GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 1.1 51 collection of various types of kinematic indicators (mechanic striae, shear veins, slickensides, etc.) on main and secondary fault planes. Finally, we compared the position of the active or potentially active faults with the earthquake epicenters and the available focal mechanisms. Along the Apennines-Po Plain margin, numerous morphological data indicate recent deformations but sometimes active structures do not outcrop and structural analysis is not possible; so, in this area the comparison between field and subsoil data is crucial. The tectonic structures of the plain are mostly buried and only in a few cases we were able to observe surface evidence. The absence of surface evidence for many of the recognized structural elements is not directly related to their activity degree, as evidenced by the frequent seismicity. The study of the areas in the plain was therefore based primarily on the analysis and interpretation of subsoil data (geophysical surveys and bore-hole logs) acquired for oil, gas and water exploration and exploitation. Subsoil data. The definition of the geometry of active and potentially active structures in the plain and the reconstruction of the cross-sections represented in the map were based on interpretation of seismic lines previously acquired for oil and gas exploration or hydrogeological studies, calibratedwith stratigraphic profiles fromwell logs (agreement between Emilia-Romagna Region and ENI S.p.A.). This allowed us to recognize the physical surfaces which bound the main depositional sequences of the Po basin and the main geological formations (Fig. 3). Fig. 3 - Geological cross-sections accompanying the map. The main depositional sequences recognized in the study area developed within the Neogene sequence (Late Miocene-Pleistocene). On a regional scale, the most recent unit represented in the cross-sections corresponds to the Quaternary continental sequence, i.e. the Emilia- Romagna Supersynthem (0.8 My - Present), including the Lower Emilia-Romagna Synthem (0.8 - 0.45 My) and the Upper Emilia-Romagna Synthem (0.45 My - Present). Below the Neogene sequence, along the seismic profiles, it was possible to recognize and to correlate the main buried geological formations, both terrigenous (Marnoso-Arenacea, Gallare Marls) and carbonatic (Scaglia, Noriglio Limestone, Dolomia), sometimes up to the deepest formations of Permo-Trias and, in some cases, to the crystalline basement. We recognized thick-skinned thrust systems, characterized by the deformation of the deepest horizons of the Permo-Trias sequence, and thin-skinned thrusts systems characterized by fault planes developed at the roof of the carbonate succession or in the Gallare Marls and propagating into the Oligo-Miocene and Pliocene sequences.