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The marine scientific community developed new habitat mapping procedures that proved to be effective to map seafloor habitats in a holistic manner, thus refining our knowledge of benthic sea life. Several works on this topic focused on cold-water coral habitats at the global scale, with focus on the Atlantic Ocean while, only a few studies applied these methods to the Mediterranean Sea. The prime objective of this chapter is to comment the methodologies used to describe cold-water coral habitats and map their extension; secondly we discuss statistical models to outline the most suitable areas for cold-water coral settlement (habitat suitability models). Furthermore, recent technological developments in habitat mapping procedures provide geophysical data and seafloor images of higher resolution than ever before, while multi-frequency systems supply new hyperspectral images of the seabed. This new type of data could be crucial for a better characterisation of such Mediterranean cnidarian habitats. Here we reviewed the procedures for the Mediterranean cold-water coral habitat mapping applied so far, describing two case studies in the Southern Adriatic Sea and discussing caveats and future perspectives.

The marine scientific community developed new habitat mapping procedures that proved to be effective to map seafloor habitats in a holistic manner, thus refining our knowledge of benthic sea life. Several works on this topic focused on cold-water coral habitats at the global scale, with focus on the Atlantic Ocean while, only a few studies applied these methods to the Mediterranean Sea. The prime objective of this chapter is to comment the methodologies used to describe cold-water coral habitats and map their extension; secondly we discuss statistical models to outline the most suitable areas for cold-water coral settlement (habitat suitability models). Furthermore, recent technological developments in habitat mapping procedures provide geophysical data and seafloor images of higher resolution than ever before, while multi-frequency systems supply new hyperspectral images of the seabed.

Mineralogical, petrographic and stable isotope analyses were carried out on sediment and rock samples collected from a deep-sea cold seep province in the Paola Ridge (southeastern Tyrrhenian Sea). The results, coupled with the interpretation of the seafloor backscatter, constrained both the biogeochemical zonation and the spatial distribution of the cold seep habitats in the area. These have proved to change in depth in a range of few meters and laterallywithin narrow zones. The mud volcanoes, characterized by a high backscatter signature, are the site of vigorous gas venting and, in the subsurface, show a rapid transition from the oxic sea water interface toward the methane-sulfate transition zone in the sediments. Intermediate backscatter typifies areas where free venting is hampered by the presence of mudflows at the seafloor. These conditions favor: i) the oxidation of sulfides near the seafloor, ii) the precipitation of siderites a few meters below the seafloor and iii) the formation of sulfides deeper in the sub-seafloor. Faults are likely candidates to act as conduits for sulfates and metal oxides that juxtapose different redox environments. Siderites precipitated in the fast and low venting sites showed enrichment in δ13C and δ18O, which are compatible with their precipitation in the methanogenic zone. The heavy-oxygen isotopic compositions of the siderites are possibly related to the dissociation of gas hydrates, which have not been mapped so far by seismic data in the study area. Mud diapirism is characterized by low backscatter seafloor, large fields of pockmarks and is dissected bynormal faults. In coincidence with the normal faults, authigenic calcites and aragonites are present at or very close to the seafloor. They have the typical isotopic signature indicating formation during sulfate-dependent microbially-mediated anaerobic oxidation of methane.They are associated with Lucinoma borealis, the youngest being dated 640-440 BP. This suggests that the seepage activity in the mud diapirs was likely clogged by either carbonates or activity of the faults only very recently.

