Keuper

The Keuper is the uppermost of the three lithostratigraphic groups of the Germanic Triassic. This tripartite division, from which the name of the Triassic chronostratigraphic system, but applies only to the area north of the Alps ( Germanic Trias supergroup ). The Keuper is dated to around the period 235 to 199.6 million years. He follows the lithostratigraphic group of the Muschelkalk and the lithostratigraphic group of the Lias (Northern Germany ) and the Black Jura (southern Germany ) superimposed.

History

Sandstone and limestone were already at the end of the 18th century firmly established rock units. In contrast, it took the Keuper up in the 1820s, until he was recognized as a distinct rock unit. Until that time, he was usually regarded as part of the new red sandstone. The term Keuper was introduced by Leopold von Buch in the geoscience literature. However, he used the term in the sense of a rock name, not in the sense of a lithostratigraphic unit. The name " Keuper " derives from the Frankish dialect name pine, Kieber or Keiper, Keuper for colorful, friable shales. The transfer of this concept to the rock unit goes back to Friedrich Hoffmann, who used him in 1823 in oral form in this sense. Presumably, independently of him did so Christian Keferstein and so probably have these two geologists regarded as the author of the rock unit Keuper.

The Keuper was earlier and partly in the popular scientific literature still considered time interval of Earth's history ( " Keuper time ", " Keuper time "). If the term Keuper time in terms of " the time of deposition of the Keuper sediments of the Germanic Basin " is used, this is linguistically nor correct. If the term contrast to other areas (eg, " the Keuper time deposits in the Alps" ) transferred this is not correct, because Keuper is not a chronostratigraphic defined time interval, but a rock unit (or a unit of lithostratigraphy ), their sub - and upper limits from area to area can be relatively and absolutely time something different.

Definition

The lower limit of the Keuper is defined in Northern Germany with the lower edge of the so-called Lower Latvians carbon sandstone. In southern Germany, the lower limit is the basis of the " Grenzbonebeds ". The upper limit is the base of the Lias in northern Germany and the Black Jura in southern Germany. The type region is francs. In the North German Basin average thicknesses between 300 and 500 meters are reached locally up to 1000 meters. In Gluckstadt Trench let seismic surveys of a thickness close to 5000 meters. It is marine -influenced limestone and shales, lacustrine limestone and shales, fluvial and coastal sand - and siltstones, fossil soils and root horizons and powerful Salinarfolgen, where the pelvic center in northern Germany rock salt, in the randlicheren areas anhydrite (CaSO4 ) and gypsum (Ca [ SO4 ] · 2 H2O) were deposited.

Chronostratigraphic correlation

The lithostratigraphic units of the Keuper are difficult to correlate with the international chronostratigraphic stages since the Keuper sediments are often very fossilarm or do not contain useful for biostratigraphic dating of fossils. The base of the Keuper is to be dated in the lower Ladinian. The top of the Keuper reaches nearly to the base of the Hettangian. However, it should be noted that larger hiatuses are present within the Keuper; larger time steps Carnian and Norian Shares are not documented by deposits, but stuck in the hiatuses.

Lithostratigraphic subdivision

The Keuper is divided into twelve lithostratigraphic formations since 1997. The previous division into Lower, Middle and Upper Keuper (also Rhätkeuper ) is still only informally or in terms of the lithostratigraphic unit used subgroup.

Lower Keuper

The Lower Keuper (also Lower Keuper ) includes the Erfurt Formation and the upper parts of the Grafenwoehr lineup. The western and northern fringes of the Germanic Triassic basin were not divided further into lithostratigraphic units ( formations, etc.).

• Erfurt lineup, this corresponds approximately to the terms Lettenkeuper, carbon Keuper or Latvians carbon Keuper; these terms have been used but differently depending on the author, partly upper portions of the limestone group were included.
• Grafenwoehr formation, this formation is formed only on the eastern edge of the pool to Vindelician country and toothed in the upper part with the Erfurt lineup.
• " The edge for the Ardennes - threshold " and " Marginal Facies in the Baltic Sea Region". Both deposition areas are not subdivided into lithostratigraphic units.

The Lower Keuper is characterized by a cyclic alternation of sandy- clayey and clayey- calcareous sediments. Even small powerful, non- mineable coal seams occur (name Latvians carbon Keuper ). They document a rapid change of limnic - fluvial and Ablagerungsmilieulakustrinen deposition conditions to marine and brackish storage Runge conditions. The lower limit of the Lower Keuper (and the Erfurt Formation) in southern Germany is the so-called Grenzbonebed and in central and northern Germany on the basis of the "Lower Latvians carbon sandstone ".

Middle Keuper

The range of the sediments of the Middle Keuper ranges from sandstones, mudstones, marl stones, Salinargesteinen and carbonate banks. The sediments of fluvial and lacustrine come from the environment into which some marine benches are on the bottom. The Middle Keuper (rarely middle Keuper ) is divided into northern and southern Germany in different formations, which interlock laterally and correspond to each other partially.

Upper Keuper

In the Upper Keuper (Upper Keuper ) has been eliminated so far only a formation. More lithostratigraphic units have yet to be defined.

• Exter - formation in the pelvic interior includes the whole Keuper to the base of the first Liassic layers

The Upper Keuper includes dark tone and sandstones that were deposited in a deltaic environment. In marine and follow again deltaisch embossed sandstones. At the top of the unit turn limnic - deltaic sandstones were deposited. It is overlain by the Psilonotenton Formation ( Lower Jurassic )

Allostratigraphische subdivision

In the Allostratigraphie ( fins - stratigraphy ) of the Keuper is divided into six episodes, which are numbered from k1 to k6. The limits of sequences and formations often fall together.

Terms of geothermal energy in the North German Plain

The Keuper and the Rätkeuper are in Neustadt- Glewe visited in 2455 meter depth strata from which the thermal water is pumped to the geothermal power plant in Neustadt -Glewe, Germany's first geothermal power plant. The salinity of the brine is 220 grams per liter.