Bioherm

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"Mini" blue-green algae Bioherm from the Cambrian of Virginia, carved out of the rock

A Bioherm (from Greek βιός, bios , "life" and ἕρμα, herma , "rock", "stone", "ballast", " cliff ", " reef ") is a fossil biogenic limestone complex ("bioconstruction"), which is shaped like a hill or lentil and differs significantly from its often marl-like surrounding rock . It is attributed to the growth of a biogenic reef , which at the time clearly towered above its surroundings and thus had an impact on the sedimentation in its immediate vicinity. Bioherms were fast-growing lime -secreting sessile invertebrates , especially corals , in cooperation with kalkabscheidenden microorganisms (coralline red algae , blue algae established). In the geological context, the term bioherm is also used synonymously with the term reef , if biogenic reefs are meant.

Limestone complexes, their surroundings at the time not or hardly overtopped and from less rapidly growing sessile marine invertebrates, which are grown mainly in the width in the geological tradition by layering distinguished, by contrast, as bioelectricity (from Greek. Στρώμα, stroma , "Ceiling "," Upholstery "). From this distinction it follows that with a Bioherm the laterally adjacent secondary rock at the same level of the rock group is younger, while with a bio-current it is approximately the same age.

The terms Bioherm and Biostrom were originally coined in the late 1920s and early 1930s by the American geologists and paleontologists Edgar R. Cumings and Robert R. Schrock.

Bioherms can be found in numerous carbonate rock sequences all over the world. They are typical of marine deposits on the shallow shelf , where they often indicate water depths in the area of ​​the photic zone . Examples can be found in Germany in the Devonian of the Rhenish Slate Mountains (with stromatopores as important carbonate producers ) and in the Jura of the Swabian and Franconian Jura ( sponge- algae bio-thermal baths). In the shallow water facies at the edge of the Nördlinger Ries , Miocene freshwater algae bio-thermal baths have been handed down. In German, the rocks of bio-thermal baths or fossil reef bodies are also referred to as mass limestone .

swell

  • Bioherm in the spectrum online encyclopedia of geosciences
  • Lucien F. Montaggioni, Colin JR Braithwaite: Quaternary Coral Reef Systems: History, development processes and controlling factors. Developments in Marine Geology 5. Elsevier, 2009, ISBN 978-0-444-53247-3 , pp. 2 f.
  • George D. Stanley, jr .: Introduction to Reef ecosystems and their evolution. Pp. 1-39 in: George D. Stanley, Jr. (Ed.): The History and Sedimentology of Ancient Reef Systems. Topics in Geobiology 17. Springer, 2001, ISBN 978-1-4613-5446-8 .

Individual evidence

  1. ^ Edgar R. Cumings, Robert R. Schrock: The geology of the Silurian rocks of northern Indiana. Indiana Department of Conservation Publication No. 75. Indianapolis, 1928
  2. ^ Edgar R. Cumings: Reefs or bioherms? Bulletin of the Geological Society of America. Vol. 43, No. 1, 1932, pp. 331-352
  3. Gernot Arp: Lacustrine bioherms, spring mounds, and marginal carbonates of the Ries impact crater (Miocene, Southern Germany). Facies. Vol. 33, No. 1, 1995, pp. 35-89, doi: 10.1007 / BF02537444