Austrian Journal of Earth Sciences Volume 104/2 2 - 21 Vienna 2011 Tectonic significance of structures within the salt de- posits Altaussee and Berchtesgaden–Bad Dürrnberg, Northern Calcareous Alps_______________________________ Christoph LEITNER*) & Franz NEUBAUER KEYWORDS Northern Calcareous Alps Haselgebirge Structures Dept. Geography and Geology, University of Salzburg, Hellbrunner Straße 34, A-5020 Salzburg, Austria; Rocksalt Halite *) Corresponding author,
[email protected] Alps Abstract The Northern Calcareous Alps (NCA) are a fold-and-thrust belt. Its Mesozoic units were detached, thrusted and stacked along the rheologically weak, evaporitic Upper Permian to Lower Triassic Haselgebirge Formation, which represents the principal décollement level. It occurs in connection with Juvavic tectonic units, but is also widespread outside Juvavic units as indicated by occurrences at the base of Tirolic tectonic units from Hall in Tirol to Hinterbrühl next Vienna. Exposed in salt mines, rocksalt and mudrock form a two component tectonite with a wide range of fabrics: mostly as crush breccia, protocataclasite, mylonite and ultramylonite. The structural trend differs from one salt deposit to another. Nevertheless, all structures are consistent within each deposit. The axes of isoclinal folds within rocksalt are parallel to the lineation, which is typical for highly sheared ductile rocks. White halite fibers in strain shadows and white halite fibers from veins in mudrock display a similar orientation to the halite mineral lineation and axes of isocli- nal folds. Many veins in the mudrock formed as a result of a crack-and seal mechanism. Interpreting the growth direction of fibres antitaxially, the inner, often red-colored part is older relative to the white outer part.