Fabrizio Nigro

PLIO-PLEISTOCENE EXTENSIONAL TECTONICS IN THE WESTERN PELORITANI AREA AND ITS OFFSHORE (NORTHEASTERN SICILY)

Abstract Neotectonic deformations in the Western Peloritani area (northeastern Sicily) give rise to dip- and strike-slip fault systems. Dip-slip faults are predominant and subsequent with respect to strike-slip system. The S. Fratello-S. Agata Militello area has been selected for detailed mesostructural analysis and statistical treatment of field data. Sample data related to spatial arrangement of faults and fractures allowed us to infer the major direction of deformation axes. Direction of the maximum extension of the tectonic edifice has been obtained with Arthauds statistical method for fault populations. Distribution and fault geometry have been studied in the offshore area also by utilizing high-resolution seismic reflection profiles. From a seismic interpretation a Plio-Pleistocene clastic succession is recognized. The correlation between sequence boundaries occurring in the Western Peloritani offshore and those of the south and westernmost Sicilian offshore area made it possible to date these horizons, in four intervals: (1) Pre-Pleistocene (> 1.2 Ma); (2) Lower Pleistocene (1.2−0.8 Ma); (3) Middle Pleistocene (0.8−0.5 Ma); (4) Upper Pleistocene-Holocene (0.5−0 Ma). The normal fault systems have WSW-ENE trends, listric geometry and very recent age. Some of them have a basal detachment level within lowermost Pleistocene strata.

Extensional deformations during Neogene chain building in Sicily

In the Madonie-Nebrodi Mts (Northern Sicily belt) both Mesozoic carbonate platform/basin-derived deformed successions and Neogene foredeep deposits outcrop. Thrust sheets piled-up southwards in thin-skin piggy-back sequence. The chain building process began during the Oligo-Miocene. The syntectonic deposits involved in the compressional tectonics give evidence that syn-sedimentary extensional faults developed during fold nucleation and amplification. Syn-sedimentary extensional faults affect the foredeep strata at different stratigraphic levels, which are bounded by unconformities. Normal faults and bedding show constant cut-off relationships and are progressively tilted youngwards as the effect of thrust-related folding. Since their formation, these normal faults have locally interacted with the thrust geometry by means of positive inversion within the older strata and with physically connected to reverse faults crosscutting the succession youngwards.