LATE QUATERNARY GEOMORPHOLOGICAL EVOLUTION AND EVIDENCE OF POST-CAMPANIA IGNIMBRITE (40 KA) FAULT ACTIVITY IN THE INNER SECTOR OF THE SARNO PLAIN (SOUTHERN APENNINES, ITALY)

Abstract

The Sarno plain corresponds to the southernmost sector of the Campana Plain peri-Tyrrhenian graben, and it is limited towards the northwest by the Somma-Vesuvius volcanic edifice. The Sarno plain corresponds to the depocenter of a Quaternary sedimentary basin which is more than 2000 m thick and is bounded by high angle faults with NE-SW, E-W and NW-SE trends. Our study focussed on the less investigated, inner part of the Sarno plain, and aimed at reconstructing the recent (Late Pleistocene - Holocene) geomorphological and tectonic evolution of the area. The study was based on detailed geomorphological investigation combined with subsurface stratigraphic analyses of around 80 borehole logs. The geomorphological-stratigraphical approach has allowed the identification of the main geomorphological features of the alluvial plain and adjacent piedmont areas, and the reconstruction of the shallow subsurface setting of the inner Sarno Plain. The results indicate post-Late Pleistocene subsidence of the investigated area and the presence of an articulated fault system at the northeastern boundary of the investigated area. Surface morphological features and the characteristics of the drainage network are consistent with the subsurface stratigraphy in pointing to the activity of E-W and NW-SE trending fault strands during the late Quaternary. Overall evidence suggests the occurrence of vertical displacements postdating the emplacement of the Campania Ignimbrite regional chronostratigraphical marker, which implies fault activity continuing in the last 40 ka in the inner part of the densely populated Sarno Plain.