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Structure and evolution of an antiformal nappe stack (Aar massif, Central Alps): Formation of mechanical anisotropies and their bearing on natural risks

English title Structure and evolution of an antiformal nappe stack (Aar massif, Central Alps): Formation of mechanical anisotropies and their bearing on natural risks
Applicant Herwegh-Züger Marco
Number 149385
Funding scheme Project funding (Div. I-III)
Research institution Institut für Geologie Universität Bern
Institution of higher education University of Berne - BE
Main discipline Geology
Start/End 01.10.2013 - 30.09.2016
Approved amount 228'330.00
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Keywords (8)

rock deformation; natural risk; quartz; 3D; deformation mechanisms; nappe stack; seismicity; strain localization

Lay Summary (German)

Lead
Kollisionen von Erdplatten führen zur Verfaltung und Aufeinanderstapelung von Gesteinskörpern. Hierbei entstehen mechanische Schwächezonen, welche durch Hebung und Erosion an die Erdoberfläche gelangen. Diese Schwächezonen, die involvierten Prozesse und ihre 3D-Geometrie werden am Beispiel Aar-Massivs untersucht. Einmal in der Tiefe angelegt, können besagte Schwächezonen immer wieder reaktiviert werden. In diesem Sinn können sie noch heute unsere Infrastruktur an der Oberfläche gefährden.
Lay summary

Inhalt und Ziel des Forschungsprojekts

Im Rahmen von Felduntersuchungen werden die zuvor erwähnten Deformationsstrukturen via Fernerkundung und Feldstudien untersucht. Laboruntersuchungen an gezielt ausgewählten Proben  erlauben die Charakterisierung der Deformationsbedingungen, der Deformationsprozesse und ihrer zeitlichen Abläufe. Die Datierung der Strukturen mittels radioaktiver Isotopensysteme stellt hierbei einen wichtigen Beitrag zur Altersbestimmung der Deformationsereignisse dar. Ein besonderer Augenmerk wird auf das Zusammenspiel zwischen langsamen plastischen und schnellen spröden Deformationsprozessen gelegt. Dies ist äusserst wichtig, da ein verbessertes Prozessverständnis dieses Zusammenspiels neue Einblicke in die Entstehungsmechanismen von Erdbeben liefert.

 

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Unser Projekt ist bereits seit drei Jahren am Laufen und hat wichtige neue Erkenntnisse über das Deformationsverhalten der mittleren und oberen Erdkruste im Allgemeinen und für das Aar-Massiv im Speziellen, geliefert. Es wurden bereits 3D-Geometrien und ihre Entwicklung für einen Teil des Aar-Massivs in Raum und Zeit rekonstruiert. Diese Rekonstruktionen sind für unsere Gesellschaft von grosser Bedeutung, erlauben Sie uns doch nebst dem besseren Verständnis der Auslösung von Erdbeben, den Verlauf der Deformationsstrukturen in der Tiefe zu verstehen. Solche Erkenntnisse sind zum Beispiel gefragt für die Planung von Tiefengeothermieprojekten, Tiefbauten (Tunnel, Endlager) und das Potential für oberflächennahe Naturgefahren wir Bergstürze oder Murgänge. Letzteres vor allem deswegen weil die oben erwähnten mechanisch angelegten Strukturen auch wieder Schwächezonen an der jetzigen Erdoberfläche ausbilden.

 

Direct link to Lay Summary Last update: 10.10.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Large-Scale Crustal-Block-Extrusion During Late Alpine Collision
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.
Microstructures, mineral chemistry and geochronology of white micas along a retrograde evolution: An example from the Aar massif (Central Alps, Switzerland)
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.
How is strain localized in a meta-granitoid, mid-crustal basement section? Spatial distribution of deformation in the central Aar massif (Switzerland)
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.
Mechanical anisotropy control on strain localization in upper mantle shear zonesWadi al Wasit Shear Zone
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.
Murgänge und Felsstürze im Gebiet Ritzlihorn-Spreitgraben, Guttannen BE – Analyse der Felskonditionierung und des Mur- und Sturzkegels
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.
Deformation at the frictional-viscous transition: Evidence for cycles of fluid-assisted embrittlement and ductile deformation in the granitoid crust
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.

