Eo-Alpine imbrication of Middle Austroalpine units in the Gurktal Alps, Carinthia — questioning the existence of the Upper Austroalpine Murau Nappe


Structural analysis of Paleozoic Middle and Upper Austroalpine (MAA, UAA) units of the Gurktal Nappe Complex (GNC) in combination with electron microprobe analyses of multiphase garnets reveal a complex Variscan and Alpidic tectonometamorphic evolution of the GNC. Our study is focussed on the UAA ‘Murau Nappe’ and its tectonic transition to the MAA respectively to the overlying UAA Stolzalpen Nappe. The ‘Murau Nappe’ may rather be interpreted as a major zone of imbricate thrust slices of the underlying and overlying units than a distinct nappe. The results of our study lead to a reinterpretation of the ‘Murau Nappe’ as a major shear zone generated during the Eo-Alpine thrusting of the Stolzalpen Nappe over the MAA. Concerning the central GNC we conclude, that the genetic term ‘Murau Nappe’ for the lower UAA unit between MAA and Stolzalpen Nappe is not valid. Instead, its reinterpretation as a major shear zone (‘Murau shear zone’), genetically belonging to the MAA, generated during Eo-Alpine overthrusting of the Stolzalpen Nappe, is favoured. The Mesozoic Stangalm unit is interpreted as a local sequence imbricated during the northward movement of the MAA units.
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