Geology of Germany

The geology of Germany is heavily influenced by several phases of orogeny in the Paleozoic and the Cenozoic, by sedimentation in shelf seas and epicontinental seas and on plains in the Permian and Mesozoic as well as by the Quaternary glaciations.

Regional geological setting

Germany is located between the geologically very old (Precambrian) East European Craton (Baltica) to the north and north-east (that further north is exposed as the Baltic Shield), and the geologically young (Cenozoic) Alpine-Carpathian Orogen to the south. The corresponding crustal provinces of Germany are thus geologically "middle-aged" and were accreted onto the East European Craton during the Paleozoic through plate tectonic processes. These areas form the geological basement of Germany. The basement is the oldest of the four geological crustal levels (''German: '') that overlap in Central Europe, north of the Alps. The levels mainly reflect the age relationships of rocks and the great tectonic trends that the Earth's crust was subjected to in the course of its geological history: crustal extension and widespread, mostly marine, sedimentation alternating with crustal compression/orogeny and extensive erosion. The surface geology of Germany has evolved to its current configuration due to regional differences in the action and appearance of external and internal forces during the last  20 million years. Germany can be divided into three physiographic regions: the Central European Depression, the Central European Blocks and the Alps.

Physiographic regions

Central European Depression

The northern third of Germany is part of the Central European Depression (''German: Mitteleuropäische Senke''), also known as the North German-Polish Basin, corresponding roughly to the North German Plain. The Central European Depression is a long-term subsiding area containing a sedimentary rock sequence, several thousand metres thick, of Late Palaeozoic to Cenozoic age and is characterised by a strong surficial glacial overprint as well as salt tectonics of Permian underground salt diapirs together with minor long-range effects of the Alpine Orogeny.

Central European Blocks

South of the Central European Depression is the Central European Blocks area (''German: Mitteleuropäisches Schollengebiet''), which geographically includes the Central Uplands, the South German Scarplands, the Upper Rhine Plain and foothills of the Alps. The long-range effects of the Alpine Orogeny were relatively strong in this area and the effects of the Pleistocene glaciations were small. The region is divided into several structurally uplifted blocks, where extensively folded Paleozoic basement outcrops, and some subsided/non-uplifted blocks capped almost exclusively by Mesozoic or Cenozoic rocks. The uplifted blocks are the Rhenish Massif (excluding the Ardennes), the Saxon and Thuringian blocks (not to be confused with the Saxothuringian Zone) including the Harz, the Thuringian Basin, the Thuringian Forest, the Thuringian-Franconian-Vogtland Slate Mountains and the Fichtel Mountains- Ore Mountains. The latter three geological units form the north-western edge of the Bohemian Massif, which is the largest contiguous outcrop of basement in Central Europe. The north-east edge of the Bohemian Massif is the Sudeten Block. The western edge of the central part of the Bohemian Massif, the Bohemian Block, extends into Germany with the mountain ranges of the Upper Palatinate Forest and the Bavarian Forest. The subsided/non-uplifted blocks are the Lower Rhine Graben (or "Ruhr Graben") with the Cologne Lowland, the Münsterland Cretaceous Basin (Westphalian Lowland), the Solling Block (Hessian Depression), the South German Block (the South German Scarplands together with the Odenwald, the Spessart, the Black Forest and the Molasse Basin) and the Upper Rhine Graben.

Alpine-Carpathian Arc

South of the South German Block and the Bohemian Massif is the Alpine-Carpathian Arc (''German: Alpen-Karpaten-Bogen''). Although its extent in Germany is limited to the extreme south of Bavaria, this narrow strip has relatively high geological diversity. In this region, three of the four major tectonic "domains" of the Alps are found: the Helvetic nappes, the Penninic nappes (as the Rhenodanubian Flysch Zone) and the Eastern Alps (as the Northern Limestone Alps).

Geological levels

North of the Alps, four crustal "levels" of surface and underground rocks in Germany are traditionally distinguished by age and structural characteristics (from deep to shallow): the basement, the transition level, the Mesozoic platform and the Cenozoic platform. The latter three are also summarised under the generic term "platform", in contrast to the basement.

Basement

The basement (''German: '') consists of folded rocks, some of which are metamorphic rocks, mostly of marine-sedimentary and submarine-volcanic origin, intruded by granitoid plutons. Most of these rocks are of late Carboniferous age or older. Folding and metamorphism of these sedimentary and volcanic rocks, and the emplacement of the granitoids, occurred mainly in two Paleozoic orogenies: the Caledonian Orogeny in the Late Ordovician and the Variscan Orogeny in the early Carboniferous. In the oldest folded Variscan rocks, evidence exists of an older orogeny, the Cadomian Orogeny, which occurred before the accretion of the crustal blocks of Proto-Europe (Baltica) (''German: ''). The folded basement rocks originated in the Proterozoic, but even older relics of continental crust are found in a paragneiss of the Bavarian Forest, the protolith of which was probably deposited subsequent to the Cadomian Orogeny. A sample of this paragneiss contains a detrital zircon grain, whose core crystallised from a magma during the Archean eon, before about 3.48 billion years ago.

Whereas the Caledonian folded basement lies a few thousand metres below the surface of the Central European Depression, the Variscan basement or Variscides (''German: '') outcrops in the Central European Blocks area, occurring extensively in several large highland areas and also sparsely in some lowland areas in the form of basement uplifts. A distinction is made here between rock complexes, commonly referred to as "slate belts" (''German: '') made of unmetamorphosed or weakly metamorphosed rocks (slate, chert, sandstone, limestone, altered basalt, phyllite and quartzite) which are intruded only to a small extent by granitoids, and rock complexes commonly referred to as crystalline, comprising weakly to highly metamorphosed rocks (phyllite, quartzite, marble, amphibolite, serpentinite, schist, gneiss, granulite and eclogite) which are extensively intruded by granitoids. The slate belt rock units were folded at a shallow depth at relatively low temperatures, whereas the metamorphic crystalline areas sank much deeper during the Variscan Orogeny, and were subjected to high pressures and, in some places, very high temperatures which caused partial melting of the rocks. The geochemical signature of the Variscan granitoids suggests that their magma was produced by the partial melting of deeply-buried sedimentary rocks. Outcropping slate belts are found mainly in the Rhenish Massif, the Harz and the Thuringian-Franconian-Vogtland Slate Mountains. Outcropping crystalline areas are found mainly in the Black Forest, the western Odenwald, Vorspessart, as well as the German periphery of the Bohemian Massif (Upper Lusatia, the Ore Mountains, the Fichtel Mountains, the Palatinate Forest and the Bavarian Forest).

Transition

The transition level (''German: '') includes all unfolded sedimentary and volcanic rocks of late Carboniferous (Stephanian) to mid-Permian (Guadalupian) age. "Transition level" refers, in part, to the stratigraphic position of these rocks: they are younger than the folded Variscides but older than the layers of the Mesozoic platform. In addition, they stem from a geological transition phase, which is characterised by the flattening of the Variscan mountains and by post-Variscan volcanism, which was accompanied by crustal extension in the Variscan Orogen. The rocks of the transition level differ from the younger platform sediments in that they are often relatively coarse-grained ( conglomeratic) Molasse sedimentary rocks and acidic to intermediate volcanic rocks (especially rhyolite), whereas the Mesozoic platform has few conglomerates and no volcanic rocks. The transition level is divided lithostratigraphically into Stephanian and Permian (Rotliegend) sequences. Rocks of the transition level are found today mainly in the Saar-Nahe Basin, the Halle-Leipzig area (e.g. Halle Porphyry Complex), the Ore Mountain Basin

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