Mägenwil Muschelkalk
Mägenwiler Muschelkalk is a limestone that is of architectural significance for the Swiss plateau and especially in the canton of Aargau . It is a limestone that was already used in Roman times and has been mined from the 11th century until today (2010). It is named after the town of Mägenwil . Emil Fischer AG Dottikon currently operates a larger quarry near Othmarsingen .
geology
This limestone is a result of the formation of the Alps in the Triassic , Jura and Cretaceous periods . The rock debris deposited over millions of years in the primeval sea of the Tethys is known as molasses . The Tethys was displaced north of the Alps by the rising mountains of the Alps. The newly deposited rock sunk the molasses that had already formed. The subsidence in the area of the Swiss Plateau created a sea again 21 million years ago. This sea was displaced again 17 million years ago, and in the process the rivers again carried rock rubble, boulders, sands and mud. The loose rock was compacted and consolidated again, sand became sandstone , mud, clay and lime became marl and gravel and rubble became a conglomerate rock , which is also called Nagelfluh . These rocks were created through diagenesis , a geological process of rock consolidation through pressure and cementation. The Mägenwil Muschelkalk originated in the Upper Sea Molasse 21 to 17 million years ago.
The molasses layers are divided into: lower sea molasses, lower fresh water molasses, upper sea molasses and upper fresh water molasses. Shell limestone is not present as a continuous layer in the Upper Marine Molasse , but in isolated occurrences. Mägenwiler Muschelkalk formed from lime shells and shell debris from mussels, snails and also occasional shark teeth, which are characteristic of sea molasses. The shells were mostly smashed, because when the marine animals died, the shells were deposited on the ocean floor and were transported through rivers, where they were shattered.
Rock description and mineral inventory
The Mägenwiler Muschelkalk comes in two colors, yellowish and blue-gray. When the mineral glauconite appears, it gives the rock a greenish color. Partly pyrite is embedded . The porosity of the yellow rock is considerably higher than that of the blue-gray. In addition to lime, other components were stored in this rock, for example quartz grains , feldspar , mica , chlorite and coal. The lime content is different and fluctuates between 55 and 90%, the sand content reaches between 10 and 45% and the porosity varies from 4 to 22%. The weight of the rock varies considerably depending on the porosity and is between 2.1 and 2.5 tons per m³. If quartz grains are frequently stored, it is referred to as shell sandstone.
Occurrence and mining
The occurrences of Mägenwil shell limestone range in the Swiss Plateau on the one hand from Würenlos to Neuenhof in the Limmattal , on the other hand on the southern edge of the Birrfeld from Wohlenschwil via Mägenwil and Othmarsingen to Lenzburg . The rock banks vary in thickness and vary between 10 and 20 meters. Mägenwil Muschelkalk is embedded between sandstone and marl layers. The Mägenwil Muschelkalk is mined today (2010) in the Steinhof quarry in Othmarsingen by Emil Fischer AG Dottikon and also at Estavayer on Lake Neuchâtel in another quarry. At times this shell limestone was mined underground. Over this layer of ashlar is a bank of soft, marly sandstones that are thinly layered. Above it is a several meters thick bank made of solid sandstone and on this sandstone layer there are partly moraines . This is also the case at the Steinhof quarry. The marly sandstone layer had to be removed down to the hard sandstone above. In this process, large caverns were created that had to be supported by stone pillars.
Muschelkalk has not been mined underground in the Steinhof quarry since 1996. Mägenwil Muschelkalk is mined with wire saws in mining fields laid out in steps. The mining of this natural stone with an annual volume of 200 m³ is relatively low.
If the weather is good, you can take a tourist train to the quarry at Eckwil near Mägenwil. The quarry is kept in its historical form by the association "Steinbruch Mägenwil".
use
In Roman times, Mägenwiler Muschelkalk was probably mined and used near Würenlos, as in Vindonissa , a Roman military camp near Brugg . It has been used in numerous buildings since the 11th century. Today it is used as facade cladding, brick, building block and floor covering or for house plinths, fountains and sculptures. In Aarau, numerous works from the Mägenwiler Muschelkalk can be seen in public spaces, such as historical portals and fountains, but also pedestals under bronze sculptures. It is also used for stone restoration work for tracery , cornices , gable tops and coats of arms.
The most famous building made of Mägenwil Muschelkalk in Switzerland is the Zurich building of the Swiss National Bank from 1922. Wall sections of the baroque Kasteln Castle near Oberflachs in the Swiss canton of Aargau , almost all buildings in the smaller old town of Brugg north of the Aare at the foot of the Bruggerberg and components of the bridge west of Brugg consist of Mägenwil shell limestone.
Web links
- Surface of Mägenwil Muschelkalk on pronaturstein.ch
- Images of samples from the Mägenwil Muschelkalk and quarry operations
- Sculptures made from Mägenwil shell limestone on alexschaufelbuehl.ch (PDF; 517 kB)
- Restoration of a sculpture «Seated Woman» on the website of bildhauerei-rickenbacher.ch
Individual evidence
- ↑ U. Aeberli: Origin of the Mägenwil Muschelkalk. ( Memento of the original from August 15, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. At fischer-natursteine.ch.
- ↑ a b c U. Aeberli: Use of the Mägenwil Muschelkalk. ( Memento of the original from August 15, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. At fischer-natursteine.ch.
- ↑ Municipality of Othmarsingen: Partial change to the cultural land plan "Material mining zone Steinbruch Steinhof" available online ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. .
- ↑ Ecological uniqueness. At limmattalregiomagzin.ch , accessed on May 26, 2010.
- ^ Art in the public space of the city of Aarau with examples of the use of Mägenwiler Muschelkalk. Available online ( memento of the original from March 9, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 3.2 MB).
Coordinates: 47 ° 23 '28.5 " N , 8 ° 13' 48.9" E ; CH1903: 659,767 / 249238