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This paper is the outcome of the 1st Summer School on Geomorphology, Ecology, and Marine Biology in insular environments, focused on the advanced and multidisciplinary methods for the scientific investigation of marine coastal areas. It was held at Tremiti Islands, a significant laboratory for geomorphological, biological, and ecological studies because of its dynamic interaction between geodiversity and biodiversity, which makes it an ideal place for scientific research and geotourism. Landscape information was collected during field trips, while practical activities were finalized to sampling sediments and data collection of hard bottom assemblages. The map is the result of a multidisciplinary analysis incorporating geomorphological field observations and advanced methods applicable for ecological and environmental research, supported by scientific diving. This work represents a useful tool for the dissemination of environmental knowledge of the area and for understanding the relationships between landscape and natural heritage through modern and environmentally aware tourism.

Multibeam bathymetry, high-resolution seismic profiles and seafloor samples have been analyzed to characterize depositional and erosional dynamics recorded pro-deltaic deposits and outer shelf sediments along of a sector of the NE Sicilian margin (southern Tyrrhenian Sea). The deltaic deposits cover an area of ca. 15 km 2 in front of the Mazzarra River, and are morphologically characterized by waveforms trending overall along strike and incised cross-strike gullies of variable length. The gullies are shallow and characterized by small, coaxial erosive scours in the inner-middle shelf, whereas they become larger and deeper in the outer shelf-upper slope, in relation to the marked increase of slope gradients at the shelf break. Here, the wider gullies are characterized by a frame of crescent-shaped bedforms interpreted as cyclic steps, indicating the occurrence of sedimentary gravity flows in supercritical regime. Prodelta waveforms are widespread between − 50 and − 120 m, with wave lengths of 34–110 m and wave heights of 0.5–3 m. Morphometric characterization and spatial distribution of the waveforms suggests a main role in their genesis played by hyperpycnal flows, although we cannot discard the possible effect of internal waves or slow deformation processes (i.e., creep). Depositional and erosional features similar to those observed on the seafloor are evident in the subsurface stratigraphy, revealing the onset and growth of the Mazzarra Delta since the Last Glacial Maximum. The post-glacial sea level rise caused lateral shifts of the Mazzarra River mouth controlling migration of depositional lobes and intensity of seafloor incision and sediment reworking, ultimately resulting in the observed wavy bedforms extending from the inner shelf to the upper slope.

Discoveries from multibeam bathymetry and geochemical surveys performed off Zannone Island (western Pontine Archipelago, Tyrrhenian Sea) provide evidence of an undocumented hydrothermal field characterized by ongoing fluid emissions and morphologically complex giant depressions located in shallow water ( 250 m) that host pockmarks, mounds, small cones and active fluid vents, and which are interpreted as complex fluid escape features developed both through vigorous-explosive events and steady seepage. Their spatial distribution suggests that the NE-SW trending faults bounding the Ponza-Zannone structural high and the shallow fractured basement are favorable conditions for the upward migration of hydrothermal fluids. Moreover, we performed a detailed geochemical study to investigate the source of the hydrothermal fluids. The geochemical signature of the collected fluids provides information of active CO2-dominated degassing with a significant contribution of mantle volatiles, with measured 3He/4He values > 3.0 Ra that are similar to those recorded at Stromboli and Panarea volcanoes. The hydrothermal system produces volatiles that may originate from residual magma batches, similar to the Pleistocene trachytes cropping out in the SE sector of Ponza Island, that were probably intruded in the shallow crustal levels and never erupted. The discovery of the Zannone hydrothermal field updates the record of active hydrothermal areas of the Mediterranean Sea. Moreover, the recognition of several giant hydrothermal depressions characterized by a complex morphology is peculiar for the Mediterranean Sea.

The collection of high-resolution multibeam bathymetry, single-channel seismic profiles, TOBI side scan sonar data, and gravity cores allowed the characterization of the main morpho-sedimentary processes acting along the lower reach of the shelf-indenting Gioia-Mesima canyon-channel system (GMS) and the surrounding continental slope (southern Tyrrhenian Sea). This last area, developing across a depth range of 1000–1700 m, shows a complex morphology due to the interaction between downslope gravitative processes (mainly turbidite sheet flows) and abrupt changes in slope gradients related to tectonically-controlled scarps. Particularly, several erosive-depositional features (levee deposits, sediment undulations, channels) have been related to overflow processes from the northern flank of the GMS, although the lower reach of the GMS is characterized by strong entrenchment (canyon height ranging from 120 to 270 m) and low sinuosity. Morphological and seismic stratigraphy data indicate that the distribution and dimension of these features vary in response both to the proximity to the external levee of the GMS and to the topographic gradient of the lower continental slope. Particularly, we were able to discriminate between a gently sloping sector (on average 1.5°) dominated by sedimentary bypass of the turbidity currents and a steeper sector (about 3°), where the erosional capability of these currents seems to increase. Indeed, three channels, 4,3–6,5 km long and up to 20 m deep, incise this steeper sector, running parallel to each other at a distance of 1250–1500 m. To support the capability of overbanking flow in producing these channels, we used a physical model for the ignition of turbidity currents that provides realistic values for the ignitive state of the overbanking turbidity flows. More generally, the methodological approach used in this study may be useful to provide constraints on the genesis and evolution of erosive-depositional features in other tectonically-controlled margins, where sedimentary gravity flows interact with an uneven morphology.

Chiocci, Francesco L. ... et. al.-- 6 pages, 2 figures, High-resolution morpho-bathymetric data at 1:200,000 scale obtained during the FAIVI cruise (2011) and the resulting geomorphologic map of the Terceira island offshore area (central Azores, Portugal) are presented for the first time. The uneven morphology around Terceira is primarily related to volcanic features, such as linear and cone-shaped eruptive centres and lava flows. Such features are mostly concentrated on volcanic ridges and are aligned along preferential axes, suggesting a strong interaction between tectonics and volcanic processes. The occurrence of active tectonics is also demonstrated by systems of faults cutting the seafloor to the north, east and south of the island. Mapped erosive-depositional features include an insular shelf located at < 150 m water depth (wd), small landslide headwalls, erosive scarps, channelized features and crescent-shaped bedforms. The presented map may represent the base for a first-order geo-hazard assessment. © 2013 Copyright D. Casalbore