Along the NE Sicily margin, between Capo Milazzo and Capo Peloro, in the offshore Gioia Basin area facing the Castanea Ridge, a mass-transport complex (MTC) was first imaged by multibeam data acquired by the end of the 1990s. It was interpreted as resulting from the stacking of different mass-transport deposits due to repeated failures of the shelf edge and upper slope area and of the nearby Villafranca slope channel-levee wedge. New high resolution swath bathymetry and seismic data, acquired in 2009–2011, allowed the complete coverage of the headwall area of the 48 km3 Villafranca frontally-confined slide, which represents the bulk of the MTC, and that was previously not mapped. Seven smaller individual zones of instability that represent the source areas of distinct mass-transport deposits emplaced in the upper and lower slope, having surface areas between 10 km2 and 60 km2, were also mapped. The new data show that, although the Villafranca slide and the subsequent more recent failures were not sourced from the same headwall area, they are similarly associated to the activity of the faults that characterize the NE Sicily rapidly uplifting margin. The Villafranca slide has its headwall along a normal fault parallel to the coast, which is visible in the shelf at 80–85 m water depth offsetting the seafloor for 30 m. The slab slide and the debris flow lobes have their headwalls along a NNE–SSW oriented normal fault, which offsets the seafloor for 30 m and is the offshore prolongation of a regional structure on land. The largest debris flow lobe in the area was actually generated through flow transformation mechanisms from an initial slump mass. The main headwall scarps are rectilinear and exploit regional normal faults along which the principal and larger slope failures (slide and slumps) root, possibly during episodes of accelerated uplift, recognized by several authors in the area, both in Late Pleistocene and during the Holocene. Successive morphological modifications and flow transformations, resulting from smaller scale failures (debris flows), generate more complex headwalls. In addition, the MTC is bounded to the NE by a recent reverse fault which prolongs in a structural ridge (Acquarone Ridge) where evidence of seafloor fluid escapes (pockmarks) is present, implying that compressive and transpressive structures can be active in the area and play an underestimated role in the instability of the NE Sicily margin.

Tidal channels are crucial for the functioning of wetlands, though their morphological properties, which are relevant for seafloor habitats and flow, have been understudied so far. Here, we release a dataset composed of Digital Terrain Models (DTMs) extracted from a total of 2,500 linear kilometres of high-resolution multibeam echosounder (MBES) data collected in 2013 covering the entire network of tidal channels and inlets of the Venice Lagoon, Italy. The dataset comprises also the backscatter (BS) data, which reflect the acoustic properties of the seafloor, and the tidal current fields simulated by means of a high-resolution three-dimensional unstructured hydrodynamic model. The DTMs and the current fields help define how morphological and benthic properties of tidal channels are affected by the action of currents. These data are of potential broad interest not only to geomorphologists, oceanographers and ecologists studying the morphology, hydrodynamics, sediment transport and benthic habitats of tidal environments, but also to coastal engineers and stakeholders for cost-effective monitoring and sustainable management of this peculiar shallow coastal system.

The NE Sicily continental shelf, imaged by multibeam bathymetry data and CHIRP/sparker seismic profiles, is less than 5 km-wide, and is located in a tectonically active margin characterized by strong regional uplift rates. In this paper, we show how variations of geomorphic elements in the study area are tied to spatial and temporal changes in the driving forces that control the seafloor processes. This study demonstrates that the geomorphology of continental shelves can vary over very short spatial scales depending on the uneven distribution of sediment supply from rivers and sediment transfer both across and along the shelf by oceanographic currents. In the northeastern part, three sandwave fields were mapped in the highstand sediment wedge that, due to the small size of rivers, is restricted to the inner shelf. The sandwave fields are found in proximity of the Messina Straits, a shallow water sill with strong tidal currents between the Tyrrhenian and the Ionian Seas. The bedform fields have sandwaves of variable shape, wavelength and orientation, reflecting along-shelf variations of tidal current strength and sediment grain size distribution. In the southwestern shelf, rivers are larger and form deltas that shape a considerable part of the shelf, often having their distal, still channelized delta front at the shelf edge. In some cases, deltas are built close to the heads of canyons and a large volume of the river-borne sediments is directly fed to the deep sea through delta front terminal distributary channels. Where rivers are small, the outer shelf lacks recent river borne sediment and presents a relict morphology consisting of submerged coastal systems formed during previous sea-level lowstands. The tectonics of the study area mainly consist of structures that have a NNE-SSW trend similar to the extensional faults responsible for the Siculo-Calabrian Rift Zone in the nearby emerged areas. Our study extends the area affected by the regional deformation belt into the NE Sicily offshore. (C) 2014 Elsevier B.V. All rights reserved.

