Morphology of Salina offshore (Southern Tyrrhenian Sea)

In this paper, we present the first complete morphological map of the Salina offshore at a scale of 1:100,000. The submarine flanks of the Salina edifice extend down to −650 to −1300 m, are steep and characterized by an uneven morphology due to the presence of volcanic and erosivedepositional features. The volcanic features cover ∼30% of the submarine portion and include volcanic cones and bedrock outcrops. The remaining ∼70% is affected by a wide series of erosive-depositional features. Among these, features related to Late Quaternary sea level fluctuations comprise the insular shelf surrounding the island and overlying submarine terraced depositional sequences. Mass-wasting features include landslide scars, channels, fanshaped deposits and waveforms. The presented map provides useful insights for a better understanding of the morphological evolution of the edific

Imaging continental shelf shallow stratigraphy by using different high-resolution seismic sources: an example from the Calabro-Tyrrhenian margin (Mediterranean Sea)

High-resolution seismic reflection profiles of the Calabro-Tyrrhenian continental shelf were collected using different seismic sources (Sub-Bottom Profiler, Uniboom, Sparker 0.5-1-4.5 kJ). Noticeable differences and results were obtained both from a geophysical and geological-interpretative point of view. The availability of different sources permitted the definition of the most suitable seismostratigraphic characterization in terms of resolution, penetration and acoustic facies. Very high resolution stratigraphy was defined through profiles produced by different seismic systems used in parallel. This permitted the application of sequence-stratigraphy concepts with the reconstruction of a thick postglacial depositional sequence, formed by a transgressive and a high-stand systems tract. The thickness distribution of postglacial deposits reveals that the main depocenter (55-65 m) is located offshore of the Coastal Range, along a stretch of coast supplied by several small and seasonal streams ("fiumare") and characterized by the lack of a coastal plain. This suggests the greater efficiency of sediment supply and bypass in this area relatively to sectors located offshore of the main rivers. The transgressive systems tract, usually thin or nearly absent, is particularly well developed (up to 33 m) and is composed of up to three parasequences with a retrogradational stacking pattern. The high-stand systems tract, up to 30 m thick, is made up of two parasequences and has a quite regular geometry and acoustic facies.Perfis de reflexão sísmica de alta resolução da plataforma continental tirreniana de Calabro foram obtidos utilizando-se recursos sísmicos diversos (Perfilador de Sub-superfície, Uniboom, Sparker 0.5-1-4.5 kJ). Diferenças evidentes foram encontradas sob o ponto de vista geofísico e geológico-interpretativo. A disponibilidade de diferentes fontes permitiu a definição de uma caracterização sismo-estratigráfica mais acurada em termos de resolução, penetração e facies acústica. Uma estratigrafia de resolução bastante alta pôde ser obtida através de perfis produzidos por diferentes sistemas sísmicos utilizados em paralelo. Este fato possibilitou o emprego de conceitos de sequência-estratigrafia para a reconstrução de uma espessa sequência deposicional pós-glacial formada por um trato de sistemas transgressivo e de nível de base alto. A espessura dos depósitos pós-glaciais revela que o principal centro de deposição (55-65 m) está localizado ao largo da serra costeira, ao longo de uma costa distendida e alimentada por pequenos filetes sazonais ("fiumare"), sendo caracterizado pela falta de uma planície costeira. Os dados sugerem a existência de um suprimento de sedimentos bastante eficiente nessa área, em relação a setores localizados ao largo dos rios principais. O trato de sistemas transgressivo, geralmente estreito ou ausente, é aqui particularmente bem desenvolvido (acima de 33 m) e composto por até três parasequências com padrão de empilhamento retrogradacional. O trato de sistemas de nível de base alto, até 30 m de espessura, é composto por duas parasequências e apresenta geometria e facies acústica extremamente regulares

Imaging continental shelf shallow stratigraphy by using different high-resolution seismic sources: an example from the Calabro-Tyrrhenian margin (Mediterranean Sea)

