Basalt outcrop on the Hindelang - Oberjoch road

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Exposure at the hairpin of the Jochstraße with Jura submarine basalt
Detail of the above photo with occasionally recognizable cushion structures in the rock wall.

The basalt outcrop on the Hindelang - Oberjoch road is a geotope east of Bad Hindelang in the Oberallgäu district . At a hairpin bend of the federal highway 308 are on a length of ten meters basalts in the form of pillow lava minded .

geology

On the Jochstraße, in one of the lowest switchbacks in a five-meter-high rock slope above the torrent, there is a gray-green pouring rock with rounded shapes . In terms of tectonostratigraphy, these rocks belong to the Arosa Zone , a thin tectonic mélange of Mesozoic sedimentary rocks and crystalline basement of the Eastern Alps as well as Mesozoic oceanic basalts and sedimentary rocks of the South Penninic (Piedmont Ocean) and Cretaceous flysch sediments .

The effluent rock, which is often weathered reddish brown on the surface, is a basalt in the broader sense. Strictly speaking, it is a basalt that was subsequently converted by a low-grade metamorphosis , which can be classified petrographically as " Diabas porphyrit" or "Diabasspilit". The basalts contain massive amounts of xenolites from marine sedimentary rocks (including fossil fragments) that were carried away during the ascent and / or the eruption of the volcanic material and are also slightly metamorphically overprinted. In the interstices between the individual pillows, mineralization with zeolite minerals can often be observed. Supraregional comparisons with similar oceanic rocks show a Central Jurassic formation of the basalts.

The thrust of the Arosa zone onto the rocks of the Rhenodanubian flysch and thus onto the northern foothills of the Alps at that time began in the Upper Cretaceous . The tectonically heavily stressed Arosa zone is only developed as a narrow, maximally 200 meters thick shed zone, which can be traced from Vorarlberg to Oberallgäu and was pushed over by the Allgäu cover (Bajuvarikum of the Northern Limestone Alps ) itself. The rocks of the Arosa zone are only rarely exposed in the Allgäu.

The geotope basalt outcrop on the Hindelang - Oberjoch road has been classified by the Bavarian State Office for the Environment as a geoscientifically particularly valuable geotope (geotope no. 780A008) with a suitability as an excursion and research object.

See also

Individual evidence

  1. ^ Ulrich Lagally, Stefan Glaser, Elisabeth Jobe, Georg Loth, Andreas Murr, Hubert Schmid, Wolfgang Schmid, Klaus Schwerd, Stephan Sieblitz and Ulrich Teipel: Geotope in Schwaben . In: Bavarian State Office for the Environment (Ed.): Earth science contributions to nature conservation . tape 7 . Augsburg 2009, ISBN 978-3-936385-34-2 , pp. 160 .
  2. ^ Basalt outcrop on the Hindelang - Oberjoch road. Data sheet from the geotope register of the LfU Bavaria

literature

  • K. Schwerd: Helvetikum, Ultrahelveti-kum, Feuerstätter blanket, Rhenodanubian flysch and Arosa zone between Burgberg and Hindelang (excursion G on April 8, 1983) , annual reports from the Upper Rhine Geological Association, new series 65, Stuttgart 1983, p. 99 -112
  • Ulrich Lagally, Stefan Glaser, Elisabeth Jobe, Georg Loth, Andreas Murr, Hubert Schmid, Wolfgang Schmid, Klaus Schwerd, Stephan Sieblitz and Ulrich Teipel: Geotope in Schwaben , published by the Bavarian State Office for the Environment, Earth Science Contributions to Nature Conservation, Volume 7, Augsburg 2009, ISBN 978-3-936385-34-2 , p. 137
  • Dieter Richter: Allgäu Alps . Geological Guide Collection 77, Stuttgart 1984

Web links

Commons : Geotop Basalt Hindelang  - Collection of images, videos and audio files

Coordinates: 47 ° 30 '23.9 "  N , 10 ° 23' 27.9"  E