Surface Geomorphological Features of Deep-Seated Gravitational Slope Deformations: A Look to the Role of Lithostructure (N Apennines, Italy)

Abstract

The attention to deep-seated gravitational slope deformations (DSGSDs) has steadily increased in the last few decades, because such features are ubiquitous in mountain areas. Their geomorphological surface expression, especially when related to the effects of lithostructural control in sedimentary stratified bedrocks, is well characterized in theory, but sometimes not as well documented in field cases. In this contribution the investigation of several DSGSDs in the area of the Northern Apennines of Italy is reported. A survey of the area was conducted using fast and low-cost satellite imaging techniques, in order to describe the surface features of selected DSGSDs and verify how their occurrence is linked to the effect of lithostructural constrains such as bedding and folding. Surface features developed in parallel to the strike of the slope are mostly related to the main gravitative strain acting on the deformation. Features along slope dip are instead formed by the release of tension caused by compressive forces at the landslide foot or by the presence of pre-existing weak lines. One example of a DSGSD, formed on the hinge of a vertical fold, shows a corrugated appearance due to the release of vertical fractures that mask most other features usually associated with DSGSDs. This potentially impairs the detection of these landforms during field and remote surveys.

Deep-seated gravitational slope deformations in central Sardinia: insights into the geomorphological evolution

“…satellite data and space-borne interferometric synthetic aperture radar) (Frattini et al, 2018;Mantovani et al, 2016;Novellino et al, 2021) and proximal sensing such as unmanned aerial vehicle (UAV; Deiana et al, 2021;Devoto et al, 2020;Eker & Aydın, 2021) and light detection and ranging (LiDAR) have enabled a better understanding of these processes. They are characterised by extremely slow deformation rates (Cruden & Varnes, 1996) and landform assemblages such as doublecrested ridges, trenches, synthetic and antithetic (uphill-facing) scarps, tension cracks, and convex (bulged toes) and deep basal shear zones (Agliardi et al, 2001;Chigira, 1992;Crosta et al, 2013;Mariani & Zerboni, 2020;Panek & Klimeš, 2016). Shear zones exhibit the characteristics of cataclastic breccias with abundant fine matrix (Crosta & Zanchi, 2000) and thicknesses up to tens of metres (Ostermann & Sanders, 2017).…”

Evolution of Deep-Seated Gravitational Slope Deformations in Relation with Uplift and Fluvial Capture Processes in Central Eastern Sardinia (Italy)

“…Although DGSDs play an important role in slope evolution and geo-hydrological risk, knowledge about them was scarce for a long time [42]. They are characterized by very slow deformation rates [34], landform assemblages (such as double-crested ridges, trenches, synthetic and antithetic scarps, tension cracks, and convex bulged toes), and deep basal shear zones [43][44][45][46][47]. Often, shear zones present characteristics of cataclastic breccias with an abundant fine matrix [48] and thicknesses up to tens of meters [41].…”

Active faulting and deep-seated gravitational slope deformation in carbonate rocks (central Apennines, Italy): a new "close-up" view

“…Peculiar morphologies associated with DGSDs are double-crested ridges, ridge-top grabens, scarps and counterslope scarps, ridge-parallel trenches, tension cracks, and bulging slopes (Agliardi et al, 2001(Agliardi et al, , 2012. Several natural factors, and their interaction, control the formation of these large slope instabilities, such as the lithostratigraphic and structural setting (Agliardi et al, 2001;Hermann et al, 2000;Mariani & Zerboni, 2020), the topographic relief and the state of the stress (Ambrosi & Crosta, 2006Martel, 2006;Molnar, 2004), weather and climate (Agliardi et al, 2001;Evans & Clague, 1994), and seismic faulting (Jibson et al, 2004;McCalpin, 1999). Significant natural hazards are associated with DGSDs (Ambrosi & Crosta, 2006;Dramis & Sorriso-Valvo, 1994), in particular due to a sudden acceleration of the slope movements commonly induced by seismic faulting (Chigira et al, 2010;Moro et al, 2007).…”