Wetteldorfer directional cut

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Relief map: Rhineland-Palatinate
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Wetteldorfer directional cut​
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Rhineland-Palatinate

The Wetteldorfer directional cut is an artificial geological outcrop near the Schöneck district of Wetteldorf in the Eifel . As the GSSP , i.e. the international reference, for the geological “time boundary ” between Emsium and Eifelium , which is also the boundary between Lower and Central Devon, it is of outstanding geological importance. Its history is closely linked to the Senckenberg Institute in Frankfurt am Main. The Wetteldorfer directional cut is so far the only binding and generally recognized GSSP inGermany .

The reference point for the Lying limit (base) of Eifeliums is 21.25 meters above the tread base in the upper part of the formation Heisdorf, 1.9 meters below the base of leek Formation, in an approximately 5 centimeters powerful Crinoids leading limestone layer immediately below the bentonite layer "Horologium II". It is biostratigraphically characterized by the first appearance ( English first appearance date , FAD) of the conodont subspecies Polygnathus costatus partitus in the fossil record . The FAD of the conodont Icriodus corniger retrodepressus is just above this limit.

geology

The GSSP of the Eifelium lies, like every other GSSP, in a sequence of marine sedimentary rocks. This was folded in the course of the Variscan orogeny and is now in the legs of a large syncline structure in the northwest of the Rhenish Slate Mountains (Eifel), the so-called Prümer Kalkmulde . The Wetteldorfer directional cut is located in the southeastern leg of this limestone basin. Correspondingly , the layers there - at 55 to 75 degrees - dip in northerly directions.

The upper Heisdorf formation is a deposition sequence of the shallow shelf and consists of slightly carbonate -containing gray and greenish silty shales and siltstones , in the isolated marl limestone or carbonate containing sandstone layers are turned on. The proportion of carbonate layers increases towards the base of the leek formation. The lower leek formation is in the Wetteldorfer directional cut in the form of the Wolfenbach subformation. This subformation comprises an alternation of blue-gray limestones and crinoid-bearing limestones, gray and greenish silty claystones and marlstones as well as some layers of carbonate sandstone. The thickness of the limestone and marlstone layers increases towards the hanging wall . A total of seven layers of bentonite are included in the sequence: "Hercules I" and "II" and "Horologium I" to "III" in the upper Heisdorf formation and "Libra I" and "II" in the lower leek formation.

Research history

The creation of the Wetteldorfer directional section goes back to the initiative of the German geologist Rudolf Richter , who was in charge of the Senckenberg Institute in Frankfurt am Main at the time and who, together with his wife Emma Richter, pioneered the modern geological exploration of the Devonian Eifel from the 1910s . The reason for this initiative was the data situation, which was felt to be inadequate at the time, with regard to a precise definition of the boundary between the Lower and Central Devon in western Europe. In 1937 the “I. International Directional Cut Conference "in Schönecken decided to create a directional cut not far from the conference venue, since" nowhere in the whole of the Rheinische mass could a more promising place be found than here at Wetteldorf. "In the same year a 147 meter long and up to A trench 2.5 meters deep was dug through which a largely uninterrupted sequence from the Lower Devonian "Wiltzer layers" to the Middle Devonian "Laucher layers" was opened up . The head of the profile recording was Gerhard Solle . Rudolf Richter published the final research report in 1942.

The fossil collection of around 5 tons was brought to the Senckenberg Institute, where it was prepared and scientifically processed by German and, initially, also by English experts. In order to protect the collection from the Allied air raids on Frankfurt during the Second World War , it was relocated to the Glauberg Museum near Büdingen , including thousands of fully prepared trilobites , which represented a complete development sequence of the species present in the layers of the directional profile. However, important parts of this collection were destroyed by artillery fire. Important work on the basis of the "first" straightening cut are:

  • Georg Dahmer
    • (1943) The mollusks of the Wetteldorfer directional cut. Senckenbergiana, 26: 325-396, Frankfurt a. M.
  • Karl Krömelbein
    • (1953) The horizon with Spirifer ostiolatus in the sequence of the Prümer Mulde (Devon / Eifel), with a view of the Middle Devonian division of the Bergisches Land. Senckenbergiana, 34: 61-72, Frankfurt a. M.
  • Herta Schmidt
    • (1942) The rhynchonellids of the Wetteldorfer directional cut. Senckenbergiana, 25 (1/6): 389-403, Frankfurt a. M.
    • (1946) The Terebratulidae of the Wetteldorfer directional cut. Senckenbergiana, 27 (1/6): 67-75, Frankfurt a. M.
  • Wolfgang Struve
    • (1955) The question of the Eifler crinoid layer (Middle Devonian) in the light of fine stratigraphic studies. Senckenbergiana lethaea, 35 (5/6): 279-316, Frankfurt a. M.

