Moldanubian Zone
Encyclopedia
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
of Europe a tectonic
Tectonics
Tectonics is a field of study within geology concerned generally with the structures within the lithosphere of the Earth and particularly with the forces and movements that have operated in a region to create these structures.Tectonics is concerned with the orogenies and tectonic development of...
zone formed during the Variscan or Hercynian Orogeny
Variscan orogeny
The Variscan orogeny is a geologic mountain-building event caused by Late Paleozoic continental collision between Euramerica and Gondwana to form the supercontinent of Pangaea.-Naming:...
(400 to 300 million years ago, during the Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
and Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
periods). The Moldanubian Zone crops out
Outcrop
An outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. -Features:Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial deposits are covered by a mantle of soil and vegetation and cannot be...
in the Bohemian Massif
Bohemian Massif
The Bohemian Massif; or Český masiv; is in the geology of Central Europe a large massif stretching over central Czech republic, eastern Germany, southern Poland and northern Austria...
and the southern part of the Black Forest
Black Forest
The Black Forest is a wooded mountain range in Baden-Württemberg, southwestern Germany. It is bordered by the Rhine valley to the west and south. The highest peak is the Feldberg with an elevation of 1,493 metres ....
and Vosges
Vosges
Vosges is a French department, named after the local mountain range. It contains the hometown of Joan of Arc, Domrémy.-History:The Vosges department is one of the original 83 departments of France, created on February 9, 1790 during the French Revolution. It was made of territories that had been...
and contains the highest grade metamorphic rock
Metamorphic rock
Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...
s of Variscan age in Europe.
The Moldanubian Zone was introduced by German geologist Franz Kossmat
Franz Kossmat
Franz Kossmat 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....
in 1927. It has a generally higher grade of metamorphism than the Saxothuringian Zone
Saxothuringian Zone
The Saxothuringian Zone or Saxothuringicum is in geology a structural or tectonic zone in the Hercynian or Variscan orogen of central and western Europe. Because rocks of Hercynian age are in most places covered by younger strata, the zone is not everywhere visible at the surface...
to the northwest. The contact between the two is a thrust
Thrust fault
A thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lower stratigraphic position are pushed up and over higher strata. They are often recognized because they place older rocks above younger...
over which the Moldanubian Zone moved over the Saxothuringian Zone during the Variscan Orogeny. In the east the Moldanubian Zone is thrusted 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 granitoidGranitoid
A granitoid or granitic rock is a variety of coarse grained plutonic rock similar to granite which mineralogically are composed predominately of feldspar and quartz. Examples of granitoid rocks include granite, quartz monzonite, quartz diorite, syenite, granodiorite and trondhjemite. Many are...
pluton
Pluton
A pluton in geology is a body of intrusive igneous rock that crystallized from magma slowly cooling below the surface of the Earth. Plutons include batholiths, dikes, sills, laccoliths, lopoliths, and other igneous bodies...
s and nappe
Nappe
In geology, a nappe is a large sheetlike body of rock that has been moved more than or 5 km from its original position. Nappes form during continental plate collisions, when folds are sheared so much that they fold back over on themselves and break apart. The resulting structure is a...
s.
Moldanubicum
The Moldanibicum or Moldanubian sensu stricto consists of high grade metamorphic rocks. The protoliths may have a ProterozoicProterozoic
The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"...
age, but their origins or ages are mostly unknown.
The tectonostratigraphy
Tectonostratigraphy
In geology, tectonostratigraphy 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 the effects of tectonics on lithostratigraphy.-Tectonically formed stratigraphy:...
of the Moldanubian Zone sensu stricto is divided into three main units:
- At the top the Gföhl unit, a stack of south-vergentVergence (geology)In structural geology, the vergence of a fold is the direction in which an antiform is inclined or overturned. The term vergence comes from the German vergenz, which means "overturn"....
crystalline nappeNappeIn geology, a nappe is a large sheetlike body of rock that has been moved more than or 5 km from its original position. Nappes form during continental plate collisions, when folds are sheared so much that they fold back over on themselves and break apart. The resulting structure is a...
