The Teggiolo zone: a key to the Helvetic-Penninic connection (stratigraphy and tectonics in the Val Bavona, Ticino, Central Alps)

The Teggiolo zone is the sedimentary cover of the Antigorio nappe, one of the lowest tectonic units of the Penninic Central Alps. Detailed mapping, stratigraphic and structural analyses, and comparisons with less metamorphic series in several well-studied domains of the Alps, provide a new stratigraphic interpretation. The Teggiolo zone is comprised of several sedimentary cycles, separated by erosive surfaces and large stratigraphic gaps, which cover the time span from Triassic to Eocene. At Mid-Jurassic times it appears as an uplifted, partially emergent block, marking the southern limit of the main Helvetic basin (the Limiting South-Helvetic Rise LSHR). The main mass of the Teggiolo calcschists, whose base truncates the Triassic-Jurassic cycles and can erode the Antigorio basement, consists of fine-grained clastic sediments analogous to the deep-water flyschoid deposits of Late Cretaceous to Eocene age in the North-Penninic (or Valais s.l.) basins. Thus the Antigorio-Teggiolo domain occupies a crucial paleogeographic position, on the boundary between the Helvetic and Penninic realms: from Triassic to Early Cretaceous its affinity is with the Helvetic; at the end of Cretaceous it is incorporated into the North-Penninic basins. An unexpected result is the discovery of the important role played by complex formations of wildflysch type at the top of the Teggiolo zone. They contain blocks of various sizes. According to their nature, three different associations are distinguished that have specific vertical and lateral distributions. These blocks give clues to the existence of territories that have disappeared from the present-day level of observation and impose constraints on the kinematics of early folding and embryonic nappe emplacement. Tectonics produced several phases of superimposed folds and schistosities, more in the metasediments than in the gneissic basement. Older deformations that predate the amplification of the frontal hinge of the nappe generated the dominant schistosity and the km-wide Vanzèla isoclinal fol

Identificación y análisis de riesgos de deslizamientos desde una perspectiva interdisciplinaria: ventajas, oportunidades y desafíos. El caso de Uspantán, Guatemala

Las ciencias territoriales se confrontan cada vez más a objetos de estudio que benefician de un enfoque que combina disciplinas y conocimientos. Con la creciente importancia de la cuestión ambiental, la necesidad de la interdisciplinariedad se plantea en muchos proyectos de investigación, pero también en la búsqueda de soluciones aplicables en el campo. Es necesario desarrollar conocimientos y prácticas que integren aspectos tanto materiales como no materiales, para dar cuenta de la complejidad de los objetos que se encuentran en la interfaz humano-naturaleza. El propósito de nuestro trabajo es describir y analizar las formas en que se construye un enfoque de investigación interdisciplinar más amplio asociando las ciencias sociales y las ciencias naturales para identificar y evaluar los riesgos de desastres. Proponemos abrir la discusión a través de un ejemplo concreto de trabajo de identificación y evaluación de riesgos en el municipio de San Miguel Uspantán, Quiché, Guatemala. Durante esta misión de investigación, los autores de este artículo, un geólogo y una geógrafa/politóloga se encontraron trabajando juntos bajo un objeto común de estudio: los deslizamientos de terreno. La colaboración nos obligó a comparar nuestros métodos e integrar nuevas perspectivas: el geólogo incorporando el conocimiento de las poblaciones en su análisis y la científica social descubriendo los aspectos físicos del riesgo. Después de esta experiencia, decidimos valorar el aprendizaje de nuestros intercambios y presentar un enfoque interdisciplinario que concilie las contribuciones que las diversas ciencias pueden ofrecer a la hora de abordar el objeto de riesgo. Explicamos el enfoque metodológico utilizado, los problemas encontrados durante la ejecución, así como las ventajas que descubrimos durante y después de la implementación del trabajo de investigación.Fil: Fernandez, Manuela Teresa. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; ArgentinaFil: Matasci, Battista. Universite de Lausanne; Suiz

Stability assessment and evolution of the West face of the Drus (3733 m a.s.l., Mont Blanc massif)

