Geomorphic response to late Quaternary tectonics in the axial portion of the Southern Apennines (Italy): a case study from the Calore River valley

The present study focuses on the morphotectonic evolution of the axial portion of the southern Apennine chain between the lower Calore River valley and the northern Camposauro mountain front (Campania Region). A multidisciplinary approach was used, including geomorphological, field‐geology, stratigraphical, morphotectonic, structural, ⁴⁰Ar/³⁹Ar and tephrostratigraphical data. Results indicate that from the Lower Pleistocene this sector of the chain was affected by extensional tectonics responsible for the onset of the sedimentation of Quaternary fluvial, alluvial fan and slope deposits. Fault systems are mainly composed of NW‐SE, NE‐SW and W‐E trending strike‐slip and normal faults, associated to NW‐SE and NE‐SW oriented extensions. Fault scarps, stratigraphical and structural data and morphotectonic indicators suggest that these faults affected the wide piedmont area of the northern Camposauro mountain front in the Lower Pleistocene ‐ Upper Pleistocene time span. Faults affected both the oldest Quaternary slope deposits (Laiano Synthem, Lower Pleistocene), and the overlying alluvial fan system deposits constrained between the late Middle Pleistocene and the Holocene. The latter are geomorphologically and chrono‐stratigraphically grouped into four generations, I generation: late Middle Pleistocene‐early Upper Pleistocene, with tephra layers ⁴⁰Ar/³⁹Ar dated to 158±6 and 113±7 ka; II generation: Upper Pleistocene, with tephra layers correlated to Campanian Ignimbrite (39 ka) and to the slightly older Campi Flegrei activity (⁴⁰Ar/³⁹Ar age 48±7 ka); III generation: late Upper Pleistocene‐early Holocene, with tephra layers correlated to the Neapolitan Yellow Tuff (15 ka); IV generation: Holocene in age. The evolution of the first three generations was controlled by Middle Pleistocene extensional tectonics, while Holocene fans do not show evidence of tectonic activity. Nevertheless, considering the moderate to high magnitude historical seismicity of the study area, we cannot rule out that some of the recognized faults may still be active