Collaboration

Group / person Country
Types of collaboration
Prof. Dr. Th. Pettke Switzerland (Europe)
- Publication
- Research Infrastructure
PD Dr. Edwin Gnos Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Prof. Klaus Regenauer Lieb, University of Western Australia Australia (Oceania)
- in-depth/constructive exchanges on approaches, methods or results
Prof. F. Anselmetti Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Dr. Istvan Dunkl Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure
Dr. Ingo Blechschmid Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure
PD Dr. Urs Maeder Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Prof. Dr. Fritz Schlunegger Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Prof. Neil Mancktelow, ETHZ Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
EGU 2018 Talk given at a conference Late-stage Alpine continent-continent collision: Exhumation of Midcrustal Basement by Subvertical Large-Scale Block Extrusion 09.04.2018 Vienna, Austria Kissling Eduard; Herwegh-Züger Marco;
EGU 2017 Poster Formation of seismically-induced non-cohesive high-temperature cataclasites in the granitoid middle crust: An alternative to pseudotachylites? 24.04.2017 Wien, Austria Herwegh-Züger Marco; Wehrens Philip Chaim;
EGU 2016 Poster The role of Permo-Carboniferous graben systems in the development of the external Alpine massifs – an example from the Central Aar massif (Faernigen syncline) 23.04.2016 Vienna, Austria Herwegh-Züger Marco; Nibourel Lukas;
GSA 2015 Talk given at a conference Derivation and verification of a structural 3D model of the Haslital (Aar massif, Switzerland) from remote sensing and field data 01.11.2015 Baltimore, United States of America Herwegh-Züger Marco;
Alpine Workshop 2015 Talk given at a conference Structure of the proximal European margin (Central Alps) and its role during the Alpine collision 13.09.2015 Briancon, France Herwegh-Züger Marco; Kissling Eduard;
EGU 2015 Talk given at a conference Last Increments of a Continent-Continent Collision: The Exhumation of the Aar Massif as an Example 12.04.2015 Vienna, Austria Herwegh-Züger Marco; Wehrens Philip Chaim; Kissling Eduard;
EGU 2015 Talk given at a conference The Front of the Aar Massif: A Crustal-Scale Ramp Anticline? 12.04.2015 Vienna, Austria Herwegh-Züger Marco; Kissling Eduard; Wehrens Philip Chaim;
SGM 2014 Poster A new geological map of the Aar-massif (1:100’000) oder at the scale 1:100’000 22.11.2014 Fribourg, Switzerland Herwegh-Züger Marco;
EGU 2014 Talk given at a conference Cycles of fluid involved cataclasis and ductile flow at mid-crustal level during Alpine deformation in the Aar massif (Central Alps, Switzerland) 27.04.2014 Vienna, Austria Wehrens Philip Chaim; Herwegh-Züger Marco;
EGU 2014 Poster Internal structure of the Aar Massif: What can we learn in terms of exploration for deep geothermal energy? 27.04.2014 Vienna, Austria Herwegh-Züger Marco; Wehrens Philip Chaim;
EGU 2014 Talk given at a conference Earthquakes in the ductile regime? An attempt to explain fluid-based and ultra-localized deformation along the Glarus thrust 27.04.2014 Vienna, Austria Herwegh-Züger Marco;
SGM 2013 Talk given at a conference Kinematics and 3D pattern of ductile shear zones in the Gruebensee- Gelmersee transect (Hasli Valley, central Switzerland). 16.11.2013 Lausanne, Switzerland Herwegh-Züger Marco;
SGM 2013 Talk given at a conference Internal structure of the Aar Massif: What can we learn in terms of exploration for deep geothermal energy? 16.11.2013 Lausanne, Switzerland Wehrens Philip Chaim; Herwegh-Züger Marco; Kissling Eduard;
SGM 2013 Talk given at a conference Towards the semi-automated analysis of lineaments in the Aar massif: uncertainty estimates for geological surface information – A combined remote sensing and field data approach 16.11.2013 Lausanne, Switzerland Wehrens Philip Chaim; Herwegh-Züger Marco;
SGM 2013 Talk given at a conference Fluid involved, high grade cataclasis during Alpine ductile deformation in basement rocks of the Aar massif 16.11.2013 Lausanne, Switzerland Herwegh-Züger Marco; Wehrens Philip Chaim;


Associated projects

Number Title Start Funding scheme
163153 Structure And Mechanics of Seismogenic Fault Zones: Insights from advanced passive and active seismic imaging 01.05.2016 Project funding (Div. I-III)
144381 The role of sheet silicate-rich rocks during mountain building processes 01.01.2013 Project funding (Div. I-III)
143972 Age and crystallization duration of alpine cleft monazite and correlation with tectonically driven hydrothermal dissolution/precipitation events 01.04.2013 Project funding (Div. I-III)
66889 Grain growth in polyphase rocks under static and deformational conditions in nature and experiment 01.04.2002 Project funding (Div. I-III)
121578 A 4D Model of Neogene Exhumation in the Central Helvetic Alps 01.10.2008 Project funding (Div. I-III)
126560 The role of Polymineralic Rocks in the Evolution of Shear Zones 01.12.2009 Project funding (Div. I-III)
132196 Structure and evolution of an antiformal nappe stack (Aar massif, Central Alps): Formation of mechanical anisotropies and their bearing on natural risks 01.10.2010 Project funding (Div. I-III)
162340 The role of sheet silicate-rich rocks during mountain building processes 01.01.2016 Project funding (Div. I-III)
170738 New Ionpolisher for high-end surface preparation of composite materials 01.12.2016 R'EQUIP
119878 Deformation mechanisms in naturally and experimentally deformed minerals and rocks (8) 01.04.2008 Project funding (Div. I-III)
109369 Rasterelektronenmikroskop Geologie Bern 01.02.2006 Project funding (Div. I-III)
169055 Structure and evolution of an antiformal nappe stack (Aar massif, Central Alps): Formation of mechanical anisotropies and their bearing on natural risks 01.10.2016 Project funding (Div. I-III)
178785 Fluids and new fluid tracers in water under-saturated continental crust: From rifting to tectonic inversion 01.09.2018 Project funding (Div. I-III)

Abstract

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).
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