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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 169055
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 01.10.2016 - 30.04.2019
Approved amount 156'281.00
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Keywords (9)

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

Lay Summary (German)

Lead
Das Aar Massiv besteht aus Gesteinen der mittleren Erdkruste, welche in den letzten 20 Millionen Jahren an die Erdoberfläche gehoben wurden. In einer ersten Projektphase haben wir die Deformationsgeschichte und die damit verbundenen Störungszonen im Haslital untersucht. In der laufenden Projektphase dehnen wir die Untersuchungen nach Osten ins Urner Reusstal aus. Hier sollen nebst den zuvor erwähnten Zielen auch die thermische Entwicklungsgeschichte und heute aktive Bruchsysteme anhand der seismischen Aktivität rekonstruiert werden.
Lay summary


Das Aar Massiv besteht aus Kristallingesteinen in welche permische und oder mesozoische Sedimente während der Gebirgsbildung in engen Synklinalen eingeschuppt/eingefaltet wurden. Diese Sedimente wurden während der Dehnung zwischen Europa und Adria auf dem europäischen passiven Kontinentalrand abgelagert, wobei Bruchstrukturen entstanden, welche kleine Becken und Hochzonen von einander trennten. In einer fortgeschrittenen Phase der Alpinen Gebirgsbildung wurde dieser passive Kontinentalrand in den Akkretionskeil integriert und invertiert. Erste Feldresultate deuten darauf hin, dass die alten Bruchsystem zumindest teilweise reaktiviert wurden und somit die eingefalteten Sedimentkeile ehemalige Dehnungsbecken darstellen. Während dem sich die Sedimente während der Alpinen Metamorphose plastisch verhalten , erlauben die Temperaturen nur eine eingeschränkte duktile Deformation des Kristallins. Als Folge konzentriert sich die plastische Deformation entlang von engen Bewegungszonen (Scherzonen). Die untersuchten Gebiete sind von tausenden solcher Scherzonen auf allen Massstäben durchsetzt. Basierend auf Gefügeuntersuchungen können wir nachweisen, dass sogar in Tiefen von 18-20km nebst der duktilen Deformation auch Phasen schneller Spröddeformation auftreten. Wir interpretieren diese als seismisch aktiv, womit wir Zeugen fossiler Erdbeben nachweisen.

Unsere Erkenntnisse werden ein besseres Prozessverständis über die Deformationsgeschichte und die Verteilung der Deformationstrukturen im östlichen Aar Massiv liefern. Da die Scherzonen während der Hebungsgeschichte abkühlen und zu Sprödzonen werden, bilden sie heute mechanische Schwächezonen, in welchen die Erosion aktiv einsetzen kann. Steinschlag und Rutschungen stellen in diesen Bereichen grosse Naturgefahren dar, welche unsere Infrastruktur im Bereich des Reusstals bedrohen. Mit unserer Studie werden wir ein verbessertes Prozessverständnis des Ursprungs und der Entwicklung solcher Schwächezonen erlangen.
Direct link to Lay Summary Last update: 03.11.2016

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
The relation between peak metamorphic temperatures and subsequent cooling during continent–continent collision (western Central Alps, Switzerland)
Berger Alfons, Engi Martin, Erne-Schmid Silja, Glotzbach Christoph, Spiegel Cornelia, de Goede Rick, Herwegh Marco (2020), The relation between peak metamorphic temperatures and subsequent cooling during continent–continent collision (western Central Alps, Switzerland), in Swiss Journal of Geosciences, 113(1), 4-4.
Late stages of continent-continent collision: Timing, kinematic evolution, and exhumation of the Northern rim (Aar Massif) of the Alps
Herwegh M., Berger A., Glotzbach C., Wangenheim C., Mock S., Wehrens P., Baumberger R., Egli D., Kissling E. (2020), Late stages of continent-continent collision: Timing, kinematic evolution, and exhumation of the Northern rim (Aar Massif) of the Alps, in Earth-Science Reviews, 200, 102959-102959.
Large vertical displacements of a crystalline massif recorded by Raman thermometry
Nibourel Lukas, Berger Alfons, Egli Daniel, Luensdorf Nils K., Herwegh Marco (2018), Large vertical displacements of a crystalline massif recorded by Raman thermometry, in Geology, 46(10), 879-882.

