Triggering processes of deep-seated gravitational slope deformation (DSGSD) in an un-glaciated area of the Cavargna Valley (Central Southern Alps) during the Middle Holocene

Abstract

Triggering mechanisms and causative processes of deep-seated gravitational slope deformations (DSGSD) in Alpine and high mountain areas include, among others, post-glacial de-buttressing, earthquake-induced ground shaking, or co-seismic surface faulting. Distinguishing between climatic or tectonically driven factors is challenging since faults and fracture systems can play both an active and/or passive role in the process initiation. We applied an integrated approach, including morpho-structural analysis, geologic field survey, a paleoseismological approach applied to trenching, radiocarbon dating and detailed sedimentological analysis, to a DSGSD located in the Cavargna Valley (N Italy), an area that was never occupied by extensive ice tongues in the Upper Pleistocene and Holocene. We were able to document at least two phases of movement from the Middle Holocene onwards and related triggering factors. Thanks to the comparison with dated lacustrine turbidites in the Alpine Lakes, we argue a seismic triggering for the landslide onset, with a possible source located in southern Switzerland, close to the Insubric Line. The later evolution of the landslide was instead driven by climatic predisposing conditions (humid and cold), instead, corresponding to a phase of enhanced slope instability.

Topographic Changes, Surface Deformation and Movement Process before, during and after a Rotational Landslide

“…The sub-circular sliding surface of the landslide mass formed during the sliding process is one of the important signs of rotational movement [59]. Based on the mechanical properties of landslides [60][61][62][63], we think that the Lianluo landslide conformed to the stress state of circular rotation. The internal reason for the displacement and deformation of the landslide body is that its mechanical balance is broken and the sliding force exceeds the anti-sliding force of the landslide.…”

“…Remote Sens. 2023, 15, x FOR PEER REVIEW 17 of 23 mechanical properties of landslides [60][61][62][63], we think that the Lianluo landslide conformed to the stress state of circular rotation. The internal reason for the displacement and deformation of the landslide body is that its mechanical balance is broken and the sliding force exceeds the anti-sliding force of the landslide.…”

“…In addition, there are two paths for the development of the potential slip surface: (1) The fissures at the trailing edge of the landslide continue to expand; (2) The fissures at the middle and leading edge of the landslide collapse the stability. Vick et al [60] also mentioned fissures and faults are the initiation of rupture that eventually leads to progressive failure, including creeping, sliding and avalanching. During the evolution of multiple rotational landslides, the overall scale of the landslide become larger, but the scale of the first and second landslides decreases successively (Figure 13c).…”

The Lac Fallère Area as an Example of the Interplay between Deep-Seated Gravitational Slope Deformation and Glacial Shaping (Aosta Valley, NW Italy)

“…The various and complex relationship between glacial and deep-seated gravitational processes in a high-mountain environment is the subject of this study. This issue represents a poorly investigated topic due to a greater interest in the genetic mechanisms and kinematics of the deep-seated gravitational slope deformations (DSGSDs) [1][2][3][4][5][6][7][8][9], chronology [10][11][12][13][14], and current activity [15][16][17][18]; however it offers an interesting and innovative tool in the field of landscape genetics [19][20][21][22]. DSGSDs act over very long timescales [23][24][25][26] comparable, for example, to the extension of the Lateglacial period [18,27], which favours a possible interaction between glacial and gravitational processes.…”

The Lac Fallère Area as an Example of the Interplay between Deep-Seated Gravitational Slope Deformation and Glacial Shaping (Aosta Valley, NW Italy)

“…The various and complex relationship between glacial and deep-seated gravitational processes in a high-mountain environment is the subject of this study. This issue represents a poorly investigated topic, due to a greater interest in the genetic mechanisms and kinematics of the deepseated gravitational slope deformations (DGGPVs) [1][2][3][4][5][6][7][8][9], chronology [10][11][12][13][14] and current activity [15][16][17][18], however it offers an interesting and innovative tool in the field of landscape genetics [19][20][21][22]. DSGSDs act over very long timescales [23][24][25][26] comparable, for example, to the extension of Lateglacial [18,27] that favours a possible interaction between glacial and gravitational processes.…”