In the last decade great effort was put in the study of relative sea-level changes on Mediterranean coastlines through the integration of geophysical modelling and proxy data of paleo-shorelines. In this paper, we show potential and limitations of using additional marine geomorphic/sedimentary markers for earlier and lower sea levels. These markers are submarine depositional terraces (SDTs), i.e., deposits formed by a set of small prograding sedimentary wedges, having a terraced shape and found at variable shallow-water depths (mainly the first −150 m) on continental and insular shelves in the Tyrrhenian Sea. The shallowest terraces (near-shore) have their edges at depths between −10 m and −30 m, approximating the modern, local storm-wave base level. Their formation is thought to be associated with the modern sea-level highstand and thus, can be used as the modern analogue for deeper terraces formed in the past when the sea level was on the middle and outer shelf. Mid-shelf terraces have their edges at variable depths between −40 m and −90 m and probably formed during the last sea-level rise. They show a patchy spatial distribution and a large variability in their internal structure, so that they are not suitable for correlation on a regional scale. Shelf-edge terraces have their edges at depths between −120 m and −170 m, which is close or deeper than the Last Glacial Maximum (LGM) sea-level stand. They show a remarkable lateral continuity and a prograding internal structure similar to those at shallower depth and, thus, represent a proxy for the sea-level position at around 20 ka. However, the position of SDTs' edges is not a direct measure of paleo sea level positions because their depth depends on a complex interplay of several factors, such as the base of the storm wave and its variation in response to coastal physiography, as well as the occurrence of subsequent erosional or depositional processes. Depending on the geophysical and mapping methods used to determine their depth, the associated error range can also differ. Based on the analysis of these complexities and a wide range of physiographic settings of the Tyrrhenian Sea, we discuss these error ranges in order to assess potential and limitation of the SDT for analyses of vertical mobility of an area.

Submarine canyons along the Ionian Calabria margin indent large shelf sectors as the coalescing of smaller failure scarps progresses under the control of tectonic deformation and high sedimentation rates, promoted by regional uplift and rejuvenation of the drainage basin. The Punta Alice Canyon and the Ciro Canyon show such complex canyon heads, almost completely eroding the shelf and thus affecting sediment pathways along and across strike. Wavy bedforms of variable shape and size are observed both outside and inside the two canyon systems, providing an indication of how sediment is sourced and transported. We analyse the distribution of bedforms in order to define how both open shelf currents and confined sediment fluxes contribute to their formation outside and inside canyons. We also remark on the importance of the orientation of canyon heads and channels relative to flow direction of currents, and of slope failure as a sediment source.

Small-scale crescent-shaped bedforms were identified within flat-bottomed channelized features carving the submarine volcanic flanks of the Stromboli and Salina edifices. The bedforms are downslope-asymmetric, with a sub-horizontal stoss side and a steep lee side. They have a wavelength of tens of metres and a wave height of metres, and their crest-lines are roughly perpendicular to the maximum slope. Based on their size, texture and similarities to other bedforms, they can be interpreted as cyclic steps, i.e. a class of upslope-migrating turbidite sediment waves. Although their genesis must be similar, some differences are observed between the two cases. At Stromboli, repeated multibeam surveys at an 11-year scale showed a significant upslope migration of the bedforms because they lie on the bottom of a channel connected to active coastal dynamics, whose headwall is located at a few metres depth. By contrast, the surveys showed no significant morphological variations at Salina, where the bedforms are larger than at Stromboli and the channel headwall is located at about -100 m, suggesting that these feature are mostly inactive at present.

Five unconformity-bounded depositional sequences have been seismically defined on the Tyrrhenian margin offshore Southern Tuscany, Italy. The set of sequences encompasses a ~ 500 ka interval, each sequence recording a ~ 100-ka orbitally-driven climate-eustatic cycle. Similarly to most of Quaternary continental margins, sequences on the Southern Tuscany margin show an overall regressive motif reflecting shelf sediment progradation basically during the prolonged phases of sea level fall that characterise the Middle–Upper Pleistocene 100-ka cyclicity. On seismic profiles, however, progradational units within each sequence display a variable clinoform geometry, interpreted as a record of the alternation of highstand, falling and lowstand intervals within 100-ka cycles. The observed geometric variability is thus used as a key for separating systems tracts otherwise merging into a general progradational/regressive sedimentary body composing the bulk of each sequence. On a longer term, the interplay between sea level changes modulated by 100-ka cycles and regional subsidence controls the stratigraphic architecture and the growth pattern of the continental margin. This effect is documented by the overall aggradational/retrogradational stacking pattern of sequences, superimposed on shelf margin progradation and reflecting the renewal of accommodation space landward of the shelf margin and its exploitation at each cycle.

Multibeam bathymetry and high-resolution seismic profiles depict in detail the characteristics of submarine gullies present in the upper continental slope offshore of the mouths of the Tiber and Volturno Rivers in the Tyrrhenian Sea and the Simeto River in the Ionian Sea. Upper slope gullies are interpreted as depositional features, growing because of faster aggradation on intergully areas with respect to their axes. The dispersal of river-flood sediment through plunging of hyperpycnal flows has been interpreted to be the limiting factor in sedimentation in gully axes. However, the generation of hyperpycnal flows requires a sediment concentration of several tens of kilograms per cubic meter in the river flows to overcome the higher density of seawater. This threshold is difficult to reach in medium-sized rivers (i.e., catchment basin of 500–5000 km 2 ), such as the Tiber and Volturno. Two alternative scenarios of enhanced sediment availability for these rivers have been proposed. The first scenario is related to sea-level fall and lowstand stages, when the climate conditions may have been different and a huge amount of unconsolidated, fine-grained sediment deposited during the previous highstand stage may have been eroded from the river valleys, coastal plain valleys and shelf delta, as suggested in pioneering work of one of the authors (Chiocci) and Bill Normark. This scenario might explain the formation of some of the gullies offshore of the Tiber River mouth, which developed during the last glacial maximum; however, it is unable to explain the gullies within deposits related to transgressive and highstand system tracts, such as offshore of the Simeto and Volturno River mouths. An alternative scenario is thus proposed on the basis of the relationship observed between the studied rivers and the presence of large volcanic edifices in their catchment basins. Explosive volcanic activity could have drastically modified their catchment basins and caused a sudden and large supply of loose tephras, increasing the sediment load in watercourses and consequently favoring the development of gully-forming hyperpycnal flows. The timing of volcanic activity on the three study areas matches, in fact, the presence or absence of gullies in upper slope depositional sequences.

