Neogene to Quaternary tectonics and mud diapirism in the Gulf of Squillace (Crotone-Spartivento Basin, Calabrian Arc, Italy)

Abstract

The Calabrian Arc is an arcuate tectonic feature, formed during the Neogene and Pleistocene, as a consequence of the progressive retreat of the Ionian subduction system. It is a key area for understanding the geodynamic evolution of the Mediterranean Sea. The aim of this paper is to investigate the sedimentary dynamics and the possibly active deformation in the Gulf of Squillace and to highlight their relationships with the fluid escape pathways and mud mobilization. The Squillace embayment is a marine area belonging to the forearc basin of the Calabrian Arc, at the seaward prosecution of the Catanzaro depression. By interpreting public seismic profiles, at different resolutions, calibrated by well logs for hydrocarbon exploration, it was possible to define the structural setting and the Neogene and Quaternary stratigraphic architecture. The geologic setting of the Gulf of Squillace shows the occurrence of normal fault systems cutting through both Neogene and Quaternary deposits. During the Messinian, trans-tensional tectonics led to the formation of a basin whose sediments reached the major thickness in the central portion of the embayment. Since the Early Pliocene extensional tectonics was dominant and the basin depocenter progressively changed its orientation, creating a narrow basin roughly oriented NW–SE. Similar tectonic setting was also present during the Pleistocene extension. A Middle to Late Pliocene contractional event led to development of a thrust zone in the northern Crotone swell. Mud diapirs that occur in the external area of the Gulf of Squillace, are located close to the Pliocene and Pleistocene depocenter. The overpressure provided by the Pliocene and Pleistocene sediment accumulation on Messinian and pre-Messinian sediments and the evolution of normal fault systems, triggered the mud diapirs formation that progressively developed toward the upper slope. Extensional deformation and mud diapirism influence the morphologic evolution of the slope and the basin, resulting in the retrogressive erosion of canyon heads and gravity-driven slope failures.