt am Main 2005, pp. 3–12.
- Dieter Weyer, Manfred Menning: Geological time scale, stratigraphic nomenclature and magnetostratigraphy. In: German Stratigraphic Commission (Ed.): Stratigraphie von Deutschland VI Unterkarbon (Mississippium). (= Series of publications of the German Society for Geosciences. 41). Hanover 2006, ISBN 3-932537-37-8 , pp. 27-50.
Individual evidence
- ↑ a b according to the Stratigraphic Table of Germany. These ages differ slightly from the ages in the International Stratigraphic Chart from 2009
- ↑ M. Dusar: Namurian. 2006, p. 163ff.
- ↑ International Stratigraphic Chart from 2009 (PDF) ( Memento of the original from March 2, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ see M. Menning et al .: Eine numerische Zeitskala ... 2005, p. 191.
Web links
- German Stratigraphic Commission (ed.): Stratigraphische Tisch von Deutschland 2002. Potsdam 2002, ISBN 3-00-010197-7 . (PDF; 6.57 MB)
- Commission for the paleontological and stratigraphic research of Austria of the Austrian Academy of Sciences (Ed.): The Stratigraphic Table of Austria (sedimentary layer sequences). Vienna 2004. (PDF; 376 kB)