s. It consists mostly of rocks of high metamorphic grade (up to amphibolite or granulite facies). These can be metamorphic sedimentsSedimentary rockSedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
but also orthogneisses. In the lower part of the Gföhl unit contains amphiboliteAmphiboliteAmphibolite is the name given to a rock consisting mainly of hornblende amphibole, the use of the term being restricted, however, to metamorphic rocks. The modern terminology for a holocrystalline plutonic igneous rocks composed primarily of hornblende amphibole is a hornblendite, which are...
s with early Paleozoic magmatic crystallisation ages occur. The Gföhl Gneis is an orthogneiss with an Ordovician granitoidGranitoidA granitoid or granitic rock is a variety of coarse grained plutonic rock similar to granite which mineralogically are composed predominately of feldspar and quartz. Examples of granitoid rocks include granite, quartz monzonite, quartz diorite, syenite, granodiorite and trondhjemite. Many are...
protolith. These meta-intrusive rocks are intercalated with marbleMarbleMarble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite.Geologists use the term "marble" to refer to metamorphosed limestone; however stonemasons use the term more broadly to encompass unmetamorphosed limestone.Marble is commonly used for...
s (meta-sediment). Some peridotitePeridotiteA peridotite is a dense, coarse-grained igneous rock, consisting mostly of the minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium, reflecting the high proportions of magnesium-rich olivine, with appreciable iron...
lenses occur too. All of these rocks have high metamorphic grades (granulite and eclogite facies). - The Gföhl unit was thrusted over the Drosendorf unit, which consists of a ProterozoicProterozoicThe Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"...
basementBasement__FORCETOC__A basement is one or more floors of a building that are either completely or partially below the ground floor. Basements are typically used as a utility space for a building where such items as the furnace, water heater, breaker panel or fuse box, car park, and air-conditioning system...
with an early PaleozoicPaleozoicThe Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
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 igneousIgneous rockIgneous rock is one of the three main rock types, the others being sedimentary and metamorphic rock. Igneous rock is formed through the cooling and solidification of magma or lava...
(orthogneiss and amphiboliteAmphiboliteAmphibolite is the name given to a rock consisting mainly of hornblende amphibole, the use of the term being restricted, however, to metamorphic rocks. The modern terminology for a holocrystalline plutonic igneous rocks composed primarily of hornblende amphibole is a hornblendite, which are...
) and sedimentary (paragneiss) protoliths. Lenses of eclogiteEclogiteEclogite is a mafic metamorphic rock. Eclogite is of special interest for at least two reasons. First, it forms at pressures greater than those typical of the crust of the Earth...
occur, which were overprinted by granulite facies metamorphism.
Intrusions
These three tectonic units and their contacts are cut off by large batholithBatholith
A batholith is a large emplacement of igneous intrusive rock that forms from cooled magma deep in the Earth's crust...
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 ArmoricaArmorican terrane
The Armorican terrane, Armorican terrane assemblage, or simply Armorica, refers to a microcontinent or group of continental fragments that rifted away from Gondwana towards the end of the Silurian and collided with Laurussia towards the end of the Carboniferous during the Variscan orogeny...
. This small piece of continental crust
Continental crust
The continental crust is the layer of igneous, sedimentary, and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial due to more felsic, or granitic, bulk composition, which lies in...
was sandwiched in between the larger continents of Laurussia (to the north) and Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
(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
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. Its name comes from the old Armorica, a Gaul area between the Loire and the Seine rivers...
, others think a string of small microcontinents more reasonable.
Literature
; 1992: Phanerozoic structures and events in central Europe, in: (eds.): A Continent Revealed - The European Geotraverse, 297 pp., Cambridge University Press, ISBN 052142948X, 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.), ISBN 3110176971.; 1990: Geological Atlas of Western and Central Europe, Shell Internationale Petroleum Maatschappij BVRoyal Dutch Shell
Royal Dutch Shell plc , commonly known as Shell, is a global oil and gas company headquartered in The Hague, Netherlands and with its registered office in London, United Kingdom. It is the fifth-largest company in the world according to a composite measure by Forbes magazine and one of the six...
(2nd ed.), ISBN 90-6644-125-9.