Fault slip analysis and late exhumation of the Tauern Window, Eastern Alps
Résumé
Exhumation of the Eastern Alps from the early Tertiary to the late Miocene was localized mainly in the Tauern Window, a thermal and structural dome located in front of the Dolomites indenter. Stress inversions based on new structural investigations over the entire Tauern Window indicate a regional zoning of the paleostress field with a predominance of strike-slip states of stress in the core of the investigated area, and dominant extensional regimes in the eastern and western borders of the dome. Few inverse fault structures have been highlighted. We propose a two-stage deformation history in order to explain the different types of structures that characterise the ductile and the brittle domains. During the first stage of exhumation of the Tauern Window, corresponding to the folding event, the brittle crust was probably dominated by N-S shortening and compression. The second stage of exhumation was marked by normal faulting at the borders of the dome and strike-slip faulting in the core. During the second stage, the brittle part of the crust that was previously affected by compressive structures belonging to the first stage was eroded. Normal faulting associated to E-W extension along the eastern and western borders of the Tauern Window was accommodated by strike-slip faulting located in the core of the Tauern Window, yielding E-W extension and N-S shortening. The orientation of the extensional axes and the nature of the stress tensors are similar to the ones inferred for the late-stage, brittle overprint of the internal basement massifs of the Central Alps pointing to a possible common, large-scale, state of stress acting well beyond the area of the Eastern Alps.