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The correlation between onshore and offshore of the volcanic features in a complex volcanic field area is a difficult task, however, it is a fundamental step in order to better understand the geological evolution of such a complex area and for an assessment of geologic hazards. Ischia is a well exposed and densely populated volcanic field located in the Campania volcanic province of Italy. In order to improve our understanding of the recent volcanic history of Ischia Island, high-resolution seismic reflection profiles were used to identify volcanic and sedimentary features in the northern offshore. The volcano stratigraphy interpretation permitted us to recognize seismic units with a reflection-free/chaotic facies. These latter units have been associated with volcanic deposits and correlated to the main volcanic units outcropping on the northern coast of Ischia Island. They are limited in extent and interlayered with eight seismic units with continuous reflectors corresponding to clastic sedimentary units that were deposited during inter-eruptive phases. The main result of this work is the documentation of volcanic activity during the Holocene in the area offshore between Castello d'Ischia, Ischia Porto (mainly effusive products) and Punta della Scrofa (mainly shallow lava domes and dykes). The key volcanic units were mapped and 3D geological models were reconstructed. The reconstruction of the stratigraphic framework offshore a volcanic coast provides a pathway to the investigation of the stratigraphic relationships between inter-eruptive sedimentary deposits and volcanic units, and permits the assessment of a wide and continuous chronostratigraphic framework in a complex area. Furthermore, the onshore-offshore correlation of the main Holocene volcanic units allows us to better estimate their areal distribution, a critical factor in the hazard evaluation of a coastal volcanic area. The application of seismic volcano stratigraphy illustrates the remarkable possibilities that the study of submarine volcanic fields offers.

Most of the research works that aim at explaining the relationships between tectonic and volcanism focused a single volcano or eruption. Conversely, this study investigated offshore and onshore areas of the Campania margin in terms of stratigraphy, tectonics, and volcanism at a regional scale. We documented and reconstructed the three-dimensional geometry of several buried volcanoes and volcaniclastic deposits and recognized a complex Late Quaternary tectonic evolution of the region. These results suggest a strict genetic link between rifting and volcanic activity in terms of space-time evolution and because high volumes of magma rose to the surface through regional faults.

Most of the research works that aim at explaining the relationships between tectonic and volcanism focused a single volcano or eruption. Conversely, this study investigated offshore and onshore areas of the Campania margin in terms of stratigraphy, tectonics, and volcanism at a regional scale. We documented and reconstructed the three-dimensional geometry of several buried volcanoes and volcaniclastic deposits and recognized a complex Late Quaternary tectonic evolution of the region. These results suggest a strict genetic link between rifting and volcanic activity in terms of space-time evolution and because high volumes of magma rose to the surface through regional faults.

The paper by De Natale et al. (2016, https://doi.org/10.1002/2015GC006183) reported new stratigraphic and geochronological data for a borehole located at Campi Flegrei volcanic area. The authors failed to mention several significant articles on the geological evolution of the region and proposed an interpretation of their data according to the caldera model. Herein, we provide tectonic and stratigraphic data to support a fault model of ignimbrite emission. This comment will also show the inconsistency of the proposed Campi Flegrei caldera.

In the Central Mediterranean the Africa-Eurasia convergence led to the development of complex orogenic systems and backarc basins. Throughout Pliocene-Quaternary times the Southern Apennines accretionary prism migrated towards the Apulia foreland and, contemporaneously, the Tyrrhenian Sea backarc basin opened. In this study, we investigated the offshore of the southern Apulia foreland and the Southern Apennines. Using seismic reflection profiles and well data in a dedicated GIS software, we made a detailed stratigraphic analysis, reconstructed the structural pattern and built 2D geological models of the main geological surfaces. The structure of the Apulia region formed during two main tectonic stages: lower Pleistocene complex extensional faulting developed in a transtensional regime and middle-upper Pleistocene transpression/shortening. The Southern Apennines accretionary prism developed through the Pliocene-early lower Pleistocene and was overprinted by late lower Pleistocene-middle Pleistocene NW-SE sinistral faults. Through linking new data from the accretionary prism and the foreland with previous information from the Tyrrhenian Sea back-arc, we provide an original interpretation for the relationships between the various provinces that make the Central Mediterranean crustal puzzle and reconstruct the main phases of the evolution of its Pliocene-Quaternary orogenic cycle. We recognized collisional stages of uncoupled plates, followed by late lower-middle Pleistocene post-collisional stages of coupled continental plates. This Pleistocene plates re-organization of Central Mediterranean was probably due to the rupture of the Apulia/Ionian slab or to NNW intraplate shortening transmitted from Africa.

Miocene extensional sedimentary basins are being increasingly recognized in Central Mediterranean. However the paleogeographic reconstruction of the Paleo-Tyrrhenian during this time span results a difficult task because the subsequent Pliocene-Quaternary backarc opening moved away these older sedimentary basins. Our study outlines principal deformation events recorded by sediments that were deposited within minor basins of the Tyrrhenian Sea region and provides constraints on the duration of these events. The interpretation of seismic profiles, wells, and outcrops data together with a review of the middle-upper Miocene successions permitted us to recognize Miocene third order depositional sequences, reconstruct the fault pattern, and furnish a detailed evolution of the sedimentary basins that preceded the Pliocene-Quaternary Tyrrhenian high stretching. Based on the stratigraphic and tectonic constraints together with the age migration of the depocenters, we reconstructed a detailed paleogeographic evolution of central Mediterranean. Sedimentary basins architecture and fault pattern indicate a system of approximately N-S oriented normal faults and approximately E-W transform faults that were active since the Late Oligocene. Two period of extensional/transtensional tectonics (late Oligocene-Lower Burdigalian and Upper Langhian-Tortonian) were interrupted by a compressional event (late Burdigalian-Lower Langhian). Tacking in account the position of the Miocene volcanic arc (Sardinia), we propose that the coeval sedimentary basins developed in the central Mediterranean as forearc extensional/transtensional basins during the progressive collision with the African plate and before the Tyrrhenian backarc opening. Unlike published late Oligocene-Tortonian reconstructions of the western-central Mediterranean realm that report a linear migration of backarc extension, our results support a geodynamic model characterized by a progressive deformation of the forearc extension in the overriding plate.

