Allgovit

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Allgovit sectional enlargement

Allgovit ( Latin allgovia : Allgäu ) is a historical local term for a series of porphyry , basaltic rocks from the Allgäu Alps . The term was introduced by Gustav Georg Winkler (1859) for exotic basaltic rocks in the Allgäu, because he could not address these isolated occurrences as either Trapp or Melaphyr due to the uncertain age and lack of regional tectonic ideas . Mineralogically, Allgovit consists of feldspar , mainly labradorite , augite and hematite, and is referred to petrographically as augite porphyrite or melaphyrite, depending on its composition. The name is derived from the Latin name Allgovia or Algovia for Allgäu.

Most of the occurrences of the rocks described as Allgovit are located in the area of ​​the Eastern Alpine ceiling edge between Bad Hindelang and Oberstdorf .

Current geological research assumes that the basaltic rocks, which Winkler described as allgovites , are genetic components of a heterogeneous, tectonic melange zone , the Arosa zone in the Oberallgäu district . These isolated basaltic rocks occurring in the Bavarian Alps between the Fidere Pass and Bad Hindelang are regarded as Jurassic formations of oceanic crust , which were sheared in a base mass of extremely tectonically stressed turbiditic marls and sandstones during the formation of the Alps and pushed onto the northern foreland . This tectonic mélange of different rocks was created when the Adriatic-African continental plate drifted northward in a deep-sea channel in the chalk . When the African plate was pushed onto the Eurasian plate , the rocks of the Arosa zone - including the basic effluent rocks - were sheared and pushed onto the Rhenodanubian flysch at the base of the Northern Limestone Alps, where they were intensely scaled.

Petrographically , the basaltic rocks vary greatly. In addition to the Augitporphyriten already mentioned, Diabasspilite or Diabasporphyrite often occur, which are often characterized by a pillow structure and thus demonstrate lava formation under water. A diabasporphyrite outcrop was identified as a particularly valuable geotope ( geotope no. 780A008) in the Wildbach valley cut near Hindelang .

Individual evidence

  1. ↑ RW Le Maitre (Ed.): Igneous Rocks. A Classification and Glossary of Terms. Recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks. 2nd ed. Cambridge University Press, Cambridge / New York / Melbourne 2002, ISBN 0-521-66215-X .
  2. ↑ Geognostische Jahreshefte , Vol. 35–36, 1923, p. 21.
  3. ↑ a b GG Winkler: Allgovit (Trapp) in the Allgäu Alps of Bavaria. In: New yearbook for mineralogy, geognosy, geology and petrefacts. 1859, pp. 641-671.
  4. ^ Franz Loewinson-Lessing: Petrographisches Lexikon: Repertory of petrographic terms and names . Ax. z. the meeting reports of the Natural Research Society 1893, p. 9.
  5. ↑ Max Richter: The Flysch in the area of ​​Oberstdorf in the Allgäu . Jb. Geol. Reichsanstalt, No. 72, Vienna 1922, pp. 49–80.
  6. ^ K. Schwerd: Arosa Zone and Walserberg Series. In: W. Freudenberger & K. Schwerd: Explanations of the Geological Map of Bavaria 1: 500,000 , 4th edition, Munich 1996, p. 218 f.
  7. ↑ a b St. Glaser, E. Jobe, U. Lagally, G. Loth, A. Murr, H. Schmid, W. Schmid, K. Schwerd, St. Sieblitz, U. Teipel: Geotope in Schwaben. Bavarian State Office for the Environment (Ed.), Earth Science Contributions to Nature Conservation, Volume 7, Augsburg 2009, ISBN 978-3-936385-34-2 .
  8. ↑ Bavarian State Office for the Environment: Geotope description of basalt outcrop on the Hindelang - Oberjoch road , accessed on October 21, 2014.