Hazard investigation of the Portillo Rock Avalanche site, central Andes, Chile, using an integrated field mapping and numerical modelling approach

Welkner, Daniela; Eberhardt, E.; Hermanns, Reginald L.

doi:10.1016/j.enggeo.2010.05.007

Cited by 43 publications

(31 citation statements)

References 40 publications

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“…This result could possibly explain the gravimetrically estimated thickness of up to about 400 m accumulated chaotic material of the Mesón Alto deposit (Marangunic and Thiele, 1971). This interpretation is also supported by the at least 300 m water depth of the Laguna Negra Lake (Aguas Andinas, personal comunication, 2012) and the Antinao and Gosse (2009) dating of surface blocks, which coincide with similar rock slide dates in Portillo, Aconcagua Valley (32.8°S, Welkner et al, 2010) that may suggest high landslide activity between 4 and 5 ka in the region.…”

Section: Discussionsupporting

confidence: 55%

Nuevas observaciones sobre el origen del Depósito Mesón Alto, Valle del Yeso, Chile central: un depósito compuesto de procesos glaciares y de remoción en masa?

Deckart

Pinochet

Sepúlveda

et al. 2014

Andgeo

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ABSTRACT. The Mesón Alto chaotic deposit, located in the Main Cordillera at about 33°40'S, is an important landform with a volume of ca. 4.5 km 3 unconsolidated material deposited downstream of the Yeso Dam in the Yeso Valley, Río Maipo drainage basin. Historical work related this large deposit to a glacial origin whereas later on, it was assigned to a megalandslide that originated in the Cerro Mesón Alto Massif. First results of integrated fieldwork along with petrographic and geochemical laboratory work on granitoid blocks from five different portions of the deposit, compared with the major outcropping intrusive units in the neighbourhood (La Gloria Pluton, Cerro Mesón Alto Massif and Cerro Aparejo Intrusion) point to a landslide origin of the surface blocks. The results suggest that granitoid fragments of the deposit most likely belong to the Cerro Mesón Alto Massif, the proposed source of the rock avalanche. However, morphometric parameters and field observations support the idea of a rock avalanche deposited on top of glacial material. Therefore, the Mesón Alto deposit should be assigned to a composite origin. Confirmation of a post-glacial, large volume rock avalanche in a strategic area for existent infrastructure for Santiago water supply and ongoing energy projects is fundamental for a correct hazard and risk assessment of the region. Keywords: Mesón Alto deposit, Landslide, Glacial material, Granitoids, Yeso Valley, Geological hazard. RESUMEN. Nuevas observaciones sobre el origen del Depósito Mesón Alto, Valle del Yeso, Chile central: un depósito compuesto de procesos glaciares y de remoción en masa? El depósito caótico de Mesón Alto, localizado en la cordillera Principal a los aproximadamente 33°40'S, es un rasgo morfológico con un volumen de 4,5 km 3 de material no consolidado depositado aguas abajo del embalse El Yeso, en el valle del río Yeso, cuenca del río Maipo. Históricamente, este enorme depósito se relacionó con un origen glacial, mientras que más tarde fue asignado a un megadeslizamiento proveniente del macizo Cerro Mesón Alto. Los primeros resultados de un trabajo integrado de campo, análisis petrológico y geoquímico de bloques de granitoides de diferentes sectores del depósito, comparados con datos de las mayores unidades intrusivas de la zona (el plutón La Gloria, el macizo Cerro Mesón Alto y el intrusivo Cerro Aparejo) apuntan a un depósito compuesto por bloques superficiales de procedencia de remoción en masa. Los resultados sugieren que los granitoides del depósito provienen del sector Cerro Mesón Alto. Sin embargo, observaciones de campo y parámetros morfométricos soportan la idea de una avalancha de rocas emplazada sobre material glacial. En consecuencia, se asignaría un origen compuesto al depósito del Mesón Alto. La confirmación de una remoción en masa postglacial de gran volumen en un área con infraestructura crítica para suministro de agua de Santiago y donde se emplazan proyectos energéticos en desarrollo es clave para realizar correctas evaluaciones del peligro y riesgo geol...

