The Calcari con Selce formation (CSf) is a low-porosity multilayer carbonate, partially dolomitized, formation that extensively crops out in the Lucania Apennine chain. This lithostratigraphic succession represents to depth a key formation concerning hydrocarbon exploration and a potential confined acquifer system. In this work we describe the structural features affecting the CSf related to burial and tectonic deformation with emphasis on normal faults related to post-orogenic extensional deformation. A field investigation led to recognition of background structures such as: i) strata-bounded sub-vertical fracture sets (OBj) and bedding-parallel solution seams (BPss), related to lithostatic load; and: ii) oblique-to-bedding solution seams (BOss) induced by syn-orogenic flexural slip. Furthermore, different sets of dolomitic veins extensively affect dolomitized parts of the CSf showing structural relationships with bedding interfaces. Localized low-angle normal faults (LANFs) post-dating the previous structures formed further anisotropies locally associated with subvertical fracture sets (SVfs). These structures, enhancing permeability within carbonate beds, promoted fluid compartmentalization. Highangle normal faults and associate fracture sets, characterized by well-connected features, mainly localized along the mature fault zones, further enhanced the permeability of the CSf allowing the development of preferential fluid-flow pathways moving parallel to the fault-zones, as inferred from the structure of calcite veins. This work provides an enhanced characterization of the fracture network affecting the CSf and represents a useful tool aimed at improving hydrological models for fluid circulation within fractured reservoirs.

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