High-resolution seismic reflection profiles of the Calabro-Tyrrhenian continental shelf were collected using different seismic sources (Sub-Bottom Profiler, Uniboom, Sparker 0.5-1-4.5 kJ). Noticeable differences and results were obtained both from a geophysical and geological-interpretative point of view. The availability of different sources permitted the definition of the most suitable seismostratigraphic characterization in terms of resolution, penetration and acoustic facies. Very high resolution stratigraphy was defined through profiles produced by different seismic systems used in parallel. This permitted the application of sequence-stratigraphy concepts with the reconstruction of a thick postglacial depositional sequence, formed by a transgressive and a high-stand systems tract. The thickness distribution of postglacial deposits reveals that the main depocenter (55-65 m) is located offshore of the Coastal Range, along a stretch of coast supplied by several small and seasonal streams ("fiumare") and characterized by the lack of a coastal plain. This suggests the greater efficiency of sediment supply and bypass in this area relatively to sectors located offshore of the main rivers. The transgressive systems tract, usually thin or nearly absent, is particularly well developed (up to 33 m) and is composed of up to three parasequences with a retrogradational stacking pattern. The high-stand systems tract, up to 30 m thick, is made up of two parasequences and has a quite regular geometry and acoustic facies

Morphology of Lipari offshore (Southern Tyrrhenian Sea)

High-resolution multibeam bathymetry was recently collected around Lipari, the largest and most densely populated island of the Aeolian Archipelago (Southern Tyrrhenian Sea). The data were acquired within the context of marine geological studies performed in the area over the last 10 years. We present the first detailed morphological map of the Lipari offshore at 1:100,000 scale (Main Map). A rugged morphology characterizes the submarine portions of Lipari volcano, reflecting both volcanic and erosive-depositional processes. The volcanic features include cones, lava flows and bedrock outcrops. Erosive-depositional features include an insular shelf topped by submarine depositional terraces related to LateQuaternary sea-level fluctuations, as well as landslide scars, channelized features, fanshaped deposits and wavy bedforms. The different distribution of volcanic and erosivedepositional features on the various sectors of Lipari is mainly related to the older age of the western flank with respect to the eastern one. The map also provides insights for a first marine geohazard assessment of this active volcanic area

The first ultra-high resolution Digital Terrain Model of the shallow-water sector around Lipari Island (Aeolian Islands, Italy)

Very high resolution bathymetric map obtained through multibeam echosounders data are crucial to generate accurate Digital Terrain Models from which the morphological setting of active volcanic areas can be analyzed in detail. Here we show and discuss the main results from the first multibeam bathymetric survey performed in shallow-waters around the island of Lipari, the largest and the most densely populated of the Aeolian Islands (southern Italy). Data have been collected in the depth range of 0.1-150 m and complete the already existent high-resolution multibeam bathymetry realized between 100 and 1300 m water depth. The new ultrahigh resolution bathymetric maps at 0.1-0.5 m provide new insights on the shallow seafloor of Lipari, allowing to detail a large spectrum of volcanic, erosive-depositional and anthropic features. Moreover, the presented data allow outlining the recent morphological evolution of the shallow coastal sector of this active volcanic island, indicating the presence of potential geo-hazard factors in shallow waters

Benthic foraminifers and siliceous sponge spicules assemblages in the Quaternary rhodolith rich sediments from Pontine Archipelago shelf

The bottom samples (Quaternary in age) of two cores (CS1 and Caro1) collected at 60 and 122 m water depth in the marine area near Ponza Island (Pontine Archipelago, Tyrrhenian Sea) are investigated. In particular, benthic foraminifers and siliceous sponge spicules are considered. The coralline red algae (pralines, boxworks and unattached branches) are abundant in both samples and, particularly, in the CS1 bottom as well as the benthic foraminifers. The siliceous sponge spicules also are very diversified and abundant in the CS1 bottom sample, while in the Caro1 bottom they are rare and fragmented. Benthic foraminiferal assemblage of two samples is dominated by Asterigerinata mamilla and Lobatula lobatula, typical epiphytic species but also able to live on circalittoral detrital seafloors, adapting to an epifaunal lifestyle. Based on these data the bottom of the studied cores represents the upper circalittoral zone, within the present-day depth limit distribution of coralline red algae in the Pontine Archipelago (shallower than 100 m water depth)

The limits of seaward spreading and slope instability at the continental margin offshore Mt Etna, imaged by high-resolution 2D seismic data