Seafloor mapping and morphometric analysis of landslide scars can provide useful insights for marine geo-hazard assessment, as demonstrated by several studies performed on different geological settings. The availability of high-resolution Digital Elevation Models (DEMs) obtained through swath bathymetry allows us to apply this approach to the submarine portions of Stromboli volcano, affected for about 90% of their extension by mass-wasting features. Two main kinds of tsunamigenic landslides have been recognized and analyzed. Large-scale sector collapses are catastrophic events that mobilize up to few km 3 of material, generating huge tsunami waves that may affect Stromboli and propagate in surrounding areas. The related hazard is not very high as these collapses show recurrence periods of some (or more) thousand years. Conversely, medium-scale landslides are more hazardous as they occur at higher frequency with respect to the previous events, i.e. from some hundreds up to a few tens of years. These events are able to generate local but severe tsunamis when occurring in shallow-water, as demonstrated by the recent 2002 tsunamigenic landslides that struck the Stromboli coasts with waves up to 10 m high. Medium-scale landslides mobilize volumes up to some millions of cubic meters and may also evolve landwards through retrogressive processes, thus affecting coastal sectors. This study highlights that the main predisposing factors controlling medium-scale slope failures at Stromboli are high slope gradient and sedimentation rates; eruptive activity also plays a key role, as recently witnessed by the 2002 landslide.

The analysis of high resolution morpho&ndash, bathymetric data on the Calabro Tyrrhenian continental margin (Southern Italy) enabled us to identify several morphological features originated by mass&ndash, wasting processes, including shallow gullies, shelf&ndash, indenting canyons and landslides. Specifically, we focus our attention on submarine landslides occurring from the coast down to &minus, 1700 m and affecting variable areas from thousands of square meters up to few tens of square kilometers. These landslides also show a large variability of geomorphic features which seems strictly related to the physiographic/morphological domains where the landslide formed. Tectonically&ndash, controlled scarps and canyon flanks are typically characterized by several coalescent and nested landslides, with diameters ranging from hundreds to a few thousands of meters. Canyon headwalls are commonly characterized by a cauliflower shape due to an array of small (diameters of tens of meters) and coalescent scars. In all these sectors, disintegrative&ndash, like landslides dominate and are generally characterized by a marked retrogressive evolution, as demonstrated by their morphology and comparison of repeated bathymetric surveys at the canyon headwall. Only in the lower part of tectonically&ndash, controlled scarps, a few cohesive&ndash, like and isolated landslides are present, indicating the main role of slope gradients and height drop in controlling the post&ndash, failure behavior of the mobilized material. Open slopes are generally characterized by large&ndash, scale (diameters of thousands of meters) and isolated scars, with associated landslide deposits. A peculiar case is represented by the Capo Vaticano Scar Complex that affected an area of about 18 km2 and is characterized by an impressive variability of landslide morphologies, varying also at short distance. The large extent and variability of such scar complex are thought to be associated with the occurrence of a mixed contouritic&ndash, turbidite system. By integrating the high&ndash, resolution morpho&ndash, bathymetric dataset with the results of previous studies, we discuss the main factors controlling the variability in size and morphology of submarine landslides developed in a tectonically&ndash, controlled setting and provide preliminary considerations on their potential geohazard in a densely populated coastal area.

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.

The marine volcaniclastic system extending to 3 km water depth on the northwest flank of Stromboli volcano has been surveyed using seismo-acoustic profiling, multibeam bathymetry, deep-towed long-range side-scan sonar imaging and box-core sampling. Deposits and sea-floor topography record repeated flank collapses that have occurred during the last 13 ka and created the present Sciara del Fuoco scar. An extensive (170 km2) debris-avalanche deposit characterized by subdued hummocks (megablocks) is buried by turbidites formed from gravity currents that originated in Sciara del Fuoco. The currents were mainly deflected along the margin of the avalanche deposit, but also spilt over onto it. The turbidites reflect topographic flow stripping and their thinning towards slightly steeper slopes indicates that some material that settled there drained further downslope as secondary higher concentration flows. The estimated volume of the entire fan-shaped bulge amounts to 12 ± 2.5 km3, about 3.5 km3 of which is attributed to the post-collapse sedimentation. The remaining 8.5 ± 2.5 km3 is in the order of the volume computed for the material removed by the multiple sector collapses that affected the NW Stromboli flank. Two units are identified in the distal part of the bulge, through the recognition of their fronts, and these indicate a layered structure for successive debris-avalanche deposits. Granulometric and particle-type characterization of seabed samples shows clast population evolution with sedimentary transport distance, from the main entrance point of debris in Sciara del Fuoco, to the confluence with the Stromboli Canyon, and into the Marsili Basin some 45 km from the island. Changes in particle populations are due to selective sedimentation and also mixing with a wide range of terrigenous detritus brought by currents that descended the main Stromboli Canyon from the continental shelf. Abundant fine sand and silt is produced at the volcano and occurrence of mainly coarse-grained material along the channel to the Marsili Basin indicates that a considerable volume of volcaniclastic material from Stromboli lies in the sedimentary succession accumulating on the distal basin floor, where a deep-sea fan is growing.

In order to monitor the Stromboli submarine slope after the 30 December 2002 landslide and tsunami, repeated marine surveys were carried out offshore of Sciara del Fuoco. The morphological changes and depositional processes that brought to the gradual filling of the slide scar have been studied in detail. Thirteen surveys in a period of little more than 4 years provided a unique opportunity to reconstruct the morpho-sedimentary evolution of the submarine slope and its recovery after the mass-wasting event. The scar has been progressively filled with lava and volcanoclastic debris; in the first month and a half, the filling rate was very high due to the entrance of lava flows into the sea and to the morphological readjustment of the slope; in the following months/years the rate dramatically decreased when the eruptive vents moved upwards and the eruption finally stopped. After 4 years (February 2007) more than 40% of the scar was already filled. In early 2007, a new eruption occurred and a lava delta was constructed in the 2002 scar, influencing the natural readjustment of the slope; therefore, our reconstruction only encompasses the period between the 2002 and 2007 eruptions. The swath bathymetry reconstruction of geometry and volume of scar filling during the period 2002–2007 evidenced a punctuated and fast shift of depocenters and debris emplacement through avalanching processes. This process quickly obliterated the features produced by the 2002 tsunamigenic landslide so that a major question about the preservation potential of mass-wasting features on active volcanic flanks emerges.

