Münchberger plateau
| Münchberger plateau | |
|---|---|
 The Münchberg plateau in northeast Bavaria, between the Franconian Forest in the northwest and the Fichtelgebirge in the southeast |
|
 View over flat, undulating terrain near Weißdorf, east of Münchberg, looking east. In the background the silhouette of the northwestern edge of the Fichtelgebirge. |
|
| Highest peak | Kriegswald ( 728 m above sea level ) |
| location | Bavaria |
| part of | Thuringian-Franconian low mountain range |
| Classification according to | Handbook of the natural spatial structure of Germany |
| Coordinates | 50 ° 13 ′ N , 11 ° 40 ′ E |
| rock | mainly gneiss |
The Münchberg plateau is a flat, undulating plateau in northeast Bavaria. Münchberg , the eponymous town, is centrally located on the plateau .
geography
General
The Münchberg plateau lies between the Franconian Forest in the north-west and the Fichtel Mountains in the south-east and the Vogtland in the north-east and the Upper Main Hills in the south-west. Its length (north-east-south-west) is about 35, its transverse extent (north-west-south-east) about 15 kilometers. The mean height is about 600 m above sea level. NN . In the natural division of Germany, the Münchberg plateau is listed as main unit 393 in main unit group 39 ( Thuringian-Franconian low mountain range ). Since September 2010 there has been a new design for the natural areas of northeast Bavaria.
The name "Münchberger Hochfläche" is not a traditional name and the north-western part of this landscape is commonly assigned to the Franconian Forest, its south-eastern part to the Fichtel Mountains (see also place names ).
relief
The landscape is characterized by low knolls with a height of 400 to 700 m above sea level. NN determined, between which wide and shallow hollows spread out. The difference in height between the crests and valleys is 70 to 130 meters.
mountains
Some of the highest points or most prominent elevations on the Münchberg plateau have the following names, sorted by height in meters (m) above sea level (NN):
| mountain | Height (m) | location |
|---|---|---|
| War forest | 728 | approx. 500 m southwest of Ort bei Helmbrechts ⊙ |
| Hohberg | 708 | On the ridge, approx. 1.5 km southwest of Wüstenselbitz ⊙ |
| Haidberg | 692 | approx. 1.0 km southwest of Zell ⊙ |
| Stadelberg | 688 | on the western edge of Helmbrechts ⊙ |
| Ahornberg | 672 | immediately west of the village of the same name ⊙ |
| Weissenstein | 668 | approx. 1.5 km south of Stammbach ⊙ |
| Karlberg | 664 | approx. 1.0 km northeast of Förstenreuth ⊙ |
| Kotterberg | 632 | approx. 1.0 km south of Schödlas ⊙ |
| Rauschenberg | 627 | approx. 1.0 km north of Güntersdorf bei Helmbrechts ⊙ |
| Hammerberg | 593 | approx. 500 m south of Markersreuth ⊙ |
climate
| Average annual temperature | +5 to +6 ° C |
| Growing season | <200 days |
| Average annual rainfall | 8 00-1000 mm |
Localities
vegetation
The Münchberg plateau is generally heavily influenced by human management, which mainly manifests itself in extensive deforestation . Only on the hilltops and ridges are there remains of forest dominated by monoculture spruce trees . Deciduous forest remnants are only found on steep slopes. Near-natural ravine , alluvial and swamp forests only take up a very small part of the area.
From a geobotanical point of view, particular mention should be made of the individual serpentinite occurrences with their special plant communities, which are characterized by numerous endemic species, among the very sporadic dry sites .
geology
General
The natural spatial unit of the Münchberg plateau corresponds to the regional geology of the Münchberg mass (also Münchberg gneiss mass or Münchberger gneiss slab ). The latter forms an occurrence of gneiss and other metamorphic rocks that is structurally clearly separated from the surrounding mountains . Depending on the origin model (allochthonous or parautochthonous, see below ) it is assigned either to the Saxothuringian zone or to the Bohemian of the Moldanubian zone of the Central European varisticum .
