Title
Evolution stages of large deep-seated landslides at the front of a subalpine meridional chain (Maritime-Alps, France)
Date Issued
01 February 2012
Access level
metadata only access
Resource Type
journal article
Author(s)
Lebourg T.
Universidad de Nice Sophia-Antipolis
Abstract
Studying long term-evolution of gravitational slope evolution is a key to understanding deep-seated landslide processes. This paper deals with three large Deep-Seated Landslides (DSLs) at a front of a subalpine meridional chain, on the "La Marbrière" slope near the town of Grasse (Alpes-Maritimes, France). The geological framework controlling the stability and morphology of the DSLs is associated with thick and tamped Triassic layers of mudstone with gypsum overlain by highly faulted Jurassic limestone. Gravitational deformation affects the entire slope, involving a movement of about 1.1×108m3 of rock material. It creates large disturbances in landscape morphology, such as scarps, counter-slope scarps, trenches and other typical gravitational morpho-structures. Geomorphological mapping coupled with deep electrical resistivity tomography (ERT) reveals a strong correlation between these morpho-structures and inherited brittle tectonic features. This observation relies on spatial and geometrical relations (on the surface and at the depth of more than 150m, checked by ERT) between the most persistent fault and the gravitational morpho-structures. The specific distribution of the morpho-structures on the basis of their morphological typologies and variations in the stage of evolution of three DSLs provides an interpretation of their kinematics during the last 400ka. It appears that soft substratums combined with inherited persistent anisotropies are key factors in the development of the DSLs. Indeed, outflow of mudstone due to the lithostatic pressure imposed by individual limestone compartments has led to general slope subsidence. Then, a progressive toppling of a rock mass may have led to the catastrophic rock collapse along bedding planes. The evolution of the DSLs can be divided into three distinct stages represented by three zones: a young collapse stage (zone 1), a pre-collapse stage (zone 2) and an old mature stage (> 400. ka, zone 3). As the DSLs occur on the same slope and in the same geological context, this area offers interesting perspectives for understanding factors controlling the long-term gravitational evolution of slopes. © 2011 Elsevier B.V.
Start page
390
End page
403
Volume
138
Issue
1
Language
English
OCDE Knowledge area
Geología
Scopus EID
2-s2.0-82855161268
Source
Geomorphology
ISSN of the container
0169555X
Sponsor(s)
This work is supported by the PACA Region and the SCOT'OUEST Alpes-Maritimes . The authors gratefully acknowledge Sofiya Leonova, Richard Bringtown and Sarah Melick for their contribution in editing the manuscript. The authors would like to thank the reviewers for their fruitful comments.
Sources of information: Directorio de Producción Científica Scopus