Red sandstone
The red sandstone is the lower of the three lithostratigraphic groups of the Germanic Triassic . It is superimposed on the Zechstein group and overlaid by the Muschelkalk group.
The name "Buntsandstein" does not refer to a specific type of rock, i.e. not a brightly colored sandstone of any age, but a sequence of rocks from the Lower Triassic , up to several hundred meters thick , made up of sandstones, but also siltstones and claystones as well as sometimes limestone and gypsum rock . In the past, the red sandstone (as well as Muschelkalk and Keuper) was also understood as a unit of time or time interval in the history of the earth and equated with the Lower Triassic (or Middle and Upper Triassic). The red sandstone sedimentation does not begin at the same time in the entire distribution area ( diachrony ). This is one of the reasons why “red sandstone” is unsuitable as an interval for the international geological time scale . The current boundary between the Lower and Middle Triassic , defined by fossils (i.e. biostratigraphically ), does not coincide with the Buntsandstein / Muschelkalk boundary, but lies somewhat deeper, still within the youngest section of the Buntsandstein. Thus, "Buntsandstein" can only be understood today as a name for a sequence of rocks (i.e. for a unit of lithostratigraphy) of the early Triassic age.
history
The term red sandstone (in the sense of “colorful sandstone” as opposed to “red sandstone” = red-lying ) goes back to Abraham Gottlob Werner , who used it from around 1780 in his lectures at the Bergakademie in Freiberg. In 1834, when the Triassic system was established by Friedrich August von Alberti , the term “colorful sandstone” was already generally recognized. Since the 1990s, the red sandstone has been viewed as a group in the sense of the lithostratigraphic hierarchy and divided into formations whose boundaries and relative position to other formations are precisely defined. Alternatively, allostratigraphy divides the red sandstone into sequences, the boundaries of which, however, in this case also coincide with the formations of the red sandstone. Allostratigraphy and lithostratigraphy are slightly different methods of subdividing rock units.
definition
The lower limit of the red sandstone (and thus also the limit of the Germanic Triassic supergroup) corresponds to the base of the Calvörde series in the basin center . In the Spessart and Odenwald the lower limit of the red sandstone is defined by the base of the Heigenbrücken sandstone, in the Black Forest by the base of the so-called (lower) Eck conglomerate. The upper limit of the red sandstone (and thus at the same time the lower limit of the shell limestone) is the basis of the so-called border yellow limestone.
Chronostratigraphically, the red sandstone sedimentation begins locally in the youngest Changhsingian , i. H. before the end of the Permian. The transition of the Buntsandstein to Muschelkalksedimentation falls into the lower Anisian , d. H. in the early Middle Triassic. According to the Stratigraphic Table of Germany 2002, this corresponds to the period between 251 and 243 million years ago, i.e. H. a duration of 8 million years.
The rocks of the red sandstone consist mainly of continental deposits such as red conglomerates, sandstones and claystones . The Rötsalinar with several tens of meters in thickness is characteristic of the upper red sandstone in the north German natural gas provinces. These evaporites are evidence of a widespread marine influence. The red sandstone sequence in Central Europe stretches from France ( Alsace ) and Luxembourg ( Gutland ) in the west to Poland and Belarus in the east, and from southern Switzerland to Scandinavia in the north. In the south-west German layered plain , the red sandstone emerges on the eastern flank of the Black Forest and in the eastern Odenwald . In the basin center in southern Lower Saxony and northern Hesse, thicknesses of up to 1000 m are reached.
structure
In the hierarchy of lithostratigraphy, the red sandstone is given the rank of a group within the supergroup of the Germanic Triassic . The red sandstone group is divided into three subgroups (lower, middle and upper red sandstone), which in turn are made up of allostratigraphic sequences or lithostratigraphic formations.
- Upper Buntsandstein (with the red formation )
- Middle red sandstone , with the Volpriehausen Formation , the Detfurth Formation , Hardegsen Formation and the Solling Formation
- Lower Buntsandstein , with the Calvörde Formation and the Bernburg Formation
The formation of the layers of the red sandstone is not the same in the entire distribution area, but varies regionally. In the Lower Buntsandstein of the Palatinate Forest , for example, the Trifels, Rehberg and Schlossberg layers are separated out instead of the Calvörde and Bernburg Formations. The same applies z. B. also for the subdivision of the Solling formation in its area of distribution (see Wesersandstein ).
