GNGTS 2016 - Atti del 35° Convegno Nazionale

190 GNGTS 2016 S essione 1.1 Fig. 3 – Geological profiles across the Catania region (for location see Fig. 2). part of the slope is draped by a thin recent volcanic cover, whose attitude still reproduces the staircase subvolcanic morphology, due to the occurrence of the Late Quaternary marine terraces. The boreholes P1 and P2, at the base of the slope, drill the recent (Holocene and Middle Pleistocene) covers, consisting of lava flows and marine sediments, that unconformably cover the marly clays substratum. The boreholes P1 intercepts the tholeiitic lavas at a depth of about 280 m b.s.l., thus confirming the prolongation at depth of the forelimb of the Aci Castello flexure. The borehole P2, at a distance of few tens of meters, does not intercept the tholeiitic lavas at depth, thus suggesting a sharp interruption of the volcanic horizons that we interpret as due to a blind thrust ramp at the leading-edge of the flexure. At its northern edge, the Catania-Aci Castello coastal slope is bounded by a roughly E-W oriented tectonic alignment, along which the tholeiitic lava flows - that are interfingered with the marly clay horizons - abruptly interrupts. This tectonic alignment, extending from the village of San Gregorio to the coast of Aci Trezza, immediately to the north of Aci Castello (Fig. 2), has been analyzed in detail in the area of San Gregorio (Profile 5 in Fig. 3). In this area, the E-W north-dipping thrust ramp has been recognized. The hanging wall of the surface consists of a culmination of the Middle Pleistocene lavas and the underlying marly clays substratum. The geometry of the hanging wall is partly obscured by younger normal faults that caused the collapse of the original, wide gentle ramp-anticline. In the footwall of the structure, the Middle