VOLCANICLASTIC DEPOSITION AND MIGRATION OF BASIN DEPOCENTRES AFTERTHE ERUPTION OF THE NEAPOLITAN YELLOW TUFF: THE POZZUOLY BAY(NAPLES, ITALY)

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Abstract

The Campi Flegrei is an active caldera located on the coastalzone of SW Italy (Fig. 1), close to the town of Naples Bay, that hasbeen characterized by explosive activity and unrest throughout theLate Quaternary. This area represents a very active segment of theEastern Tyrrhenian margin and may be regarded as an ideallaboratory to understand the mechanisms of caldera dynamics andthe interplay between volcanism, tectonics and sedimentaryprocesses along a continental back-arc margin. Recent research atCampi Flegrei has shown that a significant part of the offshorevolcaniclastic products and structures, the late-stage geodynamicevolution of the inner caldera resurgence and the stratal geometryof the caldera fill are still poorly known. Particularly, highresolutionseismic data highlight the presence of an intra-calderaresurgent dome in the inner sector of the Pozzuoli bay thatunderwent significant uplift/subsidence after the eruption of theNYT (Sacchi et al., this volume). In this study we integrate geophysical data of differentresolution/penetration obtained from high-resolution reflectionseismic profiles (Chirp and Sparker sources) partly calibrated bygravity core in order to provide a 3D depositional model of densityflows and migration of basin depocentres for the Pozzuoli Bayafter the eruption of the NYT.The new data document the occurrence of two distinct layersof resediments, mostly represented by density flow deposits,separated by an interval of hemipelagic sediments. The two densityflow units display a remarkable difference in their thickness andinternal geometry. Across the bay, the lower unit is ca 5m thick inthe western sector and reaches its maximum of ca 10 m in thecentral sector while it is absent towards the east. The upper unit, onthe contrary, displays the minimum thickness of 10m close to thecentral sector of the bay and increases up to ca 16 and 12m in thewestern and eastern sector of the bay, respectively. The variation inthickness of the density flow deposits appears to be related withthe amount of sediments available. The upper density flowdeposits is also internally more chaotic respect to the lower one,suggesting higher energy and/or turbulence (Fig. 2). Sections and isopach maps clearly illustrate that the basindepocentre topography is not fixed at one position but migratessouthwards in time (Fig. 3). Based on the above observations, we suggest that the uplift ofthe resurgent dome and subsidence of the southern sector, occurredafter the eruption of the Neapolitan Yellow Tuff, acted as a majorcontrol in the increase of the sea-floor gradient in the Pozzuoli bay.This may have triggered in turn, the deposition of gravity flowdeposits along with a progressive migration of basin depocentresthrough time.
Lingua originaleEnglish
Numero di pagine0
Stato di pubblicazionePublished - 2012

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