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  • Elsevier  (201,203)
  • Wiley  (26,109)
  • 2020-2022  (227,310)
  • 2005-2009  (2)
  • 2020  (227,312)
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  • 1
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    DOMOIC acid, Pseudo-nitzschia spp and potential vectors at the base of the pelagic food web over the northern Patagonian coast, Southwestern Atlantic (2020)
    Elsevier
    In:  EPIC3Journal of Marine Systems, Elsevier, 212, pp. 103448, ISSN: 09247963
    Details
    Publication Date: 2021-11-01
    Description: Plankton composition and density, and domoic acid (DA) content in microplankton and mesozooplankton were assessed over the northern Patagonian coastal shelf in late austral summer 2013. Maximum values of DA in these two plankton fractions as well as maximum densities of both Pseudo-nitzschia spp. (mainly the toxigenic P. australis) and DA potential vectors were only detected on the southern coast of San Matías Gulf and the eastern coast of Valdés Peninsula. In this zone, waters were characterized by low temperature, high nitrate, and intermediate values of silicic acid and phosphate. Based on the high association between the DA values recorded and the values of either micro- and mesozooplankton grazer density or biomass, we inferred that DA transfer from Pseudo-nitzschia spp. occurred largely through the small copepods Euterpina acutifrons and Oithona nana, Calanidae nauplii and Calanidae copepodites, Noctiluca scintillans, and euphausiid developmental stages. Small copepods, Calanidae nauplii and copepodites, and cladocerans were proposed as novel DA vectors although this suggestion requires experimental confirmation. This study provides the first lines of evidence of the co-occurrence of Pseudo-nitzschia spp. blooms with DA production and accumulation in mesozooplanktonic grazers at the base of the food web and of the environmental and oceanographic conditions that seem to favor these processes over the northern Patagonian shelf coasts.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
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  • 2
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    Volatile segregation and generation of highly vesiculated explosive magmas by volatile-melt fining processes: The case of the Campanian Ignimbrite eruption (2020)
    Elsevier
    Details
    Publication Date: 2021-09-03
    Description: The late Pleistocene trachytic Campanian Ignimbrite (〉 300 km3 DRE, ca. 39 ka) covers the Campanian Plain (Italy) around Naples. It is found behind ridges〉1000m high at 80 km from the source in the Campi Flegrei caldera. This points towards very dilute currents, that together with the huge amount of discharged magmatic material, suggest a magma reservoir highly enriched in volatiles. The huge volume of magma that extruded during the Campanian Ignimbrite eruption differentiated and mixed at shallow depth (6–3 km), as shown by modelling of the petrologic and geochemical features of the erupted products together with melt inclusion-based studies of gas-melt saturation. With respect to compositionally similar but lower magnitude Phlegraean eruptions (e.g., Agnano-Monte Spina,〉1 km3 DRE, ca. 4.6 ka), the large amount of volatiles discharged by Campanian Ignimbrite was likely due to fractional crystallization of the lowermost portion of its magmatic reservoir. Because of the long residence time of the Campanian Ignimbrite magmatic system within the crust, an efficient decoupling took place during the upward migration of volatile elements in response to a chromatographic fractionation between H2O and CO2. This caused early pulses of nearly pure CO2 (CO2-fluxing), followed by a long-lasting H2O enrichment which yielded dissolved H2O contents up to 6–7 wt%. An overpressurized CO2- dominated gas cap was consequently produced, uniformly distributed at the top of the magma chamber. The onset of the eruption tapped this cap and generated Plinian columns, causing depressurization and fast volume decrease that facilitated, or even drove, the caldera collapse. H2O-rich magma was discharged during the following phase, characterised by pyroclastic density currents. The uniform distribution of the high values of void fraction (〉 70%) and the high degree of vesicle connectivity throughout the magma body testify to the huge abundance of volatiles. These percolate from the crystallizing basal layers and determine the volatile-melt fining process yielding an efficient separation between H2O and CO2. The gas saturation-based estimates of the tapped foamy magma are compatible with the extent of magma chamber roof collapse, the strong expansion revealed by textural data, and the transport and deposition mechanisms, reflecting depressurization and inflation of the volatile-rich magma within the collapsed and laterally confined caldera.