17 pages, 13 figures, 4 tables supplementary data https://dx.doi.org/10.1016/j.jmarsys.2016.01.005, In this paper, we used multibeam bathymetry and backscatter, high-resolution seismic profiles, ROV video images and sediment samples to identify the principal morpho-sedimentary features and related megabenthic communities along the upper reach of the Gioia Canyon (depth < 600 m) and the surrounding shelf and slope areas. Interpretation of the multidisciplinary dataset was undertaken to evaluate the relationships between seafloor characteristics and faunal distribution along a submarine canyon in an active tectonic setting. The results from this study indicate that physical disturbance on the seafloor at the canyon head and surrounding shelf, related to high sedimentation rates and occasional turbidite flows, may limit the variability of megabenthic communities. Evidence of diffuse trawl marks over soft sedimentary bottoms indicates anthropogenic impact due to fishing activities, which could explain low abundances of megabenthic species observed locally. The canyon margins and flanks along the continental slope host octocorals Funiculina quadrangularis and Isidella elongata, species that are indicative of vulnerable marine ecosystems (VMEs) and relevant in terms of sustainable management priorities. At the Palmi Ridge, the occurrence of outcropping rocks and bottom currents related to the presence of Levantine Intermediate Waters, provide conditions for the development of hard-bottom assemblages, including the black coral Antipathella subpinnata and deep-sea sponges fields, This research was performed in the framework of the Flagship Project RITMARE (SP4-WP2-A1)

Newly collected multibeam and seismic data on the intra-slope Palmarola ridge show widespread pockmarks and landslide-related morphologies along its flanks. In detail, two main types of slope failures were identified: disintegrative-like and cohesive like landslides. The first type is characterized by a complex of small, nested scars affecting the steep and tectonically-controlled eastern flank of the ridge, suggesting a genesis related to retrogressive processes. The cohesive landslides affect the northern flank of the ridge and are characterized by larger scars, where material was not completely evacuated, and well-defined debris deposits at their base, with the development of pressure ridges. Tectonic activity and slope gradients represent the main controlling factors for the development of instabilities; moreover, we noted a relationship between pockmarks and landslide scars.

10 pages, 5 figures, 2 tables, Regional inventories and magnitude-frequency relationships provide critical information about landslides and represent a first step in landslide hazard assessment. Despite this, the availability of accurate inventories in the marine environment remains poor because of the commonly low accessibility of high-resolution data at regional scales. Evaluating high-resolution bathymetric data spanning the time interval 2007–2011 for the Gioa Basin of the southern Tyrrhenian Sea yielded a landslide inventory of 428 events affecting an area of >85 km2 and mobilizing approximately 1.4 km3 of sediment. This is the first time that this area is studied in such detail, justifying comparison with other areas both onland and offshore. Statistical analyses revealed that the cumulative distribution of the dataset is characterized by two right-skewed probability distributions with a heavy tail. Moreover, evidence of a rollover for smaller landslide volumes is consistent with similar trends reported in other settings worldwide. This may reflect an observational limitation and the site-specific geologic factors that influence landslide occurrence. The robust validation of both power-law and log-normal probability distributions enables the quantification of a range of probabilities for new extreme events far from the background landslide sizes defined in the area. This is a useful tool at regional scales, especially in geologically active areas where submarine landslides can occur frequently, such as the Gioia Basin, This study was supported by the Italian MaGIC and RITMARE projects, and by the Spanish projects MOWER (CTM2012-39599-C03), FAUCES (CTM2015-65461-C2-1-R) and Eurofleets2 project LGT GIOIA 77

The Messina Strait, situated along the southern sector of the Italian peninsula, provides a good setting to study the source-to-basin relationships and, thus, the complete transect from continental to deep-marine environments. This work concerns the chemical and mineralogical composition of the fine-grained sediments collected along the Messina Strait, since the distribution of major and trace elements related to the mineralogical assemblages allow us the reconstruction of sedimentary evolution and geological processes affecting the studied sediments and, thus, the relationships developed between source area and sedimentary basin. Studied sediments are very-fine sand, silt and clay mainly phyllosilicates and quartz-bearing. Specifically, sediments located on submerged Calabrian and Sicilian slopes generally show high quartz content, whereas samples of the Calabrian and Sicilian continental slopes generally show high phyllosilicates content. Calcite and feldspars (plagioclase and K-feldspar) occur in different amounts. Few samples contain Fe-oxides. The geochemical signatures of the sediments reflect a provenance from felsic lithotypes. The A-CN-K diagram shows a linear trend parallel to A-CN join reflecting, primarily, weathering from granitoid rocks. This trend may result from non-steady state weathering conditions where active tectonism and uplift, as shown by morpho-structural conditions of the Messina Strait and its complex tectonic network, enhance mechanical erosion of mineralogical zones differentiated along weathering profiles developed on source rocks. Weathering efficiency at source area suggests weak intensity, related to a temperate Mediterranean climate similar to that characterizing the present-day study area.

The interaction between ocean bottom currents and topographic obstacles often results in sedimentary processes that form intriguing sedimentary deposits. However, without a thorough knowledge of both fluid mechanical processes and oceanographic settings regarding these sedimentary deposits, such an inherited interaction is not easy to understand. We here analyze the interaction between a bottom, geostrophic current and a local topographic depression, a slide scar offshore Cape Suvero, an Italian headland in the southern Tyrrhenian Sea, in order to explain the presence of contourite drifts off this cape. We apply the classical conservation of marine water potential vorticity and demonstrate the presence of a steady cyclonic circulation over the scar, which in turn affects contourite deposition. We thus show that the application of the potential vorticity conservation provides a simple but powerful, general tool for the understanding of the complex relations among ocean current, seafloor morphologies and sedimentary structures. (C) 2016 Elsevier B.V. All rights reserved.

Very high resolution bathymetric map obtained through multibeam echo-sounders 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 ultra-high 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.

26 pages, 14 figures, 3 tables, Our investigation is centred on the continental slope of the Antarctic Peninsula and adjacent basin. Type of sediments, sedimentary stratigraphy, and physical and geotechnical characterization of the sediments have been integrated. Four different types of sediments have been defined: diamictons, silty and muddy turbidites, muddy, silty and muddy matrix embedded clast contourites. There is a close correspondence between the physical properties (density, magnetic susceptibility and p-wave velocity) and the texture and/or fabric as laminations and stratification. From a quantitative point of view, only a few statistical correlations between textural and physical properties have been found. Within the geotechnical properties, only water content is most influenced by texture. This slope, with a maximum gradient observed (20°), is stable, according to the stability under gravitational loading concepts, and the maximum stable slope that would range from 22° to 29°. Nevertheless, different instability features have been observed. Volcanic activity, bottom currents, glacial loading-unloading or earthquakes can be considered as potential mechanisms to induce instability in this area. Copyright © Taylor & Francis Inc.