Further publications based on the directional cut material appeared and appear in the Senckenberg series of publications Senckenbergiana lethaea and Natur und Museum , including works by Klaus Fahlbusch , Rudolf Birenheide , Karsten Weddige and many others.

Not least because of the war losses, there was still a need to research the Lower / Middle Devonian border interval after 1945. So at the beginning of the 1950s, not far from the position of the “first” Wetteldorfer directional cut, another trench was created in the Middle Devon (“Schönecker Richtschnitt”), which was extended into the border interval (Heisdorf layers) in 1973 (and henceforth called Dingdorfer Richtschnitt ). In 1970 the Wetteldorfer directional cut in the area of ​​the Heisdorf and Laucher layers was reopened and scientifically examined. A third directional cut in the limit interval was opened in 1972 in the Gerolsteiner Kalkmulde near Lissingen ( Lissinger directional cut ). All of these excavations, carried out in the early 1970s, were carried out under the direction of Senckenberg paleontologist Rolf Werner .

After the desire for a globally valid geological standard time scale grew more and more in the professional world in the first decades of the second half of the 20th century and the GSSP concept was developed in the course of this , the ICS Subcommission for the Devonian (Subcommission on Devonian Stratigraphy, SDS) at the conference in Binghamton, New York (USA), officially announced the Wetteldorfer directional cut as GSSP for the Emsium-Eifelium border. This election decision was finally ratified in 1984 by the International Union for Geosciences (IUGS), the umbrella organization of the ICS, in Moscow . To this day, the Wetteldorfer Richtschnitt is the only GSSP in Germany, and with the exception of the Salzgitter-Salder quarry ( Turon - Coniac border) there are no candidates for other German GSSPs.

In 1990, the Ludwig-Happel-Baude , named after a South German oil geologist, was built above the directional cut to protect it from weathering , but also from vandalism .

Individual evidence

  1. ↑ GSSP Wetteldorfer Richtschnitt (Ems / Eifel border) on the website of the Senckenberg Institute; accessed on September 10, 2017.
  2. ^ Frank Auffenberg (2015): A world-famous piece of the Eifel: Why almost every geologist knows Wetteldorf ; Trierischer Volksfreund from February 4, 2015.
  3. ↑ a b c d e f Willi Ziegler and G. Klapper (1985): Stages of the Devonian System. In: Episodes. Vol. 8 (2): 104-109, 9 illustrations; Ottawa ( PDF 1.1 MB; stratigraphy.org).
  4. ↑ a b c d e f g h i j k l m n Sabine Rath (2003): The history of exploration of the Eifel geology - 200 years a classic area of ​​geological research. Approved dissertation to obtain the academic degree of Doctor of Natural Sciences at the Faculty of Georesources and Materials Technology of the Rheinisch-Westfälische Technische Hochschule Aachen ( PDF 6.4 MB, RWTH Aachen University); see also the literature cited therein.
  5. ↑ Klemens Oekentorp and Dieter Brühl (1999): Tabular fauna in the border area Lower / Middle Devonian of the Eifeler Richtschnitte (S-Eifel / Rheinisches Schiefergebirge). In: Senckenbergiana lethaea. Vol. 79 (1): pp. 63-87, 3 figs., 5 plates; Frankfurt a. M.
  6. ^ Ferdinand Trusheim (1988): Obituary for Ludwig Happel (1907–1986). In: Annual reports and communications from the Upper Rhine Geological Association. Vol. 70: pp. 13-14; Stuttgart
  7. ^ Rolf Werner (1990): Refuge above the border stratotype Lower / Middle Devon in Schönecken-Wetteldorf / Eifel. In: Nature and Museum. Vol. 120 (5): 160–163, 3 illustrations; Frankfurt am Main.

Coordinates: 50 ° 8 ′ 59 ″  N , 6 ° 28 ′ 18 ″  E