The evolution of the Austroalpine nappe stack in the hanging wall of the Giudicarie fault system


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Inproceedings: an article in a conference proceedings.
The evolution of the Austroalpine nappe stack in the hanging wall of the Giudicarie fault system
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Pomella  H., Flöss D., Speckbacher R., Fügenschuh B.
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During the Eoalpine orogenic cycle S-Apulia overthrusted N-Apulia along a SE dipping intracontinental shear zone (SCHMID ET AL. 2004). High pressure metamorphic overprint affected the south-eastern-most parts of N-Apulia: the Texel complex experienced pressures of 12-14 kbar (HABLER ET AL. 2006), the Schneeberg complex 8-10 kbar (KONZETT AND HOINKES 1996) during this stage. In the hanging wall of this pressure-dominated corridor a nappe stack formed on top of the Ötztal nappe. The Cretaceous metamorphism within the SE-dipping Ötztal nappe increased from NW to SE, whereas the higher nappes (i.e. Meran-Mauls basement, Tonale nappe, Mesozoic Blaser nappe, Paleozoic Steinacher nappe) were almost unaffected.
At app. 80 Ma the Schneeberg- and the Texel complex were isothermally exhumed within the shear zone to reach a similar position as the Ötztal nappe, as indicated by time-, temperature-,
and pressure constraints. Probably during this stage the Schneeberg complex was highly deformed to form a megascopic sheath fold. Late-Cretaceous E-SE directed normal faulting (e.g. FROITZHEIM ET AL. 1994; WAGREICH 1995) brings the Ötztal nappe and its Mesozoic cover in the footwall in contact with the Mesozoic Blaser nappe, the Paleozoic Steinacher nappe and the Meran Mauls basement. During the Tertiary this Cretaceous-age nappe stack overthrusted Penninic units and rather open folds developed within this orogenic lid (MEIER 2003). In the hanging wall of the Meran-Mauls fault the wide folds were narrowed and finally overturned during NNW-ward indentation of the Southern Alps. This resulted in the present NW-dipping orientation of the Jaufen fault and the formation of a narrow syncline between the Jaufen and the Meran-Mauls fault. On the other hand in the hanging wall of the sinistral transpressive Northern Giudicarie fault less shortening due to the indentation of the Southern Alps occurred. The Paleogene folds of the Austroalpine nappes stack were only slightly affected and not overturned. Also the Pejo fault, separating the Campo nappe and the Tonale nappe, was not overturned and still dips towards SE, i.e. it preserved its original orientation. A comparison of the evolution of the Austroalpine nappe stack in the hanging wall of the Meran-Mauls fault and the Northern Giudicarie fault argues for similar geometries and orientations during the Cretaceous and Tertiary deformation, with the present-day differences caused only by the Miocene indentation of the Southern Alps.
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30/11/2010 16:32
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20/08/2019 14:48
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