An active giant pockmark located offshore Zannone Island (central Tyrrhenian Sea, Italy), is analyzed by very high resolution multibeam bathymetry, high resolution seismic profiles, ROV video observations, sediment and water sampling. The active fluid emission area is located on the outer shelf, between 110 and 130 m water depth, and affects the Late Quaternary lowstand and highstand deposits resting on rocky bedrock. A variety of fluid-escape features characterizes the area, including the Zannone giant pockmark, several smaller pockmarks, hummocky terrains and areas of positive relief. Ground-truth video data show active seepages, bacterial communities, widespread lithified pavements, mounds, and cone-shaped structures. Evidence of active seepage includes both continuous and intermittent bubble release from the seafloor and a well-defined plume rising 70 m above the seafloor. The Zannone giant pockmark is about 900 × 500 m (surface of some 0.5 km 2 ). It represents the first evidence of an active shallow-water seepage area in the central Tyrrhenian Sea (Italy) and the first record of a morphologically complex giant pockmark in the entire Mediterranean Sea. Some speculations on processes originating the observed features are explored, including possible occurrence of multiple eruption events, processes of fluidization–liquefaction and minor slides that may have modified the original morphology. Factors peculiar to the study area – shallow depth, thin sedimentary cover resting on a faulted rocky basement, seeping occurring through non-cohesive sandy sediments – appear to have been key to the formation and morphology of the Zannone giant pockmark.

19 pages, 12 figures, 2 tables, supplementary material http://dx.doi.org/10.1007/s00445-015-0905-3, Terceira Island, in the Azores Archipelago, lies at the intersection of four submarine volcanic ridges. New high-resolution bathymetric and seismic reflection data have been used to analyze the main volcanic, tectonic and mass-wasting features of the island offshore. Volcanic features such as linear volcanic centers, and pointy and flat-topped cones are mainly concentrated on the narrow western and north-western ridges, characterized by an overall rugged morphology. Fault scarps dominate mainly the broad eastern and south-eastern ridges, which are characterized by an overall smooth and terrace-like morphology. On the eastern ridge, faults form a series of horsts and grabens related to the onshore Lajes Graben. The strikes of the fault scarps, linear volcanic centers and alignment of volcanic cones on the ridges reveal two main structural trends, WNW–ESE and NNW–SSE, consistent with the main tectonic structures observed on the Azores Plateau. In contrast, a large variability of strike was observed in inter-ridge areas, reflecting the relative importance of regional and local stresses in producing these structures. Mass-wasting features are subordinate and mostly represented by hundred meter-wide scars that indent the edge of the insular shelf surrounding the island, apart from two large, deeper scars identified on the southern steep flank of the western ridge. Finally, the remarkable morpho-structural differences between the western and eastern ridges are discussed in the framework of the evolution of the Terceira volcanic edifice and hypothesized to reflect successive stages of ridge evolution. © 2015, Springer-Verlag Berlin Heidelberg, Data acquisiton was conducted within the framework of the project >Features of Azores and Italian Volcanic Islands (FAIVI)>, supported by the European Commission 7th Framework Programme under EUROFLEETS grant agreement no. 228344

The interpretation of approximately 100 km of EM12 multibeam bathymetry and backscatter data together with high resolution TOPAS profiles obtained during a transit over the Orinoco deep-sea fan, near the Barbados accretionary prism, shows that the braided drainage pattern seen on GLORIA images by Belderson et al. (1984) corresponds to wide (∼10 km), low relief (

Shelves from volcanic ocean islands result from the competition between two main processes, wave erosion that forms and enlarges them and volcanic progradation that reduces their dimension. In places where erosion dominates over volcanism, shelf width can be used as a proxy for the relative age of the subaerial volcanic edifices and reconstruction of their extents prior to erosion can be achieved. In this study, new multibeam bathymetry and high-resolution seismic reflection profiles are exploited to characterize the morphology of the insular shelves adjacent to each volcanic edifice of Terceira Island in order to improve the understanding of its evolution. Subaerial morphological and geological/stratigraphic data were also used to establish the connection between the onshore and offshore evolution. Shelf width contiguous to each main volcanic edifice is consistent with the known subaerial geological history of the island; most of the older edifices have wider shelves than younger ones. The shelf edge proved to be a very useful indicator in revealing the original extent of each volcanic edifice in plan view. Its depth was also used to reconstruct vertical movements, showing that older edifices like Serra do Cume-Ribeirinha, Guilherme Moniz, and Pico Alto have subsided while more recent ones have not. The morphology of the shelf (namely the absence/presence of fresh lava flow morphologies and several types of erosional, depositional, and tectonic features) integrated with the analysis of the coastline morphology allowed us to better constrain previous geological interpretations of the island evolution.

High-resolution bathymetry and seafloor sampling have been used to characterize the 1891 submarine eruption of the Pantelleria volcanic complex. This submarine eruption has been documented mainly by historical reports, describing basaltic scoria bombs floating on the sea surface (i.e., lava balloons). In this study, the 1891 eruptive vent has been identified as a small cone (volume of ∼700,000 m3) rising ∼90 m from 350 m w.d., and located within a newly discovered submarine volcanic field covering a wide area offshore from the NW coast of Pantelleria; recently, Kelly et al. (2012) confirmed this location by a multibeam and ROV survey. Pyroclasts from the 1891 eruption crop out directly on the seafloor and are fresh scoria clasts (i.e., small bombs, bomb fragments, and lapilli) and glass ash-sized grains; both have been characterized in their morphology, textures, and geochemistry. The distinctive vesicularity and crystallization characteristics displayed by the scoriaceous pyroclasts reflect modes of degassing in both syn and posteruptive regimes; these characteristics, along with the distribution of deposits suggest for the strongest eruptive phase of the 1891 eruption a style analogous to Hawaiian fountaining. Glass grains from a buoyant plume were dispersed northward from the vent, up to distances of 1.5 km, redirected by the Levantine Intermediate Water. The identification of the 1891 submarine eruptive vent offshore Pantelleria, as well as the features of erupted pyroclasts improve our knowledge of submarine explosive eruptions that occur at shallow-intermediate depths and, among these, of the rare eruptions producing lava balloons.

Ischia volcanic island is one of the few cases in the Mediterranean where a clear relationship between constructional volcanism, volcano-tectonic uplift and cyclic multi-scale gravity failures is evident. One of these collapses involved the island’s southern flank and led to the emplacement of a submarine debris avalanche spreading over an area of 150 km2 with an estimated volume of 1.5 km3. C14 stratigraphy suggests that it may have occurred during pre-historical times or even during the Greek colonisation of the island (around 7th century BC). This very large mass movement i.e. the “Ischia debris avalanche” is still apparent on the seafloor with a mega-blocks field detectable until 40 km from the island along the lower continental slope. Its high mobility is proved by the very low H/L ratio when compared to other submarine debris avalanches. Here we report the preliminary results of a back-analysis in which we modeled a land-sea collapse based on some simplified assumptions. The implemented code used in this study assumes a fluid-solid mixture with given rheological behaviors and was already used for simulate the mobility of some terrestrial debris flows in volcanic areas.

