In this study we integrate high-resolution swath bathymetry, single channel reflection seismic data and gravity core data, to provide new insights into the shallow structure and latest Quaternary to Holocene evolution of the submerged sector of the Neapolitan Yellow Tuff (NYT) caldera (Campi Flegrei) in the Pozzuoli Bay. The new data allow for a reconstruction of the offshore geometry of the NYT caldera collapse-ring fault system, along with the style and timing of deformation of the inner caldera resurgence. Our interpretation shows that the NYT eruption (~15 ka BP) was associated with a caldera collapse bounded by an inward-dipping ring fault system. The ring fault system consists in a 1-2 km wide fault zone that encircles an inner caldera region~5 km in diameter and is often marked by the occurrence of pore fluids ascending through the fault zone, up to the seafloor, particularly in the western sector of the bay. A shallow magmatic intrusion along the ring fault zone was also detected offshore Bagnoli in the eastern part of the Pozzuoli Bay. Following the NYT eruption, the inner caldera region underwent significant deformation and resurgence with a maximum cumulative uplift of the offshore structure in the order of 180 m. The net uplift rate of the caldera resurgent dome was~9-12 mm/year during the period 15.0-6.6 ka BP. The style of deformation of the resurgent structure can be described in terms of a broad doming, accompanied by subordinate brittle deformation, mostly concentrated in a small apical graben at the summit of the resurgent dome. Chronostratigraphic calibration of seismic profiles obtained by three tephra layers cored in the Pozzuoli Bay indicates 5 to 25 m of post-Roman differential subsidence and tilting towards ESE of the inner caldera resurgence, as recorded by the drowning of the infralittoral prograding wedge below the present-day storm wave base.

We present an up-to-date stratigraphic framework for the Late Miocene (postrift) non-marine strata of the western Pannonian Basin, based on unconformity-bounded units as they are derived from seismic interpretation. The data set used for this study consisted of some 1700 km of conventional, multi-channel reflection seismic profiles across western Hungary integrated by 190 km of high-resolution, single-channel seismic profiles acquired on Lake Balaton in June of 1993. Seismic stratigraphic analysis has been constrained by selected geological mapping, well-logs and borehole data. A magnetostratigraphic record was also available from a corehole in the study area, together with recent K/Ar dating of basaltic rocks from the Balaton highland.Five third-order (with 106 year periodicities) stratigraphic sequences have been recognized at regional scale in the Late Miocene succession of the western Pannonian Basin. We have designated these sequences, from bottom to top, as Sarmatian-1 (SAR-1) and Pannonian-1 (PAN-I) to Pannonian-4 (PAN-4). Reliable time constraints were only available for the two maximum flooding surfaces of sequences PAN-2 and PAN-3, namely mfs-2 (9.0 Ma) and mrs-3 (7.4 Ma), and the boundary of sequence PAN-2 (PAN-2 SB) which is approximately dated at 8.7 Ma. PAN-2 sequence boundary is associated with evidence of relative water-level drop in the Pannonian Lake and significant exposure of lake margins that is widely recorded in the so-called 'marginal facies' of western Hungary.The higher rank unit bounded by PAN-1 SB and PAN-4 SB includes most of the Pannonian s.l. succession of the central Paratethys and approximately correlates with the Tortonian-Messinian of the standard chronostratigraphy. Seemingly, no major palaeoenvironmental impact was perceptible in the western Pannonian Basin during the Messinian salinity crisis of the Mediterranean. However a significant change in the regional stratigraphic patterns may be observed since earliest Pliocene (after PAN-4 SB), possibly associated with the very beginning of a large-scale tectonic inversion within the intra-Carpathian area. The case of Late Miocene non-marine strata of Pannonian Basin is a textbook example of how single categories of stratigraphic units do not fit (sometimes do not even approximate) chronostratigraphic correlation. The use of unconformity-bounded units offers new insights into the complex and long debated problem of stratigraphic correlation between Late Neogene deposits of the Pannonian Basin and 'similar' non-marine strata of the Central Paratethys realm. Our study shows that the so-called 'Pontian facies' of western Hungary correspond to an unconformity-bounded unit which is older than the Pontian s. s. facies of the stratotype area (Black Sea basin). Accordingly, we suggest that different stages may be used to discriminate between such similar-in-facies but different-in-age strata. We hence recommend the introduction of a new chronostratigraphic unit ('Danubian' or 'Transdanubian') in the Late Miocene series of Central Paratethys...

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