Giovanni Bortoluzzi

National Research Council, Roma, Latium, Italy

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Publications (82)111.04 Total impact

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    ABSTRACT: Hydrothermal alteration processes involve mineralogical, chemical and textural changes as a result of hot aqueous fluid-rock interaction under evolving boundary conditions. These changes affect the physico-chemical properties of the rocks, enabling high-resolution geophysical prospecting to be an important tool in the detection of seafloor hydrothermal alteration. Here we present the results of recent geophysical investigations of Marsili and Palinuro volcanic complexes, southern Tyrrhenian Sea during the 2010 TIR10 and 2011 MAVA2011 cruises by the R/V Urania. The new dataset includes a dense grid of multibeam bathymetry; seafloor reflectivity, magnetic and gravity lines; and high-resolution single (CHIRP) and multichannel seismic profiles. The surveys were focused on areas known to host intense hydrothermal alteration in order to provide a more detailed description of the Marsili and Palinuro hydrothermal systems. Ground-truthing was based on earlier discoveries of hydrothermal vents and their associated deposits, and on direct observations made by ROV dives. High-resolution morpho-bathymetry, sonar reflectivity, rock magnetization and density distribution together enabled us to assess the extent of seafloor hydrothermal alteration and its relationship to local volcanic and tectonic structures. Hydrothermal alteration associated with the Marsili seamount is largely distributed along primary volcano-tectonic structures at the ridge crest. By contrast, at Palinuro hydrothermal alteration is mostly associated with secondary volcanic structures such as collapsed calderas and volcanism reactivation along ring-faults. In particular, evidence for intense hydrothermal activity occurs at Palinuro where volcano-tectonic features interact with regional tectonic structures.
    Economic Geology 10/2014; 109(8):2103-2117. · 2.49 Impact Factor
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    ABSTRACT: Near-bottom magnetic field data were collected using a towed magnetometer over selected parts of Palinuro and Marsili submarine volcanoes in the southern Tyrrhenian Sea, Italy. We obtained equivalent magnetizations maps at these sites by inverting the corresponding magnetic anomalies, highlighting the seafloor expression of hydrothermal alteration. Zones of reduced magnetization are interpreted as evidence for alteration related to hydrothermal processes; they are associated with water-column and seafloor observations of hydrothermal activity and altered host rocks. At Marsili volcano, a large elliptical area of reduced magnetization is located south of the summit cone and perpendicular to the trend of Marsili volcano itself. This confirms the presence of a large hydrothermal system centered over the more recent eastern volcanic ridge and its associated magma chamber. Similarly, areas of reduced magnetization over Palinuro caldera are consistent with hydrothermal venting occurring along the caldera walls, consistent with permeability structures related to caldera ring faults providing preferred pathways for the upflow of hydrothermal fluids.
    Economic Geology 10/2014; 109(8):2119-2128. · 2.49 Impact Factor
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    ABSTRACT: Within the complex of deep, hypersaline anoxic lakes (DHALs) of the Mediterranean Ridge we identified a new, unexplored DHAL and named it "Lake Kryos" after a nearby depression. This lake is filled with MgCl2-rich, athalassohaline brine (salinity >470 practical salinity units), presumably formed by the dissolution of Messinian bischofite. Compared to the DHAL Discovery, it contains elevated concentrations of kosmotropic sodium and sulfate ions, which are capable of reducing the net chaotropicily of MgCl2-rich solutions. The brine of Lake Kryos may therefore be biologically permissive at MgCl2 concentrations previously considered incompatible with life. We characterized the microbiology of the seawater-Kryos brine interface and managed to recover mRNA from the 2.27-3.03 M MgCl2 layer (equivalent to 0.747-0.631 water-activity) thereby expanding the established chaotropicity window-for-life. The primary bacterial taxa present there were KB1 candidate division and DHAL-specific group of organisms, distantly related to Desulfohalobium. Two euryarchaeal candidate divisions MSBL1 and HC1, detected in minority in the overlaying layers, accounted for more than 85% of the rRNA-containing archaeal clones analyzed in 2.27-3.03 M MgCl2 layer. These findings shed light on the plausibility of life in highly chaotropic environments, geochemical windows for microbial extremophiles, and have implications for habitability elsewhere in the Solar System.
