New structural and seismological evidence and interpretation of a lithospheric-scale shear zone at the southern edge of the Ionian subduction system (central-eastern Sicily, Italy)

Abstract

Geological, gravimetric, and seismological data from the central-eastern Sicily (Italy) provide evidences of a NW-SE oriented shear zone at the southern edge of the Ionian subduction system. This structure consists of a near 100 km long lithospheric-scale structural and seismic boundary. In the near-surface, it shows Plio-Pleistocene vertical-axis structural rotations, kilometer-scale topographic imprint, progressive wrenching, and large down-faulting. All these features, together with its location south-west of the subduction system, allow us to interpret the shear zone as the upper plate expression of an abandoned Subduction Transform Edge Propagator fault, working before slab detachment, currently reactivated by elastic rebound or mantle upwelling mechanism triggered by slab detachment, to form an incipient transform belt separating compartments characterized by different motion in the modern context of Africa-Europe convergence.

Geometry of the Deep Calabrian Subduction (Central Mediterranean Sea) From Wide‐Angle Seismic Data and 3‐D Gravity Modeling

“…Recent geodetic work provided evidence for toroidal flow around the retreating slab edges of the Calabrian subduction system expressed by counterclockwise rotations at the northern and clockwise rotations at the southern edge of the slab corresponding to movements predicted by STEP faults (Palano et al, ). Recent tomographic studies imaged a trench‐parallel slab break‐off on both sides of the slab, which might be still propagating, narrowing the slab (Barreca et al, , ; Scarfì et al, , ). Horizontal tearing affecting both sides of the slab was proposed to result in a narrowing of the subduction system and enhanced subsidence along the still‐intact segment of the slab (Scarfì et al, ).…”

Three‐Dimensional Modeling of Mount Etna Volcano: Volume Assessment, Trend of Eruption Rates, and Geodynamic Significance

“…A high‐velocity body, the detached portion of the slab originally separating the Aeolian magmatic province (subduction‐related, calc‐alkaline to shoshonitic volcanism; Peccerillo, ) from the Etnean one (plume‐related, mostly Na‐alkaline volcanism; Corsaro & Pompilio, ), is currently sinking in the asthenosphere, lying beneath the western sector of the Aeolian Archipelago (Alicudi and Filicudi islands) at a depth of ~130 km (see Figure c). This accounts for trench‐parallel slab breakoff and subduction cessation in the area with the consequent opening of a large and horizontal slab window right between the Etnean and Alicudi‐Filicudi sectors (see also Barreca et al, ).…”

“…Immediately north of Mount Etna, along the Peloritani block (Figure a), a local maximum of heat flow (~100 mW/m 2 ) and a local minimum of Bouguer gravity anomaly (~50 mGal) occur (Figure b). Upwelling hot material in this sector could also have contributed to the substantial uplift of the Peloritani block (Barreca et al, ; Gvirtzman & Nur, ; Westaway, ), whereas mantle wedging beneath the Etnean sector could be evidenced by deep crustal compressive earthquakes currently occurring in the area (De Guidi et al, ; Lavecchia et al, ; Scarfì et al, ).…”

“…The red dashed lines represent the Benioff‐Wadati contours of the slab (Sartori, ). Slab edge deformation is expressed by an array of NW‐SE trending oblique faults running from the southern Tyrrhenian Sea (ATLFS‐Aeolian‐Tindari‐Letojanni Fault System, see Barreca et al, , ; Cultrera et al, ) to the Ionian offshore (IF, Ionian Fault; NAF, North Alfeo Fault; see Gutscher et al, ; Polonia et al, ).,. (b) Geological and structural sketch map of the Etna volcano (modified from Branca, Coltelli, Groppelli, & Lentini, ) showing the distribution of volcanic products erupted during the main volcanic phases (a) Milo and Chiancone volcaniclastic deposits.…”

Ionian Abyssal Plain: A window into the Tethys oceanic lithosphere

“…The gradation from the deep-ocean environment of the IAP to the shallow water carbonate platform of the continental Malta-Hyblean plateau is marked by the Malta Escarpment. This distinct, 290 km long and 3.2 km high scarp is an inherited transform margin from the early Mesozoic [Argnani and Bonazzi, 2005;Micallef et al, 2016;Dellong et al, 2018] that traces the transition from the oceanic domain of the Ionian Sea to the Tertiary-Quaternary continental foreland domain of the Pelagian platform [Barreca et al, 2016]. 5…”