The structure of Mediterranean arcs: New insights from the Calabrian Arc subduction system

Abstract

The formation of Cenozoic mountain belts in the Mediterranean realm was preceded by tens of millions of years of subduction, forming volcanic arcs, and frontal contractional systems. In addition, subduction usually involves slab rollback and formation of oceanic backarcs. Although such structure must have influenced the orogeny of Mediterranean mountain belts, no active analog has been mapped with modern crustal-scale seismic methods. Here, we study the entire Calabrian subduction system to map the structure resulting from Tethys lithosphere subduction and slab roll back, in a process that must be akin to that operating during a phase of the formation of the Mediterranean orogenic belts. We present a crustal-scale cross section of the entire Calabrian subduction system obtained from on-and offshore wide-angle seismic data. The 2D P-wave velocity section shows spatially abrupt (< 5 km of profile distance) structural and petrological transitions from the Ionian sedimentary wedge and Calabrian arc, to the rifted NW Calabrian margin, where the Quaternary Aeolian arc is emplaced. The margin, then, transitions northwards into the Marsili backarc region, where exhumed mantle and localized volcanism occurred during its formation. This complex structure implies rapid temporal and spatial changes between magmatic and amagmatic processes, and between compressional and extensional regimes during the evolution of this subduction system. We find that some terranes involved in the Alpine orogeny share petrological and tectonic similarities with some domains of the Calabrian subduction system. Based on the results of this study we propose the Calabrian Arc system as an analog for the subduction structuration that preceded the formation of Alpine orogenic systems.

The evolution of the westernmost Mediterranean basins

“…The Ligurian and Tyrrhenian break-ups were followed by local magmatism (Prada et al, 2014;Merino et al, 2019). The interpretation of these bodies as magmatic back-arc oceanic crust is based on their two-layer structure (Grevemeyer et al, 2018;Prada et al, 2020). In the Tyrrhenian, opening subsequently led to mantle exhumation (Prada et al, 2015;, but extension has stopped and the basin is currently being inverted (Zitellini et al, 2020).…”

Active Tectonics of the North Tunisian Continental Margin

“…These faults form horsts and grabens associated to the opening of the Tyrrhenian Basin. North of our study area, these faults dip eastward, indicating that the shallow SE‐dipping active faults, identified in the North‐eastern Domain and northern sector of the Eastern Domain, might be extensional faults formed during Tyrrhenian opening (Loreto et al., 2020; Prada et al., 2020) about approximately 8–6 Ma (Mascle & Rehault, 1990; Trincardi & Zitellini, 1987). These previously normal faults are currently being inverted on a transpressional system in the frame of the present NW–SE convergence between the Nubia and Eurasian plates (Figure 4).…”

Arc and forearc rifting in the Tyrrhenian subduction system

“…Based on these differences, EM cannot be interpreted as oceanic crust. Prada et al (2020) 38 suggest that the basement of the eastern Marsili basin is made of exhumed mantle based on wide-angle seismic data. The average velocity-depth profile of the southeast Marsili basin fits the velocity-depth reference function for exhumed mantle regions of the Tyrrhenian and the Gulf of Cadiz 39 .…”