    Environmental Microbiology 08/2014; · 6.24 Impact Factor
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    ABSTRACT: Abstract High-resolution multibeam morpho-bathymetric maps and a dense grid of seismic reflection profiles show relict and palimpsest geomorphologic features along the Montenegro/Northern Albanian Continental Margin. This sector of the Eastern Adriatic shelf, at the external front of the Dinarides Chain, is characterized by highly variable seafloor patterns and depositional styles, and shows a peculiar alternation of large-scale troughs and ridges, probably caused by tectonic compressive deformations. These tectonically controlled morphologies are overprinted by the result of sedimentary processes, such as progradation at river outflows, erosion, and reworking of sediments by longshore currents, as well as gravity-driven process caused by sediment loading and seismic shaking. Physiographic domains along this shelf-slope margin include (i) an inner and an outer shelf, separated by two major topographic highs, the Kotor and the Bar ridges; (ii) a drowned lobate delta formed during the last phase of sea level fall, likely fed by the Buna/Bojana drainage basin; and (iii) a continental slope affected by gravity-driven faulting and mass-wasting processes. Seafloor reflectivity maps, ground-truthed by grain-size analysis of bottom sediments, reveal that fine-grained deposits accumulate in the inner shelf, while other sectors appear starved. The effects of the last sea-level rise is testified by the presence of seabed forms diagnostic of erosion or depositional processes, such us large dunes, sediment ridges and sediment waves, which were studied to infer the effect of bottom currents under the present-day oceanographic regime and in the recent past. This paper presents a first description of geomorphologic features observed along the Montenegro/Northern Albanian Continental Margin, in the context of Late Quaternary sea-level changes.
    Geomorphology 01/2014; · 2.58 Impact Factor
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    ABSTRACT: An updated bathy-morphological setting of the Aeolian Islands is presented, based on new detailed bathymetric maps of the western, central and eastern sectors of the archipelago. In recent years, the acquisition of multibeam swath bathymetry has greatly expanded knowledge of the submarine portions of the Aeolian volcanic edifices, revealing that their submarine extension is much wider than that of the islands. Indications given by the submarine setting are fundamental for better understanding of the evolution of volcanism and the control exerted by main structural lineaments, as well as to locate large-scale flank instability events and recent submarine eruptive activity.
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    ABSTRACT: An updated bathy-morphological setting of the Aeolian Islands is presented, based on new detailed bathymetric maps of the western, central and eastern sectors of the archipelago. In recent years, the acquisition of multibeam swath bathymetry has greatly expanded knowledge of the submarine portions of the Aeolian volcanic edifices, revealing that their submarine extension is much wider than that of the islands. Indications given by the submarine setting are fundamental for better understanding of the evolution of volcanism and the control exerted by main structural lineaments, as well as to locate large-scale flank instability events and recent submarine eruptive activity.
    The Aeolian Islands Volcanoes, Memoirs, 37 edited by Lucchi, F, Peccerillo, A, Keller, J, Tranne, C. A. & Rossi, P. L., 10/2013: chapter 4: pages 27-36; Geological Society of London., ISBN: 978-186239-365-3
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    ABSTRACT: [1] The impact of tides in the circulation of the Adriatic Sea is investigated by means of a nested baroclinic numerical ocean model. Tides are introduced using a modified Flather boundary condition at the open edge of the domain. The results show that tidal amplitudes and phases are reproduced correctly by the baroclinic model and tidal harmonic constants errors are comparable with those resulting from the most consolidated barotropic models. Numerical experiments were conducted to estimate and assess the impact of (i) the modified Flather lateral boundary condition; (ii) tides on temperature, salinity, and stratification structures in the basin; and (iii) tides on mixing and circulation in general. Tides induce a different momentum advective component in the basin, which in turn produces a different distribution of water masses in the basin. Tides impact on mixing and stratification in the River Po region (northwestern Adriatic) and induce semidiurnal fluctuations of salinity and temperature, in all four seasons for the former and summer alone for the latter. A clear presence of internal tides was evidenced in the northern Adriatic Sea basin, corroborating previous findings.