In Alsace , the red sandstone is divided as follows:
-
Voltziensandstein (rich in fossils) consisting of
- Grès argileux, in the transition to the shell limestone
- Grès à meule
- Saint Odile Conglomerate ("Main Conglomerate ")
- Vosges sandstone (poor in fossils)
The Vosges sandstone is correlated with the Middle Buntsandstein east of the Rhine. There are no equivalents of the Lower Buntsandstein in northeastern France.
Economical meaning
The rocks of the red sandstone, in particular those from the layer of the middle red sandstone, were often used as building material for structures (e.g. churches, castles, bridges) due to their favorable properties (e.g. easy cleavage ). The Freiburg and Strasbourg Minster , the Kaiserdom of Frankfurt / Main, the Heidelberg Castle , the church of the Alpirsbach Monastery , the Basel Minster and the Johannisburg Castle in Aschaffenburg were built using rocks from this lithostratigraphic group.
Former mining
In some layers of the red sandstone, copper ores are used to a small extent. On Heligoland, for example, these very small chunks were collected and smelted on the beach.
Natural monuments
The red sandstone often forms spectacular weathering forms in its area of distribution: isolated rocks several dozen meters high. They are often designated as natural monuments, such as the landmark of the Palatinate Forest, the Teufelstisch near Hinterweidenthal . In the Palatinate you will find the so-called Altschlossfelsen near Eppenbrunn . With a length of around 1.5 km and a height of up to 25 m, the massif is probably the largest red sandstone massif in the Palatinate. The 47 meter high " Lange Anna ", the most famous landmark on the island of Helgoland , was also designated a natural monument in 1969. Other "red sandstone rocks" that are designated as natural monuments are, for example
- the boot rock near Rentrisch , a district of St. Ingbert (Saarland)
- the Heidenstuben in Ehrang , a district of Trier (Rhineland-Palatinate).
Some of these natural monuments probably served cultic purposes as early as the Neolithic.
literature
- Christiane David: Buntsandstein - building sandstone. Marburg sandstone under a magnifying glass. Marburg geosciences. Vol. 3. Marburg Geoscientific Association e. V., Marburg 2006, ISBN 3-934546-02-1 .
- Hans Hagdorn, Edgar Nitsch: On the term "Trias" - a historical outline. In: Norbert Hauschke, Volker Wilde (Hrsg.): Trias - A whole different world: Central Europe in the early Middle Ages. Publishing house Dr. Friedrich Pfeil, München 1999, pp 13-21, ISBN 3-931516-55-5 .
- Gerhard H. Bachmann, Gerhard Beutler, Hans Hagdorn, Norbert Hauschke: Stratigraphy of the Germanic Trias. In: Norbert Hauschke, Volker Wilde (Hrsg.): Trias - A whole different world: Central Europe in the early Middle Ages. Publishing house Dr. Friedrich Pfeil, Munich 1999, pp. 81-104, ISBN 3-931516-55-5 .
- Jochen Lepper, Dietrich Rambow, Heinz-Gerd Röhling: The red sandstone in the stratigraphic table of Germany 2002. In: Newsletters on Stratigraphy. Vol. 41, No. 1-3, 2005, pp. 129-142, ISSN 0078-0421 .
- Peter Brack, Hans Rieber, Alda Nicora, Roland Mundil: The Global boundary Stratotype Section and Point (GSSP) of the Ladinian Stage (Middle Triassic) at Bagolino (Southern Alps, Northern Italy) and its implications for the Triassic time scale. In: Episodes. Vol. 28, No. 4, 2005, pp. 233-244 (digital full text on stratigraphy.org 1.5 MB).
- German Stratigraphic Commission (Hrsg.): Stratigraphic Table of Germany 2002. Potsdam 2002, ISBN 3-00-010197-7 , ( PDF large 6.57 MB).
Web links
References and comments
- ↑ According to the latest geochronological correlations by Menning u. a. (2005) the red sandstone sedimentation begins about 252.6 million years ago and ends 246.6 million years ago, which corresponds to a period of about 6 million years. However, the authors recommend continuing to use the numbers from the Stratigraphic Table of Germany until the new data are confirmed by further research.
- ^ Jean-Claude Gall: Alsace, des Fossiles et des Hommes (une histoire géologique de la plaine rhénane et du massif vosgien). La Nuée Bleue, Strasbourg 2005, ISBN 2-7165-0655-8 , pp. 37-50.
- ↑ Marc Durand: The red sandstone in northeast France. Series of publications of the German Society for Geosciences. Vol. 69, 2014, pp. 635–646 ( abstract )