Bärenthaler Kalktuff

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Still operating quarry, western side of the river Bärenthal with tufa from the Holocene
Surface of a polished pattern (approx. 12 × 12 cm) of the Bärenthaler Kalktuff, which shows the different pore formation of this rock
Detail of a tufa limestone sediment, Bärenthal-Ensisheim
Remnants of a large tufa bar , former quarry, Bärenthal-Ensisheim, Bäratal

The Bärenthaler Kalktuff is a freshwater limestone from the Swabian Alb , which is still mined in the Bärenthal community in the Tuttlingen district . These limestone tuffs are widespread in Germany in the Jura (especially the Swabian Alb) and in the shell limestone of northern Württemberg and have been mined in many places. Most of the tufa deposits there are now (2020) exhausted. In the 1890s and 1930s, the tufa limestone from the Bäratal was a frequently used building block in southwest Germany. In Bäratal there is only a sideline mining of this natural stone .

Occurrence

On the western side of the Bärenthal valley, there is still a 700 meter long lenticular tufa ceiling of the Bära valley . On the slopes of the Bära valley (Obere- and Untere Bära, Ensisheim) another six tufa sedimentations have been detected. At the southern end of the tufa limestone cover, a waterfall is registered as a natural monument "Bärenthaler Tuffsteinkaskaden". Fresh tufa is still forming here today. Part of the large tufa ceiling is still a part-time quarry to this day. The deposited layer suitable for the extraction of ashlar, which is well consolidated, is about 4 to 5 meters. There used to be several stone quarries in the Bäratal. The thickness in Bärenthal can be up to 9 meters, in Ensisheim even more.

In the hamlet of Ensisheim, 2.1 km to the north, but still belonging to the municipality of Bärenthal, there are still large parts of a tufa bar that are freely accessible and well worth seeing. You can see two well-preserved mining remains with vertical walls, on which the structure and structures of the limestone tuffs are clearly visible, and the process of their mining is understandable. Caves, niches and typical karstification phenomena (e.g. remains of leaves, tree branches, hollow spaces) are still preserved.

Rock description

This white to cream-colored rock type is a rock with large pores. It consists of lime-coated reeds, grasses, mosses and occasional branches and other freshwater plants. But there are also dense areas in the rock.

use

The rock quarrying of the Bärenthaler Kalktuff was in great demand in the 1890s, as the stations on the Tuttlingen – Inzigkofen railway were built from this tuff. In the 1930s this tuff was used for road structures on motorways in southwest Germany.

Tufa is currently (2020) used only to a limited extent. It is mainly used for cover plates, bricks, in garden design for the construction of artificial grottos and as quarry stone in aquariums. It is also used for the restoration of historical buildings. In solid form, as a natural stone, it is good heat-insulating, weatherproof and frost-resistant, but not resistant to aggressions. It cannot be polished.

This tufa was used, for example, at the city gate in Mühlheim an der Donau , for the city churches in Spaichingen and Stetten an der Donau or for the Bärenthaler rectory. Bärenthaler Kalktuff was also used for retaining walls and bridges on the Albaufstieg Aichelberg and for the Drachenlochbrücke , fortifications, Reduit in Ulm , for numerous train stations between Tuttlingen and Ulm and for the city church in Geislingen an der Steige .

Dismantling

The Bärenthaler Kalktuff is mined with the use of a sword saw without using cooling water. Rough blocks with an edge length of 0.50 to 1.00 meters can be extracted. Larger rough blocks are rarely extracted. From a processing point of view, the solid limestone tuff is a soft stone . Tuff limestone from the Bäratal can be worked with a hatchet, hand saw or knife when it is damp in the mountains .

Individual evidence

  1. ↑ The limestone tufa areas are shown on the current geological maps of the LGRB .
  2. ↑ See the photo
  3. ↑ See the two photos
  4. ↑ a b Friedrich Müller ... See literature
  5. ↑ Wolfgang Werner, Roman Koch… See literature
  6. ↑ The stone is transported in the terraced quarry with wheel loaders

literature

  • Wolfgang Werner, Roman Koch: Kalktuffe . In: Natural stone from Baden-Württemberg - occurrence, procurement and use . Ed. State Office for Geology, Raw Materials and Mining. Rüsselsheim 2013. ISBN 978-3-00-041100-7
  • Friedrich Müller: INSK compact. The international natural stone index for the current market . Volume 2. Index sheet 76.6. Ebner Verlag Ulm 1997

Web links

  • Karst in Baden-Württemberg [1]