Publications des scientifiques de l'IRD

Schwartz S., Zerathe S., Jongmans D., Baillet L., Carcaillet J., Audin Laurence, Dumont T., Bourles D., Braucher R., Lebrouc V. (2017). Cosmic ray exposure dating on the large landslide of Sechilienne (Western Alps) : a synthesis to constrain slope evolution. Geomorphology, 278, p. 329-344. ISSN 0169-555X.

Titre du document
Cosmic ray exposure dating on the large landslide of Sechilienne (Western Alps) : a synthesis to constrain slope evolution
Année de publication
2017
Type de document
Article référencé dans le Web of Science WOS:000392555000024
Auteurs
Schwartz S., Zerathe S., Jongmans D., Baillet L., Carcaillet J., Audin Laurence, Dumont T., Bourles D., Braucher R., Lebrouc V.
Source
Geomorphology, 2017, 278, p. 329-344 ISSN 0169-555X
The 60 x 10(6) m(3) Sechilienne landslide (Belledonne Massif, Western Alps) is located on the right bank of the East-West trending Romanche valley which is shaped by glacial and alluvial processes during the Quaternary. Its head scarp (>35 m high) was dated by Le Roux et al. (2009) using the cosmic ray exposure (CRE) method. Even though these previous results revealed that the initiation of the instability occurred several thousand years after ice down-wastage in the valley, the internal landslide evolution is not constrained. In this paper, we provide 63 additional Be-10 samples collected from the internal scarps and the main scarp, as well as on glacially polished rock surfaces. The aim is to constrain the global landslide kinematics (internal and head scarps) and its relationship with glacier retreat. Results from glacially polished surfaces point out that complex shielding processes (relict moraines, soil deposits and seasonal snow cover) might have affected rock dating. Despite scattering of the resulting ages, the dataset shows that the glacial retreat was achieved between 17.5 and 13 ka. Exposure ages obtained on gravitational scarps reveal that the landslide initiation occurred 8 to 6 ka ago. From the initiation until 2 ka the gravitational kinematics was slow (similar to 2 mm" year(-1)) and focused around the head scarp, leading to a general slope subsidence. After 2 ka, the exposure rates increased significantly (similar to 8 min. year(-1)) with the development of pervasive internal deformation of the landslide mass. This new scenario for the 58chilienne slope reflects a progressive rock-slope weakening since 8 ka, associated with a continuous activity of a deep-seated surface failure.
Plan de classement
Géologie et formations superficielles [064]
Description Géographique
FRANCE ; ALPES
Localisation
Fonds IRD [F B010068925]
Identifiant IRD
fdi:010068925
Contact