    Journal of Geophysical Research: Oceans 01/2013; 118(1):166-183. · 3.44 Impact Factor
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    ABSTRACT: A hierarchy of medium (2 km) and high (0.5 km) resolution operational models cast in the Adriatic sea (NE Mediterranean Sea), relying on an updated core w.r.t. previously existing one, characterized by having a wide variety of applications ranging from civil protection to scientific ones, is presented and described. The computing core of the system sits at Hydro-Meteo-Clima Service (SIMC, Bologna), and the scientific supervision is provided by DISVA Polytechnic University of Marche and CNR-ISMAR Venice. The core of the operational system is based on the Regional Ocean Modeling System, version 3.4. The hydrodynamic variables (e.g. sea surface elevation, currents, temperature, salinity, storm surge height), and wave parameters are predicted every day for the next 72 hours. The surface forcing for the hydrodynamic (AdriaROMS 4.0) and wave (SWAN) operational models is derived from the predicted results of the operational meteorological model COSMO-I7 (7 km resolution) which forecasts atmospheric fields over the whole Italian seas. Hydrodynamic results are verified against oceanographic and wave buoys, tide gauges, bottom mounted acoustic current meter profilers, available in the coastal waters of the Adriatic Sea and oceanographic surveys. More specifically, CNR-ISMAR in the northern Adriatic Sea manages a meteo-oceanographic buoy network and the fixed ocean observatory tower “Acqua Alta”, SIMC manages a wave buoy. Aiming to obtain forecast improvements in coastal areas of northern Adriatic Sea, a newly implemented, more resolved (0.5 km) ROMS version two-way coupled with SWAN is nested in the operational AdriaROMS 4.0 covering the Adriatic Sea at 2 km horizontal resolution. Outputs of operational models drive dedicated submodels for oil-spill transport and dispersion, coastal morphodymanic, sediment transport, saline wedge, water quality.
    OCEANS - Bergen, 2013 MTS/IEEE; 01/2013
  • T. Tudino, G. Bortoluzzi, S. Aliani
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    ABSTRACT: Marine water dynamics in the near field of a massive gas eruption near Panarea (Aeolian Islands volcanic arc, SE Tyrrhenian Sea) is described. ADCP current-meters were deployed during the paroxysmal phase in 2002 and 2003 a few meters from the degassing vent, recording day-long time series. Datasets were sorted to remove errors and select good quality ensembles over the entire water column. Standard deviation of error velocity was considered a proxy for inhomogeneous velocity fields over beams. Time series intervals had been selected when the basic ADCP assumptions were fulfilled and random errors minimized. Backscatter data were also processed to identify bubbles in the water column with the aim of locating bubble-free ensembles. Reliable time series are selected combining these data. Two possible scenarios have been described: firstly, a highly dynamic situation with visible surface diverging rings of waves, entrainment on the lower part of the gas column, detrainment in the upper part and a stagnation line (SL) at mid depth where currents were close to zero and most of the gas bubbles spread laterally; secondly, a less dynamic situation with water entraining into the gas plume at all depths and no surface rings of diverging waves. Reasons for these different dynamics may be ascribed to changes in gas fluxes (one order of magnitude higher in 2002). Description of SL is important to quantify its position in the water column and timing for entrainment–detrainment, and it can be measured by ADCP and calculated from models.
