Kalktuffquelle

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Kalktuffquelle (Helokrene) near Thalheim
Tufa spring at Gordale Scar Waterfall in North Yorkshire (Rhenokrene)
Tufa formation on the Tuffbach near Innsbruck

A tufa spring is a source that is fed by calcareous groundwater and is characterized by the precipitation of calcium carbonate ( tufa ) in the immediate source area. Local plants, especially mosses such as Palustriella commutata, play a decisive role in the formation of the limestone tuffs .

Characteristic and origin

In limestone springs, calcareous spring water with a temperature of 2 to 7 ° C comes to the surface all year round . During the underground passage of the infiltrating, weakly acidic rainwater in limestone, calcium carbonate is dissolved and carried away with the groundwater flow. At the source outlet, as a result of the increase in temperature and pressure relief - combined with an escape of the carbon dioxide dissolved in the groundwater - calcium carbonate precipitates again. This process is reinforced by algae and mosses , which additionally remove carbon dioxide from the spring water through photosynthesis . Mosses and plants are covered with a thin crust of precipitated calcium carbonate, which over time forms filigree, porous limestone.

Source types

Tufa springs are preferred as rhenokrene (flowing springs) with a punctual groundwater outlet and helokrene (seepage springs). In seepage springs, the groundwater usually emerges slowly to the surface in a more or less large spring swamp. Flow sources, on the other hand, can usually have a significantly higher bed . In the immediate source area of ​​limestone springs, both organic and stony substrates can be observed.

flora

Starknervenmoos

In the vicinity of the source outlets, a characteristic source flora forms under optimal conditions. In addition to blue algae and diatoms , mosses dominate, especially strong-nerved mosses. In addition to strong nerve mosses (Pallustriella commutata), fern-like Stark nervous mosses (Cratoneuron filicinum) and fat Shining Ohnnervmoosen (Aneura pinguis) tufa springs are also common with watercress (officinale Nasturtium), giant horsetails (Equisetum telmateia), Red Small Fork Teeth mosses (Dicranella varia), members-rushes ( Juncus articulatus) and alternate leaf spleen (Chrysosplenium alternifolium).

The strong-nerved mosses in particular are of particular importance in the formation of the calcareous tuffs. This otherwise rare type of moss is often widespread in the area around the spring. On the one hand, the moss cushions enlarge the surface wetted by water and, through photosynthesis, remove the dissolved carbon dioxide from the water , thus promoting lime precipitation and thus the formation of tufa. The rocks can "grow" through permanent resettlement of the calcareous crusts formed by the mosses and form the characteristic stone channels .

fauna

As swelling typical fauna of tufa springs next are freshwater shrimp (Gammarus sp.), Cordulegastridae (Cordulegaster sp.), Spring snails ( Bythinella sp.), Genabelte pupillidae ( Lauria cylindracea ) also occasionally sadleriana ( sadleriana to find). The larvae of certain species of stoneflies and caddis flies , which rely on calcareous water, can also be found at tufa springs.

Occurrence

Tufa spring of the Dard in Baume-les-Messieurs
Lime sinter terrace above the Güterstein waterfalls

Tufa springs are genetically linked to the distribution areas of carbonate rock formations ( limestone , dolomite ). Tufa springs are a relatively seldom widespread type of spring. In Europe, such sources occur, for example, in the limestone Alps , in the area of ​​the Alpine foothills , which are mostly covered by calcareous glacial pebbles , in the Franconian and Swabian Alb on the Jasmund chalk coast , but also in other regions. In Lower Austria , tufa springs can be found up to heights of 1000 m in the Vienna Woods , in the north-eastern peripheral Alps and in Ötscher - Dürrenstein .

Danger

Tufa springs are sensitive biotopes . In addition to the mechanical destruction of the fragile tufa formations through the impact of animals and people when using the spring as a cattle trough or for tourist purposes, tufa limestone springs can be endangered by a wide variety of factors. In addition to the change in the hydrological and hydrochemical characteristics of the spring due to the lowering of the groundwater and the associated reduction in spring discharge, eutrophication , the entry of pollutants and fertilizers into the groundwater, materials (anthropogenic waste and tree cuttings from forestry) that cause the formation of Prevent or significantly disrupt lime tuffs. Technical and tourist spring catchments as well as clearing in the spring area can significantly disrupt the biological balance.

Protection of the limestone springs

Due to the rarity and small area of ​​the formations, the site-specific flora and fauna and their high risk potential, limestone tufa springs are often designated as biotopes, natural monuments , geotopes , Natura 2000 areas (Cratoneurion: NATURA 2000 - Code: 7220) and as priority habitats. In some countries, special programs for the protection and preservation of limestone springs have been set up as part of the Natura 2000 program.

Well-known limestone sources (selection)

Individual evidence

  1. ↑ kalktuffquellen.de here: Source types , accessed on September 6, 2014.
  2. ↑ Ulrich Lagally: Germany's longest channel: The spring limestone "Growing Rock" from Usterling in Lower Bavaria. In: Ernst-Rüdiger Look, Ludger Feldmann: Fascination Geology: The most important geotopes in Germany . Academy for Geosciences in Hanover eV (Ed.)., E. Schweizerbart'sche Verlagsbuchhandlung (Nägele and Obermiller), Stuttgart 2006, ISBN 3-510-65219-3 , p. 164f.
  3. ↑ Natura2000 profile of tufa springs in Mecklenburg-Western Pomerania , accessed on September 6, 2014.
  4. ↑ Nature Conservation Sources Lower Austria: Kalktuffquellen ( Memento of the original from September 6, 2014 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed September 6, 2014. @1@ 2Template: Webachiv / IABot / noe-naturschutzbund.at
  5. ↑ FFH profile 7220: Kalktuffquelle , accessed on September 6, 2014.
  6. ↑ Hans-Dieter Krienke: The geotopes worthy of protection of the islands of Rügen, Hiddensee and Vilm. Brandenburg. geowiss. Articles, Issue 7, Kleinmachnow 2000, pp. 166f , accessed on September 6, 2014.

literature

  • Heiko Rein: Natural treasures of the Rhön: Limestone fens and limestone tuff springs: habitats of the Rhön biosphere reserve in the NATURA 2000 network of protected areas, natural treasures of the Rhön , LIFE project Rhön of the EU, 1997, 11 pp.

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