The Tyrrhenian Sea (Central Mediterranean) is an extensional area that formed during the collision between Africa and Eurasia. Through the analysis of well logs and seismic profiles we reconstructed the stratigraphic successions and the structural style of the Tyrrhenian sedimentary basins. The sequence stratigraphy interpretation of well logs permitted us to recognize third and fourth order depositional sequences and the stratigraphic signatures of the rift stages. The study area features several sediment overfilled/balanced infill basins that resulted from the superposition of several rifting events characterized by high rates of basin subsidence. These outcomes led us to propose five rifting episodes occurred from Miocene to Quaternary affecting the upper plate. The suggested geodynamic scenario takes into account a progressive rupture of the slab and formation of sedimentary basins in the upper plate.

Coeval rifting processes affecting both backarc, thrust belt and foreland occurred in offshore western Sicily (Central Mediterranean) as indicated by the analysis of a large seismic data set calibrated with well data, onshore data and dredges in a dedicated GIS software environment. Structural pattern of the investigated area, 3-D geological models and a Pliocene-Lower Pleistocene evolution of extensional sedimentary basins have been reconstructed. In detail, two zones characterized by basins with different directions of extension have been recognized: one trending NE-SW, located south of the Egadi Islands; another trending E-W, positioned north of the Egadi Islands. The first group of basins represents the continuation of those of the Africa foreland basin (Pelagian Block), as the second one characterizes the opening of the backarc (southern Tyrrhenian margin). Both basins affect the collisional chain (Maghrebian thrust belt). An eastward progression of extension, from lower Pliocene to lower Pleistocene, based on different onset of the basin fill, has been documented in the Southern Tyrrhenian margin. The study area represents the meeting place of backarc and foreland rifting that affected the late Miocene thrust belt. The recognized pattern of extensional deformation of the upper plate adds some constraint on the geodynamic evolution of the African and Eurasia plates and supports a model of westward dipping slab in the Central Mediterranean. It is hypothesized that the along-trench variation of the nature of the plates, due to paleo-margin configuration, has a profound impact on the upper crustal deformation during the convergence and thus the meeting place of backarc and foreland rifting could represent the surficial signature of the slab detachment since Pliocene times.

The direction of extension and the architecture of the Messinian basins of the Central Mediterranean region is a controversial issue. By combining original stratigraphic analysis of wells and seismic profiles collected offshore and onshore Calabria, we reassess the tectonic evolution that controlled the sedimentation and basement deformation during Messinian times. Three main deep sedimentary basins in the Calabria area record a Messinian succession formed by two clays/shales-dominated subunits subdivided by a halite-dominated subunit. The correlation with the worldwide recognized stratigraphic features permit to define the chronology of the stratigraphic and tectonic events. Three main rift basins that opened in a N-S direction have been recognized. On the contrary a fourth supradetachment basin opened toward the East. We found that the basin subsidence was controlled by two stages of activity of normal faults and that Messinian rift basins evolve in a deep-water environment. The overall pattern of extensional faults of the Central Mediterranean corresponds to normal faults striking parallel to the trench and normal faults striking at an oblique angle to the trench (Fig. 14). In particular in Campania and Calabria regions are present two rifts parallel to trench and an intervening rift orthogonal to the trench. We maintain that the recognized Messinian rift basins can be interpreted according to the “Double-door saloon tectonics”.

The southern Apulia foreland recorded a strong (Imax=X MCS) earthquake in 1743 and a concomitant tsunami, which struck the southeastern Salento coast. The seismo-genetic fault and the triggering factors of the tsunami are unknown. Three-dimensional interpretation of multichannel seismic profiles calibrated by wells using a GIS software enabled the recognition of the stratigraphic succession, structural framework, and submarine landslides offshore Salento. A thin Pliocene unit overlying the Mesozoic-Cenozoic substrate is covered by a Pleistocene succession separated by a Middle Pleistocene unconformity that formed during the regional uplift of Salento. The latter gave rise to the morphologic conditions for the deposition of a prograding wedge off the Salento coast, with a shelf break located at 150 m depth. Normal faults, mainly oriented NW-SE, displaced the early Lower Pleistocene succession and are buried by younger deposits. Since the Middle Pleistocene, a compressional event gave rise to the Apulia uplift and large folds and basement-involved reverse faults that are active in the eastern part of Apulia. A huge (58 km(3)) slump affecting the Middle Pleistocene prograding wedge has been documented offshore the southeast coast of Salento. The proposed geological scenario of the 1743 earthquake and subsequent tsunami is (1) an initial strong earthquake (Imax=X MCS) associated with a thrust fault located in the eastern sector of the Apulia offshore, (2) a shacking-induced large-volume slump offshore Otranto, and (3) landslide-triggered tsunamis that struck the Salento coast.