Five consecutive multibeam bathymetries collected before, during, and after the 2007 Stromboli eruption, combined with visual inspections, allowed us to document the morphological evolution of an ‘a’ā lava-fed delta and to reconstruct the main processes acting during its submarine emplacement. The 2007 Stromboli delta extended down to 600-m water depth and covered an area of 420 × 103 m2, with a maximum thickness of 65 m and a total estimated volume of ≈7 × 106 m3, i.e., three times larger than its subaerial counterpart. The lava delta grew mainly through the emplacement of discrete lobes about 50–150 m in size. Lobes were fed from point sources along the paleoshoreline, and their subaqueous pathways seem to be mainly controlled by the submarine morphology, with flows mostly filling in depressions left by previous lobes. The main controlling factors on the lobe morphology and thickness are the effusion rates and the pre-eruption morphology, i.e., the geometry and gradients of the basal surface. Data also shows that sudden slope failure of portions of the submarine delta may occur simultaneously with accretion, implying that a significant part of the delta material can be transported to greater depths by submarine gravity flows. The present study is relevant for future monitoring and hazard assessment during the growth of active lava-fed deltas as well as for a better interpretation of ancient volcaniclastic successions inland.

High-resolution multibeam data in the central and eastern part of the Aeolian volcanic arc (Southern Tyrrhenian Sea) reveal widespread large-scale waveforms on the submarine flanks of these insular volcanoes. These features show high variability in wave parameters (wavelength of 60-1600. m and wave height of 4-200. m) and morphology (from sinuous to arcuate in plan-view, and from undulating to stepped, with very steep scarps, in cross-section), indicating that different processes, at variable spatial and temporal scale, are responsible for their genesis. By relating the morphological characters of the different waveforms and the local boundary conditions (morphological setting, regional slope gradients, sediment source and dynamics) where these features form, we were able to distinguish bedforms formed by sedimentary gravity flows from bedform-like features due to gravity instability processes. In detail, bedforms have been interpreted as coarse-grained sediment waves according to their wave parameters, geometry and texture. Bedforms are always found where the slope gradients markedly decrease to values

High-resolution multibeam bathymetry acquired around Ventotene and S. Stefano islands (eastern Pontine Archipelago, Italy) enabled us to map main mass wasting features affecting their submarine portions. Large-scale instability morphological features are absent (apart from a 4 × 2.5 km caldera in the western sector), whereas 126 landslide scars of 100-m of length scale were identified between 130 and 1,150 m of water depth (wd). Two main groups of scars can be distinguished: the first one affects the edge of the insular shelf between 130 and 260 m wd. The second group affects the lower slope and surrounding basins, representing cases of retrogressive failure at the heads of channelized features. The different morphological relief of the scars coupled with the recognition of crescent-shaped bedforms made it possible to distinguish two mass-wasting/erosive stages and consequently to map the more active sectors of the edifice. The future evolution of the mass wasting processes will produce the enlargement of erosive sectors with possible formation of large channels, which will carve wide sectors of the edifice, as suggested by available geological constraints and by comparison with the nearby and older western sector of the Pontine archipelago, where a more mature organization of mass wasting processes is observed. The present study can provide useful insights for hazard assessment and future planning of risk mitigation in such islands that are densely populated and touristically exploited during the summer months.

In December 2002, an effusive eruption at Stromboli triggered a complex instability phenomenon, which affected both the subaerial and submarine portion of the Sciara del Fuoco slope, causing destructive landslide(s) and tsunami waves. Among the monitoring activities coordinated by the Italian Civil Defence Department, systematic photogrammetric and bathymetric surveys were carried out. Digital photogrammetry technique and multibeam soundings were used to obtain high-resolution digital elevation model of land and sea-floor surface of the NW flank of Stromboli (Sciara del Fuoco depression). Merging the subaerial and submarine data, and comparing multitemporal digital models, we first estimated the mass volumes involved in the failures of the subaerial and shallow submarine slope to be about 24 x 10 6 m 3 , and then, we monitored the continuous and relevant morphological changes induced by erosional―depositional processes during the various syneruptive and posteruptive stages. Filling processes of the scar by lava flow and debris and the morphological evolution of the slope in the 2 years after the event were described.

High-resolution multibeam bathymetry is used as basis for detecting instability processes on the Tyrrhenian margin offshore Calabria (Italy). Among the many evidence at different spatial scale, we focus on selected cases that may represent a potential geohazard because of their scale, shallow/proximal location and state of activity. These include failures along coastal cliffs and canyon headwalls indenting narrow shelves. Coastal rocky failures impacting shallow water offshore Scilla and Palmi retain significant tsunamigenic potential, as proved by the 1783 Scilla event. Slide scars at canyon headwalls offshore Bagnara Calabra and Gioia Tauro indicate retrogressive failure active at water depth

La Fossa Caldera (LFC) on Vulcano island, in the Aeolian archipelago (Italy), is a multi-collapse caldera whose north-eastern part lies underwater. Through the integration of marine geophysical surveys and sampling carried out in the last decade, its submarine extension and offshore areas have been reconstructed in unprecedented detail. Strong erosive processes breached the submarine portion of LFC and gradually dismantled the caldera rims and infill, leading to the emplacement of a wide volcaniclastic fan from the base of LFC down to over 1000 m. The bathy-morphologic setting, seismoacoustic facies and analyses of sediment samples from the fan, together with volumetric considerations, suggest that this feature is the pathway/deposit of submarine unconfined gravity flows and turbidity currents deriving from the gradual dismantling of LFC. Submarine erosive processes are still active and the progressive erosion of the northern caldera sector threatens the stability of the active La Fossa Cone and the nearby coastal settlements. (C) 2012 Elsevier B.V. All rights reserved.

