Paramoudra

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Paramoudra in a chalk outcrop on the south of England's North Sea coast. The hollow of this large flint bulb was originally filled with chalk that was washed out by the lake water. The chalk formation at this outcrop is only visible at low tide and is covered by a thin layer of rock.

Under the term Paramoudra , a special morphological appearance of flint bulbs is controversially discussed in the literature (in the English-speaking world under the name Potstone , in Denmark known as Flintkrukke ).

Names

The name "Paramoudra" goes back to William Buckland (1817), who was the first to describe flints of this type that he found in Northern Ireland. The word is borrowed from Irish. One of several interpretations of the meaning of this term says that Irish quarry workers once called themselves that, another explanation refers to the root word padhramoudras , which can be translated as "nasty Irish". These interpretations suggest that Buckland chose the name “Paramoudra” because the flint stones already posed a riddle for him that has not yet been finally solved. Another interpretation leads the term back to pair of murderer , which means something like "murderer stone", a term that leaves room for speculation about the former use of these stones.

Flints from the Upper Cretaceous and the Danium of northwestern Europe often contain large, relatively straight, more or less cylindrical cavities open on both sides. Such stones come in different sizes. The smaller ones are popularly referred to as " chicken gods ", the larger ones - the actual Paramoudras - in northern Germany as "Saßnitz flower pots". The latter name goes back to the fact that these perforated flint stones, which can weigh up to 200 kg and more, were often used as flower tubs on Rügen , which can still be found there today.

Locations and peculiarities of the find situation

Paramoudras are found in particular in chalk outcrops in England, Denmark and northwestern Germany, but also in Sweden, Belgium, the Netherlands and France. In the Maastrichtian of Hemmoor (Niedersachsen) shotgun have been found with a length of up to four meters. What is also remarkable about these objects is the find situation. As a rule, these extremely heavy pieces are always found "perpendicular to the flint bands [standing]", i.e. columnar at a 90-degree angle to the orientation of the sediment and the horizons of flint lumps inside. Circular arrangements are also known from England. Not least from these deposit features, indications of the rather complex diagenetic processes for the formation of the paramoudras, but also of "normal" flint nodules, have emerged. Further indications of the formation of pyrite and glauconite , which are often found in the paramoudra cavity filled with chalk (lime), as well as narrow, long burial tunnels (detailed in Bromley et al., 1975), give further indications of the origin of the finds.

Theories of origin

It is therefore often assumed that the cause of the holes in Paramoudras is an animal that creates burrows and lives on the seabed. Beard worms and cordworms in particular are considered as the builders of these living tubes, which have entered the literature as a trace fossil under the name Bathichnus paramoudrae (before the first description by Bromley et al., 1975, this name was used for the Paramoudra shotgun, but not for used the tombs). The cavities in the Paramoudras have a much larger cross-section than the burial tunnels, which are often only a few millimeters in diameter but up to nine meters long and can still be traced locally in the chalk segments. The significantly larger holes in the flint bulbs are the result of special biochemical conditions in the formation of the flint; Due to the excretion of metabolic products and, after death, also due to the decomposing bodies of the builders of the burial tunnels , the pH value of the environment fell, which led to the precipitation of silica , which accumulated in a ring around the burial tunnel a few centimeters away and formed the basis for the evolution of flint formed. This happened after the horizons of today's flint deposits in the chalk had already passed through the first phase of their genesis.

At times the sponge Poterion cretaceum was seen as the originator of the " burial tunnels ". There is also the opinion that these holes in the flint could be of inorganic origin, which does not necessarily contradict the origin theory presented above, according to which the burial tunnels or their producers are only indirectly involved in the formation of the cavities in the flint by being with The metabolic products emanating from them created the prerequisites for the (bio) chemical processes that are probably responsible for the shape of these large flints. It is questionable whether the cavities of the much smaller "chicken gods" or these themselves have the same origins as the Paramoudras.

Exhibitions

Paramoudras are exhibited in numerous museums in north-western Europe. For example, a tube flint from Hemmoor can be seen in the Mineralogical Museum Hamburg , Danish material in the Geological Museum Copenhagen and Dutch material in the Natural History Museum Maastricht; English material is on display in the Castle Museum Norwich ; two of the paramoudras from Northern Ireland examined by Buckland are in the Natural History Museum at Oxford University .

literature

  • Steen Andersen & Steen Sjørring (Red.): Det nordlige Jylland (published as the third of five volumes in the Geologisk set series ) - 208 p., Numerous. Fig. And maps, Geografforlaget, Brenderup (DK) 1997 (2nd edition of the 1st edition).
  • Rolf Reinicke: Flints - Chicken Gods . - 80 p., Numerous Fig., Demmler-Verlag, Schwerin, 2009
  • Bromley, RG, Schulz, M.-G. & Peake, NB: Paramoudras: Giant flints, long burrows and the early diagenesis of chalk. - Det Kongelige Danske Videnskabernes Selskab, Biologiske Skrifter 20, 10, pp. 1-31, 5 panels, 1975.
  • Steen Sjørring: Rings af flint. Varv 4, 1991.
  • Erik Thomsen: Relation between currents and the growth of Palaeocene reef-mounds. Lethaia, Vol. 16, pp. 165-184, Oslo, 1983. ISSN  0024-1164

Web links

Individual evidence

  1. ↑ u. a .: NB Peake & JM Hancock: The Upper Cretaceous of Norfolk. In: Trans. Norfolk Norwich Naturalists Soc. 19, Norwich 1970.
  2. ↑ a b F. J. Krüger: The Paramoudra shotgun of the Maastrichtium. In: Der Geschiebesammler 10, Nr. 3–4, Hamburg 1976.
  3. ↑ H. Nestler: The fossils of the Rügen writing chalk. Wittenberg 1975.