    Description: Published
    Description: 1-14
    Description: 4V. Processi pre-eruttivi
    Description: JCR Journal
    Keywords: Ignimbrite ; Extremely dilute pyroclastic density currents ; Magmatic volatiles ; Fluxing ; Chromatographic separation
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Detecting shifts of submarine sediment boundaries using side-scan mosaics and GIS analyses (2020)
    Elsevier
    In:  EPIC3Marine Geology, Elsevier, 430, pp. 106343, ISSN: 00253227
    Details
    Publication Date: 2021-08-24
    Description: Detecting changes of sediment boundaries on the seafloor is important for a better understanding of sediment dynamics and related impacts to benthic habitats. Side-scan sonars (SSS) perform more cost-effectively in shallow waters than other acoustic systems because of their larger swath widths, and the resolution of its images does not change with varying water depth. However, as they are generally towed behind the survey vessel, they tend to have lower positioning accuracy, which makes them unreliable for change detection analyses. In this study, we present a workflow that processes SSS data in a way that makes them fit for change detection analyses. To test the capacity of SSS mosaics for change detection, we used a free software called “Digital Shoreline Analysis System”, which was developed by the United States Geological Survey for ArcGIS version 10.4 onwards. The methods were applied in three areas in the Sylt Outer Reef, German Bight, North Sea. Our results showed that with appropriate processing, SSS mosaics could be used for change detection of sharp sediment boundaries. We found a common trend in the sediment distribution patterns of coarse sediments by monitoring the movement of their boundaries. The boundaries moved in northeast-southwest direction and boundary movements of less than 20 m were typically observed. The methods presented here are semi-automated, repeatable, and replicable, which has potential for wide-scale monitoring of sediment distribution patterns.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
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    Evolution of the Upper Ocean Stratification in the Japan Sea Since the Last Glacial (2020)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, 47(16), pp. e2020GL088255, ISSN: 0094-8276
    Details
    Publication Date: 2021-08-05
    Description: Paleoceanographic evidence commonly indicates that Last Glacial Maximum surface temperatures in the Japan Sea were comparable to modern conditions, in striking difference to colder neighboring regions. Here, based on a core from the central Japan Sea, our results show similar UK′37‐ and TEXL86‐derived temperatures between 24.7 and 16.3 ka BP, followed by an abrupt divergence at ~16.3 ka BP and a weakening of divergence after ~8.7 ka BP. We attribute this process to a highly stratified glacial upper ocean controlled by the East Asian Summer Monsoon, increasing thermal gradient between surface and subsurface layers during the deglaciation and the intrusion of Tsushima Warm Current since the mid‐Holocene, respectively. Therefore, we suggest that threshold‐like changes in upper‐ocean temperatures linked to sea level rise and monsoon dynamics, rather than just sea surface temperatures, play a critical role in shaping the thermal and ventilation history of this NW Pacific marginal sea.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
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    Toxic dinoflagellate blooms of Gymnodinium catenatum and their cysts in Taiwan Strait and their relationship to global populations (2020)
    Elsevier
    In:  EPIC3Harmful Algae, Elsevier, 97, pp. 101868, ISSN: 15689883
    Details
    Publication Date: 2021-08-01