Submarine portions of Stromboli volcano account for about 98% of the whole extent of the volcanic edifice and are mostly covered by volcaniclastic sediments that made up a modern volcaniclastic apron. The architecture and main sedimentary processes acting within the apron are depicted through the integration of geophysical evidence (multibeam, long-range side scan sonar and seismic data) and seafloor sampling. The apron shows, on the whole, a large variability both across and along slope of morphologies and deposits related to mass-wasting and reworking processes, passing into areas covered by hemipelagic sedimentation. A large spectrum of erosive-depositional features was recognized on the surface of the apron. On shallower areas (i.e. submerged shelves, shore platforms and depositional terraces), submarine features related to wave action and sea-level fluctuations are present; they mainly act as temporary storing and reworking areas for volcaniclastic material derived from subaerial portions. Unconfined cohesionless inertial flows commonly dominate the upper slope, where gradients are very high (up to 35°) and grain-to-grain and grain-to-bed collisions are favoured within the flows. These flows tend to evolve into turbidity currents on the lower slope, in response to a marked decrease of slope gradients below ~ 8°, generating various erosive-depositional features, such as erosive furrows, troughs, channel-levee features and coarse-grained sediment waves. The most active area of the apron lies offshore Sciara del Fuoco (on the NW flank), where a large amount of coarse-grained volcaniclastic material, derived by the persistent Strombolian activity, is collected and deposited by means of high- and low-density turbidity currents on the lower slope down to 2600 m bsl, more than 20 km far from the island. Conversely, other areas are mostly dominated by deposition via settling of suspended sediments, related both to hemipelagic sedimentation and to the dispersion of fine tephras by the prevailing wind and marine currents. Such processes interfinger and overlie in space and time, giving rise to a very complex morpho-sedimentary facies distribution. However, the structural bilateral symmetry of Stromboli volcano allows defining distinct morpho-sedimentary zones, where one (or more) type of processes dominates, and related different stratal architecture of the apron. The unbuttressed portions of the island (NW and SE) are characterized by the emplacement of wide and thick debris avalanche deposits (volume in the order of 1-2 km3 for each event) related to large-scale sector collapses, representing the most important and efficient mass-wasting processes making up the apron. Such deposits are embedded within different volcaniclastic sequences and can be eroded or exhumed by successive gravity flows. The result is a highly complex (both spatially and vertically) succession of facies, where it is often difficult to depict an arranged series of processes. Conversely, on buttressed flanks (SW and NE) a more ordered evolution of processes and deposits making up the apron is observed, giving rise to a less complex apron architecture. © 2010 Elsevier B.V. All rights reserved.

The complex relationship between currents flowing around capes and their related contourite deposits (i.e. marine sediments deposited and/or reworked by the persistent action of bottom currents) is still an interesting and debated topic, both from a sedimentologic and oceanographic perspective. We analyze here contourite drifts located at intermediate depths off promontories in the southern Tyrrhenian and in the southern Adriatic Sea. The comparison between bathymetric-stratigraphic data and numerical, tank and analytic results, allows us to investigate the occurrence of contourite deposits around capes. We found that the presence of turbulence, and thus, of erosive conditions for sediments in the lee-side of a cape, can be detected by using dimensionless numbers related to cape dimension and ocean current features. We, moreover, analyze the additional sedimentary processes caused by seafloor unevenness offshore the cape such as local topographic depressions by applying the classical conservation of potential vorticity. The resulting effect is a steady cyclonic circulation over the depression that affects contourite deposition. We show that the application of the potential vorticity conservation provides a simple theoretical tool for the understanding of complex relations among ocean current, seafloor morphologies, and sedimentary processes. This work can be seen as a new approach to bridge the gap between marine sedimentology and physical oceanography.

The first high-resolution bathymetric and backscatter maps of offshore Stromboli Island are presented, together with an interpretation of its volcanic, structural and sedimentary features. The volcanic edifice is characterized by a sub-conical shape with a quasi-bilateral symmetry with respect to a NE-SW axis. The dimensions of the Strombolicchio volcanic centre, to the NE of Stromboli, have been restored by redrawing its morphology before wave action that eroded it in Late Quaternary time. On the NE submarine flank of Strombolicchio, a N64°E structural trend controls the shape of Strombolicchio Canyon. On the southern side of Stromboli, the submarine flank has a radial structural trend, possibly reflecting a volcanic stress regime. Landslide scars at various scales are ubiquitous on the submarine slopes of Stromboli. Repeated large-scale lateral collapses have affected both the northwestern and southeastern unbuttressed flanks of the volcano, producing large debris avalanche deposits.

We reconstruct the sequence of landslides that occurred soon after the beginning of the December 2002 eruption on the NW Hank of Stromboli volcano. Landslides involved the northeastem part ofthe Seiara del Fuoco (SdF) slope, an old collapse scar filled by products of volcanic activity, producing tsunami waves that severely damaged the coast of the island of Stromboli. Volumes of the mass detached from the subaerial and submarine slope were quantified by comparing preslide and postslide slope surfaces obtained by aerophotogrammetric and bathymetric data, which also allowed, in conjunction with field observations and helicopter surveys, the reconstruction of geometry and kinematics of landslides. According to the reconstructed sequence, 2 days after the beginning of the eruption, the upper part ofthe NE sector ofthe SdF slope experienced major displacements (few tens of meters). Movements propagated downslope and affected the nearshore portion ofthe submerged slope without a rapid sliding ofthe displaced mass into the sea. The following hours were characterized by a progressive increase ofdeformations, localized along shear zones extending over two thirds of the subaerial slope. This phase proceeded until a submarine slide about 6 millions of cubic mters in volume occurred, causing a first tsunami wave. The subaerial mass delimited by the shear zones and unbuttressed at its foot, then slipped into the sea producing a second tsunami wave. The main landslide event (and the minor slumps which followed) removed a volume of about l0 millions of cubic mters of the infilling deposit, to a thickness of at least 65 m. Hypotheses were fomulated on the mechanisms that controlled the different phases of the instability sequence. Since hydraulic and stress/strain conditions progressively changed during the slope evolution, the formulated mechanisms are also based on geotechnical analyses and considerations on the mechanical behavior of volcaniclastic materials. The process that led to the landslide events was initiated by forces exerted by magma intruded into the slope, while further steps ofthe evolution of slope stability conditions (especially the submarine failure) were controlled by the particular shear behavior of the volcaniclastic material, mainly iniiuenced by grain crushability. ln fact, strength progressively decreased as shear strains proceeded, and the intensely sheared saturated material forming the submarine slope may have become susceptible of failure when sudden strain/stress increments occurred.

