GNGTS 2014 - Atti del 33° Convegno Nazionale

The great popularity of this interpretation is really surprising, since the implications of the proposed driving mechanism can hardly be reconciled with major features of the observed deformation pattern, as discussed in the following. a) In a large part of the Apennine belt and Calabrian Arc upward vertical movements are clearly recognized for the Pliocene and Quaternary (e.g., Argnani et al. , 2003; Bartolini, 2003; Schiattarella et al. , 2003; Boccaletti et al. , 2010). This evidence contrasts with the downward motion predicted by the experimental and numerical modelling of the slab- pull model in the trench zone and surroundings (e.g., Shemenda, 1993; Hassani et al. , 1997; Buiter et al. , 2001; Hampel and Pfiffner, 2006), as sketched in Fig. 1. Fig. 1 – Stress regimes in a subduction zone predicted by numerical modelling (modified after Hassani et al. , 1997). A) Three evolutionary phases (3.8, 6.4 and 7.2 My) of a subduction process, under the action of plate convergence and gravitational sinking of the slab. Red arrows show the computed velocity field. B) Enlargement of the velocity field in the last phase. Thin arrows above the section indicate the predicted vertical motions. C) Stress field computed for the last phase. Red convergent and blue divergent arrows indicate the maximum (compressional) and minimum (tensional) principal axes of the deviatoric stress tensor, respectively. b) The results of deep seismic reflection survey in the central Mediterranean region [CROP Project: Finetti (2005a)] clearly indicates that during the formation of the Tyrrhenian back arc basin the migrating orogenic wedges (Arc) and the Adriatic foreland underwent strong shortening. Some examples of the CROP cross sections, which provide significant constraints on the structural evolution of the central (Magnaghi-Vavilov) and southern (Marsili) Tyrrhenian basins and of the surrounding Adriatic-Apennine domains, are shown in Fig. 2. The migrating arc is constituted by remnants of the old Alpine-Apennine belt, detached from the Corsica-Sardinia block around the upper Miocene (Tortonian), and of the Etrurian- Adriatic domain, which have migrated towards east, mainly at the expense of the Ionian Tethys oceanic domain (e.g., Finetti et al. , 2005). In the wake of these continental fragments, crustal stretching has developed generating the central-southern Tyrrhenian basin. The presence of numerous thrust faults, cutting the whole crust and of major folds (Fig. 2) clearly indicates that 152 GNGTS 2014 S essione 1.2