Quaternary Tectonics, Sub-Surface Morphology and Hydrogeology of the Floridia Graben (Siracusa, Southeastern Sicily)

In this paper, we provide new insight into the Quaternary tectonics of the Floridia Graben (southeastern Sicily) and develop 3D geologic and ground-flow models of its subsurface. The Floridia Graben is a structural depression bounded by NW–SE trending normal faults and represents the main water reservoir that supplies the city of Siracusa (southeastern Sicily) and its countryside. The knowledge of the subsurface geology and neo-tectonic evolution of the Floridia Graben, as well as the spatial distribution of groundwater volumes is crucial for the management and protection of water resources. Within the government project of the new Italian geological cartography (ISPRA-CARG, Sheet N. 646 Siracusa), field and well data (both publicly available and newly acquired) have been collected and reinterpreted. NW–SE and NE–SW buried tectonic–structural features, inferred in the sub-surface of the graben, are consistent with the orientations of Quaternary faults diffusely observed inside and outside the investigated area. The Quaternary tectonic activity of bounding and buried faults has had a strong influence on the control of the morpho-structural pattern and, consequently, the groundwater flow of the Floridia Graben. The study allowed for the redefinition of the timing of these structures as well as their tectonic–structural control on the graben’s architecture and related water flow. The study represents a valuable tool for the better prediction of the spatial distribution of geologic and hydrogeologic volumes, thus enhancing the efficiency in the management and protection of natural resources.