    Journal of Marine Systems 01/2013; · 2.48 Impact Factor
  • tobia tudino, giovanni bortoluzzi, stefano aliani
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    ABSTRACT: Marine water dynamics in the near field of a massive gas eruption near Panarea (Aeolian Islands volcanic arc, SE Tyrrhenian Sea) is described. ADCP current-meters were deployed during the paroxysmal phase in 2002 and 2003 a few meters from the degassing vent, recording day-long time series. Datasets were sorted to remove errors and select good quality ensembles over the entire water column. Standard deviation of error velocity was considered a proxy for inhomogeneous velocity fields over beams. Time series intervals had been selected when the basic ADCP assumptions were fulfilled and random errors minimized. Backscatter data were also proc- essed to identify bubbles in the water column with the aim of locating bubble-free ensembles. Reliable time series are selected combining these data. Two possible scenarios have been described: firstly, a highly dynamic situation with visible surface diverging rings of waves, entrainment on the lower part of the gas column, detrainment in the upper part and a stagnation line (SL) at mid depth where currents were close to zero and most of the gas bubbles spread laterally; secondly, a less dynamic situation with water entraining into the gas plume at all depths and no surface rings of diverging waves. Reasons for these different dynamics may be ascribed to changes in gas fluxes (one order of magnitude higher in 2002). Description of SL is important to quantify its position in the water column and timing for entrainment–detrainment, and it can be measured by ADCP and calculated from models.
    Journal of Marine Systems 01/2013; · 2.48 Impact Factor
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    ABSTRACT: The Messina Strait, that separates peninsular Italy from Sicily, is one of the most seismically active areas of the Mediterranean. The structure and seismotectonic setting of the region are poorly understood, although the area is highly populated and important infrastructures are planned there. New seismic reflection data have identified a number of faults, as well as a crustal scale NE-trending anticline few km north of the strait. These features are interpreted as due to active right-lateral transpression along the north-eastern Sicilian offshore, coexisting with extensional and right-lateral transtensional tectonics in the southern Messina Strait. This complex tectonic network appears to be controlled by independent and overlapping tectonic settings, due to the presence of a diffuse transfer zone between the SE-ward retreating Calabria subduction zone relative to slab advance in the western Sicilian side.
    Scientific Reports 12/2012; 2:970. · 5.08 Impact Factor
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    ABSTRACT: We obtained areal variations of crustal thickness, magnetic intensity, and degree of melting of the sub-axial upwelling mantle at Thetis and Nereus Deeps, the two northernmost axial segments of initial oceanic crustal accretion in the Red Sea, where Arabia is separating from Africa. The initial emplacement of oceanic crust occurred at South Thetis and Central Nereus roughly ∼2.2 and ∼2 Ma, respectively, and is taking place today in the northern Thetis and southern Nereus tips. Basaltic glasses major and trace element composition suggests a rift-to-drift transition marked by magmatic activity with typical MORB signature, with no contamination by continental lithosphere, but with slight differences in mantle source composition and/or potential temperature between Thetis and Nereus. Eruption rate, spreading rate, magnetic intensity, crustal thickness and degree of mantle melting were highest at both Thetis and Nereus in the very initial phases of oceanic crust accretion, immediately after continental breakup, probably due to fast mantle upwelling enhanced by an initially strong horizontal thermal gradient. This is consistent with a rift model where the lower continental lithosphere has been replaced by upwelling asthenosphere before continental rupturing, implying depth-dependent extension due to decoupling between the upper and lower lithosphere with mantle-lithosphere-necking breakup before crustal-necking breakup. Independent along-axis centers of upwelling form at the rifting stage just before oceanic crust accretion, with buoyancy-driven convection within a hot, low viscosity asthenosphere. Each initial axial cell taps a different asthenospheric source and serves as nucleus for axial propagation of oceanic accretion, resulting in linear segments of spreading.
    Geochemistry Geophysics Geosystems 08/2012; 13(8):Q08009. · 2.94 Impact Factor
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    ABSTRACT: The impact of tides in the circulation of the Adriatic sea has been investigated by means of a nested baroclinic numerical ocean model. Tides have been introduced using a modified Flather boundary condition at the open side of the domain. The results show that tidal amplitudes and phases are reproduced correctly by the baroclinic model and the tidal harmonic constants errors are comparable with those resulting from the most consolidated barotropic models. Numerical experiments were conducted to estimate and assess the impact of (i) the modified Flather lateral boundary condition, (ii) the tides on temperature, salinity and stratification structures in the basin, and (iii) the tides on mixing and circulation in general. Tides induce a different momentum advective component in the basin which in turn produces a different distribution of water masses in the basin. Tides impact on mixing and stratification in the Po river region (north-western Adriatic) and induce fluctuations of salinity and temperature on semidiurnal frequencies in all seasons for the first and only winter for the second.
