The Zechstein (
German
German(s) may refer to:
* Germany (of or related to)
**Germania (historical use)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizens of Germany, see also German nationality law
**Ger ...
either from ''mine stone'' or ''tough stone'') is a unit of
sedimentary rock
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
layers of Middle to Late
Permian
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...
(
Guadalupian
The Guadalupian is the second and middle series/epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It is named after the Guadalupe Mountains of New Mexico and Texas, and dates between 272.95 ± 0. ...
to
Lopingian
The Lopingian is the uppermost series/last epoch of the Permian. It is the last epoch of the Paleozoic. The Lopingian was preceded by the Guadalupian and followed by the Early Triassic.
The Lopingian is often synonymous with the informal terms l ...
) age located in the
European Permian Basin which stretches from the east coast of England to northern Poland. The name Zechstein was formerly also used as a unit of time in the
geologic timescale
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronol ...
, but nowadays it is only used for the corresponding sedimentary deposits in Europe.
The Zechstein lies on top of the
Rotliegend
The Rotliegend, Rotliegend Group or Rotliegendes (german: the underlying red) is a lithostratigraphy, lithostratigraphic unit (a sequence of rock strata) of latest Carboniferous to Guadalupian (middle Permian) age that is found in the subsurface of ...
; on top of the Zechstein is the
Buntsandstein or Bunter.
Formation
The evaporite rocks of the Zechstein formation were laid down by the Zechstein Sea, an epicontinental or
epeiric sea
An inland sea (also known as an epeiric sea or an epicontinental sea) is a continental body of water which is very large and is either completely surrounded by dry land or connected to an ocean by a river, strait, or "arm of the sea". An inland se ...
that existed in the Guadalupian and Lopingian epochs of the Permian period. The Zechstein Sea occupied the region of what is now the
North Sea
The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...
, plus lowland areas of Britain and the north European plain through Germany and Poland. The Zechstein sea lay in the
rain shadow
A rain shadow is an area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds, known as its leeward side.
Evaporated moisture from water bodies (such as oceans and large lakes) is carrie ...
of the
Central Pangean Mountains
The Central Pangean Mountains were an extensive northeast–southwest trending mountain range in the central portion of the supercontinent Pangaea during the Carboniferous, Permian and Triassic periods. They were formed as a result of collision b ...
to the south.
At times the Zechstein Sea may have connected with the
Paleotethys Ocean through southeastern Poland; the point is disputed by researchers.
Though situated at the time near the equator (where high temperatures and arid conditions facilitated evaporation), the sea's inception likely stemmed from a
marine transgression
A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling ...
rooted in a phase of de-glaciation; the southern portion of
Pangaea
Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million y ...
, the former (and future)
Gondwanaland
Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...
, supported
ice sheet
In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at Las ...
s in the early Permian. The eventual disappearance of the Zechstein Sea was part of a general
marine regression
A marine regression is a geological process occurring when areas of submerged seafloor are exposed above the sea level. The opposite event, marine transgression, occurs when flooding from the sea covers previously-exposed land.
Evidence of marine ...
that preceded and accompanied the
Permian-Triassic extinction.
[Moores, Eldridge M., and Rhodes Whitmore Fairbridge, eds. ''Encyclopedia of European and Asian Regional Geology.'' London, Chapman & Hall, 1997; pp. 97, 263.]
Stratigraphy
The Zechstein is usually given the status of a lithostratigraphic
group
A group is a number of persons or things that are located, gathered, or classed together.
Groups of people
* Cultural group, a group whose members share the same cultural identity
* Ethnic group, a group whose members share the same ethnic ide ...
and as such encompasses a number of
geologic formation
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...
s. It consists of at least five
depositional cycle Cyclic sediments (also called rhythmic sediments) are sequences of sedimentary rocks that are characterised by repetitive patterns of different rock types ( strata) or facies within the sequence. Processes that generate sedimentary cyclicity can b ...
s of evaporite rocks, which are labelled Z1 to Z5, respectively. The
lithologies
The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lit ...
found are
halite
Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, p ...
("rock salt"),
anhydrite
Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the ...
,
dolomite Dolomite may refer to:
*Dolomite (mineral), a carbonate mineral
*Dolomite (rock), also known as dolostone, a sedimentary carbonate rock
*Dolomite, Alabama, United States, an unincorporated community
*Dolomite, California, United States, an unincor ...
, and
shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...
.
Economic importance
The Zechstein has significant economic importance in the
North Sea Oil
North Sea oil is a mixture of hydrocarbons, comprising liquid petroleum and natural gas, produced from petroleum reservoirs beneath the North Sea.
In the petroleum industry, the term "North Sea" often includes areas such as the Norwegian Sea and ...
province. In the southern gas basin, it forms the main cap rock to the gas fields with Rotliegend reservoirs. It also forms a reservoir in the
Auk oilfield
The Auk Oilfield is situated east, southeast of Aberdeen, Scotland, in block number 30/16.
Reservoir
It was discovered in October 1970 in a water depth of 182 metres. The oil reservoir is a Rotliegendes sandstone overlaid with Zechstein carbo ...
in the central part of the North Sea. Further north, the Zechstein salt becomes
diapiric, forming salt domes which form the structure for several oil fields, such as Machar. Zechstein dolomites crop out near the coast of
County Durham
County Durham ( ), officially simply Durham,UK General Acts 1997 c. 23Lieutenancies Act 1997 Schedule 1(3). From legislation.gov.uk, retrieved 6 April 2022. is a ceremonial county in North East England.North East Assembly â€About North East E ...
, England where they are known as the
Magnesian Limestone
The Magnesian Limestone is a suite of carbonate rocks in north-east England dating from the Permian period. The outcrop stretches from Nottingham northwards through Yorkshire and into County Durham where it is exposed along the coast between Ha ...
.
Just above the base of the Zechstein formation is a fairly thin layer of shale, or slate, where it has been metamorphized, known as the ''kupferschiefer'' for its high copper content. In its unmodified form, this layer is high in sulfur compounds that are typical of silt deposited in stagnant shallow marshland. Where faults have allowed mineral-rich groundwater to circulate through this layer, the sulfur has oxidized metal ions to metallic sulfide ores. From the Middle Ages into the modern era, this thin but widely dispersed constellation of ore bodies has been of immense importance as a source of copper across much of northern Europe.
The Zechstein salt layer is also used for underground gas storage in England, Germany and France.
See also
*
List of stratigraphic units in the Netherlands
*
Marl Slate Formation
The Marl Slate Formation is a geological formation in England. Despite its name, it is mostly dolomite rock. The Marl Slate Formation was formed about 273 to 259 million years ago, during the Guadalupian and Lopingian epochs of the late Permian ...
References
{{Authority control
Changhsingian
Lithostratigraphy of Germany
Wuchiapingian
Permian System of Europe
Sedimentology