GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione A matrice 31 of the Fosso Morricone, at the base of the eastern flank of Mt. Vettore, where the villages of Pretare and Piedilama are located (Fig. 1). The valley is floored by the deposits of a palaeo- landslide containing large carbonate blocks from the hangingwall of the Sibillini Mountains Thrust (MTIa1 in Fig. 1). On the right side of the valley, the turbidites of the Laga Formation (LAG4b, c, e) form a N10° oriented, west-dipping very steep (> 55°) monocline that represents the reverse limb of a E-verging anticline, whose hinge zone is exposed to the north of the village of Pretare, towards the village of Montegallo. On the left side of the valley, the succession of the Laga Formation forms a N5-10° trending, east dipping monocline that constitutes the upright, very steep (> 50°) western limb of a vast asymmetric syncline, whose eastern limb extends for several kilometers as far as the village of Acquasanta terme. The two east verging cylindrical fold domains, exposed on the opposite sides of the Fosso Morricone, are interrupted by a N10° oriented, west dipping normal fault, which is roughly parallel to the trend of the turbidites bedding. The fault is located at the base of the left side of the valley that represents the footwall of the structure. Morphological,geologicalandgeophysicalevidence. DuringourstudythePretare-Piedilama fault line has been followed for a length of about 5 km, from the surroundings of Montegallo, to the north, to the village of Arquata del Tronto, to the south. The structure was analyzed in detail in the central part, for a length of about 2 km, in the area of Piedilama-Pretare (Fig. 1). In the study area the fault line is characterized by well defined trapezoidal facets, deriving from the dissection of a sharp linear scarp which is modelled on the pelitic-arenaceous succession of the Laga Formation. The height of the fault scarp varies from about 70 m, near Piedilama to about 40 m at Pretare. The main geological evidence of the normal fault is the sharp juxtaposition of Fig. 2 – A) Seismic refraction tomography (for location see B); B) northern sector (Pretare area) of the Fig. 1; C) geological cross sections (for location see B and for the legend see the Fig. 1 caption).