New evidence of the outer Dinaric deformation front in the Grado area (NE-Italy)

A well Grado-1 was drilled down to 1,108 m reaching Mesozoic shelf carbonates which occur in the structural highs in the Lignano–Grado area. The well was completed with geophysical logs in the open-hole interval from −700 to −1,108 m. The drilling bit met the nummulitic shelf Palaeogene limestone at −616.5 m and Mesozoic (Upper Cretaceous) platform around −1,007 m. About 400 m thick Palaeogene interval appears affected by open fractures which we consider linked up to a reverse fault and a tectonic duplex of the Palaeogene limestone interval is hypothesized. The feature corresponds to the outer deformation front of the Dinaric thrusts system and looks still active. Palaeogene limestone sequence is analogous to the outcrops in the northern Istria and the stratigraphy in the oil wells offshore northern Dalmatia. The drilling target was the characterization of the nature of geothermal resources in the Friuli lower plain and lagoons region, following the long-term investigations of the Department of Civil and Environmental Engineering of the Trieste University. The geothermal resource was found in correspondence of the above mentioned open fracture zone and below it, with salty hot waters at a temperature of 42°C, increasing with depth, and a flow of 25 l/s arriving to the surface with 2.8 pressure bars.