[1] On 30 December 2002, a major instability event, deeply involving the submarine slope, occurred on the Sciara del Fuoco, on the western flank of Stromboli volcano, in the Aeolian Islands. Tsunami waves with a maximum runup of over 10 m in Stromboli were generated, having a measurable impact as far as the Sicily coast. Just 10 months before the event, a multibeam bathymetry had been collected in the area down to 1000 m of depth. A repetition of the survey after the slide allowed the unique opportunity to verify the occurrence of a large submarine slide and to define volumes involved and morphology generated by the event, through the comparison of the preevent and postevent bathymetric grids. A morphological characterization of the slope before and after the submarine landslide is presented, showing how the preexisting features interacted with the slide event in controlling the instability. Mechanisms of the submarine failure are discussed on the basis of the geometrical characters of the landslide event, structural and stratigraphic setting of the submerged slope, and geotechnical considerations on the behavior of slope material.

The complex sequence of large-scale tsunamogenic instability phenomena occurred on the subaerial and submarine NW flank of the Stromboli Volcano soon after the beginning of the December 2002 eruption is reconstructed and its relationship with volcanic activity is evidenced. After a brief description of slope morphology and stratigraphy, geometry and kinematics of the landslides are described. Finally, instability mechanisms that controlled the subaerial and submarine slope failures are proposed with reference to the different geotechnical, hydraulic, and loading/strain conditions that characterized the different stages of the slope evolution.

The best possible policy in relation to contrast beach erosion and coastal retreat in coasts heavily exploited by tourists is artificial beach nourishment. The success of such a policy strongly depends on the availability of large quantity of sand (in the order of millions of cubic metres). The exploitation of marine sand deposits buried in the continental shelf may meet such a large need. The prospection of sand is mainly realised with reflection seismic profiles, first shot at a regional scale then concentrated in the most promising areas. Seafloor sampling is then used to verify the geophysical data and characterise the sand. The identification of sand-prone deposit is based on a detailed geological interpretation of the seismic data that allows definition of the evolution of the shelf during the last glacial cycle (20 000 years). In fact, the sea level rose from -120 m to 0 in less than 20 000 years and caused the coastline to migrate across the shelf, possibly leaving relict sand prone deposits at various depths. Unfortunately, such deposits are rare, relatively difficult to image and usually buried below the present-day shelf mud. A typical stratigraphic situation, taken from the Regione Lazio, is described as reference.

A suite of modern, shore-normal channels was discovered on the southern shoreface of Sable Island, Canada. Repetitive multibeam and side scan surveys of these features, as well as box coring and sampling, showed that the depressions were perennial features of the shoreface. They occurred in fine and medium sand and were most abundant in-depths less than 20 m. They were up to 1 m deep and 50 m wide, increased in size seawards, and generally followed the seabed slope. The channels dominated the inner shoreface becoming wider and deeper seawards to depths in excess of 40 m. There is a continuum of scales in width and depth of these channels, the smallest of which are equated with gutters preserved in the geological record. The internal structure of the shoreface sediments where the gutters are found is characterized by normally graded tempestites composed of cut-and-fill structures overlying an erosion surface. Thus, the environmental setting, internal structure, and scale are similar to ancient counterparts. Gutters have been interpreted to result from downwelling over palaeo-shorefaces during ancient storms [Myrow, 1992b]. The composition of gutter infill, as well as the stability, evolution, associated bed forms, and hydrodynamic conditions under which they formed, were examined to verify genetic interpretations of the ancient counterparts. The multisensor benthic lander RALPH was deployed within a field of shore normal channels for 17 days during late winter 1998. RALPH burst-sampled flow at hourly intervals while imaging the seabed. Resulting sequential imagery revealed the genesis of a group of five gutters during storm spin-down that was coincident with the formation of large-scale wave ripples. This was followed by infilling of the gutters and wave ripple destruction within 20 hours by longshore sand transport. The gutters were located within, and parallel to, a larger channel (50 m wide and 0.50 m deep). They were formed by coastal set-up and subsequent downwelling that was triggered by the rotation of storm winds from seawards (onshore wind) to landwards (offshore wind). The gutters formed within 2–3 hours during spin-down of a winter storm under “live-bed” conditions of sand transport. Wave height and mean tidal flows were well below those of the storm peak and so they were not directly responsible for creating the gutters. The mechanism we propose for the evolution of gutters supports the geological interpretations; that is, a storm-driven, downwelling event as described by Swift and Niedoroda [1985]. However, the downwelling event appeared to take place suddenly (rapid acceleration in flow), briefly (few hours duration), and within narrow corridors guided by wider and deeper channels of the shoreface. High turbidity during the time of gutter formation leads us to believe that the phenomenon of inner shelf turbidity currents [as suggested by Walker, 1985] exists and may be instrumental in channel formation.

Wave-built terraces formed during sea-level Stillstands at depths lower than present are found along margins with fairly steep morphology and no- to ill-developed continental shelf, for instance the margin of volcanic islands. Terraces deposits are up to 20–30 m thick and are flat-topped with well-defined edges. They extend up to 1 km in dip section. The deposits are composed of intrabasinal sediments, mainly bioclastic sand and silt and are probably due to deposition below the storm wave-base during large-scale energy episodes. Two areas of the Tyrrhenian Sea have been analysed, one in a volcanic context (the Pontine archipelago) and the other in a highly active structural context (the Calabrian Arch). Similar wave-built terraces were found in both areas, with a main terrace placed at a depth of 100–150 m, which is thought to be Wurmian. Older terraces are also present, emplaced during the preceding lowstands in the Late Pleistocene. A possible present-day terrace is found at about 20 m depth in the Pontine archipelago. A mechanism of subsequent formation below wave base-level and removal because of sea level lowering has been hypothesised during long-lasting periods of Late Pleistocene sea level falls. Terraces are thus thought to preserve only at the minimum lowstand position and to remain relict on the slope during sea level rise and highstand. The analysis of the distribution and depths of these terraces allows some neotectonic interpretation. For example, in the volcanic archipelago, whose western sector has probably risen at an average rate of 2.5 mm/yr over the last 20,000 years.

The upper slope and outer shelf in front of the Tiber River mouth (east-central Tyrrhenian Sea) exhibits a series of about 15 gullies that are not clearly related to present-day erosional or depositional processes. An extensive, high-resolution, seismic-reflection profiling survey of a 450 km 2 area in front of the Tiber delta shows several generations of similar features within the older depositional sequences underlying the outer continental shelf. The gully relief appears dominantly depositional, probably developed during lowstand periods when the Tiber River mouth was relatively near the shelf break. The position of the gullied intervals, including those on the modern slope relict from the last lowstand, shows a successive northward shift with time. This northward shift indicates continued tilting of this part of the eastern Tyrrhenian continental margin, probably resulting from a continued subsidence to the north.