    Description: Gymnodinium catenatum is able to produce paralytic shellfish toxins (PSTs) and was responsible for a massive bloom in the Taiwan Strait, East China Sea, in June 2017, which resulted in serious human poisoning and economic losses. To understand the origin of the bloom and determine the potential for blooms in subsequent years, water and sediment samples collected in the Taiwan Strait from 2016 to 2019 were analyzed for cells and cysts using light microscopy (LM) and/or quantitative polymerase chain reaction (qPCR). The morphology of both cells and cysts from the field and cultures was examined with LM and scanning electron microscopy (SEM). Large subunit (LSU) and/or internal transcribed spacer (ITS)-5.8S rRNA gene sequences were obtained in 13 isolates from bloom samples and five strains from cysts. In addition, cells of strains TIO523 and GCLY02 (from the Taiwan Strait and Yellow Sea of China, respectively) were subjected to growth experiments, and cysts from the field were used for germination experiments under various temperatures. Our strains shared identical LSU and ITS-5.8S rRNA gene sequences with those from other parts of the world, and therefore belonged to a global population. A low abundance of G. catenatum cells were detected during most of the sampling period, but a small bloom was encountered in Quanzhou on June 8, 2018. Few cysts were observed in 2016 but a marked increase was observed after the bloom in 2017, with a highest density of 689 cysts cm−3. Cysts germinated at temperatures between 14 and 23 °C with a final germination rate over 93%. Strains TIO523 and GCLY02 displayed growth at temperatures between 17 and 26 °C and 14 and 26 °C, respectively, with both strains displaying the highest growth rate of ca. 0.5 divisions d–1 at 23 °C. The PSTs of the three strains and cysts from the sediments were analyzed by liquid chromatography with tandem mass spectrometry (LC-MS/MS). All strains were able to produce PSTs, which were dominated by N-sulfocarbamoyl C toxins (C1/2, 53.0–143.5 pg cell−1) and decarbamoyl gonyautoxins (dcGTX2/3, 26.7–52.1 pg cell−1), although they were not detected in cysts. However, hydroxybenzoyl (GC) toxins were detected in both cells and cysts. Our results suggested that the population in the Taiwan Strait belonged to a warm water ecotype and has a unique toxin profile. Our results also suggested that the persistence of cells in the water column may have initiated the bloom.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    The evolving paleobathymetry of the circum-Antarctic Southern Ocean since 34 Ma – A key to understanding past cryosphere-ocean developments (2020)
    Wiley
    In:  EPIC3Geochemistry Geophysics Geosystems, Wiley, 21, ISSN: 1525-2027
    Details
    Publication Date: 2021-07-19
    Description: The Southern Ocean is a key player in the climate, ocean and atmospheric system. As the only direct connection between all three major oceans since the opening of the Southern Ocean gateways, the development of the Southern Ocean and its relationship with the Antarctic cryosphere has influenced the climate of the entire planet. Although the depths of the ocean floor have been recognized as an important factor in climate and paleoclimate models, appropriate paleobathymetric models including a detailed analysis of the sediment cover are not available. Here, we utilize more than 40 years of seismic reflection data acquisition along the margins of Antarctica and its conjugate margins, along with multiple drilling campaigns by the International Ocean Discovery Program (IODP) and its predecessor programs. We combine and update the seismic stratigraphy across the regions of the Southern Ocean and calculate ocean-wide paleobathymetry grids via a backstripping method. We present a suite of high-resolution paleobathymetric grids from the Eocene-Oligocene Boundary to modern times. The grids reveal the development of the Southern Ocean from isolated basins to an interconnected ocean affected by the onset and vigor of an Antarctic Circumpolar Current, as well as the glacial sedimentation and erosion of the Antarctic continent. The ocean-wide comparison through time exposes patterns of ice sheet development such as switching of glacial outlets and the change from wet-based to dry-based ice sheets. Ocean currents and bottom-water production interact with the sedimentation along the continental shelf and slope and profit from the opening of the ocean gateways.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 7
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    Present-day uplift of the European Alps: Evaluating mechanisms and models of their relative contributions (2020)
    Elsevier
    Details
    Publication Date: 2021-06-25
