Zechstein Sea

The Zechstein Sea was a flat Epikontinentalmeer that existed in the Late Permian ( Lopingium ) in front of about 258-250 million years ago in what is now Central Europe. It extended with an area of about one million square kilometers, more than twice the area of the Black Sea, from today's England to present-day Baltic and from what is now northern North Sea region to present-day southwest Germany. The sediment basin, which was covered to a large extent from the Zechstein Sea is called Zechsteinbecken. It represents the earliest phase in the history of the Germanic Basin.

• 3.1 Effect on topography and geology
• 3.2 raw Materials 3.2.1 Historical
• 3.2.2 Industrial Promotion

Emergence of the Zechstein Sea

After the Variscan orogeny in the Upper Carboniferous, the ablation of the Variscan Mountains began. The corresponding sediments ( molasse ), which were deposited between the Upper Carboniferous and Mittelperm in the northern foothills, and in small pools in the interior of the mountain, reddish sandstones and conglomerates are called Permian. In the Upper Permian then large areas of the massif lowered from and formed together with the former foreland a vast plain, the Germanic Basin. More or less simultaneously arose between Norway and Greenland, then immediately adjacent, because the North Atlantic should arise until more than 150 million years later, a grave breach. Due to this the sea from the north penetrated to Central Europe and flooded the plain, now the Zechsteinbecken. This marine intrusion is preserved in the rock strata of Central Europe as Zechstein transgression. The earliest deposits of the Zechstein Sea are both Rotliegend sediments to lie as well as directly on folded rocks of the Variscan vorpermischen Mountains. In the latter case one speaks of the Zechstein unconformity.

The name derives for sea and pool are left behind or contained deposits that are grouped together under the name lithostratigraphically Zechstein. They consist largely of gypsum and rock salt ( halite ), which belong to the class of sedimentary evaporites, and are now widespread in the subsurface of central Europe. The evaporitreichen deposits of the Zechstein are also called Zechstein salt deposit. Contrast, are clastic deposits of the coastal plain of the Zechstein Sea ( Marginal Facies ) that do not contain evaporites.

Zechstein transgression and Kupferschiefer

Traditionally, the so-called Zechstein conglomerate, a sedimentary, the (pre- oberpermischer ) rocks originated in the area of ​​advancing shoreline of the Zechstein Sea by the workup (erosion and redeposition ) of older, regarded as the first geological evidence of the Zechstein transgression. But since it is already in the period of deposition of the Permian were smaller marine burglaries in Central Europe and a Zechstein conglomerate where Rotliegend deposits pass into the Zechstein deposits, is difficult to distinguish from subjacent Permian conglomerates, formally the Kupferschiefer is now considered the oldest deposit of the Zechstein Sea. The Kupferschiefer, a Schwarztonstein, which is known mainly for its ore and fossil guide, represents a period of rapid sea level rise (English: maximum flooding ) with very low sedimentation rates (that is, it took a relatively long time until a was deposited relatively small amount of sediment). Only after the sea-level rise slowed and began the deposition of the Zechstein Salinars, the sedimentation rates increased dramatically in some cases.

Emergence of the Zechstein Salinars

The evaporite deposits could form because in the region of Zechsteinbeckens very dry and warm climate prevailed (→ arid climate ). Due to high evaporation rates and of the only narrow connection to the sea to the ocean to the north, gradually increased the concentration of dissolved salts in seawater. These salts were according to their solubility, first the sparingly soluble carbonates (limestone, probably diagenetic subsequently converted to dolomite) and gypsum ( diagenetic in anhydrite converted ), the quantitatively dominant sodium chloride (as halite ) and finally the potassium and magnesium chlorides and - sulfate ( commonly referred to as potassium salts or inert salts). Every now and then learned the sea water, for example, due to a temporary weakening of the drought a Aussüßung and the progressive precipitation ( precipitation of sparingly soluble to slightly soluble) was reversed ( recessive precipitation: from slightly soluble to slightly soluble ) or completely broke down, to deploy again after returning to the drought. The period between onset and interruption of precipitation and the corresponding rock sequence is called Eindampfungszyklus. Because of continuous, gradual reduction of the pelvic base ( subsidence ) and the conversion between drier and wetter periods as developed over millions of years, a locally more than 1500 m thick sequence in which multiple Eindampfungszyklen are documented. Since they have the most extreme conditions of formation, now called commodity especially coveted layers of potash ( potash seams ) are not more powerful than three to eight meters. The deposits of two Eindampfungszyklen separated ideally by clay sediments, which are attributed to each younger Eindampfungszyklus and were probably deposited in the Aussüßungsphasen.

