The Neapolitan Yellow Tuff tephra in the northern sector of Gaeta Gulf (Eastern Tyrrhenian margin, Italy)

The Neapolitan Yellow Tuff (NYT) caldera-forming eruption (ca. 15 ky) is a large event occurred at Phlegraean Fields during the late Pleistocene-Holocene. The eruptive products represent a widespread isochron marker which links marine and terrestrial archives of the central Mediterranean area and northern Europe. In this research we describe the stratigraphic signature of the NYT deposits in the Late Pleistocene-Holocene shelf sequence of the Gulf of Gaeta (northern Campania region, southern Tyrrhenian sea) by using a grid of high and very high-resolution seismic lines. The Gulf of Gaeta represents the northern Campania continental margin that is part of a large extensional Plio- Pleistocene basin associated with normal and strike-slip faults linked to the evolution of the eastern Tyrrhenian Sea margin. Since mid-late Pleistocene, extensional tectonics took place across the continental margin and it was accompanied by intense volcanism, from several districts of which the Phlegraean Fields activity has greatly influenced the sedimentation in this sector. The upper Pleistocene-Holocene stratigraphic architecture of the continental shelf is characterized by an offlap prograding succession followed by a very thick transgressive onlapping unit and by the upper highstand unit mainly characterised by undulations probably linked to gas prone sediment. High resolution seismic stratigraphy has been described in detail as a valuable technique of analysis of seismic profiles and has been herein applied in the geological interpretation of seismic. The seismo-stratigraphic interpretation of seven significant Chirp seismic profiles was improved in order to map the trend of the seismic horizon NYT. The NYT reflector is parallel and displays a high amplitude. It has been continuously detected from the shelf to the slope within the transgressive deposits. On the inner shelf its continuity is interrupted by shallow gas pockets. The NYT depths ranges from 2 ms bsf on the slope to 28 ms bsf on the continental shelf. The NYT event appears to have played a key role in controlling the stratigraphic architecture of the studied area during the last transgression, acting as a trigger for the formation of the aggradational sedimentary successions fed by pyroclastic and volcaniclastic deposits.