The metaophiolitic Voltri Massif underwent a complex tectono-metamorphic evolution, resulting from subduction to collision events during the Alpine orogenic cycle, and was subsequently involved in the first stages of the Apennine Orogeny. So this is a key area to investigate the late orogenic Alpine tectonics and its time relationship with the first Apenninic deformation events.We performed detailed mapping, fault-slip analysis and study of fault rocks in a study area located at the eastern border of the Voltri Massif. Here we recognized two main generations of reverse shear zones (RSZ). The first one (RSZ1) is associated to mylonites and protomylonites in greenschist to low-greenschist metamorphic facies and is characterized by a ductile to ductilebrittle behaviour; RSZ1 display either top-to-N-NW or to-SW kinematics. The second generation of reverse shear zones (RSZ2) is characterized by fault breccia, crush breccia or protocataclasite; RSZ2 sense of tectonic transport ranges from top-to-NW, -SW and -NE.RSZ1 structures are locally folded by 10 m-scale, open chevron folds with fold axes gently plunging to SW that likely represent the last phases of deformation during Alpine collision.RSZ2 structures locally reactivate RSZ1, with a more brittle behaviour and produce a huge volume of fault rock. They are coeval with low-greenschist to zeolite-facies metamorphic conditions. The RSZ2 fit a transpressional regime active at the eastern border of the Voltri Massif at least during the late Oligocene-early Miocene.

The Voltri Massif underwent a polyphasic tectono-metamorphic evolution that records both the Alpine and part of the Apennine deformation events. So this is a key-area to investigate the relationships between Alpine and Apennine deformation events. This paper focus on the upper crustal deformations (UCD) that characterize the last stages of the tectonics of the Voltri Massif. In the Voltri Massif UCD are characterized by the superpositions of ductile, brittle-ductile and brittle structures that can be attributed to three main tectonic events (from D3 to D5). The oldest UCD event (D3) developed folds and reverse shear zones under ductile to brittle-ductile conditions. Main compressive NW-SE oriented regime characterized D3 event. Brittle-ductile to brittle reverse shear zones and important strike-slip/transpressive systems overprinted D3 structures. This D4 event was significant at the regional scale and occurred under main transpressive, NE-SW oriented, regime. The latest normal and transtensional brittle structures, that formed during UCD D5 event, locally reactivated the older structures.

The aim of this work is to present a new georeferenced geological map of an area in the Ligurian Western Alps (Lavagnina Lakes area) that includes both a unique geodiversity and great biodiversity, a peculiar geological heritage, and cultural features. The study area is located in the northern part of the Capanne di Marcarolo Regional Natural Park, occurring in the southern Piedmont Region (Alessandria, NW Italy) and close to the suburbs of Genoa. This area has been studied by multi-disciplinary scientific researchers who, so far, have focused their attention on the occurrence of alkaline springs and investigation of different endemic floral species. Moreover, in the past, the Lavagnina Lakes area has been exploited due to the presence of gold mineralization, and several mining records are still visible. We performed detailed geological mapping at a 1:10,000 scale, and collected data that were later integrated into a digital GIS map. The database associated with the map contains information that may be interesting from different points of view: (i) scientific research; (ii) outreach and dissemination activities; and (iii) geotourism (i.e., trail networks and panoramic viewpoints). The area represents a section of the Jurassic Piedmont Ligurian oceanic lithosphere, showing several geologic processes on different scales, such as the serpentinization process and intense and widespread carbonation of ultramafic rocks; the area is, moreover, characterized by fault systems showing paleoseismic structures. Beyond scientific research activities (i.e., geology, geoarchaeology, and mining archaeology), the area can also be promoted for geotourism, outreach and dissemination activities, field trips for schools, and gold panning activities. Hence, our new digital map and our 3D model could be a useful tool to illustrate the main characteristics of the area, leading a non-expert public to explore different geological features in a relatively “small” area. In this way, our map could help to improve geotourism, be used as a tool for educational activities, and, finally, could also help the Capanne di Marcarolo Regional Natural Park to be recognized as a geopark.

No abstract

No abstract