Abstract. We have performed scaled lithospheric experiments to simulate the behavior of a ocean-continent plate system subjected to compressional strain over a geological timescale. Experiments have been constructed using sand and silicone putty, representing the brittle upper crust and the ductile lower crust/upper mantle, respectively; the layers floated on glucose syrup simulating the asthenosphere. Compressional stress is achieved by displacing a piston at constant velocity perpendicular to the plate margin. We investigate the influence of four parameters: (1) the negative buoyancy of oceanic lithosphere, (2) the horizontal body forces between continent and ocean, and (3) the brittle and (4) the ductile strength of the passive margin. Two numbers express the importance of these parameters: the Argand number (Ar), representing the ratio between the body force of continent and its integrated strength, and the buoyancy number (F), representing the ratio between the buoyancy force of ocean and its ductile resistance. We obtain three scenarios. In experiments with Ar 3 and F < 1 the ocean deforms by distributed folds, resembling the undulations observed in the Indian Ocean. In experiments with Ar 7 and F >1 the continent collapses toward the ocean, producing back-arc extension and subduction, simulating the postAlpine Neogene evolution of the Mediterranean area. In experiments with Ar 3 and F > 1 the passive margin slowly evolves toward trench nucleation with the formation of a viscous mantle instability. We conclude that the latter model can be applied to the evolution of Atlantic-type margins, where there is evidence of this ongoing process.

We report on new stratigraphic, palaeomagnetic and anisotropy of magnetic susceptibility (AMS) results from the Amantea basin, located on‐shore along the Tyrrhenian coast of the Calabrian Arc (Italy). The Miocene Amantea Basin formed on the top of a brittlely extended upper plate, separated from a blueschist lower plate by a low‐angle top‐to‐the‐west extensional detachment fault. The stratigraphic architecture of the basin is mainly controlled by the geometry of the detachment fault and is organized in several depositional sequences, separated by major unconformities. The first sequence (DS1) directly overlaps the basement units, and is constituted by Serravallian coarse‐grained conglomerates and sandstones. The upper boundary of this sequence is a major angular unconformity locally marked by a thick palaeosol (type 1 sequence boundary). The second depositional sequence DS2 (middle Tortonian‐early Messinian) is mainly formed by conglomerates, passing upwards to calcarenites, sandstones, claystones and diatomites. Finally, Messinian limestones and evaporites form the third depositional sequence (DS3). Our new biostratigraphic data on the Neogene deposits of the Amantea basin indicate a hiatus of 3 Ma separating sequences DS1 and DS2. The structural architecture of the basin is characterized by faulted homoclines, generally westward dipping, dissected by eastward dipping normal faults. Strike‐slip faults are also present along the margins of the intrabasinal structural highs. Several episodes of syn‐depositional tectonic activity are marked by well‐exposed progressive unconformities, folds and capped normal faults. Three main stages of extensional tectonics affected the area during Neogene‐Quaternary times: (1) Serravallian low‐angle normal faulting; (2) middle Tortonian high‐angle syn‐sedimentary normal faulting; (3) Messinian‐Quaternary high‐angle normal faulting. Extensional tectonics controlled the exhumation of high‐P/low‐T metamorphic rocks and later the foundering of the Amantea basin, with a constant WNW‐ESE stretching direction (present‐day coordinates), defined by means of structural analyses and by AMS data. Palaeomagnetic analyses performed mainly on the claystone deposits of DS1 show a post‐Serravallian clockwise rotation of the Amantea basin. The data presented in this paper constrain better the overall timing, structure and kinematics of the early stages of extensional tectonics of the southern Tyrrhenian Sea. In particular, extensional basins in the southern Tyrrhenian Sea opened during Serravallian and evolved during late Miocene. These data confirm that, at that time, the Amantea basin represented the conjugate extensional margin of the Sardinian border, and that it later drifted south‐eastward and rotated clockwise as a part of the Calabria‐Peloritani terrane.

. The revised structural and metamorphic scenario is here integrated into a new tectonic evolutionary reconstruction, which involves an early high-P/low-T top to the east crustal thickening episode during the construction of the Apennine orogenic wedge (Eocene-Oligocene), followed and overprinted by a top to the west extensional shear, probably active from the !ate Oligocene.

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