Dismicrit

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Foil removal of a Dismikrit LF-Type A (Devonian lagoon limestone, Elbingeröder complex )
Dismikrit LF type B, in thin section and in polarized light (below)

As Dismikrite are micritic limestones with less than 1% foreign components referred. They are characterized by the appearance of late- filled cavities. The spatula can be distributed irregularly in the rock or arranged like a string of pearls. The term dismicrit was introduced into the carbonate classification in 1959 by Robert L. Folk .

Education, genesis and dissemination

The void structures in Dismikriten are often referred to as laminar window structures (loferite), with two types being distinguished: the pearl-like arranged spatula bubbles are called loferite (LF) type A, while the loferite type B is characterized by irregularly distributed spatula bubbles.

The cavities can be created in different ways. You do cavities below microbial mats , as gas bubbles rotting interpreted organisms, as a result of various subversive activities endobionts than shrink pores in the sediment drying, air bubbles or triggering structures in the recrystallization of anhydrite be considered. The cavities are usually filled with coarse calcite. In some cases, formations can be observed in which the cavities are geopetal filled with internal sediments (mostly dark lime mud) and the remaining pore volume is cemented out with calcite. These formations can then be interpreted as fossil spirit levels.

Dismicrites are a characteristic facies feature of the tidal coastal area and the lagoons (intertidal and shallow subtidal). These limestones occur preferentially in lagoons with partially hypersaline conditions. Dismicrites occur worldwide in many limestones that were formed in the lagoon milieu, for example in the southern German Malmkalk, in the Dachstein limestone or Devonian reef limestone in the Rhenish Slate Mountains or the Elbingeröder complex .

Individual evidence

  1. ^ Author collective: Lexicon of Geosciences. Volume I, Spektrum Akademischer Verlag, Heidelberg / Berlin 2000, ISBN 3-8274-0299-9 , p. 342f.
  2. ^ Robert L. Folk: Practical petrographic classification of limestones. In: American Association of Petroleum Geologists Bulletin. Volume 43, 1959, pp. 1-38.
  3. ^ AG Fischer: The Lofer Cyclothems of the Alpine Triassic. In: Kansas Geological Survey Bulletin. Volume 169, Lawrence 1964, pp. 107-149.
  4. ↑ GE Tebbutt et al: Lithogenesis of a distinctive carbonate rock fabric. In: Contributions of Geology. University of Wyoming, Volume 4, 1965, pp. 1-13.
  5. ↑ Erik Flügel: Microfacies of carbonate rocks. Analysis, Interpretation and Application. Springer Verlag, 2004. (2nd edition, 2010).

literature

  • Robert L. Folk : Practical petrographic classification of limestone. In: Bulletin of the American Associations of Petroleum Geologists. 43, Boulder 1959, pp. 1-38.
  • Erik Flügel : Microfacies of carbonate rocks. Analysis, Interpretation and Application . Springer Verlag, 2004. (2nd edition, 2010)
  • Erik Flügel: Microfacies analysis of limestones . Springer Verlag, 1982.
  • Erik Flügel: Microfacial methods of examination of limes. Springer Verlag, 1978.