Saar-Nahe basin
In terms of geology, the Saar-Nahe Basin is an intramontane molasse basin (or inner molasse ), which was created at the end of the Variski mountain formation in Central Europe . It contains deposits from the Upper Carboniferous and Permian , which have a maximum thickness of up to 8000 m. The basin has or had economic importance initially due to sidereal iron ores and later mainly due to the stored coal seams .
Extension and location
The Saar-Nahe basin in the geological sense has a size of about 300 × 100 km, of which only about a third is exposed , i.e. H. comes to light; the remainder is covered by recent deposits and only proven by drilling. It extends from the Rhine in the east to the Champagne-Ardenne region (France) in the west. As early as the German-French border, the deposits of the Saar-Nahe basin are covered by younger deposits to the west. The entire basin is therefore also referred to in the literature as the Lorraine-Saar-Nahe basin. In the north it is relatively sharply delimited by the Hunsrück-Südrand Fault ; the thickness is reduced north of the fault over a short or very short distance to 0 m. To the south it extends far below the younger cover to about the northern edge of the Vosges in the west and the northern Black Forest in the east. From a tectonic point of view, the basin forms a saddle structure that is now slightly south-vergent. Within the Saar-Nahe basin, several sub-basins (e.g. Saar sub-basin, Nahe sub-basin) and nest structures (Sprendlinger nest) can be identified that are perpendicular to the Hunsrück-Südrand fault from faults and those during the formation of the entire basin were active. The larger disturbances were: Trombach disturbance, Potzberg disturbance, Lorraine disturbance and the like. a. They were active at different times and were responsible for the vastly different thicknesses of the formations, differences in facies and the shifting of the deposition centers during the sedimentation of the Rotliegend in the Saar-Nahe basin.
Emergence
The structure of the Saar-Nahe basin is known relatively well through seismic investigations. It is a strongly asymmetrical basin , the greatest depression and greatest thicknesses of which are on its north side immediately south of the Hunsrück-Südrand fault. It was created by a right-handed, transtensive movement along the Hunsrück-Südrand Fault, which was later also further impressed as a right-handed shear surface. It is therefore a right-handed blade displacement basin ( Strike-slip fault to interpret basin).
Deposits, delivery areas and ages
During the subsidence of the Saar-Nahe basin, there was a marked change in climatic conditions from tropical to arid . Correspondingly, the deposit conditions changed from limnic-fluvial , limnic-lacustrine to terrestrial- arid. The living world was also exposed to major changes.
With coarse conglomerates at the base and pelites at the upper limit (top), the Spiesen formation, known only from boreholes, initiates the fluvial sedimentation of the Saar-Nahe basin. It lies discordantly on the marine viséum and is dated to the Namurium . This is followed by the productive Upper Carboniferous (productive due to the minable coal seams) with the Saarbrücken and Ottweiler groups. During the Westphalian period , the center of the deposit was south of the strata of the Saar-Nahe basin that are now exposed. The ablation area was north in the Rhenish Slate Mountains , it provided silizi clastic sediments. During the Stefanium , the delivery area and the composition of the rubble changed. From the Black Forest , the Vosges and the French Massif Central , i.e. from areas south of the basin, sediments with granitic- clastic components were delivered. The center of the deposit shifted closer to the Hunsrück southern rim fault and along it from southwest to northeast. Layer gaps are probably present within Westfalium A and B, the Namurium is not complete due to its small thickness. The Westfalium D is superimposed discordantly by the Stefanium. There are no discernible discordances within the Stefanium; the Rotliegend is also concordant on top of the Stefanium. According to Boy & Schindler (2000), the chronostratigraphic boundary Carbon / Perm is probably in the Wahnwege formation.
The lower part of the Rotliegend still has mostly gray-green colored sedimentary rocks with a small proportion of volcanic ash tuffs that come from outside the basin. In the higher part of the Rotliegend the deposits are predominantly red in color and contain a high proportion of latitic - andesitic and rhyolite lavas and ash tuffs that were extracted within the basin. The sediments were deposited in vast lakes, deltas, river systems and alluvial fans.
Lithostratigraphic structure of the deposits
The deposits of the Saar-Nahe basin can be understood as a supergroup in the sense of lithostratigraphy . They are divided into three lithostratigraphic groups , Saarbrücken group, Ottweiler group and Glan group. The following further subdivision of these groups is based on Schäfer (2005) and Boy in Mennig et al. (2005). Saarbrücken Group and Ottweiler Group were deposited in the Upper Carboniferous, the Glan Group in Permian. The two subdivisions differ in the Permian part, which is why they are placed side by side here. The 151 coal seams drilled in the Saar 1 well play a very important role in the subdivision of the carbonic strata. In Rotliegend, on the other hand, there are rather striking changes in the rock composition that make a subdivision possible. They enable the formations to be divided into sub-formations.