International audienc

Discrete fracture network modelling using Coltop3D for rockfall potential assessment at Glacier Point, Yosemite Valley

We performed regional and site-specific structural studies of the cliff below Glacier Point in Yosemite Valley using Coltop 3D software analyses of previous Aerial Laser Scanning (ALS) and new local Terrestrial Laser Scanning (TLS) data. Coltop3D computes the spatial orientation (dip direction and dip) of each point within a point cloud with respect to its neighboring points. Coltop3D attributes a unique RGB color to each spatial orientation, allowing accurate identification of the major discontinuity sets. It is thus possible to quickly obtain a great number of measurements for joint orientations responsible for shaping a rock cliff. We performed manual measurements of fracture spacing and trace length on the point clouds using Polyworks (Innovmetric). The 3D view of the TLS dataset was compared to high-resolution photographs to accurately follow the discontinuity traces. We used these input parameters to generate a discrete fracture network (DFN) model of the fractured rock mass at Glacier point cliff. The model was calibrated to match field observations. Several possible DFN models of the site were generated. These DFN were then used to assess rockfall potential on specific sections of the Glacier Point cliff

The three-stage rock failure dynamics of the Drus (Mont Blanc massif, France) since the June 2005 large event

International audienc

Assessing rockfall susceptibility in steep and overhanging slopes using three-dimensional analysis of failure mechanisms.

Rockfalls strongly influence the evolution of steep rocky landscapes and represent a significant hazard in mountainous areas. Defining the most probable future rockfall source areas is of primary importance for both geomorphological investigations and hazard assessment. Thus, a need exists to understand which areas of a steep cliff are more likely to be affected by a rockfall. An important analytical gap exists between regional rockfall susceptibility studies and block-specific geomechanical calculations. Here we present methods for quantifying rockfall susceptibility at the cliff scale, which is suitable for sub-regional hazard assessment (hundreds to thousands of square meters). Our methods use three-dimensional point clouds acquired by terrestrial laser scanning to quantify the fracture patterns and compute failure mechanisms for planar, wedge, and toppling failures on vertical and overhanging rock walls. As a part of this work, we developed a rockfall susceptibility index for each type of failure mechanism according to the interaction between the discontinuities and the local cliff orientation. The susceptibility for slope parallel exfoliation-type failures, which are generally hard to identify, is partly captured by planar and toppling susceptibility indexes. We tested the methods for detecting the most susceptible rockfall source areas on two famously steep landscapes, Yosemite Valley (California, USA) and the Drus in the Mont-Blanc massif (France). Our rockfall susceptibility models show good correspondence with active rockfall sources. The methods offer new tools for investigating rockfall hazard and improving our understanding of rockfall processes

Morphological evolution and stability modeling of the West face of the Drus (Mont Blanc).

International audienc

11 years of ground-based LiDAR monitoring in the west face of the Drus (Mont-Blanc massif, France), after the little rock avalanche of June 2005.

International audienc

Highly energetic rockfalls: back analysis of the 2015 event from the Mel de la Niva, Switzerland

International audienceProcess-based rockfall simulation models attempt to better emulate rockfall dynamics to different degrees. As no model is perfect, their development is often accompanied and validated by the valuable collection of rockfall databases covering a range of site geometries, rock masses, velocities, and related energies that the models are designed for. Additionally, such rockfall data can serve as a base for assessing the model's sensitivity to different parameters, evaluating their predictability and helping calibrate the model's parameters from back calculation and analyses. As the involved rock volumes/masses increase, the complexity of conducting field-test experiments to build up rockfall databases increases to a point where such experiments become impracticable. To the author's knowledge, none have reconstructed rockfall data in 3D from real events involving block fragments of approximately 500 metric tons. A back analysis of the 2015 Mel de la Niva rockfall event is performed in this paper, contributing to a novel documentation in terms of kinetic energy values, bounce heights, velocities, and 3D lateral deviations of these rare events involving block fragments of approximately 200 m 3. Rockfall simulations are then performed on a "per-impact" basis to illustrate how the reconstructed data from the site can be used to validate results from simulation models