The Münchberger Masse is surrounded on almost all sides by the de facto unmetamorphic, but Variscan folded, Paleozoic , marine sediments and diabases of the Thuringian-Franconian-Vogtland slate mountains. Only in the southeast is it bordered by a narrow strip of phyllites , which belong to the fringe of the granites of the Fichtelgebirge that adjoin directly to the southeast . At their tip the Southwest Münchberger mass is about from northwest to southeast trending Frankish line with unfolded Triassic sedimentary rocks of Obermainischen fraction Scholl country in contact.
The longitudinal axis of the Münchberger Masse stretches from southwest to northeast and runs roughly parallel to the axes of the saddle and hollow structures of the neighboring slate mountains.
Tectonic structure
The Münchberger mass consists of four metamorphic units lying on top of each other, from the highest to the lowest as
- Hanging series,
- Lying series
- Randamphibolite series and
- Phyllite-Prasinit series
are designated. The tectonostratigraphically highest unit - the hanging series - is the unit with the highest grade metamorphic rocks and the tectonostratigraphically deepest unit - the phyllite-prasinite series - the unit with the lowest grade metamorphic rocks. One therefore also speaks of “inverse zoning”. The entire pile is in turn stored on the non- or weakly metamorphic units of the so-called “Bavarian facies” of the Thuringian-Franconian-Vogtland slate mountains.
The Hangend series shows very different types of lithologies: Hornblende band gneiss, amphibolite and paragneiss in which calcium silicate rocks and marbles are inserted. At its base, serpentinite , eclogite and eclogite amphibolite bodies occur, which vary in size between a few dozen meters and several kilometers in diameter. With the eclogites, the hanging series is the only tectonic unit of the Münchberg mass that has high-pressure metamorphic rock. The corresponding metamorphosis took place around 390 million years ago. The igneous protoliths of the eclogites probably originated in the late Cambrian or early Ordovician .
The reclining series is relatively monotonous. It consists of paragneiss in which lenses made of orthogneiss and meta gabbros are inserted. The intrusion of the protoliths of the orthogneiss and metagabbros into the protoliths of the paragneiss took place at the turn of the Cambrian-Ordovician. The metamorphosis was predominantly amphibolite facial and took place around 380 million years ago.
The Randamphibolite series owes its name to the fact that it is composed almost exclusively of amphibolites and only bites off the edges of the Münchberg mass . The amphibolites are massive as well as banded or slate- shaped , partly also retrograde green slate facies . The strong mylonitization of the rock at the tectonic contacts to the overlying or underlying unit is particularly characteristic . The age of metamorphosis is between 400 and 380 million years.
The Phyllit - Prasinit series is an alternating layer of basic to intermediate lavas and pyroclastics with silty clay stones, metamorphosed under green slate facial conditions. The phyllites are dated to the late Proterozoic (lower Vendian ) by means of microfossils, in this case acritars . The Phyllite metamorphic age is at least 370 million years. At the transition to the Randamphibolite series, there are numerous serpentinite bodies , some of which are talked .
Emergence
There are essentially two hypotheses about the origin of the Münchberger Mass. One says that, to put it simply, it is a more or less directly squeezed out clod of soil . The other and now generally accepted hypothesis interprets the Münchberg mass as an erosion residue ( tectonic cliff ) of a ceiling thrust , the individual units of which only came into contact with each other in the course of the higher Paleozoic Era (probably in the middle or upper Devonian, corresponding to the age of metamorphosis) and finally all came into contact with one another were transported to their current position at a greater distance. The reclining and hanging series only came into contact with each other from around 385 million years ago and cooled down together from around 380 million years ago. The rocks of the "Bavarian Facies" that erupt in the immediate vicinity of the Münchberger Mass and underlying the metamorphic units are interpreted as a blanket. Both together are therefore also referred to as the "Münchberger ceiling stack". In the last phase of the thrust tectonics in the early Lower Carboniferous, when the Münchberg mass and the “Bavarian facies” were already in contact, a north-westerly transport took place at a very shallow depth with brittle deformation along the thrust orbits.
In the course of the tertiary tectonics as a result of the long-range effects of the formation of the Alps, the Thuringian-Franconian-Vogtland slate mountains and with it the Münchberg ceiling stack on the Franconian line were lifted out and the current state developed through erosion .
