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Geodynamics of the Calabrian subduction: Evidence from new seismic and bathymetric surveys

By: Andre Gutscher, CNRS, University of Brest

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Results from recent marine geophysical surveys in the forearc of the Calabrian subduction zone and adjacent Eastern Sicily margin will be presented. These data include: a new compilation of multi-beam bathymetry, high-resolution seismic profiles and wide-angle seismic profiles. Several distinct morpho-tectonic provinces are imaged by the bathymetric mapping 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. Wide-angle seismic data acquired the by the R/V Meteor in 2014 and recorded by 32 French (Ifremer) and 30 German (Geomar, Kiel) ocean-bottom seismometers and hydrophones (OBS, OBH) as well as 6 landstations (INGV Rome) image the deep crustal structure.

Host: Jamie Austin, UTIG

When: Fri Jan 20, 2017 11:30am – 12:30pm Central Time