Florian Humair

From the source area to the deposit: Collapse, fragmentation, and propagation of the Frank Slide

The combination of structural data from the source area and descriptive data from the deposit’s carapace, as well as remote sensing and statistical analysis, allows a better understanding of the collapse, fragmentation, and propagation processes of the Frank Slide rock avalanche. The in situ observed conservation of the stratigraphic sequence of the Turtle Mountain anticline’s normal limb in the deposit is interpreted as the consequence of the collapse mode, involving simple shearing of the mass accompanied by a rotational movement, i.e., a “simple shear” parallel to the topography, and a breakage of the hinge, followed by overthrusting of the normal limb on the inverse limb. Coherence between the block size distributions of the source area and the deposit carapace is interpreted as a demonstration of the primary control of preexisting fracturing on the fragmentation processes. Remote-sensing indexes allow us to uncover a priori hidden morphological features preserved on the surface of the deposit, i.e., longitudinal and compressional features, as well as lobes. Their location on the carapace provides evidence of lateral heterogeneity in the propagation, highlighted by three different types of propagation behaviors. This comprehensive study not only provides elements that contribute to an understanding of the Frank Slide rock avalanche, but it also provides insight into essential parameters to take into account in further modeling of these types of phenomena.

Geological mapping and fold modeling using Terrestrial Laser Scanning point clouds: application to the Dents-du-Midi limestone massif (Switzerland)

Abstract Geological mapping in vertical rock faces is extremely challenging because of access difficulties and limited possibilities of recognition, localization and measurement of features at large distance with traditional tools. Moreover, vertical areas can be of primary interest since they often display good quality outcrops and relevant geological information. This study focuses on the detailed remote identification of rock types and fold structures using intensity values acquired by Terrestrial Laser Scanning. A correction of the intensity is proposed proportional to the square of the range and to the cosine of the incidence angle. Furthermore, two methods of remote lithological mapping in 3D have been developed using a manual and a semi-automatic approach. Both delivered good results that are consistent with the spatial distribution of rock-types and allowed us to generate an accurate 3D lithological map of Dents-du-Midi massif (Valais, Swiss Alps). The bedding orientation near the hinge of a Km scale fold was measured on LiDAR data in order to define the fold axis. Then, the result was used to build a model of the hinge in 3D.

Inventory of Rock Slope Deformations Affecting Folded Sedimentary Layers in Moderate Relief Context: The Case of the Livingstone Range Anticlinorium, AB, Canada

This contribution investigates the distribution of rock slope deformations (RSD) and their relationships with tectonic structures, lithological and topographic contexts. This is performed in a moderate relief context (1,100–2,500 masl.) affected by thin-skin tectonic. The proposed inventory, along the Livingstone range anticlinorium (LRA), contains 160 gravitational events that are spatially clustered in four areas. The thrust-folds properties (density, geometry and lithology) and the local relief appear to primary influence the development of RSD in this context.