Highlights: - Analysis of a combined new high-resolution 2D seismic and bathymetric data set offshore Mt Etna - Extensional domains are mapped at the shallow subsurface of the continental margin - Compressional structures are mapped at the toe of the continental margin - A coupled volcano edifice / continental margin instability is proposed Mount Etna is the largest active volcano in Europe. Instability of its eastern flank is well documented onshore, and continuously monitored by geodetic and InSAR measurements. Little is known, however, about the offshore extension of the eastern volcano flank, defining a serious shortcoming in stability models. In order to better constrain the active tectonics of the continental margin offshore the eastern flank of the volcano, we acquired a new high-resolution 2D reflection seismic dataset. The data provide new insights into the heterogeneous geology and tectonics at the continental margin offshore Mt Etna. The submarine realm is characterized by different blocks, which are controlled by local- and regional tectonics. A compressional regime is found at the toe of the continental margin, which is bound to a complex basin system. Both, the clear link between on- and offshore tectonic structures as well as the compressional regime at the easternmost flank edge, indicate a continental margin gravitational collapse as well as spreading to be present at Mt Etna. Moreover, we find evidence for the offshore southern boundary of the moving flank, which is identified as a right lateral oblique fault north of Catania Canyon. Our findings suggest a coupled volcano edifice / continental margin instability at Mt Etna, demonstrating first order linkage between on- and offshore tectonic processes

Depositional response to Quaternary fourth-order sea-level fluctuations on the Latium margin (Tyrrhenian Sea, Italy)

More than 10 000 km of high-resolution seismic profiles permit detailed study of six fourth-order seismic stratigraphic sequences deposited during the last million years on the Latium continental shelf, Tyrrhenian Sea, Italy. Sedimentation occurred on a relatively young passive margin characterized by a narrow and relatively steep shelf where sediment storage capacity in adjacent subaerial basins was limited. The Late Pleistocene deposits are locally tilted and eroded to different levels along the sea-floor so that carefully placed seafloor gravity cores help constrain the age of the seismic sequences by the dating of microfauna. Correlation with a deep well located on the coast constraints the basal third-order sequence boundary on the shelf. The seismic and a limited core database make it possible to: (1) detail variability in the architecture, stratal patterns and bounding surfaces of the sequences across the shelf and adjacent continental slope; (2) define a hierarchy of seismic units and their bounding surfaces; (3) make a correlation with the published oxygen-isotope curves; (4) develop a detailed stratigraphic framework and model for the fourth-order sequences deposited during last 0.8 Ma; (5) define the effects of the long-lasting eustatic falls on margin sedimentation; (6) recognize volumetric partitioning of sedimentation between systems tracts. The seismo-stratigraphic expression of the third- and fourth-order sequence boundaries varies greatly from the inner to the outer part of the margin. Where subsidence allowed the preservation of lowstand systems tract (LST) deposits on the shelf, they are bounded by erosional unconformities interpreted to reflect fourth-order glacioeustatically-driven cycles. Relatively thin (<10 m) lens-shaped bodies mark the transition from the unconformities to their correlative conformities and are interpreted to have been deposited during the eustatic minimum. The deposits bounded between correlative conformities show an upward loss in acoustic transparency thought to indicate upward-coarsening and regression within the sequences. Downdip on the continental slope, sequence boundaries are concordant surfaces correlative with unconformities on the shelf. However, these surfaces are locally scoured by channellized features, interpreted to record slope erosion related to the discharge of river bedload during lowstands. There is marked asymmetry and volumetric partitioning between systems tracts; most of the Late Quaternary deposits that comprise the Latium continental margin are interpreted to have formed during forced regression and lowstand. Offshore of the northern and central Latium shelves forced regressive and lowstand deposits account for some 1000 km3 of shelf and slope deposition during the last eustatic cycle. In contrast, sediments attributed to the transgressive and highstand systems tracts account for approximately 37 km3. High-frequency, high-amplitude asymmetric sea-level changes driven mainly by glacioeustasy are interpreted to have controlled deposition. Following classic three-fold sequence stratigraphic models, the unconformities created by shelf subaerial exposure and erosion represent sequence boundaries at the base of depositional sequences. However, if as is the case of the Latium margin during the Late Pleistocene, where a continental margin is formed almost exclusively of forced regressive deposits, each sequence basal boundary will paradoxically be situated above the forced regressive deposits that are deposited as the subaerial exposure surface forms, i.e. above the whole of its own depositional sequence. In this respect, the incorporation of a fourth forced regressive or falling stage systems tracts specific to times of base-level fall would help avoid this inconsistency