LATERAL SHIFTS OF APENNINIC FOREDEEP DEPOCENTERS REFLECTING DETACHMENT OF SUBDUCTED LITHOSPHERE

The hypothesis of lateral migration of slab detachment was formulated on the basis of seismic tomography results on the 3-D structure of sub duction zones in the Mediterranean region [M.J.R. Wortel and W. Spakma n, Structure and dynamics of subducted lithosphere in the Mediterranea n region, Proc. K. Ned. Akad. Wet. 95 (1992) 325-347]. The redistribut ion of slab pull forces associated with the tearing process is taken t o affect foredeep development by adding a lateral component to interna l-external depocentre migrations. In the case of the Apenninic Are the direction of detachment and associated depocentre migration is expect ed to be southeast. This prediction has been confronted with the tecto nostratigraphy of Oligocene to Recent Apenninic foredeeps. Results sho w there are two episodes marked by important lateral shifts of foredee p depocentres. During the early Late Miocene (Tortonian) the depocentr e of the Northern Apennines foredeep shifted towards the southeast. Th is is evidenced by the relative positions of the depocenters of the Bu rdigalian-Serravallian Marnoso Arenacea and the Tortonian Umbrian-Marc hean and Lazian ''Minor Basins''. A further, stepwise southeastward mi gration can be inferred from the Plio-Pleistocene records of the Centr al and Southern Apennines. In a more general sense, our results indica te that slab detachment may play a significant role in the evolution o f foredeeps along convergent plate boundaries. (C) 1998 Elsevier Scien ce B.V.