The digital geological map of a treasure chest of geodiversity: the Lavagnina Lakes area (Alessandria, Italy)

We present the digital geological map of an area located in the Regional Natural Park of “Capanne di Marcarolo” (http://www.areeprotetteappenninopiemontese.it/, Alessandria, Italy), that has a great number of standing features both for its geodiversity and biodiversity. The aim of this work is to illustrate the geodiversity of an area that is not yet a geopark, but that has all the potentiality to become one. We performed a detailed geological mapping at 1:10000 scale and collected data that have been subsequently integrated into a GIS map as geometries and alphanumeric data. We used Open Source software QuantumGIS, with Qgis2threejs plugin for DEM and 3D model management. For this work we particularly focused on the Lavagnina Lakes area, that has been studied by several researchers of different branches, focusing on the occurrence of alkaline springs, of floral endemic species and others. This area has driven also the attention of mining companies, because of the gold mineralization and the past gold mining exploitation. For such reasons this area, beyond the scientific research activity, can also be interesting for geoturism, geoarcheology, outreach for schools, and for gold panning activities. The gold occurrences were known since the Roman age, and the area was site of mining exploitation with the presence of a metallurgical plant, dedicated to the manufacturing of gold ingots, and a mining village (1589 until the end of 1800). After the depletion of mines, the construction of the two dams, that gave rise to artificial lakes, caused metallurgical plant and the mining village to be submerged. From the geological point of view, the area is located at the north-eastern boundary of the metaophiolitic Voltri Massif, close to the Sestri-Voltaggio Line, at the contact with the Tertiary Piedmont Basin. The main remarkable geological features of the area are the occurrence of: i) various lithologies and geologic units derived from different paleogeographic environments: i.e. from the Jurassic oceanic lithosphere, from a continental margin Triassic carbonate platform, and from Eocene-Oligocene sedimentary continental to marine deposits; ii) fossil-bearing rocks; iii) fault systems, characterised by intense and widespread carbonation, that represent the natural analogue of the industrial process of CO2 storage; iv) gold mineralization; v) serpentinization of ultramafic rocks, important for studing fluid-rock interactions, developed at the ocean floor or in subduction zones; vi) alkaline springs; and vii) geomorphological landscapes. The databases associated to the map contain all the information that can be interesting from different points of views: i) research (i.e. structures, carbonated fault zone, geomorphology); ii) geoturism (i.e. trail network); and iii) geoarcheology (i.e. mine network). Our map could be useful both for scientific purposes, and for outreach and dissemination in order to preserve the geo-biological diversity of the area.