GNGTS 2014 - Atti del 33° Convegno Nazionale

Devoti et al. , 2008). Despite the very slow present-day plate convergence, subduction might be locally still active. GPS measurements of Calabrian site motion relative to Apulia show systematic residuals directed towards the Ionian Sea. This suggests active crustal compression and an outward motion of the CA as a result of active subduction and shortening taken up in the accretionary wedge, eventually accommodated by long-term slip on the subduction interface. The submarine subduction complex. Four main morpho-structural domains have been identified across strike in the accretionary wedge (Figs. 2 and 3). From SE to NW they are: 1) the post-Messinian accretionary wedge; 2) a slope terrace; 3) the pre-Messinian accretionary wedge; and 4) the inner plateau. Variation of structural style and seafloor morphology in these domains are related to different tectonic processes, including frontal accretion, out-of-sequence thrusting, underplating and complex faulting. The post-Messinian accretionary wedge (Figs. 2 and 3) is a salt bearing accretionary complex, where frontal accretion of the Messinian and Plio-Quaternary units do actually occur along a basal detachment located at the base of the Messinian evaporites. The pre-Messinian accretionary wedge is constituted by Tertiary and Mesozoic sediments, and the basal detachment is located either at the top of the Mesozoic carbonates, or on the oceanic basement. Underplating processes and duplex formation are active in this region. The transition between post and pre- Messinian accretionary wedges is site of out-of-sequence thrusting, that as in the Nankai margin has been called “splay faults”. Complex faulting along the transition between the pre-Messinian wedge and the Inner plateau causes fluid flow and mud volcanism (Panieri et al. , 2013). The CAsubduction complex is segmented into two different lobes (Fig. 3) that show different basal detachment depths, structural styles and deformation rates (Fig. 2), interpreted as due to different rates of plate coupling on the subduction thrust. The Western Lobe (WL), offshore the Messina Straits region, has a very low tapered (taper about 1.5°) salt-bearing outer accretionary wedge (Fig. 2a), bounded towards the continent by a slope terrace that is the site of a Messinian thrust-top basin. The thrust-top basin develops in the region where the basal detachment cuts through deeper reflectors down to the basement. The Eastern Lobe (EL), in front of central Fig. 2 – a: PSDM (Pre Stack Depth Migrated) MCS line CROP M-2B with superimposed the line drawing. b: PSDM 36 fold MCS line CROP M-4 and line-drawing. Location of seismic profiles is shown in Fig. 1. These profiles have been collected in the western (offshore Sicily) and eastern (offshore Calabria) regions of the Calabrian Arc subduction complex respectively. Yellow domain: Messinian and Plio-Quaternary sediments; Green domain: Tertiary and Mesozoic sediments; Dark pink colour: African plate basement. GNGTS 2014 S essione 1.2 165