GNGTS 2021 - Atti del 39° Convegno Nazionale

GNGTS 2021 S essione 1.3 134 region (Calcagnile & Panza, 1980; Geiss, 1987; Lucente & Speranza, 2001; Lucente et al., 2006; Maino et al., 2013). We want to evaluate the influence on trench shape and on the occurrence and timing of slab tears (e.g. (Mason et al., 2010)) of the structural heterogeneities within the Adria plate. We explore a wide range of models (Fig.2) where we varied the geometry of the Adria plate and the buoyancy and stiffness of the Adria promontory and Adria thin margin crust. It is found that the opening of back-arc extensional basins in response to the south-eastward retreat of the Ionian slab is a common feature in all models and slab lateral tearing or break-off occurs when Adria continental margin enters the trench. More importantly, our results (Fig.2) show that: 1. the presence of a thin continental margin (Models CM and B) favours the curvature of the Northern Apenninic trench and its retreat till the Adriatic Sea, which suggests that the arched shape of the northern Apennines is a consequence of deep processes occurring inside the Earth; 2. the development of a double arcs geometry and a wide slab window below the Central Apennines, as shown by seismic tomographies, occurs in the models where a stiffer con- tinental promontory in central Italy is inserted (Model CM and A) and/or the Thyrrenian passive margin of the Adria plate is curved (Model F1); 3. the presence of both structural heterogeneities within the Adria plate (promontory and thin margin) helps the retreat of the Ionian slab till the present-day position in the Cala- bro-Peloritan region. Fig. 1 - Initial model setup for the reference Model CM. It consists of a subducting oceanic plate (Ionian Ocean;light blue), two lateral continental blocks (Adria and Africa; orange), an overriding plate (Iberia and Europa: orange; thin upperplate: light grey) according to paleogeographic reconstructions of 30 Ma proposed by Faccenna et al. (2014); van Hinsbergen et al. (2014). The Adria plate is characterized by the presence of a stiffer continental promontory (dark orange) and a thin continental margin (red) as proposed by Lucente and Speranza (2001); Lucente et al. (2006). A wide slab is located from Gibraltar to Corsica extending down to 300 km. The solid black line indicates the coastlines at 30 Ma (van Hinsbergen et al., 2014), while the dashed black line the present-day coastlines of peninsular Italy (Picture from Lo Bue et al. , 2021).