H. Ortner
Local and far field stress analysis of brittle deformation in the western part of the Northern Calcareous Alps, Austria

GPM 26, p. 109-136

Brittle deformation was analysed in 86 stations with in the western Northern Calcareous Alps (NCA). Six paleostress tensor groups were defined, which constrain the deformational history since onset of Alpine deformation and can be related to distinct stages of deformation in other parts of the orogen. The superposition of deformational events with stress tensors of the same geometry, but different ages was estblished. The evolution of the far field stresses (1st order stress), which are thought to be related to plate movements, was simple: Cretaceous NW-directed compression was followed by Paleocene/Eocene NNE-directed compression, which in turn was replaced by Oligocene/Miocene NNW-directed compression. Local stress fields (2nd order stress) complicate the picture: Cretaceous NW-compression was partitioned into NNW-directed compression in the NCA and W-directed compression in the Central Alps. Oligocene/Miocene NNW-directed compression was superposed by secondary stress fields related to lateral escape of crustal blocks during formation of the metamorphic core complex of the Tauern Window: N- to NNE-directed compression near large faults delimiting eastward moving blocks and E-directed extension. Third order stress fields are related to folding. The succession of these 3rd order stress fields is not systematic. Additionally, stress tensors related to Late Miocene E-W compression were recorded, which are related to collision in the Carpathian orogen.

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