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Master Thesis

Grandes ruptures de versants rocheux dans la vallée de Chamonix : origines et évolutions

Abstract : Deep-seated gravitational slope deformations have slow displacement rates and can reach the size of an entire slope section. They are combined with morphostructures typical of the ground deformations taking place at the surface and at depth. Such a structure has been discovered in the Aiguilles Rouges massif overlooking the town of Argentière in Haute-Savoie (upper Arve valley). We studied a pluri-kilometers long failure divided into two distinct rock crevasses. Two vertical profiles along the NE top scarps (11 samples) were carried out to define the chronology (both the initiation and evolution) of the slope failure using 10Be (beryllium-10) surface exposure dating. Glacially polished surfaces cut by the SW gravitational scarps were also sampled to determine glacial retreat timing as well as to constrain the pre-exposure 10Be inheritance. A total of twenty samples were collected in the valley and analyzed. Other tools and methods allowed us to reach a global understanding of the rock slope failure of the Aiguilles Rouges. We have shown that the exposure ages of the glacial morphologies are between 13.9 ± 0.8 ka et 18.9 ± 0.6 ka. For the gravitational morphologies, we obtain younger ages between 0.5 ± 0.1 et 2.1 ± 0.4 ka. The time lag between the glacial retreat and the opening of the crevasse indicates a delay in the effects of the glacial debuttressing but does not exclude this factor as being partly responsible for the event. The close proximity with the active fault of La Rémuaz could be another hypothesis for the initiation of the rock slope failure. Young ages of gravitational morphologies agree with the ground displacement rates of a few millimeters per year estimated by InSAR time series between 2014 and 2018 and are a reminder of the hazard the structure poses to the town downstream.
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Master Thesis
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https://dumas.ccsd.cnrs.fr/dumas-03358272
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Submitted on : Wednesday, September 29, 2021 - 11:45:55 AM
Last modification on : Wednesday, April 13, 2022 - 3:40:44 AM

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  • HAL Id : dumas-03358272, version 1

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Léa Courtial-Manent. Grandes ruptures de versants rocheux dans la vallée de Chamonix : origines et évolutions. Géographie. 2021. ⟨dumas-03358272⟩

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