    04/2012;
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    ABSTRACT: We present the preliminary results of a marine high-resolution magnetic and gravity survey of Panarea and Stromboli (Aeolian Islands, cruise R/V Urania PANSTR-2010), in the active, eastern sector of the volcanic arc in the Southern Tyrrhenian Sea (Italy). The Aeolian Arc can be subdivided into western, central and eastern sectors characterized by different structural and volcanological features and evolution. The eastern sector includes the two major volcanic edifices of Panarea and Stromboli. Active volcanism occurs at Stromboli with explosive eruptions and at Panarea with fumaroles and submarine degassing, including the recent, large burst of November 22nd 2002, that lasted several months with a consistent and sustained flux of CO2-dominated gas , orders of magnitude above the steady-state activity. On February 2010 a detailed network of sea-surface gravity (Microg LaCoste Air Sea S-54 model) and magnetic data (Marine Magnetics SeaSPY) were collected with line spacing of 500 m offshore Panarea and Stromboli, including a more detailed acquisition pattern around Panarea with 120 m spacing. Geophysical data acquired offshore Panarea and Stromboli provide a new insight into the deep crustal setting of these volcanic edifices. Low-frequency magnetic anomaly and positive complete Bouguer anomaly identify an intriguing local variation of the crustal properties in this area. Particular attention was drawn to the high-resolution data obtained in the area of the Islets (Lisca Nera, Lisca Bianca, Bottaro, Panarelli, Dattilo) located East of Panarea, where the last 2002 exhalative gas-crisis occurred. The comparison of the data sets of 2002, 2006 and 2010 showed variations of the magnetic properties, reflecting the modification of shallow crustal features and providing information on the hydrothermal system and the structural style of the area. In detail, analysis of new marine gravity data pointed to a local variation of density in the 2002 degassing area (between Dattilo and Lisca Bianca) with a sharp separation, in term of density properties, between the western group of islets and the eastern one. This differentiation seems not correlated to a variation of lithologies in the area, but it suggests the occurrence of local variation of density and/or of a thermal gradient between the two groups of islets. The contrasting structural setting of the eastern and western area of the Islets is also suggested by available GPS geodetic measurements. Detailed strain-rate analyses have been performed showing local, different deformation patterns.
    AGU Fall Meeting Abstracts. 12/2011;
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    ABSTRACT: [1] Reliable piercing points on both sides of the Sea of Marmara enabled us to obtain an estimate of the slip-rate over time scales of 10–15 ka on different fault strands of the North Anatolian Fault (NAF) system. We analyzed geomorphic features in the gulfs of Izmit, Gemlik (Sea of Marmara) and Saros (NE Aegean Sea), which were passively displaced by the NAF strands after their abandonment related to the post-glacial sea level rise. Results for the main northern strand, consistently similar on both sides of the Marmara pull-apart, are in the order of 10 mm/yr, about one half of that expected from geodetic measurements and accepted plate-tectonic models. In the southern branch of the NAF, the estimated rate of ∼4 mm/yr is only slightly higher than that given by geodetic models. Our findings have implications for both neo-tectonic reconstructions of the submerged portion of the NAF system, and fault interactions and seismic hazard estimates in the Marmara region. They suggest that, either the total Anatolia/Eurasia plate motion is more diffuse than previously reported, or geodetic data are not representative of the geological time-scale deformations. Moreover, they suggest that a significant amount of stress is accommodated along the southern strand of the NAF system, on which the last large (M ≈ 7) earthquakes dates back to 1419, 1855 and 1863 AD.