Classically, four main Eindampfungszyklen, represented by four rock salt consequences distinguished:

• Werra Cycle ( Z1 ) and Werra Formation ( zW )
• Staßfurt cycle (z2 ) or Staßfurt Formation ( zS )
• Line cycle ( z3 ) and leash lineup ( zL )
• Aller- cycle ( z4 ) or all- formation ( zA )

Especially in the subsurface of northern Germany and the North Sea three more Salinar cycles can be detected: Ohre-Zyklus/-Formation ( z5/zO ) Friesland-Zyklus/-Formation ( z6/zFr ) and Fulda-Zyklus/-Formation ( z7 / ZfU ), but do not reach in thickness and Evaporitführung far to the four Haupt-Zyklen/-Formationen. The cycle z7 was formerly considered to be represented by the Mölln sequence. Meanwhile, the latter as Mölln- Subformation has been integrated into the upper part of Friesland formation and thus part of the 6th cycle ( the lower part of Friesland lineup is called Eider Subformation ). The seventh cycle is represented now by the Fulda Formation, which in turn is largely identical to the crumbling shale sequence of older literature.

As the degree of restriction of the consequences z5 - z7 points to northern Germany and the North Sea area, is not the same everywhere formed powerful or alike within Zechsteinbecken the Zechstein series. To further during the first Eindampfungszyklus the precious salt phase only in the Werra Basin is ( therefore also called Werra- formation or Werra cycle) in present-day Hesse and Thuringia, in the Lower Rhine Basin ( North Rhine -Westphalia) and Peribaltic in the so-called pool achieved in the Russian exclave of Kaliningrad. On the other hand are no longer deposited in the following cycles ( Staßfurt and leash ) potassium salts in these sub-basins, but in extensive areas of the central Zechsteinbeckens. This may be due could be that on the one hand, these three sub-basin were during the Werra cycle in each case by a relatively pronounced emerging from the rest of the Zechstein Sea, where the concentration of solutes was apparently less defined, and secondly, that during subsequent cycles subsidence in the three sub-basins was lower, so these were largely silted up before reaching the potash mineral phase. In early stages of Eindampfungszyklen to carbonates formed (partly with reefs ) mainly in the shallowest parts of the sea, near the pool edges and in emerging areas.

Life in the Zechstein Sea

Multicellular living things there were in the Zechstein Sea probably only during the phases in which the sea water was not extremely over salted. Fossils therefore occur only in the respectively lowest layers of the Eindampfungszyklen, in the tone and carbonate rocks.

Especially in the Kupferschiefer (lowest Werra Formation) is a variety of vertebrate fossils before, where it is both to fish that have lived in the Zechstein (eg Palaeoniscus freislebeni ), as well as to land vertebrates, on the dry land of the Zechsteinbeckens have lived and were rinsed until after her death in the sea (eg the Pareiasaurier Parasaur geinitzi or early Diapside Protorosaurus speneri ).

In the carbonates are found in some cases large numbers brachiopods (eg, the spiny form Horridonia horrida ) and bryozoans ( especially in the Riffkomplexen the Werra- formation, such as the genus Fenestella ).

During the Ausfällungsphasen of gypsum, rock salt and potash nurmehr likely extremophile unicellular organisms have survived in the waters of the Zechstein Sea. The interactions of the metabolic products of some of these single-celled organisms with the Earth's atmosphere may have contributed to the Permian-Triassic mass extinction with.

Importance

Influence on topography and geology

The deposits of the Zechstein Sea are in fact the only sediments in the geological history of Central Europe, which contain large amounts of rock salt. This device rock salt by the static load of the outer layers under high pressure, it behaves plastically, it starts to flow, and that there, where the pressure of auflagernden layers is lowest ( Halokinese ). Where the salt migrates, ultimately arise salt domes. The overlying overburden is lifted and, inasmuch as the prominent rocks are resistant to erosion than the rocks of the area, formed there mountains or entire mountain ranges, such as the Elm at Braunschweig. The red sandstone cliffs of Helgoland has also pushed through the activity of a salt dome from the ground by younger layers through to the surface. Where the salt migrates, the overburden is lowered, there arise so-called edge sinks. The Halokinese the Zechstein Salinars had a lasting influence on sedimentation in northern Germany from about the second half of the Mesozoic through the creation of depositional environments ( Lower edge ) or delivery areas ( mountain ranges ). The so-called saxonische tectonics is strongly influenced halokinetisch at least in Northern Germany.

