The Messinian Salinity Crisis in the Central Mediterranean: Paleogeography and sedimentary evolution of two North Calabria basins (South Italy)

An integrated analysis of subsurface dataset and outcropping successions permitted to define a sedimentary and paleogeographic evolutionary model during the Messinian Salinity Crisis (MSC) of the wedge-top Rossano and Crotone Basins, located along the Ionian side of North Calabria. During the late Tortonian-early Messinian, open normal marine conditions characterized the studied basins, as suggested by the deposition of deep-water claystones followed by diatomites (Tripoli Fm). The first basin restriction occurred during the early Messinian (ca. 5.96 Ma) when a relative sea-level still stand triggered the formation of a carbonate platform system (Calcare di Base Fm - CdB). This latter was characterized by sabkha to shallow-water environments grading into a gentle slope to basin setting. A successive relative sea-level drop (ca. 5.60 Ma) induced a general exposure of the CdB platform system and the creation of a marked erosional surface linkable with the Messinian Erosional Surface (MES). Consequently, progradational early LST forced regression wedges deposited and, as the reduction of open-sea connections, more severe restricted conditions took place. Later on, during the late LST, the massive deposition of salt dominated bodies brought to sedimentary filling of the basins and to the consequent leveling of the paleobathymetric differences. Afterwards, a transgression phase (TST) inundated again the basins, causing firstly the sedimentation of clay dominated deposits, and successively, during a further sea-level still stand (HST), the reestablishment of evaporitic conditions and the deposition of widespread shallow-water sulphate deposits. Lastly, a new severe sea-level drop (LST) exposed again all the previous deposits, as testified by the superimposition of alluvial conglomerates along incised paleovalleys above the HST sulphate deposits. This event marks the transition to the Lago-Mare event that typifies the latest stage of the MSC, which definitely terminated with the reflooding of the Mediterranean at the Pliocene base (ca. 5.33 Ma).