Structural control on the Upper Pleistocene ignimbrite eruptions in the Neapolitan area (Italy): volcano tectonic faults versus caldera faults

In this paper, we present an interdisciplinary study of the Upper Pleistocene ignimbrites of the Campanian margin in the Neapolitan area performed using outcrops, cores and seismic reflection data. We established a physical correlation between onshore and offshore stratigraphic units and reconstructed three regional geological sections. The stratigraphic succession in Naples is formed, from older to younger, by: Middle Pleistocene marine sediments; ancient ignimbrites reaching a maximum thickness of 200 m; 100-150 m thick tuffs of the 39 ka-old Campanian Ignimbrite; and products of 15 ka-old Neapolitan Yellow Tuff. The whole ignimbrite succession is thicker in Naples city and thins progressively towards the Bay of Naples, thus suggesting that some of the vents of these ignimbrites were possibly located near the city of Naples. NW-SE and NE-SW normal faults were rectognized in the Neapolitan area. In particular, NW-SE trending normal faults displace both the pre-CI tuffs and the Campanian Ignimbrite downthrowing the blocks towards the Bay of Naples in the order of hundreds of metres and feature ignimbrite thicknesses that are higher in the footwall than in the hangingwall blocks, whereas NE-SW normal faults formed after the Neapolitan Yellow Tuff eruption. In conclusion, the key result of our work is that NW-SE volcano tectonic normal faults were active during the Upper Pleistocene when ignimbrites were emplaced in the Neapolitan area in conforming with a model of fissure emission related to regional fault systems.