The Romagna Apennines, Italy: an eroded duplex

The study of clast composition carried out on the alluvial gravels of the R omagna Apennines of northern Italy has provided evidence for an extensive c overing of allochthonous units (Ligurian nappe and Epiligurian succession) above the Miocene foredeep deposits (Marnoso-Arenacea Formation), which has been subsequently eroded during the Late Miocene-Pleistocene uplift. This result is confirmed by the burial history outlined in the Marnoso-Arenacea Formation through vitrinite reflectance and apatite fission-track analyses. The Romagna Apennines represent, therefore, a regional tectonic window whe re the thrust system that displaced the Marnoso-Arenacea Formation crops ou t. The geometric relations between this thrust system and the basal thrust of the Ligurian nappe, exposed at the boundaries of the Romagna Apennines ( Sillaro Zone and Val Marecchia klippe), are consistent with a duplex struct ure. Thus, the Romagna Apennines thrust system is an eroded duplex. The dup lex roof-thrust corresponds to the surface of the synsedimentary overthrust of the Ligurian nappe on the Marnoso-Arenacea Formation; the floor-thrust is located in the pelagic pre-foredeep deposits (Schlier Formation). Copyri ght (C) 2001 John Wiley & Sons, Ltd.