Geological model of the Stiffe-San Martino d’Ocre ridge (Central Apennines, Italy). Evidence of multiple factors driving a mountain-scale deformation

The following paper illustrates the geological model of the Stiffe-San Martino d'Ocre ridge, which features a morpho-structural setting attributable to a Deep-Seated Gravitational Slope Deformation (DSGSD) process. The model reconstruction is based on geological and geomorphological surveys accompanied by remote sensing, geomechanical characterization, and geophysical investigations. Based on the results of the multidisciplinary analyses, it can be supposed that the Stiffe-San Martino d'Ocre ridge is affected by a DSGSD process, as diagnostic morphologies are significant at surface. The geological survey highlighted that the main morphological scarp of Fonteavignone-Terranera, does not coincide with any of the tectonic elements that influence the morphological structure of the relief. On the other way, a possible morphogenetic role for karst processes can be hypothesized, as the mountain ridge features numerous sinkholes and dolines, and the Stiffe Caves. The morpho-evolutionary setting of the ridge can be summarised in three main phases: a first phase, when gravity- driven deformations favoured by the relief energy of the incised Aterno Valley, affected the tectonic discontinuities, causing the development of minor DGPV in the marginal sectors of the ridge; a second phase, during which karst processes dominated the ridge, facilitated by discontinuities, controlling local lateral unconfinement in the middle part of the ridge thus allowing the gravitational process to extend to the FonteavignoneTerranera scarp; a third and last phase, when the infilling of the Aterno Valley has redefined the ridge morphology, leading the deformational process to a state of apparent quiescence.