TECTONICS OF THE PUNTA-BIANCA PROMONTORY - INSIGHTS FOR THE EVOLUTIONOF THE NORTHERN APENNINES NORTHERN TYRRHENIAN SEA BASIN

The structural setting of the eastern headland of the La Spezia Gulf ( Punta Bianca promontory) provides some constraints on the contractiona l and extensional framework of the Northern Apennines-Northern Tyrrhen ian Sea basin geodynamic system and allows a detailed reconstruction o f a complex evolutionary path. Out-of-sequence thrusting is supposed i n the inner side of the chain. Two different extensional events are id entified; the older (early-middle Miocene) may be related to the imbri cation of the deeper metamorphic units of the Apenninic thrust wedge. Younger extension fits very well into an eastward asymmetrical faultin g framework, related to the opening of the Northern Tyrrhenian Sea bas in, from the late Miocene to the Pliocene-Pleistocene (?). Well-expose d low-angle normal faults developed during this event. Extensional str uctures were then overprinted and reactivated by a mainly strike-slip regime in the Quaternary.