Opalinus Clay Formation
Abbreviations:
The Opalinus Clay Formation is a lithostratigraphic formation of the southern German Jura . It is common in almost the entire area of the southern German Jura. It is underlain by the Jurensis marl formation and overlaid in different regions by the Murchisonaeoolith formation (in the Upper Rhine region), the Eichberg formation (in the Wutach region) and the iron sandstone formation on the Swabian Alb. It is dated to the Lower Aalenium .
history
In the Quenstedt division of the South German Jura of 1856/57, the Opalinus Clay Formation is equated with the Dogger alpha. The formation is named after the ammonite Leioceras opalinum (Reinecke, 1818) (previously called Ammonites opalinus ). It is now defined as a lithostratigraphic formation.
definition
The Opalinus Clay Formation consists of fairly uniform clays and mudstones with individual clay ironstone layers. The thickness is between 100 and 120 m. The Opalinus Clay Formation in the Swabian Alb essentially comprises only one ammonite zone, the Opalinus Zone. This means that the Opalinus Clay Formation must have been deposited in a very short time. This biozone is the lowest (of the four) biozone (s) of the Aalenium of the Middle Jurassic series. However, the formation continues in some areas of the South German Law (z. B. Oberrheintal and Oberfranken ) already in the top Jurassic and thus still extends into the Pleydellia aalensis of the zone, the top zone Ammoniten Toarciums inside.
Lithology and subdivision
It is therefore currently not subdivided further. The low water permeability of the clays means that spring horizons often form at the upper layer boundary of the Opalinus Clay Formation .
Economical meaning
The clays of the Opalinus Clay Formation used to be mined in many clay pits and baked into bricks. Today only a few mines are still in operation that produce expanded clay pellets (Liapor near Tuningen ).
The Opalinus Clay Formation is being examined in Switzerland as a possible horizon for the final disposal of nuclear waste ; the formations are mainly located in the area of the Swiss Jura . In addition, there is also a study by the Federal Institute for Geosciences and Natural Resources (BGR) on nuclear final disposal in the Opalinus Clay of southern Germany. The Opalinus Clay is open . a. at Neunkirch am Randen .
In Switzerland, the proof of disposal is considered to be the fundamental proof of suitability for final storage in the opaline rock, but the specific proof of location is still pending . Recently, however, doubts have been raised about the suitability: In the Mont Terri rock laboratory , bacteria and residues of salt water from the sea were found in the rock. According to Laboratory Director Paul Bossart, these findings are taken seriously and scientifically investigated, such as B. the corrosion caused by the salt water on the steel tanks by means of sulfate-reducing bacteria (pitting corrosion). Alternative materials such as containers with a copper jacket or ceramics will also be examined in the future. This would allow the long-lived nuclides to be trapped in the waste for much longer.
literature
- Friedrich August Quenstedt : The Jura. Laupp Publishing House, Tübingen 1856–57.
- Gert Bloos, Gerd Dietl & Günter Schweigert: The Jura of Southern Germany in the Stratigraphic Table of Germany 2002. Newsletter on Stratigraphy, 41 (1-3): 263-277, Stuttgart 2005 ISSN 0078-0421
Individual evidence
- ↑ Magazine of the Swiss Energy Foundation , No. 1, 2010
Web links
- Geological overview of the sequence of layers in Baden-Württemberg (PDF; 183 kB)
- Middle Jura in Baden-Württemberg (PDF; 20.5 kB)