The Moldanubian Zone is in the regional

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

of Europe a

tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents ...

zone formed during the Variscan or Hercynian Orogeny (400 to 300 million years ago, during the Devonian and Carboniferous periods). The Moldanubian Zone crops out in the

Bohemian Massif The Bohemian Massif ( cs, Česká vysočina or ''Český masiv'', german: Böhmische Masse or ''Böhmisches Massiv'') is a geomorphological province in Central Europe. It is a large massif stretching over most of the Czech Republic, eastern Ger ...

and the southern part of the

Black Forest The Black Forest (german: Schwarzwald ) is a large forested mountain range in the 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 t ...

and

Vosges The Vosges ( , ; german: Vogesen ; Franconian and gsw, Vogese) are a range of low mountains in Eastern France, near its border with Germany. Together with the Palatine Forest to the north on the German side of the border, they form a single ...

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 Franz Kossmat ( 22 August 1871 in Vienna – 1 December 1938 in Leipzig) was an Austrian-German geologist, for twenty years the director of the Geological Survey of Saxony under both the kingdom and the subsequent German Republic. Kossmat wa ...

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 sys ...

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 A granitoid is a generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz- ...

plutons and

nappe In geology, a nappe or thrust sheet is a large sheetlike body of rock that has been moved more than or above a thrust fault from its original position. Nappes form in compressional tectonic settings like continental collision zones or on the o ...

Moldanubicum

The Moldanubicum or Moldanubian ''sensu stricto'' consists of high grade metamorphic rocks. The protoliths may have a Proterozoic age, but their origins or ages are mostly unknown.Franke (2000) The

tectonostratigraphy In geology, tectonostratigraphy is stratigraphy that refers either to rock sequences in which large-scale layering is caused by the stacking of thrust sheets, or nappes, in areas of thrust tectonics or to the effects of tectonics on lithostratigr ...

of the Moldanubian Zone sensu stricto is divided into three main units: *At the top the Gföhl unit, a stack 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, macros ...

s. It consists mostly of rocks of high metamorphic grade (up to amphibolite or

granulite facies Granulites are a class of high-grade metamorphic rocks of the granulite facies that have experienced high-temperature and moderate-pressure metamorphism. They are medium to coarse–grained and mainly composed of feldspars sometimes associated ...

). These can be metamorphic

sediments Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity In physics, gravity () is a fundame ...

but also

orthogneiss Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures an ...

es. In the lower part of the Gföhl unit contains amphibolites with early Paleozoic magmatic crystallisation ages occur. The Gföhl Gneis is an orthogneiss with an Ordovician

protolith. These meta-intrusive rocks are intercalated with

marble Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Marble is typically not foliated (layered), although there are exceptions. In geology, the term ''marble'' refers to metamorphose ...

s (meta-sediment). Some peridotite 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 Proterozoic basement with an early

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

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 (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or ...

(orthogneiss and amphibolite) and sedimentary (

paragneiss Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures an ...

) protoliths. Lenses of

eclogite Eclogite () is a metamorphic rock containing garnet (almandine- pyrope) hosted in a matrix of sodium-rich pyroxene (omphacite). Accessory minerals include kyanite, rutile, quartz, lawsonite, coesite, amphibole, phengite, paragonite, ...

occur, which were overprinted by granulite facies metamorphism.

Intrusions

These three tectonic units and their contacts are cut off by large batholith 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 Continental crustal fragments, partly synonymous with microcontinents, are pieces of continents that have broken off from main continental masses to form distinct islands that are often several hundred kilometers from their place of origin. Caus ...

called Cadomia or Armorica. This small piece of

continental crust Continental crust is the layer of igneous, sedimentary, and metamorphic 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 '' sial'' be ...

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 ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pan ...

(to the north) and Gondwana (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 (french: Massif armoricain, ) 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 Dov ...

, 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