Helsighausen mica sand pit
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Helsighausen mica sand pit
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 View of the mica sand pit in Helsighausen |
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| location | Helsighausen, Raperswilen (TG) | |
| Geographical location | 47 ° 39 ' N , 9 ° 4' E | |
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| Sea level | 610 m | |
The Helsighausen mica sand pit is located near Helsighausen in the municipality of Raperswilen , Canton Thurgau . The artificial geotope is given national importance as it provides information about the geological history of the region.
geography
The mica sand pit is located a little northwest of Helsighausen and extends over a few hectares . Since the sand and gravel deposits are usually formed by flowing water, the location of the mica sand pit on the Seerücken , around 200 meters above Lake Constance , is very unusual.
The dismantling walls are between six and ten meters high and relatively easily accessible.
geology
Formation of the mica sand pit
Sand and gravel layers such as the mica sand pit in Helsighausen usually come from a river . This can also be seen in the obliquely cut layers on the excavation walls of the sand pit. The structure of the sediments suggests a wide river plain with a meander . A broad stream came from northern Bavaria and the Hohe Tauern south of Salzburg , flowing along the Alpine foothills from east to west and flowing into the Mediterranean . This deposited the mica-containing sand on its bottom 16 to 12 million years ago. This ultimately resulted in the light, lime-rich Knauersandstein, which is also called mica sand and is one of the youngest molasse layers in eastern Switzerland.
The former river valley , which lies roughly on the axis of today's Constance , Frauenfeld , Winterthur and Zurich , left a mica sand channel. However, only a few of these mica sand deposits were developed and are visible today.
In the Molasse period, the Alpine foothills sank . Large amounts of stones and sand were deposited . These layers are altogether up to 4000 meters thick. Later the Alpine foothills were also covered by the Alpine elevation. This created new rivers, which cut valleys into the plain. The erosion was also supported by the glaciers from the ice ages . That is why the mica sand pit in Raperswilen is now above the valley level. The layers of fine sand, which are more at the top, were deposited in a low-energy environment. The lowest meters in particular have coarser sandstones that contain knuckle formations and sometimes also conglomerate layers .
Geological finds
By weathering numerous fossil structures in the sandstone were visible, including macro fossils and driftwood accumulations. Between the mica sand there are also accumulations of marl , some of which contain valuable small mammal fauna. At one point a layer of leaf remains was found in good condition. The sand pit is also one of the most important mammalian discovery sites in the Upper Freshwater Molasse (OSM) in eastern Switzerland.
use
The mica sand has been removed for roof tile production since 1986. The dismantling was divided into different stages so that areas that had been fallow for a long time can be recultivated and partially filled up. This created replacement biotopes and networking corridors. The only sporadic dismantling resulted in good exposure conditions with easily accessible dismantling walls over time.
The mica sand pit is an anthropogenic outcrop (created by humans) and is therefore one of the geotopes of the Canton of Thurgau. They are geoscientifically significant, mostly natural, mapped and pedagogically processed.
Individual evidence
- ↑ a b c d e f Glimmersandgrube Helsighausen. (No longer available online.) Office for Spatial Planning of the Canton of Thurgau, 2007, archived from the original on February 22, 2016 ; Retrieved April 17, 2017 . 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.
- ↑ a b c Geo-Radroute - On the trail of disappeared glaciers, rivers and lakes. Office for Spatial Development Thurgau, 2016, accessed on April 23, 2017 .
- ↑ a b fire ice and water. Retrieved April 17, 2017 .
- ↑ a b c Technical Report 99-08 - Geological Development in Northern Switzerland, Neotectonics and Long-Term Scenarios in the Zürcher Weinland. National Cooperative for the Disposal of Radioactive Waste, December 2002, accessed April 23, 2017 .
- ↑ Helsighausen mine. (No longer available online.) PLANium GmbH, formerly in the original ; Retrieved April 17, 2017 . ( 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.
- ^ Geotope inventory Thurgau. (No longer available online.) Office for Spatial Planning Thurgau, 2007, formerly in the original ; Retrieved April 17, 2017 . ( 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.
