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Structure and genesis of the Thabor rock glacier (Northern French Alps) determined from morphological and ground-penetrating radar surveys

Sébastien Monnier 1 Christian Camerlynck 2 Fayçal Rejiba 2 Christophe Kinnard 3 Thierry Feuillet 4 Amine Dhemaied 5, 6
4 LETG - Nantes - Littoral, Environnement, Télédétection, Géomatique
CNRS - Centre National de la Recherche Scientifique : UMR6554, EPHE - École pratique des hautes études, UNICAEN - Université de Caen Normandie, UBO - Université de Brest, UR2 - Université de Rennes 2, IGARUN - Institut de Géographie et d'Aménagement
6 cermes - Géotechnique
navier umr 8205 - Laboratoire Navier
Abstract : Landform analysis and ground-penetrating radar (GPR) were used to investigate the Thabor rock glacier, in the Northern French Alps. The surface features of the rock glacier were classified and described, with emphasis on massive ice exposures. The retreat of the former Thabor glacier since the Little Ice Age (LIA) was documented through an analysis of historical sources, and recent movements of the rock glacier were inferred from orthophoto-based measurements. Two-dimensional (2-D) models of the radar wave velocity were derived from the raw GPR data, using the numerous diffraction hyperbolae for local determinations of the velocity and kriging interpolation techniques. Subsequently, the profiles were migrated through a 2-D Kirchhoff migration method using the interpolated velocities. The 2-D velocity models exhibit pronounced spatial variations and, in several locations, high values (> 0.15 m ns−1) potentially corresponding to massive ice. On the other hand, while the migrated profiles show numerous layers, the internal stratigraphy of the rock glacier is dominated by a few prominent internal boundaries. The integration of morphology, radar wave velocity, and internal stratigraphy allowed us to identify the main structural units of the rock glacier as well as to explain its genesis: the rock glacier was formed by the imbrication of a massive ice core, originating from the retreat of the former Thabor glacier since the LIA, into pre-existing glacial deposits.
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https://hal-normandie-univ.archives-ouvertes.fr/hal-01740096
Contributor : Fayçal Rejiba <>
Submitted on : Wednesday, March 21, 2018 - 3:48:49 PM
Last modification on : Thursday, September 24, 2020 - 4:00:35 PM

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Sébastien Monnier, Christian Camerlynck, Fayçal Rejiba, Christophe Kinnard, Thierry Feuillet, et al.. Structure and genesis of the Thabor rock glacier (Northern French Alps) determined from morphological and ground-penetrating radar surveys. Geomorphology, Elsevier, 2011, 134 (3-4), pp.269-279. ⟨10.1016/j.geomorph.2011.07.004⟩. ⟨hal-01740096⟩

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