The main objective of this work is to deduce the geologic setting of the San Leo cliff from the natural sections exposed in its own rock walls. The line-drawings of the rock walls, coupled with a detailed geologic map and framed in a tectonostratigraphic scheme, allow us to reconstruct a 3D geological model of the San Leo cliff . The interpretation of the collected data also allows us to establish the relationships between lithostratigraphy, tectonics and geomorphology that control the evolution of this spectacular and delicate landscape emergency of Val Marecchia. The 2014 landslide (BORGATTI et alii, 2015) has been only the latest event in the evolution of the San Leo cliff, where fractures and faults of Late Pliocene to Present age have predisposed rock masses to fall, so that the current slope morphology is the result of a very long series of rockfalls (BENEDETTI et alii, 2011).

The Casaglia-Monte della Colonna is one of the best exposed “fossil” mass-transport complex (MTC) cropping out in a foredeep succession exhumed in a mountain chain and represents a unique opportunity to study an internal architecture resulting from the (geologically) simultaneous collapses of an accretionary wedge front, slope, and basin plain deposits. The high variety of internal structures and the different MTC-substratum interactions depend on the geometry of MTC basal contact and the provenance of the remobilized sediments. In the 20 years from our first studies on this MTC, the better condition of some outcrops and the advances in methodological and interpretative tools enable us to provide an update scenario, with more details on the internal structures and a better comprehension of the complex interactions with the substratum.

Landslides of the lateral spreading type, involving brittle geological units overlying ductile terrains, are a common occurrence in the sandstone and limestone plateaux of the northern Apennines of Italy. The edges of these plateaux are often the location of rapid landslide phenomena, such as rock slides, rock falls and topples. In this paper, we present a back analysis of a recent landslide (February 2014), involving the north-eastern sector of the San Leo rock slab (northern Apennines, Emilia-Romagna Region) which is a representative example of this type of phenomena. The aquifer hosted in the fractured slab, due to its relatively higher secondary permeability in comparison to the lower clayey units leads to the development of perennial and ephemeral springs at the contact between the two units. The related piping erosion phenomena, together with slope processes in the clay-shales have led to the progressive undermining of the slab, eventually predisposing large-scale landslides. Stability analyses were conducted coupling terrestrial laser scanning (TLS) and distinct element methods (DEMs). TLS point clouds were analysed to determine the pre- and post-failure geometry, the extension of the detachment area and the joint network characteristics. The block dimensions in the landslide deposit were mapped and used to infer the spacing of the discontinuities for insertion into the numerical model. Three-dimensional distinct element simulations were conducted, with and without undermining of the rock slab. The analyses allowed an assessment of the role of the undermining, together with the presence of an almost vertical joint set, striking sub-parallel to the cliff orientation, on the development of the slope instability processes. Based on the TLS and on the numerical simulation results, an interpretation of the landslide mechanism is proposed.

In this study we combine observations and analytical data from large-scale (10-100s of m-thick and 100 m(2)-extensive), siliciclastic and carbonate MTD/MTCs belonging to the Oligocene - Miocene foredeep and wedge-top successions of the Northern Apennines and the Paleocene - Eocene Friuli basin of the northwestern Dinarides (Italy and Slovenia), to discuss the deformation processes critical to the emplacement of submarine landslides. We focus on the identification of meso-scale structures, used as diagnostic kinematic indicators of local paleo-transport directions. These structures, represented by linear-planar and complex-shaped elements such as tabular shear zones and detached slump-type folds, are the product of ductile-plastic deformation developed at relatively low-confining pressure that involves water-saturated, un- to poorly-lithified sediments, along with liquefaction/fluidization processes. Their final appearance is thus mainly controlled by the mechanical-rheological behavior of deformed sediments, and eventually by tectonic fabrics inherited from deeper structural levels of deformation. Due to this parallelism these structures have been termed and classified accordingly. They reflect strain partitioning due to differential movements within the slide mass, which is in turn controlled by the overall landslide typology. Due to the parallelism with classified tectonic structures and structural associations, we have thus redefined and classified accordingly meso-scale kinematic indicators in ancient MTD/MTCs.