The Southern Tyrrhenian Sea is an extensional basins linked to the Neogene evolution of the Calabria subduction zone located in the western Mediterranean realm where controversial kinematic and geodynamical models have been proposed. Our study provides a key to unravel timing and mode of extension of the upper plate and the breakup of Calabria from Sardinia. By combining original stratigraphic analysis of wells and seismic profiles off Calabria with a stratigraphic correlation to onshore outcrops, we re-assess the tectonic evolution that controlled the sedimentation and basement deformation of the Southern Tyrrhenian basin during Serravallian–Tortonian times. We document the tectono-stratigraphic evolution of adjacent extensional basins characterized by 3rd order depositional sequences (Ser1, Tor1 and Tor2) and different modes of extension, subsidence and opposite dipping faults. Episodic basin development is recorded by a coarsening-up and fining-up trend of the sedimentary succession and by tectonically enhanced unconformities that reflect three episodes of fault activity. We reconstruct Serravallian–Tortonian paleogeographic maps and propose a block faulting model for the evolution of the Sardinia–Calabria area. Sardinia was disconnected from Calabria through N–S normal faults forming Tyrrhenian extensional basins that formed contemporaneously to the E–W opening of the Algerian basin. Unlike published Serravallian–Tortonian reconstructions of the western Mediterranean realm, our results support a geodynamic model characterized by rapid trench retreat, trench-normal extension in the entire overriding plate and very weak coupling between plates.

Current models for the opening of the Tyrrhenian Sea invoke a unique extension vector throughout the rift to drift process, accommodated by margin parallel faults, but the role of the Campania margin faults in the opening of the Tyrrhenian back-arc basin is still poorly constrained. Gaeta Bay, located on the Campania mar- gin, was investigated through the interpretation of seismic reflection and borehole data together with a strat- igraphic correlation of dated outcropping units. The interpretation of a seismic grid using seismic and sequence stratigraphy and structural geology approaches in a dedicated GIS environment led to the genera- tion of 2-D models of relevant geological surfaces, isochron maps, a 3-D digital model of the subsurface and to the reconstruction of the geological evolution of the margin with a resolution of 100 ka. Gaeta Bay is formed by three basins (northern, central and southern) and features a complex stratigraphic architecture: in the northern and central basins a syn-rift deposit (unit PP) is buried by the oldest aggradational deposit (unit A) that fills the accommodation space; a post 0.7 Ma succession (units B and C) filled the northern basin with a lateral aggradational geometry; a syn-tectonic wedge (unit B) was deposited in the central basin between 0.7 and 0.4 Ma; post 0.4 Ma thick deposits (unit C) are testimony to the collapse of the southern basin. A correlation between the geology of the bathyal basin and that of the Campania margin was established using a CROP seismic section that extended from the Vavilov basin to Gaeta Bay. Based on original and literature data we propose a kinematic evolution of the Tyrrhenian Sea upper plate over the last 10 Ma. This evolution consists of older extensional events (stages 1-2) off Sardinia and in the Vavilov basin (leaving the Campania margin unaffected). Younger events (stages 3-5) developed in the eastern (with a Pliocene-Quaternary change of the extension direction along the Campania Margin) and central Tyrrhenian region. This paper suggests that the Tyrrhenian Sea opening was a polyphase rifting with a migration of activity and a change of style over time (including a period of lithospheric detachment faulting). © 2013 Elsevier B.V. All rights reserved.

The style of extensional basins provides key insights into the magnitude of extension and their kinematic evolution. The newly documented Stilo rift (off Calabria, Italy) features a Serravallian–Tortonian rift basin bounded by a high-angle normal fault and a Messinian adjacent supradetachment basin bounded by a low-angle normal fault. We propose a kinematic model suggesting the abandonment of the high-angle normal fault and the beginning of low-angle normal fault activity, followed by a rapid increase in extension. The triggering mechanism of the low-angle normal faults can be attributed to rapid rollback of the subducting plate and/or to isostatic crustal uplift. Supplementary material: The seismic dataset and methods of interpretation are available at http://www.geolsoc.org.uk/SUP18794.

Three crustal geological sections of the Campanian Volcanic Zone (Italy) were reconstructed by integrating basin architecture and deep well stratigraphies. In addition, mapping of the fault system and of large-volume ignimbrites was carried out. A linked fault system has been identified, which was responsible for asymmetric subsidence contemporaneous with the eruption of ignimbrites. Late Quaternary extension is characterized by a WNW–ESE stretching axis, NNE–SSW normal faults and reactivation of inherited structures. Structural, stratigraphic and palaeogeographical analyses reveal evidence for up to 750 m of subsidence, which has occurred at a mean rate of up to 4.9 mm a −1 over the past 154 ka. These rates suggest that extensional tectonics was responsible for the regional subsidence. A 6 km deep seismic reflector was associated with a magmatic reservoir underlying Campi Flegrei. By matching the structural and stratigraphic architecture with published geophysical and geochemical data a crustal tectonomagmatic model was constructed that displays high-angle faults that root into a low-angle detachment, which in turn roots into a deep sill-like magma reservoir. This model suggests the possible role of extensional faults in localizing magmatic activity, as faults controlled magma rise from deep to shallow reservoirs and to the surface during ignimbrite eruptions. Supplementary material: Seismic reflection profiles and interpretations are available at http://www.geolsoc.org.uk/SUP18451.

