Evolution and depocenter migration in thrust-top basins: inferences from the Messinian Velona Basin (Northern Apennines, Italy).

A structural study of the thrust-related Messinian Velona Basin is presented. This basin developed in the hinterland area of the Northern Apennines between two N-trending and E-verging thrust anticlines, the Montalcino-Castelnuovo dell'Abate anticline to the west and the Ripa d'Orcia anticline to the east. The architecture of the basin and the deformation affecting the syntectonic sedimentary deposits show that the Velona Basin was affected by two strong compressive phases during the Messinian. The results of this study fit well into the structural evolution of the nearby hinterland basins, indicating a Neogene tectonic scenario dominated by compression. The evolution of the Velona Basin is compared with simple models of thrust-top basins whose development is controlled by the kinematics of two competing thrust anticlines. The westward-directed depocentre migration recognized in the Velona Basin is related to a higher displacement rate along the eastern thrust fault (Ripa d'Orcia thrust anticline), whereas the deformations at the opposite basin margin are related to the Montalcino-Castelnuovo dell'Abate thrust anticline. The general models of thrust-top basin evolution presented here were successfully applied to the Velona Basin case, and may be compared with other natural examples as well.