Una paleospiaggia tra voltri e Palmaro (Genova): Evidenze sedimentologiche e morfologiche

Abstract

During the excavation works for the construction of the highway new turn-off between Voltri and Palmaro (tract between Genoa and Savona in Liguria, northern Italy), geological surveys were carried out and cores of 12 boreholes were examined. Morphological investigations in the field and on maps were also made. Stratigraphical and sedimentological analyses of the deposits come to light during excavations, have allowed to recognize a paleobeach and the overlying continental cover. A sand-and-gravel deposit (maximum thickness in the order of 5 m) forms the beach: the continental deposit is made up of sand-and debris-flows, changing upward into colluvium and talus breccia. Morphological analyses of the substratum have shown the presence of two marine fossil abrasion platforms and of another one of present age. The highest platform can be seen between 12 and 16 m a.s.l.; the other between 5 and 7 m a.s.l. Fossil platforms, carved on metamorphic green rocks of the "Voltri Group" evidence two ancient coastlines which correspond to distinct interglacial periods. As to the age of the old marine deposits, It can be assumed, on the basis of present knowledge on the Liguria ancient shorelines and on the uplift rates recorded up to now, that the highest deposit corresponds to stage 11 (or 11 +9) and the lowest one to stage 5. The evolutionary history of the area from middie-upper Pleistocene to now-a-days has been traced on the basis of analyses on marine and continental deposits