Active tectonics of the Calabrian subduction revealed by new multi-beam bathymetric data and high-resolution seismic profiles in the Ionian Sea (Central Mediterranean)

Abstract

International audienceThe detailed morphology and internal structure of the Calabrian accretionary wedge and adjacent Eastern Sicily margin are imaged in unprecedented detail by a combined dataset of multi-beam bathymetry and high-resolution seismic profiles. The bathymetric data represent the results of 6 recent marine geophysical surveys since 2010 as well as a compilation of earlier surveys presented as a 2 arc-sec (60 m) grid. Several distinct morpho-tectonic provinces are identified including: the deeply incised Malta–Hyblean Escarpment, numerous submarine canyons, broad regions of relatively flat seafloor dominated by fields of sediment waves, the gently undulating anticlinal fold-and-thrust belts of the external Calabrian accretionary wedge and the adjacent portion of the Western Mediterranean Ridge. The Calabrian arc can be divided into 4 domains (from SE to NW): 1) the undeformed Ionian abyssal plain, 2) the external evaporitic wedge, 3) the internal clastic wedge, 4) the Calabrian backstop (Variscan crystalline basement). The Calabrian accretionary wedge can also be divided laterally into two major lobes, the NE- and the SW lobes, and two minor lobes. The kinematics of the limit between the two major lobes is investigated and shown to be sinistral in the external (evaporitic) wedge. A network of radial slip lines within the southernmost external wedge unequivocally demonstrate ongoing dextral displacement of a rigid indenter (representing the corner of the clastic wedge) into the evaporitic wedge thereby confirming the geodynamic model of an active lateral slab tear fault here off eastern Sicily. The slab tear produces a series of major sub-parallel dextral strike-slip faults offshore Mt. Etna and south of the Straits of Messina consistent with the relative motions between Calabria and the Peloritan domain (NE Sicily). Abundant strike-slip faulting, and wide-spread folding and thrusting observed throughout the entire accretionary wedge, indicate regional shortening between the Ionian abyssal plain (foreland) and the Calabrian–Peloritan backstop caused by active subduction

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

“…A slab length offset between the originally attached Calabrian and the Kabylides slab might be at the origin of the initiation of a subduction-transform edge propagator (STEP, Govers & Wortel, 2005) fault that then separated these into two slabs ( van Hinsbergen, Mensink, et al, 2014). The modern-day fore-arc STEP fault is thought to be located either at the Alfeo Fault system (Dellong et al, 2018;Gutscher et al, 2016Gutscher et al, , 2017 or at the Ionian Fault system (Polonia et al, 2011;Scarfì et al, 2018) (Figure 2). An earlier proposition that the STEP fault follows the Malta Escarpment, a 3-km-high feature offshore E Sicily (Argnani & Bonazzi, 2005) formed during the Tethyan rifting history of the Ionian Sea (Frizon de Lamotte et al, 2011;Gallais et al, 2011), seems unlikely given the absence of tectonic deformation along the central to southern Malta Escarpment since the Messinian, on the basis of high-resolution seismic profiles shot across the escarpment (Gutscher et al, 2016).…”

“…In both cases wide-angle seismic studies have concluded that the downgoing lithosphere is most likely oceanic in nature and of Jurassic age (Sallarès et al, 2011;Dellong et al, 2018). Both subduction systems are characterized by extremely wide (~200 km downdip direction) accretionary wedge complexes, with very shallow surface angles and thus narrow tapers (Dellong et al, 2018;Gallais et al, 2012;Gutscher et al, 2002Gutscher et al, , 2009Gutscher et al, , 2012Gutscher et al, 2017). There is a broad consensus that apart from their large-scale morphotectonic similarities, both subductions formed through rollback of narrow slabs over the past 5-10 million yr (Chertova et al, 2014;Faccenna et al, 2004;Gutscher et al, 2002;Gutscher et al, 2017;Palano et al, 2017;van Hinsbergen et al, 2014).…”

“…Profiles used for the construction of the gravity model are marked by white lines. Bathymetry from Gutscher et al () and EMODnet. (b) and (c) Paleogeographic reconstruction figures are modified from van Hinsbergen, Mensink, et al ().…”

“…CROP‐M3 MCS profile is coincident to DY‐P4 (Figure ; Polonia et al, ). Bathymetry from Gutscher et al () (after Dellong et al, ). Yellow‐shaded area marks the supposed extension of tectonically thickened evaporites in the Calabrian accretionary wedge.…”

Geology of the Ionian Basin and Margins: A Key to the East Mediterranean Geodynamics

“…Tectonics (e.g., Chaumillon & Mascle, 1995, 1997Minelli & Faccenna, 2010;Polonia et al, 2016) dependent upon convergence parameters, the nature and depth of the décollement levels, and the structure of the subducting plate and backstop (e.g., Bortoluzzi et al, 2017;Chaumillon et al, 1996;Gutscher et al, 2017;Reston, Fruehn, et al, 2002;. To the south, the structure of the African margin of the Ionian Basin is complex and may be delimited by the Eastern Sicily/Malta and Cyrenaica segments, with the offshore Sirte Basin in between.…”