Eastern Sicily
In North-Eastern Sicily, the orogen is organised into two main tectono-stratigraphic domains: the Kabilian-Peloritan-Calabrian units to the North-East, and the Apenninic-Maghrebian units and the External Thrust-sheets System to the South (Catalano et al., 1996; Lentini et al., 1996; Grasso, 2001; Fig. 6 cross section D).
The Kabilian-Peloritan-Calabrian belt includes imbricate sheets of Paleozoic metamorphic and igneous rocks, and Mesozoic sedimentary covers. In NE Sicily, the belt crops out in the Peloritani Mts., which contains a series of south-verging thin continental crustal nappes (Messina et al., 2004). Upper Oligocene-lower Burdigalian wedge-top deposits of the Stilo-Capo d’Orlando Fm. (Lentini et al., 2000, and references therein) post-date their main emplacement. The crystalline nappes still widely preserve the Variscan signature (De Gregorio et al., 2003; Somma et al., 2005). Some nappes record Alpine metamorphism (Atzori et al., 1994), followed by substantial exhumation prior to their final emplacement on top of the Apenninic-Maghrebian units, as indicated by zircon and apatite fission track data (Thomson, 1994). This early exhumation is controlled by syn-orogenic extension (Cutrupia and Russo, 2005) pre-dating the overthrusting onto the Apenninic-Maghrebian belt in early Miocene times (Amodio-Morelli et al., 1976). The tectonic contact on land between the Kabilian-Peloritan-Calabrian belt and the underlying Apenninic-Maghrebian belt is marked by the Longi-Taormina lineament (Bonardi et al., 1976). Its kinematic evolution is widely debated (see Catalano et al., 1996; Pepe et al., 2000; 2005; Billi et al., 2007 for a review), and started in early Miocene (Amodio-Morelli et al., 1976) with the Kabilian-Peloritan-Calabrian belt which overthrust the innermost sedimentary units of the Apenninic-Maghrebian belt. The Apenninic-Maghrebian belt, mostly formed during Miocene time, is made up of imbricate sheets of Mesozoic-Tertiary rocks (Lentini et al., 1995). Its structurally highest, tectono-stratigraphic units are derived from the deformation of the distal pre-orogenic domain (Sicilide Complex; Ogniben, 1960) and were generally involved in the Neotethyan accretionary wedge (Lentini et al., 2005). Their present-day geometric relationships are the result of frontal accretion, activation of extensional low-angle detachments and re-imbrication that significantly reorganized the original stratigraphic setting in different tectonic units (Lentini et al., 1996). The Sicilide Complex includes south-verging units interpreted as trench deposits (M. Soro and Troina units) that are well exposed in the Nebrodi Mts. and the distant Sicilide units cropping out in the frontal zone of the present-day chain which were completely detached and scraped from the basal portion of the succession and transported to the front of the chain in early Miocene times (Bianchi et al., 1989; Carbone et al., 1990; Butler et al., 1992). Gravity-driven transport might have contributed to its far-travelled location in the present-day structural setting (Corrado et al., 2009).
Tectonically beneath the Sicilide Complex, more external tectono-stratigraphic units are present (e.g., Mt. Judica unit). They formed, in part, at the expense of the African continental paleo-margin and consist of rootless units, mainly derived from shortened and rotated pelagic Meso-Cenozoic basinal successions (Speranza et al., 2003; Monaco et al., 2004; De Guidi and Monaco, 2005). This deformation started in the early Miocene (Catalano and D’Argenio, 1982; Oldow et al., 1990; Butler et al., 1992) and continued until middle Pleistocene times (Lickorish et al., 1999). The Numidian Flysch (cropping out in the Mt. Salici, Serra del Bosco and Nicosia units) represents the earliest foredeep deposit at the onset of collision. It was affected by contractional deformation since Langhian times and was followed by the deposition of the mid-Miocene (Gagliano Marls) and the upper Tortonian (Terravecchia Formation) clastic deposits (Catalano et al., 1996). Terrigenous sedimentation continued until mid-Pliocene times in central Sicily and until the early mid-Pleistocene along the southern Sicilian margin (Bigi et al., 1990).
In summary, two major shortening events generated the present-day structural configuration of the orogen following continental collision. The first event caused the superposition of the allochthonous units onto the Mesozoic-Paleogene Hyblean foreland carbonates through low-angle thrusts in early Miocene times (Bianchi et al., 1989; Butler et al., 1992). The second event is considered to have occurred in late Miocene–early Pliocene times. It strongly modified the geometric relationships of the allochthonous units, producing the internal stacking of the Mount Judica succession (Bello et al., 2000) and breakback, out of sequence, propagation of backthrusts in central-north Sicily (Carbone et al., 1990; Grasso et al., 1995).