Multiscale integrated approach to understand the structure and evolution of the Neapolitan Yellow Tuff (NYT) caldera off the Campi Flegrei, eastern Tyrrhenian margin

Abstract

Resurgent calderas are among the largest and most dynamic volcanic structures on earth. They are typically associated with major eruptions with considerable volumes of pyroclastic deposits accompanied by large collapse structures and late stage deformation and uplift of the intra-caldera floor region. The Campi Flegrei is a vast volcanic area located on the coastal zone of the Campania region of SW Italy, a large part of which develops off the Naples (Pozzuoli) Bay. The area has been active since at least ~80 ka BP and is structurally dominated by a caldera collapse, ca. 8 km in diameter, associated with the eruption of the Neapolitan Yellow Tuff (NYT), a 30–50 km3 Dense Rock Equivalent ignimbrite dated at ca. 15 ka BP. In the past decades the shallow crustal structure of the NYT caldera has been mostly reconstructed using gravimetric and magnetic data, seismic tomography images and modelling (analogue) experiments, whereas, the structural elements of the caldera collapse in the Pozzuoli Bay have been largely inferred, based on seafloor morphology and associated deposits. Despite the conspicuous research so far conducted off the Campi Flegrei, the stratigraphic architecture of the NYT caldera structure and inner caldera deposits is still poorly understood. This is mostly because of the intrinsic limitations due to the insufficient resolution of previous seismic datasets, as well as to the lack of reliable geologic calibration of the offshore geophysical data. In this study we present a detailed structural and stratigraphic reconstruction of the submerged part of the NYT caldera obtained by full integration of swath bathymetry, high-resolution multichannel and single channel reflection seismics, gravity core, geochemical analysis of marine fluid vents and seafloor temperature profiling, recently acquired from the Pozzuoli Bay, along with existing geological, geophysical and geodetic datasets on land. Particularly, the high-resolution reflection seismic data offer unprecedented detailed insights into the stratigraphy and shallow structure of the NYT caldera collapse–ring fault zone–inner resurgence system. The results of this research provide a contribution to the understanding of structural style and timing of deformation of restless, resurgent calderas that develop along active continental margins.