Triggering mechanisms and causative processes of Deep Seated Gravitational Slope Deformations (DSGSD) in alpine areas can trigger by several processes such as post-glacial debuttressing, earthquake-induced ground shaking or co-seismic surface faulting. Distinguishing between climatic and tectonically-driven factors for such slope deformations is challenging, since faults and fracture systems can play both an active and/or passive role in the initiation of slope processes. Nevertheless this issue has major implications both in the reconstruction of the recent evolution of the landscape and in paleoseismological studies. Here we present a study on a Deep Seated Gravitational Slope Deformation (DSGSD) located in the Cavargna Valley, N Italy. The deformed slope presents a moderate relief with an elevation drop of ca. 650 meters (from 1750 to 1100 m a.s.l.), is characterized by a typical concave-convex profile and shows morpho-features commonly caused by deep-seated slope movements (e.g., Agliardi et al. 2001; Gutierrez-Santolalla et al. 2005). The DSGSD area and its surrounding was not under extensive glaciations conditions. In fact: (i) The main ice cap which covered the alpine valley during Pleistocene reached an elevation of ca. 950 m during Latl Glacial Maximum, (ii) glacial and periglacial erosional features suggest that only small cirque glaciers locally occupied higher elevations, above 1700 m a.s.l. (e.g., Bini et al. 2009). The study area experienced a considerable regional deformation due to post glacial rebound: an uplift of ca. 90 m, reached mainly between 21 kyr and 13 kyr BP (e.g., Norton & Hampel 2010). The rate of the uplift due to post-glacial isostasy decreases with time and can be considered negligible. The integrated approach of this study, including morpho-structural analysis, geologic field survey, ERT geophysical survey, a paleoseismological approach applied to the deformed slope, 14C dating and a detailed pedosedimentary analysis on trench infilling enable us to date the onset of the DSGSD to the ca. 2700 BP. We then consider different possible causative/triggering mechanisms, taking into account alternative scenarios consistent with the timing and characteristics of the described slope deformation.
Why did the slope at Cavargna Valley Sackung (N Italy) start moving? Preliminary results on causative/triggering mechanisms
LIVIO, FRANZ;CASTELLETTI, LANFREDO;
2014-01-01
Abstract
Triggering mechanisms and causative processes of Deep Seated Gravitational Slope Deformations (DSGSD) in alpine areas can trigger by several processes such as post-glacial debuttressing, earthquake-induced ground shaking or co-seismic surface faulting. Distinguishing between climatic and tectonically-driven factors for such slope deformations is challenging, since faults and fracture systems can play both an active and/or passive role in the initiation of slope processes. Nevertheless this issue has major implications both in the reconstruction of the recent evolution of the landscape and in paleoseismological studies. Here we present a study on a Deep Seated Gravitational Slope Deformation (DSGSD) located in the Cavargna Valley, N Italy. The deformed slope presents a moderate relief with an elevation drop of ca. 650 meters (from 1750 to 1100 m a.s.l.), is characterized by a typical concave-convex profile and shows morpho-features commonly caused by deep-seated slope movements (e.g., Agliardi et al. 2001; Gutierrez-Santolalla et al. 2005). The DSGSD area and its surrounding was not under extensive glaciations conditions. In fact: (i) The main ice cap which covered the alpine valley during Pleistocene reached an elevation of ca. 950 m during Latl Glacial Maximum, (ii) glacial and periglacial erosional features suggest that only small cirque glaciers locally occupied higher elevations, above 1700 m a.s.l. (e.g., Bini et al. 2009). The study area experienced a considerable regional deformation due to post glacial rebound: an uplift of ca. 90 m, reached mainly between 21 kyr and 13 kyr BP (e.g., Norton & Hampel 2010). The rate of the uplift due to post-glacial isostasy decreases with time and can be considered negligible. The integrated approach of this study, including morpho-structural analysis, geologic field survey, ERT geophysical survey, a paleoseismological approach applied to the deformed slope, 14C dating and a detailed pedosedimentary analysis on trench infilling enable us to date the onset of the DSGSD to the ca. 2700 BP. We then consider different possible causative/triggering mechanisms, taking into account alternative scenarios consistent with the timing and characteristics of the described slope deformation.
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