Thüster limestone
Thüster limestone , which is also called Serpulit or Serpelkalkstein , is extracted from small deposits in Hils , Deister , Osterwald and near Bielefeld . It is a natural stone that represents a unique local special development of the Upper Jura in the Münder Mergel . This limestone was created in a sea basin near Thüste in southern Lower Saxony . In 2008 the rock in the Thüster Berg near Salzhemmendorf is still being broken.
Rock description and names
The Thüster limestone is light gray, blue-gray to brownish. It is partially oolithic , contains rubble limes (biomicritical) from the tubes of calciferous tube worms, namely Serpula coacervata. This is a fossil worm belonging to the genus Serpel (Serpula), the calcareous tube worms , with an elongated body and bristles that hold it to stones or shells. These sea creatures form calcareous tubes that are preserved as fossil rocks. Thüster limestone is mostly porous and holey, not always limestone, but sometimes clayey. The structure and the sequence of layers vary greatly and the bench height is up to 16 meters.
The lesser-known names Serpulit and Serpelkalkstein come from the geologist Friedrich Adolph Roemer . The much more well-known variety name Thüster Kalkstein goes back to the place where it occurs in Thüste (Lower Saxony). On the edge of the Jurassic Sea ( Malm ), the Serpula worm built its calcareous tubes, which were rearranged and broke. This fossil debris formed a rock layer through solidification. Thüster limestone is open-pored, medium-grained, homogeneous and layered in parallel, as well as weather-resistant like all porous limestone. Its overall impression is light gray on the outside after a long exposure. This limestone cannot be polished.
Mineral inventory
The components in the Thüster limestone, which is now broken: 45 percent worm tube debris, 39 percent carbonate binding agent. The grain size 0.5 - 1 mm has a share of 9 percent. The proportion of the ooids is 8 percent, the quartz grains contained with a size 0.4-0.8 mm have a proportion of about 1 percent.
Quarries, uses and structures
Above the limestone banks there is overburden that is up to 4 meters high. The limestone deposit reaches a thickness of up to 11 meters and the rough blocks that are extracted are elongated due to the fissures in this deposit.
Of the originally numerous quarries, only two are being dismantled in 2008.
In the past, this limestone was burned to lime in small lime kilns. Nowadays it is used for building blocks and stone in solid construction, rarely for floor slabs, stairs, window sills and wall panels outside, and also for monuments. It is preferred by stone sculptors because of its easy workability . It was used, for example, in the construction of a church in Wallensen, a district of Salzhemmendorf , in the construction of the Volksbank in Münster , for the state parliament building in Kiel and for the bay window of the market office in Hanover in Leinstrasse. Numerous gravestones in the Engesohde city cemetery in Hanover show the sculptural possibilities that Thüster Kalkstein offers.
literature
- Jochen Lepper: natural stone. 3/98, p. 77ff.
- Otto Sickenberg: stones and earth. The deposits and their management. Geology and deposits of Lower Saxony. 5. Vol. Dorn-Verlag, Bremen-Horn 1951, p. 269ff.
Web links
Coordinates: 52 ° 0 ′ 31.6 " N , 9 ° 39 ′ 36.4" E