GNGTS 2019 - Atti del 38° Convegno Nazionale

140 GNGTS 2019 S essione 1.2 represent breakaway faults, produced by the gravitational failure of the sedimentary pile above the underlying en-echelon thrusts. ATL likely extends eastwards, down to the bathyal plain, presumably connecting with a regional-scale dextral transcurrent lineament, previously identified by several authors (Chiocci et al. , 2011 among others) and interpreted as a STEP fault (Polonia et al. , 2011 among others). Transpressive deformation could have also favoured the gravitational instability affecting the TP eastern margin, as highlighted by the presence of a remarkable landslide scar and a large deposit. The onshore tectonic arrangement points out the subaerial continuation of the strike-slip related deformation: the San Gregorio-Aci Trezza alignment represents the surficial expression of ATL, while the NW-SE trending S. Tecla and S. Venerina faults extends landward roughly from AL (Fig. 1). The westward continuation of the ATL-San Gregorio-Aci Trezza alignment was identified, on the basis of geological and geophysical data (Bianchi et al. , 1987), as a regional-scale shear zone located southwest of Mt. Etna. Here, the shear zone interrupts the continuity of the Hyblean basement and of the overlying Apenninic-Maghrebian thrust-sheet system and also produces an abrupt discontinuity in the magnetic basement (Bianchi et al. , 1987). This evidence points to the occurrence of a regional WNW-ESE trending dextral main shear zone (named “Southern Etna Shear Zone”) running south of Mt. Etna and extending offshore along ATL (Fig. 1). Fig. 1 - Morpho-tectonic map and volcanic features of Mt. Etna and the Timpe Plateau, delimited by inherited faults (orange and green lines) pertaining to the Hyblean domain (modified from Firetto Carlino et al. , 2019). The wedge- shaped push-up is centred on Aci Trezza Lineament (ATL) and northwards bounded by Acireale Lineament (AL). ATL continues to the west being part of a regional shear zone running south of Mt. Etna (Southern Etna Shear Zone). Main onshore faults: BOL: Belpasso-Ognina Lineament; TM: Tremestieri; TC: Trecastagni; SG-AT: San Gregorio- Aci Trezza alignment; AC: Aci Catena; AR: Acireale; F: Fiandaca; ST: S. Tecla; SV: Santa Venerina; MO: Moscarello; SL: San Leonardello; RN: Ripe della Naca; PD: Piedimonte; P: Pernicana; SA: S. Alfio.