Tufa

Tufa or Süßwasserkalk or Quellkalk is a porous, still a young 'secondary' sediment. In Europe it is found in some of the karst areas of the humid, temperate warm climate zone, provided that a number of condition factors are present regionally. Particularly well known and studied are deposits of the Swabian Alb, the Franconian Jura and the Alps edges.

6.1 tufa - bars
6.2 tufa, nose, tufa - cushion
6.3 stone gutters
6.4 stream terraces
6.5 Primary Caves / Tuffhöhlen

Prior to the emergence of: karstification

In addition to karstification processes of physical weathering expire but especially chemical processes of carbonic acid weathering. Carbonated water takes in brittle limestone (limestone, chalk, marble and other calcium carbonates ) of a more or less developed karst system, the carbonates to saturation in solution. Unit of transported dissolved lime under different environmental conditions, it can be redeposited by chemical precipitation. The two operations may be considered as two different states of equilibrium of a reversible chemical process; see also calcium bicarbonate.

Prior to the emergence of: precipitation dissolved lime

Interactions of karst water and carbon dioxide - underground or when re- exit to the surface - can trigger the process of precipitation of lime. Especially in Karst caves and karst springs can after considerable amounts of lime sediment by the dissolved lime under different chemical and physical condition constellations again fails. The products of these secondary sedimentation are expected in the geology of the sintering. Among the highly aqueous, soft sedimentation as lime mud, Mont or mountain milk see the moon milk.

Formation of tufa

The deposition of calcium carbonate ( CaCO3) as tufa occurs primarily behind cold layer sources in karst. Such deposits exist in some karst areas of the humid, temperate warm climate zone since the last interglacial period (see Würm ) and also currently still. Whether it can cause precipitation of lime from karst water and in what quantities generally depend on the climatic and geological conditions, but especially of other physical and chemical constellations of conditions that need to be regionally or locally. The best climatic conditions existed during the roughly two thousand years of postglaziären Atlantic period. During this period (about 8000-6000 ) the average temperatures in Central Europe were about 2 ° C higher than today, and there was more precipitation. Are the general requirements, yet are among the necessary conditions for the precipitation of the following factors:

A relatively small pile of each source,
A relatively large evaporation surface,
A favorable corridor of water temperatures,
A change in the pressure ratios and
Specific ion concentrations.

If karst water flows over moss carpets, algal mats or colonies of cyanobacteria, a greater amount of calcium can be precipitated by the biomaterials for their assimilation (photosynthesis ) refer to carbon dioxide requirement from the karst water. The carbonate sediments can grow at rates of 0.01 mm / year for inorganic and up to 20 mm / year for organic mitinduzierter precipitation.

The precipitated lime defines itself as a fine crystalline crust of everything relatively dormant small material (sand, pebbles, twigs, leaves, ferns, mosses, algae, slime, etc.). There also arise from the cast stratification upward and forward growing creation or padding on small waterfalls or stages in stream terraces. Mosses grow on their part is encrusted fresh out; they act like little pots and form a supporting framework. Thus, larger, fragile hanger ( " nose " ) arise. Biotic contaminants from algae and bacteria produce relatively fine structures., You are more porous and easier when Moose could resist the flow of energy. This Travertine is often still moist and crumbly consistency. In the best times he was after a few centuries into powerful structures, so-called " Kalktuffbarren " (see below: "Special publication factors " ) has grown.

Delineation of the various names for precipitated calcium

The solid sediments are often - even with similar morphology - variously referred to as travertine, travertine, tufa or Quellkalk; or the terms are even used interchangeably. Under the general term sintering, however, even such materials are subsumed, you do not to the specific geological phenomena counts (eg wall interaction and scale ), or even those that are formed with substantial participation of other elements. (eg silica or sulfur Inter). Yet come to denote the geological phenomena in the Karst regional, country-specific or language-related uses that have occurred historically in local deposits. For example, the regional name for the Muschelkalk " Duckstein " in the eastern Lower Saxony. For a more precise definition is the term tufa useful (although " tuff " as volcanic phenomenon rather misleading ). In German-speaking and German-speaking literature, it is still in use - probably because of the relatively frequent occurrence and of good scientific mapping of karst. See the scientific and environmental mapping as geotopes. Uniformity in the designation has not been enforced in the geology.

Tufa, travertine and travertine can be distinguished according to their declining share of free and bound water. They can be further distinguished according to their density, and porosity ( by foreign bodies ) and according to their strength ( due to drying and autogenous pressure ).

Travertine can be considered as a substance of high purity and / or dense layering, such as stalactites and stalagmites in caves. Travertine is the one referred to by abiotic, biotic possibly also "impurities " more or less porous abiding by constant stratification and thus increasing the intrinsic pressure and decreasing moisture altered sediment. Such processes as diagenesis.

Fossil Travertine: Travertine Building Material

Tufa in the cured state was used as a high quality building material for centuries and into the 20th century: it is easy to remain weather resistant, abrasion resistant, good insulating and fire resistant. The extraction in the quarry was working technically easy - in the relatively fresh porous cuboid can also be easily cut. Numerous abandoned quarries and the local obstruction prove its local economic importance. Because of its material-specific strength and weather resistance tufa - travertine was from the Swabian Seeburger tufa at many prestigious buildings such as the old castle Stuttgart, Tübingen Lower castle gate (built in 1606 ), the Ulmer Münster and even used at the Strasbourg Cathedral. The internationally acclaimed architecture of the new building of the State Gallery Stuttgart has a travertine facade from Cannstatt Travertine.

