Geomorphology of the Po Fluvial Terraces in Turin Deduced by New Subsoil Data (NW Italy)

Abstract

Urban geomorphology is a theme of increasing interest over the last decades. The present research about the Turin geomorphology (NW Italy) was carried out based on the drilling of 40 boreholes, of which 34 were designed for the construction of a new sewer collector by SMAT-Società Metropolitana Acque Torino, while other 6 were in the Valentino Park. These investigations allow us to evaluate the detailed morphology of the proglacial plain of the Rivoli-Avigliana end-moraine system (RAES) and facies, thickness and petrographic composition of fluvial sandy gravel forming this plain (Turin Unit). The local discovery of a truncated palaeosol suggests that this unit lies on a significant erosional surface shaped on more ancient fluvial sediments. New radiocarbon dating of woody macrorest above the palaeosol proves the Last Glacial Maximum (LGM) age of the Turin Unit. The same investigations suggest the presence of erosional terraces (Molinette T1 and Murazzi T2), shaped by the Po River in the proglacial sediments, and depositional terraces (Vallere T3 and Parco Stura T4), which are essentially formed by sand. Dating of woody macrorest confirms the widespread presence of RAES Late Pleistocene proglacial sediments and the subsequent entrenched Po fluvial terraces due to a significant Holocene fluvial deviation.