Constraining the slip history of the Katschberg normal fault (Eastern Tauern Window) by thermo-kinematic modeling: Implications for the tectonic evolution of the Eastern European Alps in the late Cenozoic

Abstract

The Katschberg normal fault borders the Tauern Window to the east and played a crucial role during Miocene lateral tectonic extrusion in the Eastern European Alps. In this study, we present new cooling ages from low-temperature thermochronology as well as thermo-kinematic models, which constrain the exhumation history of the Penninic units in the footwall of the Katschberg normal fault and its slip history. Zircon and apatite fission track and apatite (U–Th)/He ages from footwall units range from 16.0 ± 1.9 Ma to 12.8 ± 1.4 Ma, 10.4 ± 1.8 Ma to 7.9 ± 1.3 Ma and 8.2 ± 0.8 Ma to 3.9 ± 0.4 Ma, respectively. Thermo-kinematic modeling indicates that the Katschberg normal fault was active between 21.1 ± 1.8 Ma and 12.2 ± 1.3 Ma and accommodated 27 ± 6 km of crustal extension at a total rate of 3.5 ± 0.3 km/Myr. After the end of normal faulting, exhumation continued with a rate of 0.21 ± 0.06 km/Myr until 2.0 ± 0.5 Ma and with a rate of 0.84 ± 0.08 km/Myr until present. A comparison with another Miocene low-angle normal fault in the Eastern Alps – the Brenner fault – reveals that the amount of extension accommodated by these faults decreases from west to east, which is consistent with an eastward decrease in N-S shortening. Therefore, Miocene deformation is greatest in the western Tauern Window near the Brenner normal fault where shortening in front of the Adriatic Indenter is at its maximum.