Magnetic anomalies
The serpentinites of the prasinite-phyllite zone on the south-eastern edge of the Münchberg mass cause a clearly measurable positive magnetic anomaly due to their relatively high content of ferrimagnetic minerals (especially magnetite ) . The magnetization that can be measured today either took place during the metamorphosis with the formation of magnetite (so-called chemical remanence ) or later as a result of granite intrusions below the serpentinites (thermal remanence). A particularly high degree of magnetization of the serpentinites occurs in natural outcrops on knolls or on free-standing rocks. This magnetization is geologically very young, is constantly being renewed and is caused by lightning strikes. However, it only extends a maximum of five meters into the rock.
The famous natural scientist Alexander von Humboldt already reported on the magnetism of the serpentinite rocks on the southeastern edge of the Münchberg mass.
Gravity anomaly
In the area of the Münchberg gneiss mass and in the adjacent part of the Franconian Forest there is a relatively weak, positive gravity anomaly (approx. −10 to +10 mGal ), which was first detected in the course of measurements by the Lower Saxony State Office for Soil Research in the early 1980s. Since the densest rocks in the region (including the highly metamorphic rocks of the hillside series of the Münchberg masses; see above ) are too small to be able to generate this anomaly, a large rock body of increased density (2.85 g / cm³) started in the deeper subsurface (approx. 2500 to 7000 m), which at that time (1982) was interpreted as Cadomian basement ("scaled Assyntikum").
natural reserve
In the northern half of the landscape, individual smaller areas are designated as areas for meadow breeders. The dry sites on serpentinite are also relevant to nature conservation.
economy
In the northern part of the landscape, grain and maize are grown on intensively used arable land . Grassland and livestock farming are the main agricultural uses in the Münchberg area. There are also individual quarries . The spruce monocultures mentioned above are mainly used for forestry purposes.
Hydrography
In the hollow layers , moorlands , wetlands and ponds are strung together. The existing standing water is used intensively.
Future landscaping
A near-natural forest of beech , oak , pine and fir is to be brought into the spruce forests . The fish farming should extensified and receiving the meadow breeders areas and optimized. The dry sites on the serpentinite deposits are to be promoted and developed and the quarries to be secured as succession areas .
literature
- Johann Rohrmüller, Hubert Mielke, Dieter Gebauer: Rock sequence of the basement north of the Danube and in the molasse underground: Münchberger Masse. In: Walter Freudenberger and Klaus Schwerd (Red.): Explanations for the Geological Map of Bavaria 1: 500,000. Bavarian Geological State Office, Munich 1996, p. 34/35, order.bayern.de (PDF; 7 MB).
Web links
- Landscape profile of the Münchberg plateau at the Federal Agency for Nature Conservation
- Alfons Baier, Thomas Hochsieder: On the stratigraphy and tectonics of the SE edge of the Münchberger gneiss mass (Upper Franconia) . Website of the Friedrich-Alexander-Universität Erlangen-Nürnberg with a short version of the article of the same name in the Geological Papers for Northeast Bavaria , Vol. 39, No. 3/4, Erlangen 1989
References and comments
- ^ Emil Meynen and Josef Schmithüsen : Handbook of the natural spatial structure of Germany
- ↑ Map services of the Federal Agency for Nature Conservation ( information )
- ^ Karl Heinrich Vollrath: Viola in Northeast Bavaria (PDF, pp. 132-133).
- ↑ a b The village has the addition of "in the Fichtelgebirge" to its name, but lies within the natural boundaries of the Münchberg plateau, near the northwestern edge of the Fichtelgebirge
- ↑ Erhard Reitz, Rudolf Höll: Young Proterozoic Microfossils from the Habach formation in the middle Hohe Tauern and the north-eastern Bavarian basement. Yearbook of the Federal Geological Institute. 131, 1988, pp. 329-340, online
- ↑ Gustav Angenheister: The interpretation of the magnetic interference fields (anomalies) of several serpentinite bodies in five areas in the west of the Bohemian mass. Geologica Bavarica. Vol. 67, 1973, pp. 35–63, online (complete volume)
- ↑ cf. Peter Skiba, Gerald Gabriel: Severity map of the Federal Republic of Germany 1: 1,000,000. Leibniz Institute for Applied Geophysics (LIAG), Hannover 2010, PDF (6.2 MB)
- ^ Siegfried Plaumann: The gravity anomaly in the area of the Münchberger gneiss mass and its interpretation. Journal of the German Geological Society. Vol. 133, 1982, pp. 649-665, abstract