The rise of the salt domes also has underground in northern Germany created (especially in Lower Saxony) and the North Sea area geological structures in which were allowed to form deposits of oil and gas (known as petroleum or natural gas traps), the exploited, now still at least a certain contribute content to meet the needs in Germany.

Raw materials

Historical

Through the rock salt stock of Zechsteinbeckens Northern Germany is Europe's largest salt- field. Where salt storage to far-reaching the earth's surface (eg, in the form of salt domes ), was promoted in the Middle Ages salt. Since salt was a highly prized commodity, and created prosperity in the mining areas, such as Lüneburg. The medieval exploitation and trade of salt can be salts ( today Wieliczka ) off today at German place names such as Salzwedel, Hall, Salzdetfurth, Salzelmen or Large.

Industrial promotion

Two methods are today for the industrial extraction of rock and potash from the Zechstein salt deposit in Germany applied. Firstly, the Bohrlochsolung, wherein the reservoir is drilled, and then hot fresh water is pumped through the outer tube of two concentric tubes lying. The salt solution (brine ) is formed in this process, rises in the inner tube to the surface and is transferred from there to the processing plant (eg in Ohrensen at Harsefeld in the district of Stade, where the brine thus obtained by pipeline directly into chloro- is pumped alkali electrolysis plants ). This procedure is used primarily of rock salt, but worth only for particularly mighty deposits, such as salt domes. The German rock salt deposits are estimated at 100,000 cubic kilometers. To Staßfurt widths have been found of one kilometer.

Potash is, however, mostly mined in large mines with the help of heavy machinery.

The rock salt is obtained mainly for the production of table salt and road salt as well as raw material for the chemical industry (industrial salt). The potassium salts are further processed into fertilizer.

The Gips- or Anhydritlager of the Zechstein be dismantled. The plaster is used, inter alia, as raw material for the construction industry, for porcelain and ceramic production and for industrial production of sulfuric acid.

Up to the early 1990s was in the Mansfeld region, before that in Richelsdorfer Mountains and other regions in Germany, the copper shale, the mineralized Schwarztonsteinhorizont in the deepest part of the Werra Formation degraded to obtain various metals in mines. Today copper shale mining area is in the Lubin - Sieroszewice, promoted only in Lower Silesia. But probably from 2020, again copper mining also be operated in Germany, in Lusatia.

Others

Underground cavities caused by the solution mining of salt deposits, so-called caverns are used as underground storage facilities for oil and gas. So about 15 million tons of crude oil, heating oil and other mineral oils can be stored in 58 caverns for example at sites Heide ( Schleswig -Holstein), Lesum (Bremen), Sottorf and Rüstringen (both Lower Saxony ) from the North - West Caverns GmbH ( NWKG ). Each cavity measures 30 to 35 feet in diameter and 250 to 450 meters in height. The volume of a cavern corresponds to the volume of a single super tanker. As of December 31, 2011 there were in Germany 205 Single cavern storage of natural gas in the Zechstein salt deposit with a total volume Vn of 13 billion cubic meters of working gas ( under standard conditions ), of which a maximum of 10 billion cubic meters were used for the effective injection and withdrawal in a Gesamterdgasverbrach Vn in Germany of 86 billion cubic meters of working gas in 2011 ( or 99 billion cubic meters in 2010).

In Gorleben in Wendland a mine was established, which serves the investigation of the Gorleben salt dome - Rambow regarding its suitability as a repository for radioactive waste. An attempt to mine for the storage of problematic waste ( nuclear waste, toxic waste ) was Asse II near Braunschweig. Radioactive waste that stem from the operation of nuclear power plants in the GDR as well as other toxic waste are stored (→ Morsleben ) in the salt dome Morsleben.

The therapeutic efficacy of brine applications has meant that in many places near salt deposits spa town businesses have been. Many of these places carry the indication of this in the name, such as Bad Salzdetfurth, Bad Salzuflen or Bad Salzungen.