The Southern Campania Margin (SCM) represents a key area of the Central Mediterranean because it records all the rifting stages of the Tyrrhenian Sea. The interpretation of a seismic dataset calibrated with deep wells and outcrops, using seismic stratigraphy and structural geology methods in a dedicated Geographic Information System (GIS) environment, the seismic depth conversion, the generation of 2-D and 3-D models led to the reconstruction of a polyphased tectono-stratigraphic evolution of the SCM. During the early stage of Tyrrhenian opening a terrigenous transtensional Basin (Langhian-Tortonian Cilento Basin) formed on the Liguride accretionary prism adjacent to the Calabria crystalline terrane. In the SCM the Liguride thrust sheets tectonically overly the Apennine Platform units and both these nappes have been dismembered by Quaternary faults. Three rifting stages, not homogeneously distributed, affected the region since the Lower Pleistocene. They are associated to the deposition of a thick Quaternary succession (A, B and C units). During these Pleistocene stages there was an abrupt change of the extension direction (from NE-SW to NW-SE) accompanying a change of the nappe transport direction of the Southern Apennines. The construction of balanced sections using dedicated software, permitted us to recognize the true geometry of the faults and compute the amount of Quaternary extension of the SCM that results comparable to those calculated for other sectors of the Tyrrhenian margin and further extensional regions worldwide.

The interpretation of high-resolution seismic profiles acquired close the eastern coast of the Bay of Naples offshore Somma-Vesuvius volcano, and calibrated by borehole data, allowed us to recognize a reflection-free seismic facies consisting of a volcaniclastic debris avalanche overlain by pyroclastic density current deposits. Both are associated with the 3.5 ka 'Avellino eruption' and are in turn overlain by a marine succession. The top of the volcaniclastic unit corresponds to a deep erosional surface covered by a coarse-grained bioclastic layer with rounded pumice. We argue that these features are related to a tsunami that was triggered by the sudden entrance into the sea of the gigantic (>1km3) volcaniclastic unit. The onshore-offshore correlation and mapping of this volcaniclastic unit have allowed us to evaluate its distribution west of Somma-Vesuvius. The pyroclastic density current deposits terminate seaward at 40 m water depth; at the same depth the debris avalanche is affected by a gravitational instability. Over the last 3.5 ka the slump has been in constant movement, as documented by the angular unconformities at the top of the chaotic seismic unit and within the overlying marine deposits. © The Geological Society of London 2009.

The interpretation of high-resolution seismic profiles and core data collected in the western Somma-Vesuvius volcano documents a stratigraphic unit consisting of a voluminous debris avalanche that was covered by pyroclastic gravity current deposits after entering the sea. Based on the stratigraphic position together with the ages of the dated Somma-Vesuvius Plinian eruptions, this unit was linked to the ∼3.5 ka-old Avellino Plinian eruption and correlated and mapped in offshore and onshore areas. The deposition of the thick Avellino unit had a strong impact on the physical environment of the volcano's western sector, producing hundreds of metres of prograding coastline and the formation of a morphological barrier in the alluvial plain. The striking erosional and depositional features that characterise the top of the Avellino unit along the coast suggest that the entrance of the debris avalanche into the sea triggered a tsunami that struck the Naples Bay coast. The hazardous geologic events include both the sea-facing flank failure of the volcano (producing the debris avalanche and tsunami) and the Avellino Plinian eruption (producing pumice fall and surge clouds) that profoundly affected several human settlements located within a 20 km radius of the volcano, causing the decline of the Bronze Age communities.

The ad 79 Plinian eruption of Vesuvius that buried Pompeii and Herculaneum began with pumice falls deposited towards the SE of the volcano followed by pyroclastic currents directed towards the SW. These currents reached Herculaneum and rapidly entered the sea, forming a fan. The interpretation of seismic reflection profiles and gravity cores collected off Herculaneum documents a submarine fan-shaped pyroclastic body at 10–140 m water depth that we interpret as the submarine counterpart of the onshore pyroclastic current deposits. This fan, c . 0.3 km 3 in volume, displays a chaotic seismic facies that changes seaward to parallel reflectors and then to wavy reflectors. Gravity cores reveal a succession consisting of centimetre-thick sand- or silt-sized ash couplets followed by a graded gravelly sand-sized bed up to 180 cm thick, containing shell fragments and beach-derived pebbles, overlain by centimetre-thick graded and laminated sandy ash layers. The depositional textures and sedimentary structures of the submarine pyroclastic fan have been interpreted as the product of the interactions between pyroclasts, water waves and tsunamis induced by the ad 79 pyroclastic density currents into the Bay of Naples.

The interpretation of high-resolution seismic profiles and core data collected in the western Somma-Vesuvius volcano documents a stratigraphic unit consisting of a voluminous debris avalanche that was covered by pyroclastic gravity current deposits after entering the sea. Based on the stratigraphic position together with the ages of the dated Somma-Vesuvius Plinian eruptions, this unit was linked to the similar to 3.5 ka-old Avellino Plinian eruption and correlated and mapped in offshore and onshore areas. The deposition of the thick Avellino unit had a strong impact on the physical environment of the volcano's western sector, producing hundreds of metres of prograding coastline and the formation of a morphological barrier in the alluvial plain. The striking erosional and depositional features that characterise the top of the Avellino unit along the coast suggest that the entrance of the debris avalanche into the sea triggered a tsunami that struck the Naples Bay coast. The hazardous geologic events include both the sea-facing flank failure of the volcano (producing the debris avalanche and tsunami) and the Avellino Plinian eruption (producing pumice fall and surge clouds) that profoundly affected several human settlements located within a 20 km radius of the volcano, causing the decline of the Bronze Age communities.

