The Moldanubian Zone is in the regional

geology Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...

of Europe a

tectonic Tectonics ( via Latin ) are the processes that result in the structure and properties of the Earth's crust and its evolution through time. The field of ''planetary tectonics'' extends the concept to other planets and moons. These processes ...

zone formed during the Variscan or Hercynian Orogeny (400 to 300 million years ago, during the

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

and

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

periods). The Moldanubian Zone crops out in the

Bohemian Massif The Bohemian Massif ( or ''Český masiv'', or ''Böhmisches Massiv'') is a geomorphological province in Central Europe. It is a large massif stretching over most of the Czech Republic, eastern Germany, southern Poland and northern Austria. Th ...

and the southern part of the

Black Forest The Black Forest ( ) is a large forested mountain range in the States of Germany, state of Baden-Württemberg in southwest Germany, bounded by the Rhine Valley to the west and south and close to the borders with France and Switzerland. It is th ...

and Vosges and contains the highest grade

metamorphic rock Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, caus ...

s of Variscan age in Europe. The Moldanubian Zone was introduced by German geologist Franz Kossmat in 1927. It has a generally higher grade of metamorphism than the Saxothuringian Zone to the northwest. The contact between the two is a

thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that ...

over which the Moldanubian Zone moved over the Saxothuringian Zone during the Variscan Orogeny. In the east the Moldanubian Zone is thrust over the Moravo-Silesian Zone, which is also generally lower grade.

Geology

The Moldanubian Zone of the Bohemian Massif can be divided into two tectonic units: the Teplá-Barrandian Zone (or "Bohemicum") and the Moldanubian Zone sensu stricto ("Moldanubicum"). The last contains large granitoid plutons and nappes.

Moldanubicum

The Moldanubicum or Moldanubian ''sensu stricto'' consists of high grade metamorphic rocks. The protoliths may have a

Proterozoic The Proterozoic ( ) is the third of the four geologic eons of Earth's history, spanning the time interval from 2500 to 538.8 Mya, and is the longest eon of Earth's geologic time scale. It is preceded by the Archean and followed by the Phanerozo ...

age, but their origins or ages are mostly unknown.Franke (2000) The tectonostratigraphy of the Moldanubian Zone sensu stricto is divided into three main units: *At the top the Gföhl unit, a

stack Stack may refer to: Places * Stack Island, an island game reserve in Bass Strait, south-eastern Australia, in Tasmania’s Hunter Island Group * Blue Stack Mountains, in Co. Donegal, Ireland People * Stack (surname) (including a list of people ...

of south- vergent

crystalline A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosc ...

nappes. It consists mostly of rocks of high metamorphic grade (up to

amphibolite Amphibolite () is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase feldspar, but with little or no quartz. It is typically dark-colored and dense, with a weakly foliated or schistose ...

or granulite facies). These can be metamorphic

sediments Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

but also orthogneisses. In the lower part of the Gföhl unit contains

s with early Paleozoic magmatic crystallisation ages occur. The Gföhl Gneis is an orthogneiss with an Ordovician granitoid protolith. These meta-intrusive rocks are intercalated with

marble Marble is a metamorphic rock consisting of carbonate minerals (most commonly calcite (CaCO3) or Dolomite (mineral), dolomite (CaMg(CO3)2) that have recrystallized under the influence of heat and pressure. It has a crystalline texture, and is ty ...

s (meta-sediment). Some

peridotite Peridotite ( ) is a dense, coarse-grained igneous rock consisting mostly of the silicate minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium (Mg2+), reflecting the high pr ...

lenses occur too. All of these rocks have high metamorphic grades (granulite and eclogite facies). *The Gföhl unit was thrust over the Drosendorf unit, which consists of a

basement A basement is any Storey, floor of a building that is not above the grade plane. Especially in residential buildings, it often is used as a utility space for a building, where such items as the Furnace (house heating), furnace, water heating, ...

with an early

Paleozoic The Paleozoic ( , , ; or Palaeozoic) Era is the first of three Era (geology), geological eras of the Phanerozoic Eon. Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic (the last era of the Proterozoic Eon) and ends 251.9 Ma a ...

cover of metasediments. Internal thrusting in this unit is, like the Gföhl unit, dominantly south-vergent. The base of the Gföhl unit is formed by the "Variegated Series", an assemblage of different metamorphosed rock types. The Drosendorf unit also contains orthogneisses with Proterozoic magmatic crystallisation ages ( Svetlik and Dobra gneisses). *The Ostrong unit or "Monotonous Series" forms the lowest unit of the Moldanubian Zone. It consists of high grade metamorphic rocks with both

igneous Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

(orthogneiss and

) and sedimentary ( paragneiss) protoliths. Lenses of eclogite occur, which were overprinted by granulite facies metamorphism.

Intrusions

These three tectonic units and their contacts are cut off by large

batholith A batholith () is a large mass of intrusive rock, intrusive igneous rock (also called plutonic rock), larger than in area, that forms from cooled magma deep in the Earth's crust. Batholiths are almost always made mostly of felsic or intermediate ...

intrusions of late Variscan ages. The largest ones are the South Bohemian Batholith and the Central Bohemian Batholith. They consist of many different generations of intrusions often cutting through each other.

Tectonic history

The Moldanubian Zone is interpreted as the lower crust of a microcontinent called Cadomia or Armorica. This small piece of

continental crust Continental crust is the layer of igneous, metamorphic, and sedimentary rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as '' continental shelves''. This layer is sometimes called '' si ...

was sandwiched in between the larger continents of

Laurussia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around (Million years ago, Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during ...

(to the north) and

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

(to the south) during the Variscan Orogeny. Some authors think the microcontinent stretched far enough to also encompass the pre-Variscan basement of the

Armorican Massif The Armorican Massif (, ) is a geologic massif that covers a large area in the northwest of France, including Brittany, the western part of Normandy and the Pays de la Loire. It is important because it is connected to Dover on the British side o ...

, others think a string of small microcontinents more reasonable.See Von Raumer ''et al.'' (2003) for one reconstruction of this string of microcontinents

Notes

Literature

*; 1992: ''Phanerozoic structures and events in central Europe'', in: (''eds.''): ''A Continent Revealed - The European Geotraverse'', 297 pp., Cambridge University Press, , pp. 164–179. *; 2000: ''The mid-European segment of the Variscides: tectonostratigraphic units, terrane boundaries and plate tectonic evolution'', in: (''eds.''); ''Orogenic Processes, Quantification and Modelling in the Variscan Belt'', Geological Society of London, Special Publications 179, pp. 35–61. *; 1927: ''Gliederung des varistischen Gebirgsbaues'', Abhandlungen des Sächsischen Geologischen Landesamtes 1, pp. 1–39. *; 2001: ''The Variscan collage and orogeny (480±290 Ma) and the tectonic definition of the Armorica microplate: a review'', Terra Nova 13, 122-128. *; 2003: ''Gondwana-derived microcontinents – the constituents of the Variscan and Alpine collisional orogens'', Tectonophysics 365, pp. 7–22. *; 2003: ''Erdgeschichte – Die Entstehung der Kontinente und Ozeane'', 325 pp., Walter de Gruyter, Berlin (5th ed.), . *; 1990: ''Geological Atlas of Western and Central Europe'', Shell Internationale Petroleum Maatschappij BV (2nd ed.), . {{Authority control Geology of Europe Geology of Germany Geology of Austria Geology of the Czech Republic de:Variszische Orogenese#Gliederung der Varisziden in Mitteleuropa