Orogenic processes in the Alpine collision zone
- Published:
Late Jurassic tectonics and sedimentation: breccias in the Unken syncline, central Northern Calcareous Alps
Swiss Journal of Geosciences volume 101, pages 55–71 (2008)
Abstract
This study analyses and discusses well preserved examples of Late Jurassic structures in the Northern Calcareous Alps, located at the Loferer Alm, about 35 km southwest of Salzburg. A detailed sedimentary and structural study of the area was carried out for a better understanding of the local Late Jurassic evolution. The Grubhörndl and Schwarzenbergklamm breccias are chaotic, coarse-grained and locally sourced breccias with mountain-sized and hotel-sized clasts, respectively. Both breccias belong to one single body of breccias, the Grubhörndl breccia representing its more proximal and the Schwarzenbergklamm breccia its more distal part, respectively. Breccia deposition occurred during the time of deposition of the Ruhpolding Radiolarite since the Schwarzenbergklamm breccia is underlain and overlain by these radiolarites. Formation of the breccias was related to a major, presumably north-south trending normal fault scarp. It was accompanied and post-dated by west-directed gravitational sliding of the Upper Triassic limestone (“Oberrhätkalk”), which was extended by about 6% on top of a glide plane in underlying marls. The breccia and slide-related structures are sealed and blanketed by Upper Jurassic and Lower Cretaceous sediments. The normal fault scarp, along which the breccia formed, was probably part of a pull-apart basin associated with strike slip movements. On a regional scale, however, we consider this Late Jurassic strike-slip activity in the western part of the Northern Calcareous Alps to be synchronous with gravitational emplacement of “exotic” slides and breccias (Hallstatt mélange), triggered by Late Jurassic shortening in the eastern part of the Northern Calcareous Alps. Hence, two competing processes affected one and the same continental margin.
Author information
Authors and Affiliations
Corresponding author
Additional information
Editorial Handling: Stefan Schmid, Stefan Bucher
Manuscript received February 26, 2008; Revision accepted July 21, 2008
Rights and permissions
About this article
Cite this article
Ortner, H., Ustaszewski, M. & Rittner, M. Late Jurassic tectonics and sedimentation: breccias in the Unken syncline, central Northern Calcareous Alps. Swiss J. Geosci. 101 (Suppl 1), 55–71 (2008). https://doi.org/10.1007/s00015-008-1282-0
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00015-008-1282-0