Vorerzgebirgs Valley
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| Geological map of Germany with identification of the location of the Vorerzgebirgs-Senke (red circle). |
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The Vorerzgebirgs-Basin (also called Vorerzgebirgs-Becken , Erzgebirgisches Becken , Erzgebirge-Basin , Werdau-Hainicher Trough or also Chemnitz-Basin ) is an intramontane, fossil sedimentary basin in Saxony and Thuringia, which is consolidated in the Carboniferous and Permian north of the Variscan " Ur -Erzgebirge ”. It contains discontinuous deposits of the highest lower carbon dioxide up to Oberrotliegend II .
location
The Vorerzgebirgs-Senke is a south-west-north-east trending , approx. 70 × 30 km large fossil deposit basin , which is roughly limited by the places Hainichen in the east, Oelsnitz and Zwickau in the south, Werdau and Crimmitschau in the west and Hohenstein-Ernstthal , Glauchau and Altenburg in the north. It is therefore largely in the Free State of Saxony and in the west extends in small parts to Thuringia .
geology
The Vorerzgebirgs-Senke in its entirety is an intramontane deposit basin created in the Unterperm, which contains the erosion relics of four older, lower to upper Carboniferous, smaller sinks (Hainichen, Flöha, Zwickau and Oelsnitz partial basins), with the sub-Carboniferous Hainichen - Partial sink occupies a special position. The Upper Carboniferous sinks within the Vorerzgebirgs sink tieften postorogen located in the hercynian ceiling a, were Westfalium filled and then in Stephanian z. Some of it was removed again before the actual, larger Vorerzgebirgs depression deepened in the Unterperm. The Rotliegend sediments therefore not only lie on these older Lower and Upper Carboniferous erosion relics, but also encroach on the older layers of the Variscan consolidated subsoil . The sedimentation ends with marine and non-marine Zechstein, depending on the position within the basin. From a tectonic point of view, it is an asymmetrical basin, which, along a fault on the northern edge, has its greatest thickness in the northern part. Today the basin forms a very flat hollow structure.
Hainichen partial depression
The Hainichen partial depression in the northeast of the Vorerzgebirgs depression contains "molassoides" Lower Carboniferous (Hainichen subgroup) with previously mined coal seams and sand and clay deposits (sand pits and brickworks). In the literature it is z. Partly also further subdivided into Borna-Ebersdorf and Berthelsdorf-Hainichen partial sinks. The basis of the Hainichen subgroup (Viseum) is, where it is exposed or drilled, in tectonic contact with the Variscan consolidated underground. The total thickness is not exactly known as the deepest borehole was completed in the lower Ortelsdorf Formation . However, it is over 1000 m. The upper end of the carbonic sediments is erosively cut off and overlaid by younger sediments from the Westphalian or Rotliegend. Lithostratigraphically , two formations are maintained within the Hainichen subgroup:
- Hainichen subgroup
Flöha partial sink
The Flöha partial sink is an approximately 11 × 3 km large, disturbance-limited basin that was created at the intersection of the NW- SE trending Flöha zone and the NE -SW detachment zone between the Ore Mountains and Granulite Mountains. In the northwest of the sub-basin, the basal Flöha formation lies at a discordant angle on deposits of the sub-carbonic Hainichen subgroup. The Flöha Formation is erosively capped, and above it are the deposits of the sub-Permian Härtensdorf Formation .
Zwickau partial sink
The sub-basins of Zwickau and Oelsnitz, which together cover a size of 6 × 30 km, arose in the Westfalium C / D at the intersection of larger fault zones, the NW-SE trending Gera-Jáchymov zone, the SW-NE trending detachment zone of the Erzgebirge and Granulite mountains and the north-south running Plauen-Leipzig-Dessau zone. In the Zwickau sub-basin, the Westfalium sediments lie discordantly on a variskishly consolidated basement. The carbonic sediments are in turn overlaid by sediments of the Unterrotliegend, erosion-discordant, in the absence of the entire Stefanium. Lithostratigraphically, a formation is distinguished with three subformations:
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Zwickau formation
- Oberhohndorf subformation
- Marienthal-Pöhlau subformation
- Schedewitz subformation
The carbonic layers of the Zwickau sub-basin are approx. 350 m thick and contain 20 coal seams.
Oelsnitz partial depression
The approx. 200 m thick sediment sequence in the Oelsnitz partial depression is formally structured lithostratigraphically in Berger et al. (2010) to form a formation with four sub-formations:
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Oelsnitz formation
- Neuflöz subformation
- Hope seam subformation
- Main seam subformation
- Lugau subformation
The Westfalium deposits in the Oelsnitz partial depression contain 13 coal seams.
Outline of the layers of the Rotliegend
The Rotliegend sequence is dominated by volcanic pyroclastic deposits and lavas as well. The interposed terrestrial sediments show the change from moist humid conditions in the Unterrotliegend to a dry, arid climate in the Oberrotliegend.
- Rotliegend (from bottom to top according to the stratigraphic position)
The Rotliegend sediments have an additive thickness of over 2000 m.
The Zeisigwald tuff ( Hilbersdorfer Porphyrtuff ) of the Leukersdorf formation of the Unterrotliegend, which goes back to a pyroclastic current , contains the famous " Petrified Forest " of Chemnitz with numerous silicified trunks of u. a. Tree ferns , giant horsetail , conifers and cordaites .