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Section: Discussionsupporting

confidence: 55%

Nuevas observaciones sobre el origen del Depósito Mesón Alto, Valle del Yeso, Chile central: un depósito compuesto de procesos glaciares y de remoción en masa?

Deckart

Pinochet

Sepúlveda

et al. 2014

Andgeo

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“…Applying the relationship of distance v. magnitude of triggering earthquakes given by Keefer (1984) all rock slope failures, except the older debris-ice avalanche deposit in the Las Cuevas valley, might have been triggered by two earthquakes within the study area that had a magnitude 6 or higher. Seismic triggering is also proposed as a possible cause for rock avalanches at Laguna del Inca (Welkner et al 2010) and elsewhere in Chile close to our study area (Sepúlveda et al 2012).…”

Section: Possible Causes For Temporal Distribution Of Slope Failures mentioning

confidence: 99%

“…Excellent summaries of this method were published by Lal (1991), Cerling & Craig (1994), Kurz & Brooke (1994) and Gosse & Phillips (2001) and the method has been repeatedly used for dating mass movements (e.g. Ballantyne et al 1998;Hermanns et al 2001Hermanns et al , 2004Bigot Cormier et al 2005;Dortch et al 2009;Antinao & Gosse 2009;Welkner et al 2010;Blais-Stevens et al 2011, and references therein). Here, we briefly review only the methods of sampling, principles of the method and correction factors, as they require some special considerations.…”

Section: Mineralogical Analysesmentioning

confidence: 99%

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³⁶ Cl terrestrial cosmogenic nuclide dating suggests Late Pleistocene to Early Holocene mass movements on the south face of Aconcagua mountain and in the Las Cuevas–Horcones valleys, Central Andes, Argentina

Hermanns

Fauqué

Wilson

2014

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The morphology, sedimentology and mineralogy of deposits that previously had been associated with glacial advances (the Penitentes, Horcones and Almacenes drifts) were reinvestigated and dated using the terrestrial cosmogenic nuclide (TCN) 36 Cl. These results indicate that the deposits previously associated with the Horcones and Almacenes drifts are actually deposits of a rock slope failure from the southern face of Aconcagua mountain forming a debris-ice avalanche that were deposited 10 490 + 1120 years ago, while the deposits previously associated with the Penitentes drift is a rock avalanche from the Mario Ardito valley that deposited in the Las Cuevas valley 11 220 + 2020 years ago. Earlier in the Late Pleistocene a further rock-ice avalanche sourced from Aconcagua mountain and deposited in the Las Cuevas valley, predating related lake sediments with a calibrated 14 C age of 14 798-13 886 years and travertine deposits with a U-series age of 24 200 + 2000 years. In addition, three further rock-avalanche deposits were dated that sourced from Tolosa mountain, having 36 Cl mean ages of 14 740 + 1950 years, 12 090 + 1550 years and 9030 + 1410 years. No deposits of massive rock slope failures were found in those parts of the valleys that date younger, suggesting that climatic conditions at the transition from the Late Pleistocene to the Holocene, that were different from today's, caused the slopes to fail. Alternatively, the rock slope failures could have been seismically triggered. We suggest that the slope failures at the southern face of Aconcagua mountain have caused or contributed to a reorganization of glacial ice flow from Aconcagua mountain that might ultimately be the cause of the surging behaviour of the Horcones Inferior glacier today. Our results indicate that the glacial stratigraphy of this part of the Central Andes is still poorly understood and requires detailed mapping and dating.