In deep-sea fans, fan lobes form from the stacking of the deposits of turbidity currents and other sediment gravity flows beyond the channel mouth. Slopes lateral or oblique to the main direction of turbidity currents exiting channel confinement can profoundly affect flow behavior and the distribution of facies and lithology in fan lobes. In this paper, we report on the analysis of multibeam and CHIRP subbottom data aimed at the study of the effects of a lateral slope on turbidity-current behavior and resultant geomorphology and stratigraphy of a modern fan lobe. The Villafranca fan lobe, the subject of this study, develops on the 0.5° dipping seafloor of the Gioia intraslope basin in the southeastern Tyrrhenian Sea. The Villafranca is a transient fan lobe that has its downslope limit coinciding with a 200-m-high bathymetric step formed by the erosional flank of the Stromboli slope valley, perpendicular to the fan-lobe trend. A “lobe complex” hierarchical level is assigned to the Villafranca fan lobe. The lobe complex develops beyond the mouth of the Villafranca leveed channel, which trends N and is oblique to the regional NW-dipping slope. The depositional topography created by an adjacent channel levee wedge to the west is the cause of the observed obliquity. The western and the eastern “lobes” constitute the Villafranca lobe complex. Both lobes have mainly NW-trending channels, and therefore they do not conform to the classical divergent pattern of channels observed in deep-sea fan lobes. The channel trend is a result of the inability of flows to freely spread sideways, due to the presence of the lateral slope and the dip of the seafloor at the channel mouth. The western lobe has an up-dip apex with respect to the eastern one and is characterized by channels that nucleate on the downslope side of a channel-mouth bar and that die out distally before reaching the flank of the Stromboli slope valley. The eastern lobe, in contrast, has channels that are depositional upslope but on approaching the flank of Stromboli slope valley become mainly erosional or bypass features. The two lobes develop concomitantly, therefore an evolution due to compensational stacking with the two lobes being in different stages of development is here disregarded. It is therefore feasible that turbidity currents, which due to different initiating mechanisms have distinct magnitude and efficiency, deposit their load either in the eastern or in the western lobe. Another possibility is that single turbidity currents exiting the Villafranca channel mouth form two separate flow portions with different properties, which independently but simultaneously feed the eastern and the western lobe. In both cases, the effect of the lateral slope and the obliquity between the dip of the slope and the trend of the channel mouth are here considered as the primary factors controlling the differences in depositional style of the two lobes.

High resolution swath bathymetry and backscatter data, seismic CHIRP profiles, multibeam water column acoustic measurements and sediment samples were collected on a cold seep province in the southeastern Tyrrhenian Sea, at a water depth of 500-1000. m. The mud volcanoes, characterized by a high backscatter signature, are the site of gas venting at the seafloor that formed a 630-m-high plume in the water column. The mud volcanoes feature a precipitation of iron-oxy-hydroxide crusts and pyritized and Sulfur burrows in the sub-surface and authigenic siderites, also cementing burrows, further down, showing a sharp transition from the oxic zone toward the sulfate-methanogenic zone.The mud flows are characterized by an intermediate backscatter seafloor and by the presence of gas in the sediment only 2. m below the seafloor. The mud flows consist of 1-m-thick drapes of water-rich mud extending downslope from the mud volcanoes. They act as sealing layers that prevent large fluxes of gas venting at the seafloor (low venting) and favor oxic conditions close to the sediment-water interface and the abundant precipitation of post-oxic siderites a few meters below the seafloor.The mud diapirs are characterized by a low backscatter seafloor and large fields of pockmarks. In coincidence with the normal faults, organogenic carbonate crusts form at or very close to the seafloor and are associated with chemosymbiontic bivalves (lucinids). The youngest shells are AMS radiocarbon dated 640-440. BP, suggesting that the seepage activity may have been clogged by the carbonates, only very recently.Similarities between the normal faults in the study area and the tectonic setting of the inland Calabrian Arc show that normal faults can control the location of fluid pathways and, probably, also the rising of the mud diapirs. © 2013 Elsevier B.V.