Stratigraphic, structural and geomorphological features of the Sicilian continental shelf: study cases from Southern Tyrrhenian and Sicily Channel

Abstract

The Pelagian Archipelago is located in a complex and wide geodynamic system characterized by the occurrence of two independent tectonic processes acting simultaneously: convergence along the Apennine-Maghrebian accretionary wedge and late Miocene-early Pliocene rifting in the Sicily Channel. Through high resolution seismic profiles acquired around the Lampedusa Island offshore, the reconstruction of an updated structural setting of this area and its regional correlation has been performed. The late Miocene-early Pliocene rifting affects directly the structural evolution of the Lampedusa plateau, with the development of a graben and half-graben setting in most of the offshore area, widely filled with the syn-rift deposits. In the northern sector, the activity of the normal faults associated with the rifting is active up to the early Pliocene, whereas it is quiescent since late Miocene in southern sector. This current fabric of the Lampedusa plateau derives by its involvement in regional extensional regime, lying in a dextral-transtensive zone and marked by pull-apart basins. In particular, two systems of the normal faults in the Lampedusa offshore have been recognized. The Master Extensional Faults oriented WNW-ESE represent the main structural alignment of the Lampedusa offshore and reflect the extensional trending of the Sicily Channel. The Second order of Extensional Faults, oriented NNW-SSE, bounds smaller pull-apart basins and are probably associated with the main dextral-transtensive regional regime. From the comparison with some preexisting models, an update stratigraphic-structural model is proposed also to the southeastern continental shelf between the Gela-Catania foredeep and the Hyblean foreland offshore, along the Marina di Ragusa offshore. The seismo-stratigraphic interpretation shows a NE-SW extensional faults system that involves only the late Miocene formations, probably connected to history of the Scicli Line. Furthermore, the late Miocene extensional tectonic activity involves widely affects the offshore portions of the Hyblean foreland and its ramp, but it does not show evidences that this activity has involved the Plio-Pleistocene succession. The deposition of the Gessoso-Solfifera Formation has been widely recognized in the Hyblean foreland ramp, demonstrating that the evaporitic deposition does not is a peculiarity only of the deposits within the semi-isolated and marginal sub-basins or of the thrust top mini-basins of the Appennine-Maghrebides belt, but extends also in areas where the extensional tectonic have been dominant. Through Multibeam bathymetric data, an update characterization of the geomorphological setting of the north-east Sicily continental shelf, between Milazzo Promontory and the area offshore from the Saponara River, is provided. Furthermore, through high-resolution CHIRP seismic profiles interpretation, a reconstruction of the evolution of the last eustatic sea level cycle is performed. The lowstand succession, corresponding with the foreset of the prograding clinoforms of the continental margin deposits, determines the accommodation space for the depositional processes that occur during the rise of the sea level. In fact, the evolution of the transgressive and highstand wedges is strongly influenced by the geometry of the underlying lowstand succession. The transgressive wedge is developed in the 80-100 m bathymetric range and consists of the relict geomorphic elements that represent past landscape. These elements tracked the variations in coastline position during the last sea-level rise, formed during an interval of relatively reduced rate of sealevel rise. Furthermore, a reconstruction of the geomorphological evolution of the past coastal systems during the last transgressive stage is provided. The highstand wedge consists of the Corriolo, Muto, Niceto, Cocuzzaro and Rometta delta deposits that widely develop on the offshore portions of the inner continental shelf.