    Tectonics. 12/2011; 30(6).
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    ABSTRACT: The 500 m.y. cycle whereby continents assemble in a single supercontinent and then fragment and disperse again involves the rupturing of a continent and the birth of a new ocean, with the formation of passive plate margins. This process is well displayed today in the Red Sea, where Arabia is separating from Africa. We carried out geophysical surveys and bottom rock sampling in the two Red Sea northernmost axial segments of initial oceanic crust accretion, Thetis and Nereus. Areal variations of crustal thickness, magnetic intensity, and degree of melting of the subaxial upwelling mantle reveal an initial burst of active oceanic crust generation and rapid seafloor spreading below each cell, occurring as soon as the lid of continental lithosphere breaks. This initial pulse may be caused by edge-driven subrift mantle convection, triggered by a strong horizontal thermal gradient between the cold continental lithosphere and the hot ascending asthenosphere. The thermal gradient weakens as the oceanic rift widens; therefore the initial active pulse fades into steady, more passive crustal accretion, with slower spreading and along axis rift propagation.
    Geology 11/2011; 39:1019-1022. · 4.64 Impact Factor
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    ABSTRACT: Panarea and surrounding Islets form a volcanic edifice, that is part of the Eastern sector of the Aeolian Arc, Southern Tyrrhenian Sea. It is now considered inactive, since last documented activity is 20 Ka old. However, on 2002-11-03, gas started to flow violently from the seafloor in an area E of the Island, mainly along NE and NW structural lineaments, and lasting up to 2003-2004 with a consistent flux, orders of magnitude larger that ’steady-state’ fumarolic activity documented there in historical times. On the same period a strong effusive activity of Stromboli (10 NM to NNE) was present. Since then, several investigations have been conducted at sea and on land, with the aim of focusing on the problem of effusive activity at sea, mainly in the light of volcanic surveillance and risk. Among these investigations, some of which have been repeated over years, we present and discuss some data and results from: (a)visual inspection and sampling by divers and ROV, (b)GPS networks and mapping by multibeam and LIDAR, (c) oceanographical measurements by current meters and CTD, and water flux and dynamics measurements, (d)magnetic and gravimetric surveys, (e) multichannel reflection Seismic with OBS and land station networks. Data were used for compilation of high resolution bathymetric, magnetic and gravimetric maps, including the emerged and submerged portions of the edifice.
    Marine Research at CNR, DTA/06-2011 edited by Brugnoli E., Cavarretta G., Mazzola S., Trincardi F., Ravaioli M., Santoleri R., 06/2011: pages 1468-1486; Consiglio Nazionale delle Ricerche., ISBN: ISSN 2239-5172
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    ABSTRACT: In September 2008, an expedition of the RV Urania was devoted to exploration of the genomic richness of deep hypersaline anoxic lakes (DHALs) located in the Western part of the Mediterranean Ridge. Approximately 40 nautical miles SE from Urania Lake, the presence of anoxic hypersaline lake, which we named Thetis, was confirmed by swath bathymetry profiling and through immediate sampling casts. The brine surface of the Thetis Lake is located at a depth of 3258 m with a thickness of ≈ 157 m. Brine composition was found to be thalassohaline, saturated by NaCl with a total salinity of 348‰, which is one of highest value reported for DHALs. Similarly to other Mediterranean DHALs, seawater-brine interface of Thetis represents a steep pycno- and chemocline with gradients of salinity, electron donors and acceptors and posseses a remarkable stratification of prokaryotic communities, observed to be more metabolically active in the upper interface where redox gradient was sharper. [(14) C]-bicarbonate fixation analysis revealed that microbial communities are sustained by sulfur-oxidizing chemolithoautotrophic primary producers that thrive within upper interface. Besides microaerophilic autotrophy, heterotrophic sulfate reduction, methanogenesis and anaerobic methane oxidation are likely the predominant processes driving the ecosystem of Thetis Lake.
    Environmental Microbiology 04/2011; 13(8):2250-68. · 6.24 Impact Factor