Unravelling the evolution of an Alpine to post-glacially active fault in the Swiss Alps

Ustaszewski, Michaela; Herwegh, Marco; McClymont, Alastair; Pfiffner, Othmar-Adrian; Pickering, Robyn; Preusser, Frank

doi:10.1016/j.jsg.2007.09.006

Cited by 13 publications

(9 citation statements)

References 39 publications

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“…An M ~6 earthquake would be strong enough to trigger landslides within an epicentral distance of up to 100 km. In our study region, the Gemmi fault is an active NW-SE trending strike-slip fault, with two instances of post-glacial reactivation dated using luminescence techniques at 8.7 ± 2.0 ka and 2.4 ± 0.5 ka (Ustaszewski et al, 2007). Macroseismicity in this area of Switzerland, however, is not generally restricted to known active faults, having a typically more distributed pattern (Ustaszewski and Pfiffner, 2008).…”

Section: Accepted Manuscriptmentioning

confidence: 85%

Two early Holocene rock avalanches in the Bernese Alps (Rinderhorn, Switzerland)

et al. 2016

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Section: Accepted Manuscriptmentioning

confidence: 85%

Two early Holocene rock avalanches in the Bernese Alps (Rinderhorn, Switzerland)

et al. 2016

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“…They have striking similarities with faults reported from the SW Aar Massif. According to Ustaszewski et al (2007), these offsets record evidence for episodic cycles of brittle deformation and fluid pulses that formed the veins and cataclasites over millions of years. In addition, these faults were considered to offset Quaternary sequences (Ustaszewski et al, 2007) as well.…”

Section: Youngest Structuresmentioning

confidence: 99%

Linking Alpine deformation in the Aar Massif basement and its cover units – the case of the Jungfrau–Eiger mountains (Central Alps, Switzerland)

et al. 2018

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Abstract. The northwest (NW) rim of the external Aar Massif was exhumed from ∼ 10 km depth to its present position at 4 km elevation above sea level during several Alpine deformation stages. Different models have been proposed for the timing and nature of these stages. Recently proposed exhumation models for the central, internal Aar Massif differ from the ones established in the covering Helvetic sedimentary units. By updating pre-existing maps and collecting structural data, a structural map and tectonic section were reconstructed. Those were interpreted together with microstructural data and peak metamorphic temperature estimates from collected samples to establish a framework suitable for both basement and cover. Deformation temperatures range between 250 and 330 °C, allowing for semi-brittle deformation in the basement rocks, while the calcite-dominated sedimentary rocks deform in a ductile manner at these conditions. Although field data allow to distinguish multiple deformation stages before and during Aar Massif's exhumation, all related structures formed under similar P, T conditions at the investigated NW rim. In particular, we find that the exhumation occurred during two stages of shearing in Aar Massif's basement, which induced in the sedimentary rocks first a phase of folding and then a period of thrusting, accompanied by the formation of a new foliation.

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“…Also the fault scarps running parallel to the SW-NE-trending Urseren and Tujetsch valleys (Jäckli 1951;Eckardt et al 1983;Persaud and Pfiffner 2004;Ustaszewski et al 2007;Ustaszewski and Pfiffner 2008) might not be of neotectonic origin but most probably represent post-glacial unloading and gravitational slope movements along pre-exiting tectonic faults.…”

Section: Hypothetical P-t Modelmentioning

confidence: 99%

Late Alpine brittle faulting in the Rotondo granite (Switzerland): deformation mechanisms and fault evolution

Lützenkirchen

Loew

2011

Swiss J Geosci

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The unlined Bedretto tunnel in the Central Swiss Alps has been used to investigate in detail the fault architecture and late Alpine brittle faulting processes in the Rotondo granite on macroscopic and microscopic scales. Brittle faults in the late Variscan Rotondo granite preferentially are situated within the extent of preexisting ductile shear zones. Only in relatively few cases the damage zone extends into or develops in the previously undeformed granite. Slickensides suggest a predominant (dextral) strike-slip movement along these steeply dipping and NE-SW-striking faults. Microstructures of these fault rocks illustrate a multi-stage retrograde deformation history from ductile to brittle conditions up to the cessation of fault activity. In addition these fabrics allow identifying cataclastic flow, fluid-assisted brecciation and chemical corrosive wear as important deformation mechanisms during this retrogressive deformation path. Based on the analysis of zeolite microfabrics (laumontite and stilbite; hydrated Ca-Al-and Na-Ca-Al-silicate, respectively) in fault breccias, cataclasites and open fractures we conclude, that the main phase of active brittle faulting started below 280°C and ceased ca. 14 Ma ago at temperatures slightly above 200°C. This corresponds to a depth of approx. 7 km.

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Unravelling the evolution of an Alpine to post-glacially active fault in the Swiss Alps

Cited by 13 publications

References 39 publications

Two early Holocene rock avalanches in the Bernese Alps (Rinderhorn, Switzerland)

Two early Holocene rock avalanches in the Bernese Alps (Rinderhorn, Switzerland)

Linking Alpine deformation in the Aar Massif basement and its cover units – the case of the Jungfrau–Eiger mountains (Central Alps, Switzerland)

Late Alpine brittle faulting in the Rotondo granite (Switzerland): deformation mechanisms and fault evolution

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