Crenistria horizon

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The Crenistria horizon , also called Crenistria limestone , is a lithostratigraphic unit in the Upper Visé ( Lower Carboniferous ) of Central and Western Europe. It consists of a sequence of one to three dark limestone banks alternating with black and pebble pelites. The limestone layers were formed during the so-called Crenistria event .

The Crenistria horizon has been proven in the Harz Mountains , in the Rhenish Slate Mountains , in Belgium , in south-west England and in western Portugal . The lithological characteristics show a clear dependency on the respective paleogeographical deposit situation: In deeper basin areas the limestone layers are relatively thick and purely micritic . In the area of ​​the pelvic heights, the proportion of sound increases with reduced thickness.

Crenistria event

A temporary decrease in the oxygen content in the water ( oceanic anoxic event ) worsened the living conditions in the epicontinental inland sea of the rhenohercynian Kulm Basin. This triggered a mass extinction of the organisms living in the water. A rapid deposition of marine organism shells on the sea floor was the result. Among them were ammonites - especially goniatites of the species Goniatites crenistria , the frequent occurrence of which gave the event locations its name - as well as radiation animals and mussel shells . At the same time, the pH of the water increased, with the result that a higher degree of calcium carbonate dissolved in the water precipitated without the participation of carbonate-separating organisms (i.e. abiotic ).

literature

  • H.-G. Herbig: Contrasting carbonate facies in the crenistria-Zone (Go IIIa, Late Viséan) of the Rhenohercynian culm basin - Expression of rapid sealevel variation. European Dinantian Environments II. Developments in Lower Carboniferous Geology. University College Dublin, Technical Program & Abstracts Volume: 14-15. Dublin 1994.
  • B. Mestermann: Microfaces , paleogeography and event genesis of the crenistria horizon (Obervisé, Rhenohercynicum). Cologne Forum for Geology and Paleontology 2. Cologne 1998.
  • HJ Nicolaus: On the stratigraphy and fauna of the crenistria zone in the Kulm of the Rhenish Slate Mountains. Geological yearbook: Beih., 53. Hannover 1963.