Transpression and transtension in the Eastern Alps (TATEA): Kinematics and age of a sinistral wrench zone

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Adria, the northern spur of Africa, collided with Europe and formed the European Alps, which connect to the Dinarides in the Southeast, and intermitted by the Pannonian Basin to the Carpathians in the East. At depths, beneath this orogenic bifurcation of the European Alps, roughly coincide spatially with the triple junction (zone) between three plates. That are in the European and Adriatic plates, plus the Pannonian lithospheric fragment. Their geometry and arrangement are subject to current research (AlpArray, SPP 2017 MB-4D). At the surface, the (late) Adriatic indentation caused two (active) seismotectonic wrench zones of high-angle/perpendicular to the mountain chain that meet in the Niedere Tauern. We will focus on the tectonics and chronology of the middle–upper crust in the Radstädter, Schladminger, Wölzer and Seckauer Tauern, here summarized as the Niedere Tauern (Fig. 2). We aim to establish a kinematic model for the Cenozoic wrench zones of the Eastern Alps in the area where they meet (Fig. 2). We will combine structural geology, unravelling the Cenozoic shear and fault zone evolution, and geochronology, dating deformation and exhumation. Together these are the most promising tools to link surface expressions to the deep structure. The kinematics of the Niedere Tauern, its connection to the Tauern Window in the west and to the Pöls-, Lavanttal faults in the east, is an indispensable jigsaw piece to understand the structural bifurcation from the European Alps to the Carpathians and Dinarides (Fig. 1). The linkage of surface to deep structures in orogens promotes a process-driven understanding of orogeny that is applicable in other orogens. We will explore the kinematics, especially the structural vergence, of the Niedere Tauern by structural mapping. To quantify the timing, sequence, and regional differences in deformation, we will perform geochronology using the 40Ar/39Ar in-situ, the fission-track and the (U-Th)/He methods. The aspired outcome will be a coherent structural and temporal pattern of the exhumation in the Niedere Tauern testing whether the transpressional to transtensional wrench zones in the Eastern Alps are cogenetic, conjugated and isochronously active or whether these zones have different causes. This difference has major implication for the geodynamic reconstruction of the Alpine-Carpathian-Dinaride system.