Collaboration

Group / person Country
Types of collaboration
Dr. Istvan Dunkl Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Prof. Dr. Frederic Hermann Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Dr. Christoph Glotzbach Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
PD Dr. Meinert Rahn. ENSI Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
PD Dr. Edwin Gnos Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Dr. Tobias Diehl Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Prof. Dr. Alfons Berger Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Seminarvortrag, Victoria University, Wellington Individual talk Geodynamic and Structural Control on Orogenic Type Hydrothermal Systems: Insights from the European Alps 21.05.2019 Wellington, New Zealand Herwegh-Züger Marco;
Talks Department of Geology at University of Otago Individual talk Fluid-triggered High-speed Deformation at Different Levels of the Continental Crust 29.04.2019 Dunedin, New Zealand Herwegh-Züger Marco;
EGU2019 Talk given at a conference Young orogen-parallel growth of External Crystalline Massifs: insights from low T thermochronology in the Aar Massif (Swiss Alps) 11.04.2019 Wien, Austria Nibourel Lukas; Herwegh-Züger Marco;
GNS Talks Individual talk Geodynamic and Structural Control on Orogenic Type Hydrothermal Systems 28.03.2019 Lower Hutt, Wellington, New Zealand Herwegh-Züger Marco;
Seminar Kyoto University Individual talk Late stage continent-continent collision Deformation processes and dynamics in case of the European Alps 05.03.2019 Kyoto, Japan Herwegh-Züger Marco;
International Symposium Crustal Dynamics Individual talk Fluid-triggered High-speed Deformation at Different Levels of the Continental crust: Evidences from Paleo-earthquake Proxies 02.03.2019 Kyoto, Japan Herwegh-Züger Marco;
SGM 2018 Talk given at a conference Neogene exhumation of the Aar Massif controlled by crustal thickening and paleogeography 01.08.2018 Bern, Switzerland Herwegh-Züger Marco; Nibourel Lukas;
EGU 2018 Talk given at a conference Tectonic exhumation of isothermal planes: a crustal-scale reconstruction based on RSCM thermometry data from the Aar massif, central Alps 12.04.2018 Vienna, Austria Nibourel Lukas; Herwegh-Züger Marco;
SGM 2017 Talk given at a conference Kinematic evolution of the Aar massif – new insights from the basement-cover contact in the Reuss Valley (Switzerland) 18.11.2017 Davos, Switzerland Nibourel Lukas; Herwegh-Züger Marco;
SGM 2016 Talk given at a conference The role of Permo-Carboniferous graben systems in the development of the external Alpine massifs – an example from the Central Aar massif (Faernigen syncline) 19.11.2016 Geneva, Switzerland Herwegh-Züger Marco; Nibourel Lukas;


Knowledge transfer events

Active participation

Title Type of contribution Date Place Persons involved
Vorträge Geologische Gesellschaft Zürich Talk 29.10.2018 Zürich, Switzerland Herwegh-Züger Marco; Kissling Eduard;


Communication with the public

Communication Title Media Place Year
Media relations: print media, online media Die Berner Alpen sind eine Knautschzone Berner Zeitung German-speaking Switzerland 2018
Media relations: print media, online media Die Alpen Lesen Horizonte Western Switzerland German-speaking Switzerland Italian-speaking Switzerland Rhaeto-Romanic Switzerland 2017

