The structural hinge of a chain-foreland basin: Quaternary activity of the Pede-Apennine Thrust front (Northern Italy)

The Pede-Apennine margin (Northern Italy) is a major WNW-ESE-trending morpho-structural element that delimits the Po Plain to the southwest and consists of a system of southwest dipping thrusts, generally referred to as Pede-Apennine Thrust (PAT). The leading edge of the chain lies further north-east and is buried beneath the Plio-Quaternary marine and fluvial deposits of the Po Plain. Whereas the buried external thrust fronts are obvious active structures (as demonstrated by the 2012 Emilia earthquakes; e.g. Burrato et al., 2012), ongoing activity of the PAT is debated. Using a multidisciplinary approach that integrates structural, seismic, sedimentological and pedological field data, we describe the recent activity of the PAT structures in a sector of the Pede-Apennine margin between the Panaro and the Enza Rivers (Emilia-Romagna). We found that the PAT is emergent or sub-emergent and deforms Middle Pleistocene deposits. We also infer a more recent tectonic phase (~ 60-80 ka) by Optically Stimulated Luminescence (OSL) dating of soil profiles that have been deformed by a recent reactivation of the PAT. Furthermore, we show evidence that the PAT and its external splay thrusts strongly influenced the drainage pattern, causing fluvial diversions and forcing paleo-rivers to develop roughly parallel to the margin. Finally, numerical Trishear modelling has been used to calculate deformation rates for the PAT along two transects. Extrapolated slip rates vary between 0.68 and 0.79 mm·yr-1 for about the last 1.2-0.8 million years.