Preliminary Geodynamic Section of Central Italy between 41° and 42° N parallels

""The Central Mediterranean region represents the zone where. the evolution of the Thetian collisional chain appears the most. complex (Bigi et al., 1991; Cavinato et al., 1994; Parotto et al.. 1996; Amato et al. 1997; Cassano et al., 2001; Cassinis at al,. 2003; Billi & Salvini, 2003). In the Central Italian peninsula the. chain is elongated roughly NW-SE and results from the Thetian. suture by the collision between a European and an African. microplate. The sector between the N 41° and N 42° parallels is. one of the most complicate tiles of this puzzle (Salvini, 1993).. Important geodynamic differentiations are present along both. sides (Favali et al, 1993; De Alteriis, 1995).. An ideal E-W transect, from W, locates four main. geodynamic blocks (Fig. 1). To the W is the Sardinia-Corsica. Block of European origin with relics of the sedimentary wedge of. his Thetian margin to the E (Bigi et al, 1991). It follows the. Tyrrhenian Sea, a basin characterized by thinned continental. crust topped with Miocene-Quaternary marine sediments directly. lying on Paleozoic basement (Patacca et al., 1990; Serri et al.,. 2001).. The third block corresponds to the Italian Peninsula with its. Apenninic structures that constitutes the orogen of the chain. (Accordi & Carbone, 1988; Parotto & Praturlon, 2004). The. accretionary prism continues to the E offshore, and it is still. active, in the Adriatic Sea (Patacca & Scandone, 2004). This is. the last block and represents the African margin underthrust to. the chain and it is characterized by a meso-cenozoic carbonate. succession deposited in shallow to open seawaters.. The main accepted geodynamic interpretation states that the. Sardinia block represents a European microplates separated in. Oligocene times (about 38 Ma, Patacca et al., 2008 and ref.. therein). The Apennines is the accretionary prism formed from. the collision in Mio-Pliocene times of the collision between this. microplate and the sedimentary wedge of the Adriatic plate of the. African domain (Adriatic Sea). Many geological evidences still. wait to be properly framed:. i) the substantial lack of the European sedimentary wedge in. the reconstruction of the collision zone;. ii) slices of deep water sedimentary successions associated. with ophiolites, related to the suture zone, outcrop both to the N. and to the S (Southern Apennines);. iii) along the proposed section slices of deep water sediments. has been identified in front of both the westernmost and the. easternmost sides of the chain;. iv) carbonate facies in the Apennines shows in Mesozoic. times deeper waters conditions in the most eastern successions. that is towards the African microplate (Accordi & Carbone,. 1988);. v) in eastern Sardinia a Mesozoic succession of shallow water. limestone outcrop (Tacchi), belongs to the European sedimentary. wedge (Bigi et al., 1991), and shows strong analogies with the. westernmost portions of the Apennine carbonate platforms. (comp. Accordi & Carbone, 1988).. A preliminary, admissible balanced cross sections between. the 41°N and the 42° N parallel has been prepared at the regional. scale by using the layered-HCA method as implemented in the. numerical FORC software (Salvini et al, 2001; Salvini F. &. Storti F., 2004). This section has been compared to the computed. lithosphere flexure of the region as derived from the present. topographic profile.. Results provide the possible framing of the Apennine block. within the African vs European domains, and the location of their. suture zone. Found geometry may represent the basis for a. complete geodynamic study of this complex region.""