Geomorphological-geological characterization of an active, deep-seated rockslide in a heavily foliated rock mass – Wasserradkopf, Austria

Abstract

We present a study focusing on the geologic-geometrical characterization of an approximately1,5 km² large, deep-seated rock slide at the south-eastern slope of the Wasserradkopf (3032m a.s.l.) located in the high alpine environment of the Hohe Tauern National Park (Carinthia,Austria). The rocks composing the Wasserradkopf belong to the “Bündnerschiefer”, whichmainly consist of a highly schistose rock mass.Within our study, we performed a lithological and structural characterization, detailly mappedthe geomorphological features, and incorporated high resolution INSAR data in order todemonstrate the structural control on the rock slide process.Firstly, we conducted a geological field survey with the aim of creating a geological map of thestudy site. Petrographic investigations on the microscope helped to classify the mappedlithologies according to their mineralogy. Additionally, we recorded discontinuities to identifythe structural inventory of the rock mass hosting the rock slide allocate the discontinuities todiscontinuity sets.Secondly, we characterized and mapped the geomorphological features, i.e., scarps, counterfacing scarps and horst and graben structures on the rock slide surface to identify the unstableareas and distinguish individual rock slide slabs.Finally, we assessed the INSAR data to quantify the movement in the outlined unstable areas.By mapping areas of differential deformation rates, we confirm the presence of individual rockslide slabs.The preliminary results show that dominant brittle structures, which are represented by twosubvertical NNE-SSW and WNW-ESE striking joint sets, and several NE-SW striking steepstanding faults provide a favorable structural predisposition in interplay with the moderatelyout-slope dipping schistosity for a rock slide mechanism to develop. Moreover, we correlatethe differential movement rates observable in the INSAR data with the individual rock slideslabs identified by geomorphologic mapping.By this combination of geological, geomorphological and advanced remote sensing techniqueswe demonstrate the structural influence on the rock slide process and unravel its internaldeformation and kinematics.