Giessen nappe
The Giessen ceiling is a geological unit of the southeastern Rhenish Slate Mountains. It provides the basis of their rock sequence represents a foreign body among the surrounding geological units and has come during the Variscan orogeny by long-range thrust tectonic ceiling at its current position. Similar rock units are open including in Southern basement Forest and the Harz and the Czech Republic. These geological units are only rarely preserved in Central Europe remains the continent involved in the Hercynian collision in the upper Carboniferous micro-or continental plate and thus represent an important testimony of orogenic processes dar.
Location
The closed circulation area of Giessen ceiling is about 300 km2 and extends at the western foot of the Vogelsberg mountains about 40 miles from Braunfels about Wetzlar and Giessen almost to Marburg. Your northern part is accompanied in the east of the river Lahn, before she crosses the ceiling between Giessen Giessen and Wetzlar to zuzufließen the Rhine.
Rocks and layer sequence
The rock content of the Giessen ceiling is made up of low -mighty tone, gravel and Alaunschiefern of the Lower and Middle Devonian and greywacke of the Late Devonian and Lower Carboniferous. Especially the greywacke of the Late Devonian are in marked contrast to the clay and limestone that were deposited at the same time in the immediately below the Giessen ceiling geological units. They gave the first occasion to classify the unit of Giessen greywacke as non-local rock body. In some places, tectonic scales from basalts are preserved at the base of Giessen ceiling, which are regarded as MOR basalts because of their chemical composition.
Structure
The basic thrust of Blankets body is characterized by the presence of highly stressed cataclasites and under relatively low temperatures resulting mylonites. It is now nearly horizontal, but is locally deformed by late folding and thrusting processes. Due to the erosion at margins lying rock bodies were separated from the main mass of the ceiling and are now as cliffs in front of her, such as when Braunfels and stone village, a district of Wetzlar. The rocks in the ceiling are locally tightly folded and crossed by shear zones and faults.
History of exploration
Discussions about the nature of Giessen greywacke were after 1980 by various summary academic essays lively again after recent geological studies supported the theory of a non-local origin with new findings., Although many details remain unclear because of poor outcrops and the complicated geological conditions, has the view that unit is now established as a tectonic ceiling and shown in official maps.
Together with the Giessen ceiling a non-local origin is also discussed for other parts of the south-eastern Rhenish Massif and the associated with them in connection units of the southern basement Forest and the Harz Mountains.