Occurrence

In addition valleys, Talfüllungen or amphitheater- Talabschlüssen of Albtrauf and the Franconian Alb, in the Eifel region, the foothills of the Alps, and in the Limestone Alps to find fresh and old deposits of tufa, the elderly already fully cured rock. A rezentes Kalktuffvorkommen exists at the entrance to Ludolf blade at Diedesheim am Neckar.

For deposits ( eg in France, in England, in the Dinaric Alps or in Indiana ( USA) ) or Quellkalken very different type of conditions and climates (eg, large travertine deposits of thermal springs in Turkey and the Yellowstone National Park ) see below the section "See also ".

Particular manifestations

Tufa - bars

At the foot of the slope of the so-called Albtrauf Kalktuffbarren have emerged in many streams. At all seven slope -side streams that flow to the upper Fils between Wiesensteig and Geislingen, one or more extended old, partly extant (still active ) Kalktuffablagerungen are available. Outstanding are also multiple Kalktuffbarren the Echaz, the Wiesaz (formerly Gönninger quarries ) and the Rohrbach at Geislingen / walkways. The first and largest of seven Kalktuffbarren behind the Echazquelle with its 900x400 m area and a thickness of 24 meters and also the biggest cash of the Swabian and Franconian Alb. In the upper Ermstal (south of Bad Urach ), there are 7 impressive Kalktuffbarren, the largest of which originally locked the entire width of the valley at Seeburg and thus the Fischbach the so-called bottomless lake dammed ( until 1821 ).

The respective vicinity of the high-quality building material such Kalktuffbarren was certainly a reason for preferential colonization. In some cases, the locations ( Honau, Seeburg ) and cities grew ( Old Town Geislingen / walkways) zoom directly to a Barre. The morphology of the bars can be clearly seen in open-minded slopes and abandoned quarries. The sediments reach a thickness between 5 and 40 m. Through the powerful layers of the past millennia, the ingots rock character have adopted with the characteristics of travertine.

Travertine Nose, tufa - cushion

These unusual formations occur only rarely, and only when form on steep slopes in the lower trickling water tufa - moss that can grow "noses" with increased lime precipitation upward and forward to so called. , However, is not steep slope, dominated the development of Travertine forward, it created the so-called "stone troughs ", see below. Valuable geological sites are the nose structure Dreimühlen Waterfall in the Eifel, the goods Steiner waterfall at Albtrauf of Maisentals southwest Bad Urach and near the Bavarian Isar Growing Rock of Landau / Uster Ling. Since the lugs are extremely porous, consisting of wet, uncured lime and therefore fragile structures, such as the nose of the Neidlinger waterfall has collapsed half a century ago and still not tall again. Large terraced dumps, but they are again covered with old and fresh tufa and moss beds, below the nose of the waterfalls Urach waterfall and located 1.5 km north goods Steiner waterfall. They are evidence of repeated crashes of the nose. In Mill Valley Seeburg, the headwaters of Erin's, sources are at a distance of only 600m on the talus of the northern flank of the Kerbtals six (!) To see huge fossilized Kalktuffgehänge that arose as a wetter, less kluftigen, former karst still in layers above the valley floor to day came.

Stone troughs

Rare are the geotopes the Stone gutters. In an environment mapping in Bavaria, about a dozen were captured. Behind the small resources gentle slopes to narrow Karstwasserrinnsale meander down - all types of rough terrain below. The edge of the rivulets mosses grow, the more forward developing in the manner described above, depending on the flow rate of the Rinnsalwassers than up their Kalkgerüste to saddle-shaped dams. Back to top grows in dense sintered stratification, the water channel, the sprinkling of the sides makes the Moose to kalktuffigen moss stands grow. Depending on the gradient and accumulating Kalksediment bunk beds 13-170 cm and lengths of 7-130 m are observed. Their development is not continuous and not safe. Some specimens are due to questionable interventions no longer authentic. Probably the most significant, natural example of Europe is something 80 -meter-long stone trough at Erasbach. The channel follows the undulating, gently sloping terrain on an old, flat Kalktuffablagerung loosened in mixed forest. In Baden- Württemberg there is a nondescript stone trough at Lenningen ( Swabian Alb, LK Esslingen ) and below a former baffle overhang of the Jagst at home herb ( LK Hohenlohe ).

Stream terraces

Below Kalktuffnasen on whose screes and leading to little water headwaters of streams of Franconian and the Swabian Alb are numerous, unglamorous, small terraces stages of tufa. An imposing, but not natural state Geotop provide the terraces of the Lillach in Franconian Switzerland dar. Pronounced stream terraces are to Seeburg, above Bad Ditzenbach to find ( Ditz tributary of the Fils ) and the Zwiefalter Oh by the Wimsener cave. From a series of relatively large cascade with walls of tufa, the Plitvice Lakes in Croatia have formed (See "See also ").

Primary Caves / Tuffhöhlen

In upward and forward forming successful overmolding stratification or terminations of overhangs result in larger Kalktuffablagerungen smaller and larger cavities or even (half) caves. If the cavities are largely or completely developed in the deposits, one speaks of so-called primary caves or Tuffhöhlen, primarily because they were born together with the rock. Since they are not created as function of a waterway, they are usually only discovered when a Kalktuffablagerung breaks, used as a quarry or was otherwise engaged in it.