Bernardino Gentili

Geomorphological evidence for anti-Apennine faults in the Umbro-Marchean Apennines and in the peri-Adriatic basin, Italy

Abstract The Apennines are a relatively recent mountain chain which has been affected by uplift movements since the Upper Pliocene. In fact the remnants of an “erosional surface”, reduced close to base level, is preserved at the top of the relief. There is no general agreement on the geodynamic stress field and mechanisms which are creating the chain. However, it is largely accepted that uplift occurred together with the activation, on the western side of the chain, of extensive faults, oriented in the Apennine direction (NW-SE), which have been linked to the opening of the Tyrrhenian sea. A great debate is going on about the presence and significance of anti-Apennine faults (NE-SW) which have been observed by some authors but completely denied by others. The main evidence is represented by[ (1) block faulting of the remnants of the “erosional surface”. Along the Marchean Ridge, more elevated relief, delimiting relatively depressed areas, was created in correspondence with the Sibillini Mts. and Mt. S. Vicino. Similar evidence has been found in the Umbro-Marchean Ridge. Locally more than 1500 metres of displacement have been observed between more and less uplifted remnants. (2) Block faulting of fan deltas and related beaches, of Sicilian to Crotonian age, with more elevated sediments preserved between the Tronto and Tenna rivers and between the Musone and Esino rivers. Maximum displacement along a transect parallel to the coast is 200 metres. (3) fault-scarps affecting the Middle Pleistocene river terraces, as observed along the Esino, the Tronto, the Chienti and the Tenna river valleys. Maximum displacements are in the order of 50 metres. (4) Faulting of horizontal karst galleries and reorientation of the cave network, as in the Frasassi Gorge. Maximum displacements are about 100 metres. (5) Captures and alignments in the drainage network of the main river courses. (6) Large-scale gravitational movements, as in the Ancona landslide, and along the Chienti and Esino rivers. Their activation occurred in most cases after the Lower Pleistocene and although their displacements may be of relatively limited extent, dispite their recent activity, they played a major role in the modelling of the landscape. These faults display transtensive, extensional and trascurrent movements. Apart from the controversial geodynamic significance of these faults, from a geomorphological point of view they must be considered transverse elements of the stress field from blocks more or less uplifted along the Apennine chain. The importance and timing of activity of these faults in the Quaternary geomorphological evolution of the Umbria-Marchean Apennines is demonstrated using evidence usually underestimated by structural geologists, which can contribute to a debate based on a multidisciplinary approach.

DSGSDs Induced by Post-Glacial Decompression in Central Apennine (Italy)

During the last 30 years of studies in the field of mass movements located in the calcareous-marly and marly-sandy Apennines (Umbria-Marches and Latium-Abruzzi regions), over to a large number of landslides with different dimensions, even a lot of deep-seated gravitational slope deformations (DSGSDs) have been recognized and analysed. These phenomena are also located in that sector of central Italy affected by a cold climate during the past and actually temperate (central Apennine chain).

Clean and Healthy – Natural Hazards and Resources

The methodology adopted to classify and represent natural hazards and resources influencing the quality of land and of life is briefly reported.It aims to make as schematic and simple as possible the classification procedure, based upon available thematic maps, adopting only three levels of hazard (each subdivided into two sub-levels, depending upon the possibility to reclaim or recover the area) and two levels of resources (each subdivided into two sub-levels according to its exploitability).The proposed representation aims at simplifying the interpretation of the resulting map, where both the hazard and resources levels are displayed using full colors and hatchings, respectively.

Pliocene-Pleistocene geomorphological evolution of the Adriatic side of central Italy

Abstract This work is a significant contribution to knowledge of the Quaternary and pre-Quaternary morphogenesis of a wide sector of central Italy, from the Apennine chain to the Adriatic Sea. The goal is achieved through a careful analysis and interpretation of stratigraphic and tectonic data relating to marine and continental sediments and, mostly, through the study of relict limbs of ancient landscapes (erosional surfaces shaped by prevailing planation processes). The most important scientific datum is the definition of the time span in which the modelling of the oldest morphological element (the “summit relict surface”) occurred: it started during Messinian in the westernmost portion and after a significant phase during middle-late Pliocene, ended in the early Pleistocene. During the middle and late Pleistocene, the rapid tectonic uplift of the area and the climate fluctuations favoured the deepening of the hydrographic network and the genesis of three orders of fluvial terraces, thus completing the fundamental features of the landscape. The subsequent Holocene evolution reshaped the minor elements, but not the basic ones.

Hazard assessment of a complex landslide: the case of Vestea (Abruzzo, Italy)

This short note aims to reconstruct the geomorphological hazard scenarios connected to the complex landslide that insists on the territory of Vestea (Civitella Casanova Municipality, in the province of Pescara, Italy). The landslide, active for several decades, probably since the XIX century, is located along a wide valley and starting from its head. It manifests frequently local reactivations with varying movement typology; while total reactivations, taking place in concomitance of particular climate and hydrogeological factors, are more rare.

Deep Seated Gravitational Slope Deformations and Large Landslides Interfering with Fluvial Dynamics; Examples from Central Apennines (Italy)

The study, developed over a wide mountain sector of the central Apennines (Italy), highlights the role of Deep Seated Gravitational Slope Deformations (DSGSD) in the evolution of a mountain portion of the Chienti river valley. Radiocarbon dating and geomorphological considerations, testify that a lateral spreading, developed on a large scale, has triggered large landslides in correspondence of the thalweg. These phenomena have repeatedly dammed the river bed (certainly since the end of the late Pleistocene) creating temporary lakes which lasted also for a long time. The high seismicity and the persistence of conditions favorable to the development of gravitational phenomena, in an area currently occupied by an important communication route, attest to the high degree of risk present in this sector of the Apennine.

Slope Stability Integrate Analyses: The Study Case of Mount Falcone (Central Italy)

The proposed study case is rather interesting from a scientific-technical and social-economic point of view, since it is tied to conditions of high geological risk for inhabited, originally medieval or earlier, town of Montefalcone Appennino, where frequent damage, sometimes catastrophic are generated. Integrate geological, geomorphological and numerical analyses were carried out to understand the evolution and the kinematics of different types of gravitational movements. These remarkable phenomena are located on the relief of Falcone Mount in central Italy, where the towns of Montefalcone Appennino and Smerillo are builted. On the basis of field surveys, geomorphological interpretation and numerical analyses, turn out to be specific for falls, slides and deep-sited gravitational deformations, the phenomena were analysed, attempting to reconstruct both a geomorphological and a numerical models, checking whether or not their correspondence. The different deformations regard the arenaceous-calcarenitic-conglomeratic bodies superimposed onto marly clays or weathered levels of the pelitic-arenaceous turbidites; the kinematics are further illustrated and interpreted in detail.

Large landslides in sea-cliff areas of the central Adriatic coast (Italy)

The present work deals on an example of large landslide at Marina di Altidona, along the central Italy Adriatic coast, representative of many situations observed along the sea-cliff areas of the Marche and the Abruzzo regions; all these phenomena are located in areas which correspond to the most uplifted sectors during the Quaternary. The data collected, allow to hypothesize a past activation of a huge mass movement along a deep sliding surface, presently submarine. It was related to the high relief connected to the strong tectonic uplift of the middle-upper Pleistocene, to which a probable high seismicity was also associated. The validation of the geomorphological model has been carried out by applying a Finite Difference Numerical Code (FLAC_2D) to a huge gravitational movement and, in particular, by characterizing the dynamic evolution along significant transects.