Abstract

DEL VALLE ABASCAL, Liliana  and  GONZALEZ BONORINO, Gustavo. Sedimentacion coluvial e inestabilidad de laderas en los Andes de Tierra del Fuego. Rev. Asoc. Geol. Argent. [online]. 2015, vol.72, n.4, pp.470-481. ISSN 0004-4822.

The Fueguian Andes show steep slopes carved into friable rocks, a combination that favors debris production and instability of the colluvium. This paper analyzes the nature of the colluvium in a segment of the Fueguian Andes and evaluates the hazard of potential colluvial landslides. From the crest down to elevations of about 600 m a.s.l., firm rock is partially covered by a thin coarse-grained colluvium. At lower altitudes a Nothofagus forest covers the slopes, underlain by a sandy regolith. Part of this colluvium forms lobate sheets with evidence for solifluxion. Another part consists of talus cones that partly cover the sheet deposits and in some cases pierce the treeline, invading the forested slopes. Below the treeline develop elongated strips lacking trees, and in parts also regolith,that are interpreted a landslide scars. It is postulated that the lobate sheet deposits correspond to relict rock glaciers that were active in the last glaciation, before encroachment of the forest around 6 to 7 thousand years ago. The talus cones and the scars within the forest witness the action of raveling, snow avalanches and landslides, and developed after the forest had been implanted. Slope instability was evaluated employing the computer programs LISA and SINMAP. The results from both methods agree in indicating a moderate landslide hazard. Instability sites in the upper rocky slopes were mostly classified by SINMAP as occurring in unsaturated soil. This may mean that they were induced by snow avalanches and cryogenic processes, instead of an excess of pore water pressure.

Keywords : Landslides; LISA; SINMAP; Snow avalanches.

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