The Campania Plain is a rapidly subsiding Quaternary basin that formed on the eastern margin of the Tyrrhenian Sea in association with the younger phase of Tyrrhenian rifting. It is located in the hinge area between the Apennines fold-thrust belt and the Tyrrhenian extensional backarc basin. By combining original stratigraphic analyses of well logs and seismic profiles we built a basin subsidence curve, mapped the fault pattern of the Campania Plain and analyzed the impact of the block faulting on the sedimentology and stratigraphic architecture of the basin fill. Well data indicate that the Quaternary succession consists of offshore, shoreface and coal-bearing coastal plain deposits arranged to form thick aggradational and retrogradational units. The sequence stratigraphy interpretation of well logs permitted us to recognize thirteen depositional sequences and the stratigraphic signatures of the rift stages. The study area corresponds to a sediment overfilled/balanced infill basin type that resulted from superposition of several rifting events characterized by high rates of basin subsidence.Taking into account the geological data of the adjacent areas, we propose a Pliocene-Quaternary rifting evolution of the upper Tyrrhenian plate consisting of four episodes. Two peculiar features of the Tyrrhenian rifting are a skip of the extensional axial zone eastwards leaving the previous zone of high strain localization (Vavilov basin), followed by a dramatic change (90) of the direction of extension. Because these Tyrrhenian features cannot be accounted for by the current rifting models we hypothesized a link between the evolution of upper plate and subducting slab. The proposed geodynamic scenario is characterized by a progressive rupture of the subducting plate and formation of extensional basins in the upper plate. (C) 2015 Elsevier Ltd. All rights reserved.

Sedimentological and chemical analysis of gravity core samples, along with the interpretation of very high resolution, single channel seismic reflection profiles acquired off the Sarno prodelta system (southeastern Naples Bay), document the sedimentary facies and seismic stratigraphic signature of the tephra deposit erupted by Vesuvius during the plinian eruption of 79 AD. The 79 AD pyroclastic deposits sampled off the Sarno prodelta system revealed significantly different characters with respect to both the subaerial succession documented from the type sections of Pompeii, Herculaneum and Oplontis and the more distal pyroclastic fallout deposits that were recovered from the outer continental shelf off the northern Salerno Bay. This was likely to be expected as, in proximal subaqueous settings, both primary deposition and reworking of tephra are known to be influenced by the hydrodynamics of the water itself (induced by the pyroclastic currents entering the sea) as well as by the early instability of pyroclastic bedforms due to the exceptionally high sediment yield during volcanic eruption. According to the data illustrated and discussed in this study, we suggest that the 79 AD tephra deposit sampled off the Sarno prodelta is likely to be the result of a number of syn-eruptive genetically-related depositional and/or erosional mechanisms associated with (1) anomalous waves (tsunami) and currents generated by the entrance of pyroclastic flows and surges into the sea; (2) subaqueous density flows evolved from the impact of hot pyroclastic currents into the seawater; (3) failure of water-logged, cohesionless pumice deposits, due to instability of pyroclastic bedforms rapidly accumulating on the seafloor. Seismic interpretation revealed that the Upper Holocene sequence off the Sarno prodelta system is affected by extensive creep involving the whole post-79 AD succession. Deformation due to creep is documented by slumping of semi-consolidated strata over a basal surface represented by the lithologic discontinuity between the base of the 79 AD tephra deposits and the underlying hemipelagite. Seismic data also suggest that gravitational instability of this area has been induced, or enhanced, by significant volcanotectonic deformation and local uplift of the seafloor that ostensibly predated the eruptive event. The results of this research may be relevant to studies of other eruption events in close proximity to coastlines in terms of wave- and/or current-generated sedimentary features as a possible explanation of unusual subaqueous facies architecture.

¶The crustal structure of the Campania continental margin is synthesized from outcrop, seismic reflection and gravimetric data. Outcrop and subsurface geological data reveal the presence of NE–SW faults, E–W faults and NW–SE faults. An older extensional event occurred along NW–SE faults and was followed by the main extensional event linked to the activity of NE–SW normal faults. The latter were active between 700 and 400 ka producing half-grabens filled by more than 5 km of Quaternary deposits. The stratigraphic signature of these tectonic events corresponds to a Lower Pleistocene marine unconformity-bounded unit overlain by Middle Pleistocene rocks belonging to a transgressive-regressive cycle. A crustal section of the Campania margin displays an asymmetric linked fault system characterized by a 10–12 km-deep main detachment level, listric normal faults and rollover anticlines. Structural and stratigraphic data document that the inception of volcanic activity at Vesuvius occurred at 400 ka, just after the main extensional event, and the volcano is located at the margin of a rollover anticline.

