Gino Romagnoli

The effects of a Meso-Alpine collision event on the tectono-metamorphic evolution of the Peloritani mountain belt (eastern Sicily, southern Italy)S. CATALANO AND OTHERSAlpine evolution of the Peloritani Mountains

The Peloritani Mountains, in the southern part of the Calabrian Terranes, southern Italy, have been classically interpreted as the product of the Paleogene brittle deformation of the European continental back-stop of the Neotethyan subduction complex. This reconstruction conflicts with the occurrence of an Alpine metamorphic overprint that affected portions of both the Variscan metamorphic units and part of the Mesozoic sedimentary covers of the mountain belt. New field data, integrated with petrographic, microand meso-structural analyses and stratigraphic investigation of the syn-tectonic terrigenous covers, well constrain a Paleogene collision event along the Africa–Nubia convergent margin that caused the exhumation of the Alpine metamorphic units of the Peloritani Mountains. The syn-collisional exhumation was associated with shearing along two major Africaverging crustal thrusts arising from the positive tectonic inversion of the former European palaeomargin. Early tectonic motions occurred within the mountain belts and produced the exhumation of the external portions of the edifice. Later tectonic motions occurred along the sole-thrust of the entire edifice and caused the definitive exhumation of the entire mountain belt. The whole crustal thrusting lasted for a period of c. 10 Ma, during the entire Oligocene. The definitive southwestward emplacement of the Peloritani Mountain Belt onto the Neotethyan accretionary wedge was followed by two Late Oligocene – Early Miocene NW–SE-oriented right lateral shear zones, replacing the previous crustal thrust. These two strike-slip belts are interpreted as the surface expression of the deep-seated suture zone between the colliding Africa and Europe continental crusts.

Geological map of the Tellaro River Valley (Hyblean Foreland, southeastern Sicily, Italy)

The Geological map of the Tellaro River Valley, at the 1:25.000 scale, portrays the main stratigraphic and structural features that developed in a 300 km2 wide area of the African foreland in southeastern Sicily (Hyblean Foreland). The NW-SE-oriented Tellaro River Valley marks the transition between the eastern (Siracusa Plateau) and western (Ragusa Plateau) domains of the foreland, where a post-Tortonian structural depression, here designated as Tellaro Basin, originated. The map pictures the geometry and kinematics of the border faults and the structure affecting the basin infilling. The mapped structural pattern denounces a poliphase tectonic evolution of the region, suggesting the occurrence of a major NW-SE-oriented crustal discontinuity that, being active during the different periods of the post-Tortonian evolution of the area, could play a primary role also in the present seismotectonic picture.

Late Tortonian–Quaternary tectonic evolution of central Sicily: the major role of the strike-slip deformationS. CATALANO AND OTHERSLate Tortonian–Quaternary tectonic evolution of central Sicily

We here propose a new kinematic picture of central Sicily based on the results of detailed field mapping of the region, combined with structural analyses and the interpretation of the available literature subsurface data. Our study focused on the tectonic boundary of a structural depression, the Caltanissetta Trough, which is now filled with allochthonous terrains resting on the deep-seated inverted African palaeomargin units. Our data refer to the tectonosedimentary evolution of the thrusttop basins, from Late Tortonian to Quaternary times. The study points out the occurrence of regional E–W-oriented dextral shear zones, cutting the NE-oriented trends of the thrust belt. This new evidence would confirm the major role of the E–W trend in the tectonic inversion of the external portions of the Africa palaeomargin in Sicily. Our results could contribute to a better understanding of the location in Sicily of the tectonic lineaments accommodating the hundreds of kilometres of lateral displacement, caused by the Late Miocene–Quaternary Tyrrhenian Basin opening to the north of the island.