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“…Detailed integrative site studies (e.g., Welkner et al, 2010;Böhme et al, 2013;Booth et al, 2014) increase our knowledge of the complex processes of rock-slope failures and enable us to link the mechanism and amount of deformation to the geomorphological surface expression. Those studies combine classic geomorphological and geomechanical field mapping with various deformation monitoring techniques (e.g., Oppikofer et al, 2009;Booth et al, 2013;Wolter et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Gravitational reactivation of a pre-existing post-Caledonian fault system: the deep-seated gravitational slope deformation at Middagstinden, western Norway

Schleier¹,

Hermanns²,

Krieger³

et al. 2016

NJG

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The origin of linear features in mountain terrain that form distinct vertical steps is generally not obvious and has been discussed to be related to either tectonic faulting or gravitational slope deformation. A strong geomorphological lineament running oblique to the slope and forming a convex step in the topography is located on the mountain Middagstinden just west of the valley Innfjorddalen, western Norway. In previous studies this lineament has been interpreted to be the surface expression of a Holocene reverse fault previously called the Berill Fault, indicating the first evidence for neotectonic faulting in southern Norway. Now, detailed structural field mapping has revealed the existence of a set of normal fault planes striking subparallel to this lineament and to the main extensional faults associated with the Caledonian collapse. Electric resistivity tomography (ERT) profiles of the valley floor and excavated parallel trenches confirm the regional extent of the fault, but the sediments observed in the trenches do not indicate any Holocene activity. Furthermore, the lineament is a limiting structure of a large rock-slope instability. Kinematic feasibility tests based on structural field measurements indicate wedge failure along the intersection of the fault and the local foliation. However, this intersection line is not exposed on the slope surface. Hence, simple wedge or translational sliding along the slope is not feasible, except in its uppermost part. Both the displacements observed by differential global navigation satellite system (dGNSS) surveys and the geomorphological characteristics, for instance, counterscarps, superficial mass movements, coherent slide blocks and slope bulging, indicate complex deformation mechanisms. The deformation evidently changed along the slope in type and degree including planar sliding in the uppermost part, potentially large wedge sliding in the middle part, and incremental internal deformation in a direction out of the slope in the lower part. The complex kinematics and geomorphological characteristics account for the definition of a deep-seated gravitational slope deformation (DSGSD). Furthermore, the findings reveal that the geomorphological lineament is of gravitational origin and not neotectonic. It has formed by a reactivation of the pre-existing, Caledonian, normal fault system due to the DSGSD, and is hence an example of pseudotectonics ('apparent reverse fault').

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Hazard investigation of the Portillo Rock Avalanche site, central Andes, Chile, using an integrated field mapping and numerical modelling approach

Cited by 43 publications

References 40 publications

Nuevas observaciones sobre el origen del Depósito Mesón Alto, Valle del Yeso, Chile central: un depósito compuesto de procesos glaciares y de remoción en masa?

Nuevas observaciones sobre el origen del Depósito Mesón Alto, Valle del Yeso, Chile central: un depósito compuesto de procesos glaciares y de remoción en masa?

³⁶ Cl terrestrial cosmogenic nuclide dating suggests Late Pleistocene to Early Holocene mass movements on the south face of Aconcagua mountain and in the Las Cuevas–Horcones valleys, Central Andes, Argentina

Gravitational reactivation of a pre-existing post-Caledonian fault system: the deep-seated gravitational slope deformation at Middagstinden, western Norway

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Hazard investigation of the Portillo Rock Avalanche site, central Andes, Chile, using an integrated field mapping and numerical modelling approach

Cited by 43 publications

References 40 publications

Nuevas observaciones sobre el origen del Depósito Mesón Alto, Valle del Yeso, Chile central: un depósito compuesto de procesos glaciares y de remoción en masa?

Nuevas observaciones sobre el origen del Depósito Mesón Alto, Valle del Yeso, Chile central: un depósito compuesto de procesos glaciares y de remoción en masa?

36 Cl terrestrial cosmogenic nuclide dating suggests Late Pleistocene to Early Holocene mass movements on the south face of Aconcagua mountain and in the Las Cuevas–Horcones valleys, Central Andes, Argentina

Gravitational reactivation of a pre-existing post-Caledonian fault system: the deep-seated gravitational slope deformation at Middagstinden, western Norway

Contact Info

Product

Resources

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³⁶ Cl terrestrial cosmogenic nuclide dating suggests Late Pleistocene to Early Holocene mass movements on the south face of Aconcagua mountain and in the Las Cuevas–Horcones valleys, Central Andes, Argentina