¶The Campanian continental margin is characterised by asymmetric half grabens and large-volume volcanic deposits. Vesuvius and Campi Flegrei are active volcanoes located along the coast of Naples Bay along one of these half grabens. The interpretation of an extensive set of seismic reflection data allowed to reconstruct the stratigraphy and structural pattern in Naples Bay and their relationships with volcanism. The stratigraphic succession is characterised by a complex architecture due to the presence of 157 Ka old submarine and subaerial vents, pyroclastic flow units associated to the Campanian Ignimbrite and the Neapolitan Yellow Tuff, and numerous tuff cones younger than 12 Ka. These volcanic units occur within marine sediments deposited during the late Quaternary sea level oscillations. The structural pattern is characterised by late Quaternary NE- trending normal faults, NW-trending transtensional faults, E–W trending left-lateral faults and WNW-ESE directed folds. The overall fault kinematics and the evaluated very high displacement rates are consistent with an E-trending left-lateral transtensional shear zone located between 41° and 40° N latitude. The relationship between volcanism and tectonics in the Bay of Naples is explained with block rotation associated with this shear zone. Finally, tectonic and stratigraphic data argue against the occurrence of a caldera in the Bay of Naples.

Somma–Vesuvius is an active volcano with a breached crater close to the continental shelf of Naples Bay, Italy. The interpretation of high-resolution seismic profiles offshore of Somma–Vesuvius shows interlayered volcanic and marine units in the Late Quaternary succession. In particular, the detailed seismo-stratigraphic analysis permitted, for the first time, the identification and mapping of two thick debris avalanche deposits located on the continental shelf. With a volume of 2.9 km 3 , the older debris avalanche, linked to the 18 ka Pomici di Base plinian eruption, was emplaced in a subaerial environment and then overlain by the sedimentary deposits of the lowstand prograding wedge. The younger debris avalanche, linked to the 3.4 ka Avellino plinian eruption, has a volume of c . 1 km 3 and is interlayered within the marine sediments deposited during the sea-level highstand. The identification of two debris avalanches originating from Somma–Vesuvius has two important implications: (1) the occurrence of two sector collapses in the history of Somma–Vesuvius volcano; (2) a potential volcano slope failure and consequent tsunamis produced by the entry of a debris avalanche into Naples Bay should be considered in the volcanic hazard evaluation of this densely populated area.

The Campania Volcanic Zone, located on the eastern margin of the Tyrrhenian Sea, is a region characterized by active volcanoes and ignimbrite deposits. Well-known active volcanoes include Campi Flegrei, Vesuvius, and Ischia. Over the last 15 years, numerous volcanoes, domes, pyroclastic units, and debris avalanche deposits have been discovered offshore of Campania, which has allowed new volcanic fields to be identified and the volumes of ignimbrite deposits to be quantified. Sequence stratigraphy is focused on analysing changes in the facies and geometric character of strata and on identifying key surfaces to determine the chronological order of basin filling. The use of a sequence-stratigraphic approach for the interpretation of outcrops, well log data, and seismic reflection profiles with different resolutions and penetrations enable the correlation of areas characterized by heterogeneous data sets. Here, the sequence-stratigraphic approach was applied in the complex area of the Campania Volcanic Zone. The study was conducted by interpreting seismic reflection profiles, well logs, and outcrops, and 3-D modelling of geological surfaces was performed using Kingdom® software (copyright IHS). The results include the discovery of buried volcanic units, the reconstruction of regional geological cross-sections, the construction of a coherent chronostratigraphic framework, and the establishment of stratigraphic relationships between different volcanic fields. This study defines a complete volcanic evolution of the Campania Volcanic Zone, identifies the abrupt changes in the sedimentary environments and, consequently, individuates the volcano-tectonic subsidence events. As a result, the Quaternary stratigraphy of the volcanic events is able to be updated.

The detailed stratigraphic analysis of synkinematic stratal architectures permits the calculation of fold uplift rates and the reconstruction of fold kinematics. This approach was applied to active folds in the Bay of Pozzuoli, eastern Tyrrhenian Sea. This area features late Quaternary volcanism, shallow magmatic intrusions, and transtensional tectonics. Seismostratigraphic analysis of synkinematic strata is constrained by a physical correlation to an already established stratigraphic succession in the neighboring Campi Flegrei and by tephra layers in a gravity core located in Pozzuoli Bay. A stratigraphic resolution in thousands of years was established. Structural and stratigraphic analyses yield quantitative data on the timing of fold inception, kinematics, and the amount and rates of uplift. The folds extend over ∼2 km, and display a curved axial pattern and wedge-shaped packages of synkinematic strata. The rate of fold uplift ranges from 1 to 20 mm/yr. The structures feature limb rotation kinematics and decreasing uplift rates. The uplift rates and geometry of the Pozzuoli Bay folds suggest that they are of tectonic origin and are a product of detachment folding. Their limited longitudinal extent and arcuate axial trends are compatible with an east-trending left transtensional shear zone that was active along the eastern Tyrrhenian Sea during the late Quaternary. A relative sea-level curve was calculated for an anticline culminating in the city of Pozzuoli. This relative sea-level curve highlights the relationship between the deformation timing and the genesis of related abrupt changes in sedimentary facies and erosional surfaces.

The structural and stratigraphic interpretation of high-resolution seismic reflection profiles permitted the reconstruction of the tectonics and basin architecture of the Bay of Naples from shelf-slope to deep basin areas. The Bay of Naples half-graben experienced extensional tectonics related to the activity of NE-trending normal faults during the Middle Pleistocene. The half-graben displays asymmetric and multiple fault segments linked by relay zones. The basin infill is made up, from old to young, of an unconformity-bounded unit and seven fourth-order depositional sequences. The oldest unit marks incipient fault activity. Increases of the fault slip rates gave rise to the formation of a tectonically-enhanced unconformity on the shelf and coeval thick debris flows in the deep basin. In the shelf-slope area the fourth-order depositional sequences form a trangressive–regressive cycle. The transgressive trend is linked to fault activity, whereas the regressive trend recorded tectonic stability.