The Valmarecchia area (RN, Italy), located between the Emilia-Romagna and Marche regions, displays peculiar geological features, being characterized by rocky slabs lying on gentle slopes. The main fortified villages of the area, remarkable for historical and artistic assets, were built in the medieval period on these slabs for defense purposes. The area is affected by widespread landslide phenomena, involving both the rocky slabs and the underlying clayey shales. The main phenomena acting on the slabs are lateral spreading, with associated rock falls and topples. In this area, a multidisciplinary project, involving different expertise, like geology, geodesy, geomorphology, hydrogeology, soil and rocks mechanics is ongoing. In this particular context, in order to achieve a clear recognition of the instability phenomena, it is necessary to understand the movement patterns and the eventual differential displacement occurring in the slabs. Monitoring activities, joined with geological and geomorphological interpretation, are one of the fundamental step for a deep understanding of the movements and for the risk management purposes. In many cases, the monitoring system is missing or only poor data are available, therefore an approach for the Permanent Scatterers (PS) data analysis has been used, combining analysis on the PS velocity, on the direction of the movement and statistical consideration on the time series trend. Some preliminary results regarding the rock slab on which the town of Verucchio (RN, Italy) is located are here presented.

In the unique Italian cultural context, the use of historical documents, among which iconography, may represent a powerful tool to describe past natural events and thus add pieces of information to the hazard and risk puzzles. Besides written documents, drawings, paintings, sketches and views allow geologists to acquire a special multitemporal data set on some important landslide features: geometry (volumes, areas, thickness, runout), kinematics (type, state of activity, distribution of activity), impacts etc. Here, some examples of the representation of dynamic geomorphological processes in historical archives are presented and commented with reference to the Apennines and the Alps.

The Montardone mélange (Mm) is a chaotic, block-in-matrix unit outcropping in the Montebaranzone syncline in the northern Apennines. The Mm occurs in the uppermost part of the Termina Fm, the Middle–Late Miocene interval of a succession deposited in a wedge-top slope basin (Epiligurian succession). The Mm is closely associated with bodies of authigenic carbonates, characterized by negative values of δ13C (from −18.22 to −39.05 ‰ PDB) and chemosynthetic benthic fauna (lucinid and vesicomyid bivalves). In this paper, we propose that the Mm is a mud volcano originated by the post-depositional reactivation and rising of a stratigraphically lower mud-rich mass transport body (Canossa–Val Tiepido sedimentary mélange or olistostrome) triggered by fluid overpressure. We base our conclusion on (1) the Mm pierces the entire Termina Fm and older Epiligurian units and represents the direct continuation of the underlying Canossa–Val Tiepido mélange; (2) the geometry and facies distribution of the Montebaranzone sandstone body, which are compatible with a confined basin controlled by the rising of the Mm; (3) the systematic presence of large-scale (lateral extension 300–400 m) seep-carbonates associated with the mélange, suggesting a persistent gas-enriched fluid vent from the ascending overpressured mud; (4) blocks and clasts sourced from the Mm, hosted by the authigenic carbonates, conveyed by ascending mud and gas-enriched fluids. The Mm represents one of the few fossil examples of reactivation of a basin-scale sedimentary mélange (olistostrome); a three-stage model showing mechanisms of Mm raising is proposed.

Mélanges originated from sedimentary processes (sedimentary mélanges) and olistostromes are frequently present in mountain chains worldwide. They are excellent fossil examples of mass-transport complexes (MTC), often cropping out in well-preserved and laterally continuous exposures. In this article we will show the results of the integrated study of fossil MTCs, including sedimentary mélanges/olistostromes, with a focus on the Apennines of Italy. Fossil MTCs, especially the basin-wide ones, are composite and multi-event units involving the entire spectra of mass-transport processes. The down-slope motion of these bodies is enabled by the relative movement of discrete masses, with progressive stratal disruption of rocks/sediment involved and flow transformation. Three kinds of MTC are here distinguished, in which the movements are enabled by (1) shear-dominated viscous flows within a muddy matrix, (2) mud-silt-sandy matrix sustained by fluid overpressure, (3) concentrated shear zones/surfaces with advection of grains and fluid (overpressured basal carpets). These MTC types may represent end-members of a continuum of products and correspond to different kinematics of transport and emplacement and to different relationship with the substratum. These observations should result in a better knowledge of mass-transport processes and bodies, in relation with the basin floor geometries.

