Inverted Basins by Africa–Eurasia Convergence at the Southern Back-Arc Tyrrhenian Basin

Maria Filomena Loreto,Nevio Zitellini,Camilla Palmiotto,Valentina Ferrante,Filippo Muccini

doi:10.3390/geosciences11030117

Abstract

The southern part of Tyrrhenian back-arc basin (NW Sicily), formed due to the rifting and spreading processes in back-arc setting, is currently undergoing contractional tectonics. The analysis of seismic reflection profiles integrated with bathymetry, magnetic data and seismicity allowed us to map a widespread contractional tectonics structures, such as positive flower structures, anticlines and inverted normal faults, which deform the sedimentary sequence of the intra-slope basins. Two main tectonic phases have been recognised: (i) a Pliocene extensional phase, active during the opening of the Vavilov Basin, which was responsible for the formation of elongated basins bounded by faulted continental blocks and controlled by the tear of subducting lithosphere; (ii) a contractional phase related to the Africa-Eurasia convergence coeval with the opening of the Marsili Basin during the Quaternary time. The lithospheric tear occurred along the Drepano paleo-STEP (Subduction-Transform-Edge-Propagator) fault, where the upwelling of mantle, intruding the continental crust, formed a ridge. Since Pliocene, most of the contractional deformation has been focused along this ridge, becoming a good candidate for a future subduction initiation zone.

Highlights

Back-arc basins (BABs) are a realm of extensional tectonics controlled by the subduction and roll-back of oceanic lithosphere [1], where normal faults, listric or planar [2], dominate
We focused on the southern part of the Tyrrhenian back-arc basin by merging all available geophysical data—-single and multi-channel seismic profiles as well as multibeam and magnetic data—-with information available in literature on seismicity, numerical modelling, and geodetic information in order to define the active tectonic structures as well its evolutionary model for the Plio-Quaternary, which may help with hazard assessment of the emerged areas
We identified two main tectonic phases that have shaped the northwestern Sicilian margin: (1) the extensional Pliocene phase, dominated by the opening of the back-arc Vavilov sub-basin, and (2) the contractional or transpressional Quaternary phase, dominated by Africa-Eurasia convergence

Summary

Introduction

Back-arc basins (BABs) are a realm of extensional tectonics controlled by the subduction and roll-back of oceanic lithosphere [1], where normal faults, listric or planar [2], dominate. Lithosphere extension may lead to the thinning of continental margins up to the crustal breakup and to the mantle upwelling and/or formation of new oceanic crust [3,4] This process ends when continental crust carried by the downgoing plate enters into the subduction zone [5], the slab retreating slows down or stops, and the back-arc basins may start to be inverted, as inferred by studying the Pannonian Basin [6] or the Carpathians belt [7]. Tectonics of BABs can be further complicated by the presence of large strike-slip faults, like scissor rupturing the crust, generated by the lateral termination of the subducting slab [10]. These faults, called STEP (Subduction-TransformEdge-Propagator) faults, are observed within BABs with irregular shape and are laterally confined by large strike-slip systems [11], for instance, as in the North Fiji Basin, where a long strike-slip fault bounds the system to the south [12], or in the Eastern Caribbean plate, bounded to the south by a strike-slip fault currently considered active [13]

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