By means of information technology, 3D digital geologic models are increasingly the best methods of constraining interpretations of geology at depth. Visualization in three dimensions has allowed us to develop solutions that explain the stratigraphic and structural complexity of the Campania margin of the Eastern Tyrrhenian Sea, especially the lateral relationships among volcanoes and underlying normal faults. Using seismic and sequence stratigraphy and structural geology approaches in a dedicated GIS environment, we interpreted a seismic grid and investigated a subsurface volcanic field in Gaeta Bay (off Campi Flegrei) located within the Campania margin. The Gaeta Bay basin fill is characterized by several volcanic units that were analyzed using 2D structure contour maps and isochron maps. These volcanoes are comparable in size to the edifices of Campi Flegrei, Vesuvius, and the submerged volcanoes of the Bay of Naples. Their age spans from the Lower Pleistocene for the isolated V0 volcano sited in Central Gaeta Bay to 0.4–0.1 Ma for the volcanic field of southern Gaeta Bay. The study of the interplay between volcanic units and faults allowed us to distinguish (1) the oldest fault buried by the Lower Pleistocene V0 volcano in Central Gaeta Bay; (2) a normal fault swarm NE–SW that in the Middle Pleistocene gave rise to a half-graben filled by the V1–V5 volcanic field in southern Gaeta Bay; and (3) post-0.4 Ma normal faults that downthrow the V1 and V3 volcanoes. We correlated the >1,500-m-thick Late Quaternary volcanoes of southern Gaeta Bay to the buried lava volcanoes interlayered with volcanoclastic deposits drilled at Campi Flegrei geothermal wells.

Vesuvius is an active volcano that has been affected by late Quaternary lateral collapses and tectonic faults. Cryptodomes and two debris avalanche, 18. ka-old DA1 and 3.5. ka-old DA2, were previously documented off Vesuvius and for the younger avalanche a link between onshore and offshore stratigraphy was reconstructed. The interpretation of seismic reflection profiles off Vesuvius, borehole stratigraphies, onshore and geomorphological data allowed to recognise the relationships among debris avalanches, criptodomes and faulting.Stratigraphic data reveal a remarkable difference between the architecture of the northern and southern volcano sectors that is compatible with the occurrence of the DA1 debris avalanche in the southern volcano sector. A contour map and a three-dimensional model of a surface merging the morphology of the top of the Somma lavas, in the northern volcano sector, with that of the top of the DA1 debris avalanche, in the southern volcano sector, were reconstructed. We present a new lateral collapse model of Vesuvius Volcano and document the relevance of inherited tectonic faults in guiding collapse geometry. It is possible that the SW-directed collapse (DA1) was driven towards the hangingwall blocks of NW-SE normal faults, while the propagation of the W-directed collapse (DA2) can be ascribed to the activity of the E-W strike-slip fault. Because of their distal location a minor role of cryptodome intrusion on collapses of Vesuvius can be postulated. The detailed analysis of substrate and edifice structure presented here establishes clear connexion between substrate tectonics and lateral collapse. This approach broadens the horizons of volcanic hazard assessment of Vesuvius. © 2011 Elsevier B.V.

The Margin of Campania (including Campania Plain and the Bay of Naples) featured recurrent large-scale ignimbrite eruptions between 270 and 15 ka. These ignimbrite deposits are exposed in the valleys of the Apennines and in limited areas along the Margin of Campania, whereas are covered by younger deposits in the Campania Plain and the Bay of Naples. Of all these eruptions, the Campania Ignimbrite (39 ka) and the Neapolitan Yellow Tuff (15 ka) are the best studied and are considered to be the most important. Numerous papers suggest that these two eruptions originated from one or two nested calderas located in Campi Flegrei and the Bay of Pozzuoli, in the northern part of the Bay of Naples. The recognition of the way, the site and the timing of a volcano-tectonic collapse is of paramount importance to establish which of the structures were active during the eruption. Our study demonstrates that the recognition of the areas involved in volcano-tectonic collapses is possible by means of a three-dimensional basin analysis. In the Bay of Naples the sequence stratigraphy interpretation of more than 4000 km of single-channel and multi-channel seismic reflection profiles made it possible to reconstruct the three-dimensional architecture of the ignimbrite units. Basin analysis reveals that before ignimbrite eruptions the physiography of the Bay of Naples was characterised by a lateral variation in depositional environment ranging from shelf to deep marine. Our structural and stratigraphic analysis documents volcano-tectonic deformations that occurred during the eruptions of the Pre-Campania Ignimbrite tuffs and of the Campania Ignimbrite: these deformations were controlled by normal faults with planar geometry. The overall features of the Campania Ignimbrites and the quantitative evaluation of crustal subsidence support a model of fissural emission associated to an asymmetrical crustal subsidence of the Campania Margin.

