Architecture of the NYT caldera and inner resurgent dome (Pozzuoli Bay, Campi Flegrei): new insights from seismic reflection and DInSAR data

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The Campi Flegrei and its offshore prolongation (Pozzuoli Bay) are a volcanic area dominated by a collapse calderaassociated with the Neapolitan Yellow Tuff (NYT) eruption, occurred at ~15 ka BP, and by an intra-caldera resurgentdome. We present new insights into: a) the geometry and kinematics of faults formed inside the caldera, b) the architectureof the resurgent dome, and c) the relationship between the structural elements of the resurgent dome and grounddeformations. This work is based on the integration of high- and ultra-high resolution seismic data, swath bathymetrydata and ground deformation maps. The main results highlight that the NYT caldera, offshore, is characterized by anellipsoidal shape, elongated towards the ESE direction, with axes of ~8 km and ~7 km. It is bounded by a ~6 km long and1–2 km wide ring fault zone (RFZ) mainly consisting of an inward-dipping normal fault system and antithetic, outwarddipping,faults. The sedimentary fill of the caldera is up to 60 m thick, and can be divided into six units, characterized bydifferent seismic facies, composition and depositional process.The inner-caldera resurgent dome, ~ 5 km in diameter, islimited by inner boundary of RFZ and consists in a broad antiformal structure with brittle deformation localized in anapical graben. The base of the resurgence corresponds to the thalweg of the Epitaffio valley in the western sector of thePozzuoli Bay and the Bagnoli valley in the eastern one. The maximum cumulative uplift of the resurgent dome is ~180m while its average uplift rate is ~ 9–12 mm/year, between 15.0–6.6 ka BP. A subsidence of ~10 m is suggested by thedrowning of the infralittoral prograding wedge below the present-day storm wave base for the last 2 ka.The deformationvelocity pattern of the Campi Flegrei displays a radial symmetry centered on the Pozzuoli harbor. It is possible todistinguish three almost-concentric sectors namely S1, S2, S3 with decreasing velocity from S1 (13-32 mm/year) to S3(0.3-7.7 mm/year). The highest value (26-32 mm/year) is recorded at the Pozzuoli harbor. Sector S1 is bounded by a NE–SW-trending fault to the west and NW–SE faults to the east. The data suggests that this sector coincides with the resurgentdome of NYT caldera. The base of the latter corresponds to the faults bordering sector S1, and it can be correlated withthe base of the resurgence recognized offshore. Sector S2 represents a narrow strip located between the base of theresurgence and the onland prolongation of the inner boundary of the RFZ.The results of our research provide new insightsinto the stratigraphic architecture and the shallow structure of the NYT collapse-caldera in the Pozzuoli Bay. Furthermore,they represent a base to reconstruct the entire onshore-offshore geometry of the inner-caldera resurgence and infer newconstraints on the dynamics of the fluid flow system and magma source at depth.
Lingua originaleEnglish
Numero di pagine1
Stato di pubblicazionePublished - 2016

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