Reconstruction of river valley evolution before and after the emplacement of the giant Seymareh rock avalanche (Zagros Mts., Iran)

Abstract

Abstract. The Seymareh landslide, detached ∼10 ka from the northeastern flank of the Kabir-kuh fold (Zagros Mts., Iran), is recognized worldwide as the largest rock slope failure (44 Gm3) ever recorded on the exposed Earth surface. Detailed studies have been performed that have described the landslide mechanism and different scenarios have been proposed for explaining the induced landscape changes. The purpose of this study is to provide still missing time constraints on the evolution of the Seymareh River valley, before and after the emplacement of the Seymareh landslide, to highlight the role of geomorphic processes both as predisposing factors and as response to the landslide debris emplacement. We used optically stimulated luminescence (OSL) to date lacustrine and fluvial terrace sediments, whose plano-altimetric distribution has been correlated to the detectable knickpoints along the Seymareh River longitudinal profile, allowing the reconstruction of the evolutionary model of the fluvial valley. We infer that the knickpoint migration along the main river and the erosion wave propagation upstream through the whole drainage network caused the stress release and the ultimate failure of the rock mass involved in the landslide. We estimated that the stress release activated a mass rock creep (MRC) process with gravity-driven deformation processes occurring over an elapsed time-to-failure value on the order of 102 kyr. We estimated also that the Seymareh damming lake persisted for ∼3500 years before starting to empty ∼6.6 ka due to lake overflow. A sedimentation rate of 10 mm yr−1 was estimated for the lacustrine deposits, which increased up to 17 mm yr−1 during the early stage of lake emptying due to the increased sediment yield from the lake tributaries. We calculated an erosion rate of 1.8 cm yr−1 since the initiation of dam breaching by the Seymareh River, which propagated through the drainage system up to the landslide source area. The evolutionary model of the Seymareh River valley can provide the necessary constraints for future stress–strain numerical modeling of the landslide slope to reproduce the MRC and demonstrate the possible role of seismic triggering in prematurely terminating the creep-controlled time-to-failure pathway for such an extremely large case study.

Large-Scale and Deep-Seated Gravitational Slope Deformations on Mars: A Review

“…Numerical modelling conducted for some DSGSDs in Valles Marineris [62][63][64] shows that both the higher slope inclinations and the presence of weak layers favor development of large-scale shear planes and formation of large landslides by slope collapse. Their obtained results are congruent with the state of knowledge for terrestrial processes, for which the deep control of weak layers and inherited structures is well documented for several phenomena on Earth [25,49,108,112].…”

“…On Earth, the DSGSDs are often associated with secondary landslides and large slope collapses [17,21,25,27,30,47,49,53,54,97,[104][105][106][107][108][109][110][111][112] that can present slow to extremely rapid kinematics [20,52]. On Mars, landslides and slope collapses appear to be connected to the locations of DSGSD phenomena, even if though the few available data do not allow drawing of certain conclusions.…”

“…Although the relationship between large-scale gravitational processes and landslide have been found on Mars [59][60][61]66], many further steps forward can still be made, also through numerical modelling [62][63][64]. In fact, while control factors are well studied, there is little information on triggering factors of slope collapse even on Earth, such as tertiary creep [30,51], variation of mechanical characteristics of rock mass [21,106,115], modification of slope topography [116,117], and sudden changes in stress conditions [54,112,118].…”

Integrated Field Surveying and Land Surface Quantitative Analysis to Assess Landslide Proneness in the Conero Promontory Rocky Coast (Italy)

“…Complex morphodynamics, implicating multiscale morphoevolutionary scenarios, often characterize rock slopes affected by extensive landslide processes. Mass Rock Creep (MRC) sensu [6], has been demonstrated to represent a critical process for the long-term morphoevolution of rock slopes in different geological contexts [7][8][9]. Large disruptive landslides may represent the ultimate stage of the MRC process that can culminate in paroxysmal events (like rock avalanches); nevertheless, these ultimate events are anticipated by gravity-driven deformations which represent the strain effect of the rock mass viscous rheology.…”

Fluvial inverse modeling for inferring the timing of Quaternary uplift in the Simbruini range (Central Apennines, Italy)

“…Fluvial landscapes preserve features that reflect temporal and spatial variations in rock uplift rates, which are experienced as base-level changes (Delchiaro, Della Seta, Martino, Dehbozorgi, & Nozaem, 2019;Fox, Goren, May, & Willett, 2014;Gallen & Fernández-Blanco, 2021;Ma, Zhang, Wang, Tao, & Li, 2020;Pritchard, Roberts, White, & Richardson, 2009;Roberts & White, 2010;Rudge, Roberts, White, & Richardson, 2015).…”