Naples Bay is an extensional basin that experienced an important reactivation of regional faults associated with the emplacement of thick volcanic units during the Late Quaternary. This paper is based on the interpretation of a strictly spaced seismic grid that permitted the reconstruction of the paleogeography of Naples Bay before the onset of volcanic activity and the paleogeographic changes following the voluminous volcanic unit's emplacement. Using the estimated paleo-water depth we calculated curves of space filled with volcanics and sediments, subsidence and accommodation space in order to understand the relationship between volcanic activity and tectonic subsidence at three selected sites (Penta Palummo, Pozzuoli Bay and offshore Vesuvius) of the Naples Bay basin. Repeated volcanic events and rapid basin infill were documented for the Penta Palummo area that underwent a dramatic physiographic change, changing from a slope-basin (in the Middle Pleistocene) to a shelf (during Late Quaternary). A more gradual physiographic change from a slope-basin to a shelf occurred in Pozzuoli Bay where the basin infill was caused by clastic vertical aggradation, later followed by a tectonic subsidence related to post-15 ka faulting and folding. Finally, the area offshore Vesuvius remained a shelf and did not experience any physiographic change as a rapid increase of accommodation space was balanced by the contemporaneous filling of the space due to the emplacement of Upper Pleistocene ignimbrites. These findings question the occurrence of a caldera offshore Campi Flegrei as reported by previous workers.

Slope instability processes have sculpted numerous morphological features on the flanks of the submerged volcanoes in Naples Bay off Campi Flegrei. Geophysical data were used to define the time and spatial evolution of sediment failures. Four types of volcanic slopes were recognized: (1) highly inclined slopes with low-relief morphologic features resulting from shallow translational slump complexes; (2) highly inclined slopes with high-relief morphologic features associated with deep, rotational slump complexes; (3) highly inclined slopes corresponding to scars and slump deposition at the base on a subhorizontal surface; and (4) gently inclined slopes with a staircase morphology associated with shallow rotational slumps. All slumps occur immediately after the emplacement of the volcanoes with some of them remaining active for a long time after their formation. The volcanic landslides under study were characterized by different concomitant triggering factors (angle of slope margin, seismic activity, basement architecture, rapid sea-level changes, sea currents and high pore-fluid pressure) and featured volumes of up to 200 million m 3 . The identification of recurrent events of flank instability affecting submarine volcanoes should be considered when evaluating the potential risk that tsunamis pose to the densely populated Naples Bay coast.

In this paper, we present an interdisciplinary study of the Upper Pleistocene ignimbrites of the Campanian margin in the Neapolitan area performed using outcrops, cores and seismic reflection data. We established a physical correlation between onshore and offshore stratigraphic units and reconstructed three regional geological sections. The stratigraphic succession in Naples is formed, from older to younger, by: Middle Pleistocene marine sediments; ancient ignimbrites reaching a maximum thickness of 200 m; 100–150 m thick tuffs of the 39 ka-old Campanian Ignimbrite; and products of 15 ka-old Neapolitan Yellow Tuff. The whole ignimbrite succession is thicker in Naples city and thins progressively towards the Bay of Naples, thus suggesting that some of the vents of these ignimbrites were possibly located near the city of Naples. NW-SE and NE-SW normal faults were rectognized in the Neapolitan area. In particular, NW-SE trending normal faults displace both the pre-CI tuffs and the Campanian Ignimbrite downthrowing the blocks towards the Bay of Naples in the order of hundreds of metres and feature ignimbrite thicknesses that are higher in the footwall than in the hangingwall blocks, whereas NE-SW normal faults formed after the Neapolitan Yellow Tuff eruption. In conclusion, the key result of our work is that NW-SE volcano tectonic normal faults were active during the Upper Pleistocene when ignimbrites were emplaced in the Neapolitan area in conforming with a model of fissure emission related to regional fault systems.

The interpretation of high-resolution seismic reflection profiles permitted the identification of many geologic features in the inner shelf of Pozzuoli Bay. This area corresponds to the offshore of Campi Flegrei: A classically active volcanic area that experienced earthquakes and meter-scale vertical ground uplift before the 1538 Monte Nuovo eruption and in the period from 1970 to 1985. The detected undersea features include two small debris flows that are located in a submarine valley in the western part of Pozzuoli Bay. They may be the result of a pyroclastic flow and a pyroclastic surge that entered the sea. The younger debris flow in the uppermost marine deposits of Pozzuoli Bay formed during the 1538 Monte Nuovo eruption, and the older debris flow during the 3.8 ka-old Averno eruption. Other features detected by our survey are an undersea 8 m-high and 1 km-wide cryptodome, corresponding to a near-surface intrusion, located off Pozzuoli, that warped post-4 ka marine deposits. The interpretation of the cryptodome is based on seismic facies analysis, deformation geometry and correspondence to a magnetic high. It is suggested that this undersea dome formed during the uplift phases associated with the 1538 Monte Nuovo eruption and the two more recent bradyseismic crises of 1970-1972 and 1982-1984. Surface-breaking faults (with maximum vertical offset of 1 m) were recognized in very shallow waters near the coast of Pozzuoli. It is suggested that some of these faults were active during the 1982-1984 bradyseismic earthquake sequence. © 2000 Elsevier Science B.V.

High-resolution seismic reflection data are used to identify structural features in Naples Bay near Vesuvius Volcano. Several buried seismic units with reflection-free interiors are probably volcanic deposits erupted during and since the formation of the breached crater of Monte Somma Volcano, which preceded the growth of Vesuvius. The presumed undersea volcanic deposits are limited in extent; thus, stratigraphic relationships cannot be established among them. Other features revealed by our data include (a) the warping of lowstand marine deposits by undersea cryptodomes located approximately 10 km from the summit of Vesuvius, (b) a succession of normal step faults that record seaward collapse of the volcano, and (c) a small undersea slump in the uppermost marine deposits of Naples Bay, which may be the result of nuee ardentes that entered the sea during a major eruption of Vesuvius in 1631. Detection of these undersea features illustrates some capabilities of making detailed seismic reflection profiles across undersea volcanoes.