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An extensive apatite fission-track survey has been carried out on the Marnoso-arenacea foredeep succession in the Northern Apennines. The data show a general decrease of the maximum paleotemperature undergone by the sediments toward the foreland areas. The maximum burial calculated by using a geothermal gradient of 20 C km 1 spans from more than 5 km to less than 2.5 km and indicates that the previously assessed total thickness of the Marnoso-arenacea succession is not enough to justify the determined values. It is concluded that a now eroded Ligurian wedge, up to 5 km thick, was present on top of the Marnoso-arenacea sediments.Apatite fission-track analysis is applied to sedimentary basins to unravel their low-temperature thermal history. The Middle to Upper Miocene foredeep succession of the Northern Apennines (Marnoso-arenacea Formation) has been studied for over 30 years and provides an ideal case study for apatite fission-track analysis, because of detailed knowledge of its stratigraphy, structures and petrography. Vitrinite determinations (Reutter et al. 1983) suggest that the outcropping sedimentary succession should encompass the whole apatite partial annealing zone (60-120 C) that is the range of temperature in which considerable information about the burial history can be obtained. The aim of this study is to assess the burial history in order to place new constraints on the geological evolution of a sector of the Northern Apennine fold-and-thrust belt and of the adjacent foredeep basins. In particular, our results are addressed to check the presence and the original extent of a now eroded 'far-travelled' thrust sheet, the so-called Ligurian nappe, whose existence on top of the thrust belt in the Romagna Apennines currently is a matter of debate. Based on the modelled total burial across the exposure of the Marnosoarenacea basin and on geological evidence (such as remnants of the Ligurian nappe), we suggest that the strata were originally covered by a tapered wedge of the Ligurian nappe which has since been removed by erosion and tectonic denudation.

The report describes a recent landslide occurred in San Leo (northern Italy), an outstanding village from the historical, architectural and landscape point of view. On February 27, 2014, around 6 pm local time, about 0.30 Mm3 of rock detached from a sub-vertical cliff and fell into the facing valley, producing a roar and a shake, which was initially perceived by the inhabitants as an earthquake, then followed by a dust cloud produced by the fragmentation of material during the collapse. Fortunately, nobody was injured, neither the landslide damaged any relevant structure; anyhow, it is still posing a severe threat to the village and, above all, to the fortress that represents an architectural masterpiece dating back to the middle ages. An outlook of the event will be given, along with the description of the peculiar geological and geomorphological features driving the slope instability phenomena, which indeed are widely diffused in the entire region. Lastly, an overview of the landslides, which historically affected the village, is also given, showing how natural hazards can influence the history of a site

The ancient fortified city of San Leo is built on a limestone plateau. The rock slab is tectonized and crossed by several families of joints and faults, while the underlying foundation of the rocky cliff is composed of gentle clay slopes, modelled in the so-called “Argille Scagliose” geological units. The differential weathering of the upper rock formation with respect to the ductile clays has produced ledges and overhangs on the cliff face. Furthermore, weathering and/or movement of the underlying clays has caused the opening and widening of vertical fractures in the brittle limestone rock masses, diffused over the entire rock mass. The evolution of plastic movements (slides and flows) in the underlying clay units might undermine the limestone slab and endanger the stability of the rocky cliff, thus posing risk to the fortified city of San Leo and its notable cultural heritage. In this paper, historical and recent slope instability events are described, on the basis of historical documents and modern investigations

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