Tectonics, Salt Tectonics and Sedimentation in the Northern Crotone Basin

This study reconstructs the Messinian evolution resulted by the interplay between the coeval salinity crisis and tectonics in the north-western part of the Crotone Basin. The Crotone Basin represents the wedge-top depozone of the foreland basin system developed on the Ionian side of Calabria; it underwent very complex tectonics due to its location within the southern Tyrrenian sea - Calabrian Arc - Ionian forearc geodynamic system. The study area represents the north-western termination of the Basin, where the sedimentary sequences (Serravallian - Pliocene) close against the basement complex highs to the north and west. The angles of pinchout of the various sequences allowed to reconstruct the tectonic and/or isostatic rise of the basement complex trough time. The area presently forms a southeast-dipping homocline as a whole, where the older sequences (Serravallian - Messinian) outcrop only at the north-west, folded and thrust just after deposition, thus representing the northern border of a south-eastern basin filled by younger sequences (Upper Messinian - Lower Pliocene) onlapping the fold forelimb. Our new field data show the Late Miocene-Early Pliocene interplay between tectonics, salt tectonics and sedimentation, wheras new data on the Sr isotopic ratios found in the evaporites allow reconstructing their deposition environment. In the north-western part of the study area Messinian deepwater clastic evaporites represent the older evaporitic sediment lying just above the intra-Messinian unconformity. The following latest Messinian succession comprises halite followed by gypsum-bearing pelites and sediments containing LagoMare fauna. Local sedimentary overloading led to salt withdrawal, presently marked by weldrocks. Early Pliocene extension triggered salt diapirs, which attained the reactive stage and, somewhere, the active stage, in this case piercing through the latest Messinian cover and the lower portion of the Early Pliocene. Salt tectonics deeply influenced the sedimentary pattern of the Pliocene deposits as well. Our data show that the Crotone Basin was affected by short-lived tectonism during the acme of the Messinian salinity crisis. The structure detected in the field accommodate little deformation while the different tectonic regimes alternated rather fast. This was probably due to crustal-scale strike-slip faults alternating stick and slip periods and causing block rotations reconstructed by paleomagnetic data.