Structure according to Boy (2005)
the carbon is not dealt with in this work |
Structure according to Schäfer (2005)
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Economical meaning
In the past, the Saar-Nahe basin was of great importance for the Saarland's heavy industry. In the early days of industrialization, it was initially sidereal iron ores from the Westphalian Empire that formed the basis of heavy industry. Later, the sidereal clay iron lumps of the Lebach eggs (upper part of the Odernberg formation ) were also smelted. They established the existence of the Dillinger Hütte . The Minette ores were not smelted until the 19th century .
The Saar area is mainly known for its coal mining. In the Saar 1 deep borehole, a total of 151 seams were intersected with a thickness of less than 0.30 to 2.20 m. Coal mining was already documented in the late Middle Ages. The planned dismantling of the coal seams took place later, however. However, the mining quantities were very small and the mining was close to the surface. The coal was consumed in the region. In 1750/51 Wilhelm Heinrich von Nassau-Saarbrücken nationalized all of the mines that existed at that time. In 1766 there were 12 coal mines in operation in the Saar area: Schwalbach, Stangenmühle, Klarenthal, Gersweiler, Rußhütte, Jägersfreude, Friedrichsthal (Saar), Schiffweiler, Wellesweiler, Dudweiler, Sulzbach and Burbach. The coal now became a commercial object and the mining quantities increased dramatically.
Fossil sites
The widespread lake deposits in the Lower Rotliegend of the Saar-Nahe basin are z. Partly known fossil deposits with fossils in very good condition.
literature
- Manfred Menning, Reinhard Benek, Jürgen Boy, Bodo-Carlo Ehling, Frank Fischer, Birgit Gaitzsch, Reinhard Gast, Gotthard Kowalczyk, Harald Lützner, Wolfgang Reichel, Jörg W. Schneider: Das Rotliegend in the Stratigraphic Table of Germany 2002 - "Paternoster- Stratigraphy ”on the retreat. Newsletters on Stratigraphy. Vol. 41, No. 1-3, 2005, pp. 91-122, doi : 10.1127 / 0078-0421 / 2005 / 0041-0091 .
- Andreas Schäfer: Sedimentologically-numerically based stratigraphic standard for the permo-carbon of the Saar-Nahe basin. In: German Stratigraphic Commission (Hrsg.): Stratigraphie von Deutschland V - Das Oberkarbon (Pennsylvanium) in Germany. Courier Research Institute Senckenberg. Vol. 254, 2005, pp. 369-394.
- State Office for Geology and Mining Rhineland-Palatinate (Hrsg.): Geology of Rhineland-Palatinate. E. Schweizerbart´sche Verlagbuchhandlung, Stuttgart 2005.
- Andreas Henk: The Saar-Nahe basin. The geosciences. Jhrg. 11, No. 8, pp. 268-273, doi : 10.2312 / geoswissenschaften.1993.11.268 .
Individual evidence
- ↑ Thomas Schindler, Ulrich HJ Heidtke (ed.): Coal swamps, lakes and semi-deserts. Pollichia special release. Vol. 10, 2007.
- ↑ Jürgen A. Boy, Thomas Schindler: Ökostratigraphische Bioevents in the border area Stefanium / Autunium (highest carbon) of the Saar-Nahe-Basin (SW-Germany) and neighboring areas. New Yearbook of Geology and Paleontology, Treatises. Vol. 216: 89-152, Stuttgart 2000.
- ↑ a b Lithostratigraphy of the Permocarbon of Rhineland-Palatinate. ( Memento of the original from June 17, 2012 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. Ad-hoc-AG Geology of the State Geological Services (SGD) and the BGR - Stratigraphic Tables of the Geological Services of the Federal Republic of Germany
- ↑ In the table of the State Office for Geology and Mining Rhineland-Palatinate, the Donnersberg formation is further subdivided into Schweisweiler, Schallodenbach, Wingertsweilerhof, Höringen and Jakobsweiler sub-formations
- ^ The dinosaurs from Odernheim am Glan. ( Memento of the original from December 7, 2009 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Article on fossilien-news from June 27, 2005
