Wittlicher Valley

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Location of the Wittlich depression on the southern edge of the Eifel
Wittlicher Senke near Bekond

The Wittlicher Senke (also Wittlicher Rotliegend Senke ) is the continuation of the Trier Valley in a north-easterly direction. It is not only recognizable as an elongated depression in the landscape , but can also be described as a basin in terms of its geological structure . Naturally , the Wittlich Senke (252) occupies one of three main units of the main unit group Moselle Valley (25). The Wittlicher Senke cycle path leads through the area.

geography

The Wittlich depression runs for about 45 km from Schweich in the southwest to almost the Moselle northeast of Wittlich . The width reaches about 7 km. The mean height is about 180  m above sea level. NN , it reaches its lowest point at Wengerohr near Wittlich and on the Lieser , a tributary of the Moselle in Rhineland-Palatinate . The valley is bounded by the Meulenwald to the northwest , by the Moselle Mountains to the southeast and by the Kondelwald to the east .

The Wittlich valley is drained by the Lieser and its tributaries. The fissured rocks of the subsoil lead to larger groundwater resources compared to the surroundings of the depression. The climate is similar to the mild conditions of the Moselle valley . Due to the protected location, tobacco cultivation is possible in the Talung .

Natural structure

The Wittlicher Senke is structured as follows:

Geological overview

The depression, which appears both in its geological structure and in the current shape of the terrain, was created by subsidence of the area in the Permian more than 250 million years ago. It is to be addressed as a geological ditch , bounded in the northwest by the Wittlich main fault in the southeast by the southern edge fault. Due to paleogeomorhological, tectonic and sedimentological criteria, the trench can be described as a pull-apart basin , with a left-sided lateral displacement amount of several kilometers. The Wittlicher main fault is a removal with a vertical offset of up to 700-1000 meters. This is particularly the case in the south-western section of the depression, in the northeast section the filling of the depression lies flat trough-shaped on the subsoil in the north as well, the main fault here has dissolved into a bundle of individual faults.

The sink is in variskisch embossed Rhenish Slate Mountains collapsed. Their subsoil therefore consists of folded and tectonically stressed series of the Devonian and Carboniferous . This older subsoil can be seen in the southeast in the mighty and uniform Hunsrück schist and Taunus quartzite sequences of the Lower Devonian in the Hunsrück and in the northwest in the lower to possibly central Devonian layers of the Moselle and Olkenbacher Mulde , which already belong to the Eifel .

The rocks of the actual depression come from the Rotliegend and are in places covered by younger layers of the Middle and Upper Buntsandstein as well as by tertiary and quaternary sediments. As the storage conditions of the younger strata show, the subsidence was not only active in the Permian, but also in the subsequent periods up to the recent geological past. Even the tertiary and quaternary layers show faults of up to 20 m.

Geological evolution

Subsequent to the Variskan mountain formation , accompanied by volcanic events, isostatic compensatory movements became noticeable to the effect that (intramontane) depressions were formed in the mountains. Part of the debris from the rising mountains collected in these hollows.

Compared to other intramontaneous sinks in the Variscan Mountains, this development came about very late in the Wittlich Basin. Its filling is placed in the Oberrotliegend in analogy to the Saar-Nahe basin south of the Rhenish slate mountains . In contrast to this, neither older Permian nor Carboniferous deposits are known in the Wittlich Depression . The breakdown of these red beds must lack of fossils to lithofaziellen carried viewpoints, so rely on the formation of the rocks.

Remnants of erosion from Rotliegend sediments under red sandstone in the Eifel and Hunsrück regions show that the sedimentation has also spread beyond the actual basin area.

The Wittlich Main Ridge Fault, which forms the NW edge, appears to have been active throughout the entire Upper Rotlie region. This view is supported by conglomerate fillings in all strata, which interlock with simultaneous but finer-grained clastic deposits towards the center of the basin . With increasing jump height of the Wittlich Main Fault - the offset is between 800-900 m in the SW and 0 m in the NE - the axis of the depression shifts from the center to the NW, to finally coincide with the Main Fault. This results in a plate inclined to the NW, a strongly asymmetrical basin, especially in the SW section within the trench. At the SE edge, apart from the edge warping, the Rotliegend layers show flexure-like bending towards the interior of the depression, accompanied by elongation fractures at a low jump height.

Sequence of layers

The subsurface of the Rotliegend succession is formed by folded Lower Devonian to Middle Devonian layers. In the interior of the depression, under the trench filling, there is a displacement that pushes the Hunsrück slate onto the Middle Devonian Wissenbach slate .

The sediment filling of the Wittlich Depression was filled in the Permian with approx. 900–1000 m Rotliegend sediments. In its deeper parts, the filling consists of fanglomerates and breccias , which discordantly overlap the older subsoil. In a follow rhyolite - tuff ( ignimbrite ) of unknown origin. In the hanging wall of these pyroclastics , coarse clastic rocks, the upper conglomerates, have again been deposited. Increasingly finer clastic material intervenes in this layer segment towards the hanging wall and the pelvic center. According to the stratigraphic tables of the State Office for Geology and Mining Rhineland-Palatinate, the Rotliegend is subdivided into the following lithostratigraphic formations:

The layers of the Rotliegend are covered by the Middle Buntsandstein. In the south-west, the exposed rocks of the depression end at the closed red sandstone area of ​​the Trier Bay. The red sandstone deposits within the Wittlich depression are limited to relics such as Burgberg, Astberg and an occurrence below the village of Bergweiler. It is being discussed whether only Middle or Lower Buntsandstein was deposited.

Only very limited rock deposits are available from recent geological history. The basalt chimneys east of Wittlich, on Lüxeberg and on Neuerburger Kopf are of Middle Cretaceous age . River deposits of the Tertiary in the SW Eifel, which also encroach on the edge of the depression, could be assigned to the Upper Eocene to Oligocene Vallendar gravel.

In the Quaternary the Wittlich Depression was cleared, so that the younger cover layers and part of the Rotliegend layers were eroded away. Some of the Pleistocene deposits that have survived are assigned to a lower level of the main terrace and the upper middle terrace of the Moselle.

Individual evidence

  1. ↑ Interactive map service and descriptions of the Rhineland-Palatinate nature conservation administration
  2. ↑ a b Exact name of the natural area unknown!
  3. ↑ State Office for Geology and Mining Rhineland-Palatinate (2005: p. 120ff.)
  4. ↑ The Geological Mapping Instructions of the SGD - Stratigraphy mapping units / Stratigraphy-of-the-Federal Republic / Tables-of-the-federal states / Rhineland-Palatinate / Perm / Rotliegend. Retrieved August 15, 2020 .

literature

  • Wilhelm Meyer : Geology of the Eifel . Schweizerbart'sche Verlagsbuchhandlung, Stuttgart 1986, ISBN 3-510-65127-8 , pp. 534 ff .
  • Paul Dorn (founder), Roland Walter et al. (Editor): Geology of Central Europe . 5th, completely revised edition. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart 1992, ISBN 3-510-65149-9 , pp. 171, 181 .
  • State Office for Geology and Mining Rhineland-Palatinate (Hrsg.): Geology of Rhineland-Palatinate. E. Schweizerbart'sche Verlagbuchhandlung, Stuttgart 2005, ISBN 3-510-65215-0 .

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