Associated projects

Number Title Start Funding scheme
121578 A 4D Model of Neogene Exhumation in the Central Helvetic Alps 01.10.2008 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)
162340 The role of sheet silicate-rich rocks during mountain building processes 01.01.2016 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)
109369 Rasterelektronenmikroskop Geologie Bern 01.02.2006 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)
149385 Structure and evolution of an antiformal nappe stack (Aar massif, Central Alps): Formation of mechanical anisotropies and their bearing on natural risks 01.10.2013 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)
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)
126560 The role of Polymineralic Rocks in the Evolution of Shear Zones 01.12.2009 Project funding (Div. I-III)
192124 Deformation of Fine-Grained Granitoid Fault Rocks Microstructures, Deformation Processes & Rheology 01.10.2020 Project funding (Div. I-III)
177026 Re-equiping the noble gas laboratory to perform state of the art science, University of Geneva 01.03.2018 R'EQUIP
119878 Deformation mechanisms in naturally and experimentally deformed minerals and rocks (8) 01.04.2008 Project funding (Div. I-III)

Abstract

In the current proposal we are asking for the second prolongation for a duration of 27 months. The past three years of the project can be divided in a first part, during which the PhD theses of R. Baumberger (PhD A) and P. Wehrens (PhD B) were terminated in spring 2015 and a second part, the start of a succeeding PhD thesis of L. Nibourel (PhD D). The PhD thesis of T. Buckingham (PhD C) will not be part of this proposal. PhD A and B focused their studies on the Central Aar massif (Haslital). PhD A successfully developed a workflow for (i) the area-wide consistent mapping of lineaments, (ii) unraveled the link between tectonic pre-conditioning and today’s morphological surface incisions and (iii) designed a workflow to use surface information of shear zones for the prediction of their continuation at depth in 3D models incorporating associated uncertainties. PhD B mainly dealt with the structo-mechanical evolution of the Aar massif. In this way, (iv) the kinematic evolution and deformation stages for the Grimsel region were established, (v) the interplay between brittle and ductile processes during mid-crustal deformation was unraveled and (vi) K-Ar dating was applied to obtain age constraints on the timing of the different deformation processes/episodes. Additionally, (vii) E. Kissling, A. Berger and M. Herwegh developed a geodynamic model for the evolution of the Aar massif connecting mantle processes with physical responses in the crust and (viii) A. Berger and M. Herwegh investigated the role of the geometry of the former European passive continental margin on the inversion during Alpine orogeny. Along (i-viii) papers are either in the revision stage or close to submission. PhD student D started early 2015 and carried out extensive fieldwork and sampling campaigns in the Reuss valley region (Eastern Aar massif) and is currently working on data analysis and sample preparation. In the current proposal we are asking for a final extension of the current project for a duration of 27 months (fin de thèse of L. Nibourel). During this project period L. Nibourel will focus on three main tasks: (i) the structural and kinematic evolution of the Eastern Aar massif, (ii) the unraveling of the metamorphic and exhumation history and (iii) the link to recent seismic activity. For this purpose, different geothermometers and thermochronometers will be applied on the collected samples (i.e. Raman spectroscopy, U+Th/He in zircon) and accomplished by literature data (fission track data from zircon and apatite). Moreover, in close collaboration with the Schweizerischer Erdbebendienst (SED; T. Diehl and E. Kissling ETHZ) seismically active domains will be analysed and connected to fault structures explored in the field. Combining information on the spatial distribution of fault structures, their evolution and propagation in time and the sites of today’s seismic activity will provide new information on the deformation behavior in the middle to upper crust. This will be an important prerequisite to link the structural information with seismic hazard analysis. To close the gap, a last field campaign in summer 2017 will be necessary. In light of the Aar massif being the largest external massif of the Swiss Alps, M. Herwegh, A. Berger and E. Kissling will expand their investigations on the link between mantle processes and crustal response towards 3D combining different sections of surface/subsurface tectonics with seismic tomography. A comprehensive 3D model will be generated allowing deep insights into the evolution of the backbone of the Alps.
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