Evolution and depocentre 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 presente d. This basin developed in the hinterland area of the Northern Apennines be tween two N-trending and E-verging thrust anticlines, the Montalcino-Castel nuovo dell'Abate anticline to the west and the Ripa d'Orcia anticline to th e east. The architecture of the basin and the deformation affecting the syn tectonic sedimentary deposits show that the Velona Basin was affected by tw o strong compressive phases during the Messinian. The results of this study fit well into the structural evolution of the nearby hinterland basins, in dicating a Neogene tectonic scenario dominated by compression. The evolutio n of the Velona Basin is compared with simple models of thrust-top basins w hose development is controlled by the kinematics of two competing thrust an ticlines. The westward-directed depocentre migration recognized in the Velo na Basin is related to a higher displacement rate along the eastern thrust fault (Ripa d'Orcia thrust anticline), whereas the deformations at the oppo site basin margin are related to the Montalcino-Castelnuovo dell'Abate thru st anticline. The general models of thrust-top basin evolution presented he re were successfully applied to the Velona Basin case, and may be compared with other natural examples as well. (C) 1999 Elsevier Science B.V. All rig hts reserved.