GNGTS 2015 - Atti del 34° Convegno Nazionale

48 GNGTS 2015 S essione 1.1 with a collection of data over a wider region, could help in disentangle between different scenarios depicting the recent evolution of this sector of the Monferrato area. This site, in fact, has to be interpreted together with other key-sites located along the Monferrato Arc, showing evidence of recent tectonic activity. In particular, these preliminary results are consistent with the activity of the Valenza Deformation Zone a regional trasnpressional zone supposed to be active at least until the Late Pleistocene (Giraudi, 2015). Moreover, the following geological, geomorphic and geophysical evidence in the Po alluvial valley floor, possibly related to active tectonic shortening, is of particular value for the evaluation of the seismic potential of the area: - the Trino Isolated Hill, representing the surficial expression of a Quaternary blind thrust (GSQP, 1976; Fig. 1a); - the Quaternary, major, drainage changes that affected the fluvial network along the buried front of the Monferrato Arc (Forno, 1982; Carraro et al. , 1995; Irace et al. , 2009; Vezzoli et al. , 2010); - the complex sequence of Mid-Pleistocene to Holocene fluvial units affected by progressive tectonic uplift (Dela Pierre et al. , 2003; Festa et al. , 2009; Giraudi, 2014, 2015); - significant ongoing uplift rates based on long-term geodetic survey (e.g., Arca and Beretta, 1985); - the evidence for Late Pleistocene to Holocene tectonic displacement described by Giraudi (2014, 2015) in the Casale Monferrato (Fig. 1a); - newly exposed sections showing recent deposits affected by N-verging reverse faults described by Sassone et al. (2015; Fig. 1b) at the Cereseto and Ozzano Monferrato sites. All these observations are lacking of absolute datings, an epistemic uncertainty that is still strongly limiting a reliable reconstruction of the recent landscape evolution of the area, including its tectonic and paleoseismic imprint. It is therefore reasonable to assume that the study of this Fig. 3 – Morphotectonic map of the Pecetto di Valenza site. Basemap is a hillshade model derived from a 5 m resolution DEM.