An attempt of the Variscan (Hercynian) basement top reconstruction in some sectors of Italy (on land and offshore in the Adriatic Sea)

The last decade's growth in technology has brought a major development in computational tools, hardware and software, in the field of earth sciences. The work is the result of synergistic activity between the classical regional geology and the analytical processing methods typical of the geostatistics and geological. The main objective was to reconstruct, on the basis of available data, the Variscan top surface, preceding the pre-Alpine sedimentary cycle (Upper Carboniferous - Permian) and the Alpine properly Mesozoic and Tertiary, over an area covering the italian peninsula and the Adriatic Sea. The integration of surface geology with the underground information and the interpreted seismic reflection data has been the base of the computation, first on small scale using geostatistical tools and then on large scale with the development of a detailed 3D geologic volume model detail in a geothermal area of ​​Tuscany. The geostatistical processing has produced a series of maps on a national scale relating to the depth of the investigated surface. Available crustal seismic profile were used to this aim, and the first reconstruction was done in the time domain. Then, the velocity was calibrated using subsurface information from deep weel stratigraphy, and the obtained model were used to obtain the surface depth values. The 3D geological model constructed on the basis of subsurface data, widespread in the Tuscan geothermal provinces, has instead highlighted the volumes and geometric relationships between the various rocks taken into account, and defined in detail the shape of the Variscan surface. The resulting degree of confidence in the results is uneven, depending on the data distribution of subsurface information from weels. Howerver, this method has been readily replicable, and produce easy and fast updated result when new data were introduced. The obtained tools are powerful in supporting activities to study and identify natural deep georesources.