Economic importance and related research
The Vorerzgebirgssenke was of great economic importance mainly because of the hard coal seams contained in the Zwickau and Oelsnitzer partial sinks. Increased mining was carried out in the Zwickau sub-basin from 1830 (until 1978), in the Oelsnitz sub-basin from 1844 to 1971. A total of around 350 million tons of hard coal were extracted from the two sub-basins. Coal mining in the Zwickau partial depression has been documented since the 14th century.
The first systematic geological mapping of Saxony preceded industrial coal mining . In 1786 Abraham Gottlob Werner pointed out the advantages of nationwide prospecting for raw materials. In 1791, the Elector of Saxony commissioned Werner to carry out this recording work , as the Oberbergamt had already been asked to search for hard coal deposits in 1788. Werner expanded the research assignment for nationwide geological mapping in 107 sections, but was not able to complete it together with his students from the Bergakademie Freiberg until his death in 1817. This first modern geological survey of the land was dedicated to the coal deposits in a special way and had a decisive influence on the development of modern coal mining in the region of the Vorerzgebirge Basin. As part of the renewed geological mapping from 1835 by Bernhard Cotta and Carl Friedrich Naumann , the economically useful knowledge about the coal deposits deepened.
The tufa quarries of the Zeisigwald (mainly Leukersdorf Formation, Permian), which is largely located in the Chemnitz district of Hilbersdorf , and on the Gückelsberg (Flöha Formation, Upper Carboniferous) in Flöha , delivered large amounts of natural stone to the near and far region of Chemnitz over several centuries . The historical architecture and structural fabric of the city of Chemnitz have been shaped in a special way by this stone. However, the most famous object from the Hilbersdorfer Porphyrtuff (or Zeisigwald-Tuff ) of the Leukersdorf formation in terms of monument topography and artistically is the tulip pulpit in Freiberg Cathedral . The fossil plants and animal remains recovered from the Zeisigwald tuff and surrounding layers in Chemnitz are of high scientific value and, as exhibits, are also of high tourist value.
The sand and claystone deposits of the Berthelsdorf Formation (Lower Carboniferous) of the Hainichen partial depression, which were mined until the middle of the 20th century, were also of local interest.
swell
literature
- Werner Pälchen, Harald Walter (Ed.): Geology of Saxony I - Geological structure and history of development. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermüller), Stuttgart 2008, ISBN 978-3-510-65270-9 .
- Jörg W. Schneider, Ronny Rössler, Klaus Hoth, Peter Wolf, Matthias Lobin, Birgit G. Gaitzsch, Harald Walter, Erhard-A. Koch: Vorerzgebirgs-Senke and Erzgebirge. In: German Stratigraphic Commission (Hrsg.): Stratigraphie von Deutschland V - Das Oberkarbon (Pennsylvanium) in Germany. (= Courier Research Institute Senckenberg. Volume 254). E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermüller), Stuttgart / Frankfurt 2005, ISBN 3-510-61380-5 , pp. 369-394.
Individual evidence
- ↑ Ronny Rößler, Ludwig Luthardt, Jörg W. Schneider: The Petrified Forest Chemnitz - Snapshot of a volcanically preserved ecosystem from the Permian. In: Annual reports and communications from the Upper Rhine Geological Association. NF Volume 97, 2015, pp. 231-266 ( online ).
- ↑ Hans-Jürgen Berger, Henry Steinborn, Sascha Görne, Christine Junghans: Stratigraphy and tectonics in the hard coal district Lugau / Oelsnitz. In: Manfred Felix, Hans-Jürgen Berger (Red.): Geology and mining consequences in the hard coal district Lugau / Oelsnitz. (= Geoprofil. Volume 13). 2010, DNB 1006893628 , pp. 15–44 ( online , complete volume)
- ^ Otfried Wagenbreth : History of Geology in Germany. Enke, Stuttgart 1999, ISBN 3-13-118361-6 , p. 34.
- ^ Otfried Wagenbreth: The Saxon mineralogist and geologist Carl Friedrich Naumann (1797–1873). In: Treatises of the State Museum for Mineralogy and Geology in Dresden. Volume 29 ( Geologists of the Goethe era ), 1979, p. 358.
- ↑ Frank Löcse, Ulf Linnemann, Gitta Schneider, Volker Annacker, Thorid Zierold, Ronny Rößler: 200 years of Tubicaulis solenites (Sprengel) Cotta. Collection history, palaeobotany & geology of a unique Upper Carboniferous tree fern from the Schweddey ignimbrite from Gückelsberg near Flöha. Publications of the Museum für Naturkunde Chemnitz. Vol. 38, 2015, pp. 5-46 ( online ).
- ^ Frieder Jentsch: Saxon rocks in architecture . In: Publications Museum für Naturkunde Chemnitz. Vol. 28, 2005, pp. 5-20.
- ↑ Heiner Siedel: Materials of the pulpit and the foundation. In: Arndt Kiesewetter, Heiner Siedel, Michael Stuhr: The tulip pulpit in Freiberg Cathedral. (= Workbooks of the State Office for Monument Preservation Saxony. Volume 2). 1995, ISBN 3-87490-871-2 , pp. 68-74.
- ↑ A. Sauer, Th. Siegert, A. Rothpletz: Explanations of the special geological map of the Kingdom of Saxony. Sheet 97, Section Augustusbrg-Flöha. 2nd Edition. revised by C. Gäbert and Th. Siegert. W. Engelmann, Leipzig 1905, p. 93 f. ( online )