Helvetikum outcrop on Breitachstrasse

Geotope on Breitachstrasse

Exposure in the Helvetic Republic

Exposure on the Breitachufer

The Helvetikum outcrop on Breitachstrasse is a geotope northwest of Oberstdorf in the Oberallgäu district . Over a length of 200 m on Kreisstraße OA 5, deformed rock units of the Lower to Upper Cretaceous of the Helveticum are exposed .

geology

In the course of the road, the Geisberg anticline is cut into a 3 to 10 m high rock slope . The oldest rocks are located in the core of the anticline structure and are formed from the gray, banked Schratten limestone of the Lower Cretaceous, which is also exposed 3 km south in the Breitachklamm .

The Schrattenkalke are discordantly overlaid by a 20 m thick sandstone sequence of the Brisi subformation of the Garschella formation. The base of the Brisi - sandstone is a conglomerate formed workup horizon in which batches Phosphoritknollen and a layer with fragments of Belemnites is stored. The Brisi sandstones are exposed both to the north and south of the saddle core, even if the facial formation and thickness of the sequence of layers changes in a small area. These differences are due to regional fluctuations in sea level , which led to the changes in the deposit conditions.

To the east of the Breitach , the south wing of the Geisberg anticline is exposed in a rock slope, which is formed by rocks from the Lower Cretaceous to the Upper Cretaceous. In the north of the outcrop are the Schrattenkalke of the Lower Cretaceous, which are also overlaid here by the sandstones of the Garschella formation. About the sandstones the light gray, fine-grained follow Seewer - limes . The limestones are superimposed in the profile by the marl stones of the Amden strata . In the south, the youngest rocks are exposed in this rock slope, the silty-sandy rocks of the Wang strata .

The stratiform sequences exposed here, which were deposited in a predominantly shallow sea on the shelf on the southern edge of the European continental plate, cover a period of around 60 million years - from the Aptian to the Maastrichite .

The tectonic stress and thrust of the Helveticum on the northern Alpine foothills began in the early Tertiary .

The geotope Helvetikum outcrop on Breitachstrasse has been classified by the Bavarian State Office for the Environment as a geoscientifically valuable geotope (geotope no. 780a009), with a suitability as an excursion and research object. In 2015 the rock slope was secured against falling rocks with nets .

Individual evidence

^ ^A ^b 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 .
↑ Geotope data sheet of the Bavarian State Office for the Environment: Geotope no. 763A003 Helvetikum outcrop at Breitachstrasse NW of Oberstdorf , accessed on February 2, 2016

literature

J. Liedholz, KF Weidlich, H. Hagn, H. Scholz (1983): Helvetikum and northern flysch zone in the Allgäu west of the Iller on the Breitach and in the Balderschwanger Valley (excursion on April 7, 1983) - annual reports. u. Messages of the Upper Rhine. geological association, new series, issue 65, Stuttgart, 1983, pp. 61–83.
Dieter Richter : Allgäu Alps . - Geological Guide Collection 77, Stuttgart 1984