LATE-QUATERNARY TECTONICS ALONG THE PERI-ADRIATIC BELT OF CENTRAL ITALY: POSSIBLE EVIDENCE OF ACTIVE SHORTENING FROM TOPOGRAPHY, FLUVIAL NETWORK ANALYSIS, AND LANDSCAPE EVOLUTION

The ~ 900 km long Apennine fold-and-thrust belt dominates mainland-Italy and Sicily, where it connects with the Maghrebian chain. The belt reached its present setting following a progressive foreland-ward propagation, started about 10 Ma and continued through the Quaternary. The Apennine Outer Front is still active along its northern and central sections and a similar behaviour is also recognized in Sicily. Instrumental seismicity with compressive/transpressive kinematics relate to the occurrence of moderately energetic earthquakes, e.g. in northern Italy (2012, Mw 6.1), offshore central Italy (1987, Mw 5.1) and Sicily (1968, Mw 5.4). Differently, in the southern Apennine Outer Front (SAOF), deformation is well documented only for the Early- and part of the Middle Pleistocene. Instrumental seismicity is lacking along the SAOF.

We investigated the possible existence of late Quaternary shortening also along the SAOF. Here, the foredeep deposits appear to seal former compressional structures; notwithstanding, the regressive depositional sequences are experiencing, since the Middle Pleistocene, a general phase of regional uplift. The latter is clearly recognizable in the deep fluvial network incision and in the conditioning of the landscape evolution of the existing piedimont surface.

We investigated the transient response that fluvial networks could exhibit as a consequence of folding and uplift, exploiting the favourable orientation of the streams with respect to the chain front. Knick-point detection over along-river longitudinal profiles, along with more advanced metrics, were compared with lithological and geological-structural features known for the area.

Geomorphic indices, in particular local relief and normalized channel steepness, are relatively high between the Pescara and Saccione rivers, suggesting locally higher rock uplift rates. In addition, interpretation of a seismic line crossing the northernmost sector of the investigated area shows a buried faulted anticline interesting the Pleistocene succession.

These perturbations on the fluvial network, suggest possible Late Quaternary active shortening along the SAOF.

This work has received funding from the European Research Council under the European Union’s Horizon 2020 Research and Innovation Programme (GA #795396)