rock deformation; natural risk; quartz; 3D; deformation mechanisms; nappe stack; seismicity; strain localization
Herwegh Marco, Berger Alfons, Baumberger Roland, Wehrens Philip, Kissling Edi (2017), Large-Scale Crustal-Block-Extrusion During Late Alpine Collision, in Scientific Reports
, 7(1), 413-413.
Berger Alfons, Wehrens Philip, Lanari Pierre, Zwingmann Horst, Herwegh Marco (2017), Microstructures, mineral chemistry and geochronology of white micas along a retrograde evolution: An example from the Aar massif (Central Alps, Switzerland), in Tectonophysics
, 721, 179-195.
Wehrens P., Baumberger R., Berger A., Herwegh M. (2017), How is strain localized in a meta-granitoid, mid-crustal basement section? Spatial distribution of deformation in the central Aar massif (Switzerland), in Journal of Structural Geology
, 94, 47-67.
Herwegh Marco, Mercolli Ivan, Linckens Jolien, Müntener Othmar (2016), Mechanical anisotropy control on strain localization in upper mantle shear zonesWadi al Wasit Shear Zone, in Tectonics
, 35(5), 1177-1204.
Fölmli Christian, Herwegh Marco, Schlunegger Fritz, Anselmetti Flavio (2015), Murgänge und Felsstürze im Gebiet Ritzlihorn-Spreitgraben, Guttannen BE – Analyse der Felskonditionierung und des Mur- und Sturzkegels, in Swiss Bull. angew. Geol
, 20(2), 47-69.
Wehrens Philip, Berger Alfons, Peters Max, Spillmann Thomas, Herwegh Marco, Deformation at the frictional-viscous transition: Evidence for cycles of fluid-assisted embrittlement and ductile deformation in the granitoid crust, in Tectonophysics
In the past three project years of our activities in the Aar massif we mainly focused on (Part A, PhD Baumberger) the quantification of large-scale structures (2D & 3D) and their effect on geomorphology, (Part B, PhD Wehrens) the unraveling of the conditions, relative timing and kinematic of different deformation episodes in the crystalline rocks of the Aar massif and (Part C, PhD Buckingham) the role of the late stage deformation along the sediments of the Glarus thrust, its deactivation under brittle conditions and the hazard potential of the associated brittle deformation structures. In the present proposal, we are going to ask for a three years prolongation. The current PhD projects will be finished in the first half of this prolongation. In the second half, we suggest to start with a new PhD project (Part D). Summary Part A: Using remote sensing, R. Baumberger successfully developed and validated a lineament map of the Hasli valley, where NW-SE trending lineaments dominate in the N, NE-SW and E-W trending structures dominate in the S. These structures are the result of reactivation of old anisotropies during Alpine deformation and represent nowadays preferential sites of erosion as manifest by geomorphological incisions. Based on these data, a 3D structural model of the Hasli valley is on the way to be developed. Summary Part B: Field investigations of P. Wehrens show considerable variations in deformation structures and kinematics from N-S, which allow to unravel the evolution of the Aar massif. In most cases, Alpine shear zones reactivate pre-Alpine mechanical anisotropies. The study of the deformation microstructures allows a telescoped view of continuous strain localization from depths of 13-15 km up to nowadays surface allowing the study of the brittle-ductile transition, i.e. the former seismogenic zone. In the coming project period, the associated deformation processes will be further characterized and dated by different approaches. Summary Part C: T. Buckingham developed a large-scale 3D model of the Glarus thrust and studied the late movements along the Glarus thrust and its deactivation during steep faulting related to the updoming of the Aar massif underneath. It becomes evident, that overprinting of different mechanical anisotropies (folitaions, cataclasites, fractures) in combination with oversteepened slopes severely rise the hazard potential in the area of the Tectonic Arena Sardona (risks for mass flows and rock falls). The new results from parts A-C indicate that exhumation of the Aar massif occurred in a complex manner over a long duration. Particularly the inversion of the former European passive continental margin and its mechanical anisotropies during the continent-continent collision in a late stage of the Alpine orogeny mainly controlled the structures and kinematics o the Aar massif. In this light, the link between the upper-middle crustal structures, the locking of the continent-continent collision and the isostatic response of the subducted European lithosphere underneath the Aar massif is key to be resolved in the forthcoming prolongation in a geodynamic point of view.New project Part D: In this part, our knowledge gained on the structural 2D and 3D characterization of the central Aar massif will be expanded to the Eastern Aar massif. Remote sensing and fieldwork will be used to develop a large-scale structural and kinematic evolution model. In addition a seismotectonic-approach will be followed in which the spatial analysis of recent earthquake activity will be investigated to obtain fundamental insights into the link between the nowadays exposed upper to mid-crustal structures with their deep-seated pendants of the seismically active upper to middle crust. Special emphasis will be paid to unravel the origin (brittle vs ductile deformation) and mechanical role of the recent seismogenic zone inside the Aar massif and the Northalpine foreland.Overall, the entire project brings up new important results on the evolution of the Aar massif and its sedimentary cover (including Helvetic nappes), the 3D geometry and related potential for natural hazards (seismic activity, rock falls etc).