In the peri-Adriatic region, mélanges represent a significant component of the Apennine and Dinaride–Albanide–Hellenide orogenic belts as well as ancient and present-day accretionary wedges. Different mélange types in this broad region provide an excellent case study to investigate the mode and nature of main processes (tectonic, sedimentary, and diapiric) involved in mélange formation in contrasting geodynamic settings. We present a preliminary subdivision and classification of the peri-Adriatic mélanges based on several years of field studies on chaotic rock bodies, including detailed structural and stratigraphic analyses. Six main categories of mélanges are distinguished on the basis of the processes and geodynamic settings of their formation. These mélange types are spatially and temporally associated with extensional tectonics, passive margin evolution, strike-slip tectonics, oceanic crust subduction, continental collision, and deformation. There appears to have been a strong interplay and some overlap between tectonic, sedimentary, and diapiric processes during mélange formation; however, in highly deformed regions, it is still possible to distinguish those mélanges that formed in different geodynamic environments and their main processes of formation. This study shows that a strong relationship exists between mélange-forming processes and the palaeogeographic settings and conditions of mélange formation. Given the differences in age, geographic location, and evolutionary patterns, we document the relative importance of mélanges and broken formations in the tectonic evolution of the peri-Adriatic mountain belts.

ABSTRACTSedimentary bodies emplaced by mass‐wasting processes and exceeding tens of metres of thickness and a hundred of square kilometres in area are widespread in the Cretaceous–Pleistocene marine successions of the Northern Apennines of Italy. At least 10 such bodies are present in the stratigraphic record of the Oligo‐Miocene foredeep during the northeastern, time‐transgressive migration of the accretionary wedge‐foredeep system. The term mass‐wasting complex (MWC) is here adopted for these bodies to emphasize their multistory emplacement mechanism and polymictic composition with variously deformed slabs of different lithology, age and provenance. As one of the more intriguing features, their occurrence was associated with changes in turbidite deposition from basin plain to slope. Wide sectors of the internal margin of the basin (lobe‐fan) and even of the basin plain become a slope at the front of the accretionary wedge for a limited period of time (temporary slope). The temporary slope supplied the intrabasinal components of the MWCs, whereas the diffused extrabasinal components came from the front of the accretionary wedge. Therefore, an enhanced instability of the entire foredeep‐wedge system occurred systematically and cyclically. As a consequence, many variously consolidated sediments were transferred into the foredeep basin invading the depocentre and forcing the turbidite deposition towards the foreland, in a more northeasterly position. The presence of such MWCs therefore conditioned basin size and geometry in an analogous way as that reported for some modern convergent margins, as in the case of Costa Rica. Normal sedimentation was restored on top of the MWC only after the levelling of topographic irregularities.

The Sapigno syncline (Ss) is a narrow structure elongated in a NW-SE direction, between the Savio and the Marecchia valleys which began to form during late Tortonian with the fragmentation of the upper Miocene foredeep. The upper Tortonian-lower Pliocene sedimentary succession of the Ss is characterized by gravity driven deposits (turbidites, slides and olistostromes) related to synsedimentary growth of adjacent structural highs. Within the Ss succession three main depositional sequences bounded by regional unconformities (allounits) can be detected: T 2 , M 1 and M 2 . Slumps, slides and olistostromes are common features of the Marnoso-arenacea (MA) Fm de-activation stage (late Tortonian-early Messinian) indicating a phase of overall instability induced by tectonic activity. Whereas the intraformational slumps are widely distributed along the northern Apennines, the Ligurian-derived olistostromes associated to these slides seem to occur only in those areas where the Ligurian complex is now present. This argument should be taken into consideration in the debate about the original extent of the Ligurian unit in the northern Apennines. In our opinion, the lack of Ligurian materials between the Sillaro and the Savio valleys is suggestive of a more inner position of Ligurian Sheet in this sector of the Apennine thrust belt.

Sliding was a common phenomenon in the Marnoso-arenacea (MA) foredeep, especially in the lower Serravallian. The most extensive one is the Casaglia-M. della Colonna slide (CMC), which crops out in the northernmost sector of the Romagna Apennines. The slide body includes both intrabasinal (mainly "basin plain" lithofacies and subordinate "slope" lithofacies) and extrabasinal sediments (olistostrome from Subligurian units), which derived from the inner margin of the MA basin (SW source). The detailed stratigraphic analysis and correlation of the turbiditic beds above and below the slide body and the study of fold vergence inside the body were the tools to understand the paleomorphology and the slide emplacement mechanism. This latter may be related either to a single instantaneous or a multiphased event. The most reliable hypothesis is a retrogressive sliding mechanism during which the "basin plain" sediments slid before the "slope" and the Subligurian derived sediments. A progressive sliding cannot be excluded, in which the more marginal masses pushed ahead the basin plain sediments. In any case, at least two stages of movement occurred, because the different deposits did not mix up.