    Description: Recent measurements of surface vertical displacements of the European Alps show a correlation between vertical velocities and topographic features, with widespread uplift at rates of up to ~2–2.5 mm/a in the North-Western and Central Alps, and ~1 mm/a across a continuous region from the Eastern to the South-Western Alps. Such a rock uplift rate pattern is at odds with the horizontal velocity eld, characterized by shortening and crustal thickening in the Eastern Alps and very limited deformation in the Central and Western Alps. Proposed me- chanisms of rock uplift rate include isostatic response to the last deglaciation, long-term erosion, detachment of the Western Alpine slab, as well as lithospheric and surface de ection due to mantle convection. Here, we assess previous work and present new estimates of the contributions from these mechanisms. Given the large range of model estimates, the isostatic adjustment to deglaciation and erosion are su cient to explain the full observed rate of uplift in the Eastern Alps, which, if correct, would preclude a contribution from horizontal shortening and crustal thickening. Alternatively, uplift is a partitioned response to a range of mechanisms. In the Central and Western Alps, the lithospheric adjustment to deglaciation and erosion likely accounts for roughly half of the rock uplift rate, which points to a noticeable contribution by mantle-related processes such as detachment of the European slab and/or asthenospheric upwelling. While it is di cult to independently constrain the patterns and magnitude of mantle contributions to ongoing Alpine vertical displacements at present, future data should provide additional insights. Regardless, interacting tectonic and surface mass redistribution processes, rather than an individual forcing, best explain ongoing Alpine elevation changes.
    Description: Published
    Description: 589-604
    Description: 1T. Struttura della Terra
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Keywords: 04. Solid Earth ; 04.03. Geodesy ; 04.07. Tectonophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Mobility of REE from a hyperacid brine to secondary minerals precipitated in a volcanic hydrothermal system: Kawah Ijen crater lake (Java, Indonesia) (2020)
    Elsevier
    Details
    Publication Date: 2021-06-22
    Description: Rare Earth Elements (REE; lanthanides and yttrium) are elements with high economic interest because they are critical elements for modern technologies. This study mainly focuses on the geochemical behavior of REE in hyperacid sulphate brines in volcanic-hydrothermal systems, where the precipitation of sulphate minerals occurs. Kawah Ijen lake, a hyperacid brine hosted in the Ijen caldera (Indonesia), was used as natural laboratory. ∑REE concentration in the lake water is high, ranging from 5.86 to 6.52 mg kg-1. The REE pattern of lake waters normalized to the average local volcanic rock is flat, suggesting isochemical dissolution. Minerals spontaneously precipitated in laboratory at 25 °C from water samples of Kawah Ijen were identified by XRD as gypsum. Microprobe analyses and the chemical composition of major constituents allow to identify possible other minerals precipitated: jarosite, Al-sulphate and Sr, Ba-sulphate. ∑REE concentration in minerals precipitated (mainly gypsum) range from 59.53 to 78.64 mg kg-1. The REE patterns of minerals precipitated normalized to the average local magmatic rock show enrichment in LREE. The REE distribution coefficient (KD), obtained from a ratio of its concentration in the minerals precipitated (mainly gypsum) and the lake water, shows higher values for LREE than HREE. KD-LREE/KD-HREE increases in the studied samples when the concentrations of BaO, MgO, Fe2O3, Al2O3, Na2O and the sum of total oxides (except SO3 and CaO) decrease in the solid phase. The presence of secondary minerals different than gypsum can be the cause of the distribution coefficient variations. High concentrations of REE in Kawah Ijen volcanic lake have to enhance the interest on these environments as possible REE reservoir, stimulating future investigations. The comparison of the KD calculated for REE after mineral precipitation (mainly gypsum) from Kawah Ijen and Poás hyperacid volcanic lakes allow to generalize that the gypsum precipitation removes the LREE from water.
    Description: Published
    Description: 140133
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: 2IT. Laboratori analitici e sperimentali
    Description: JCR Journal
    Keywords: Gypsum precipitation ; Rare Earth Elements ; Hyperacid crater lake ; Kawah Ijen volcano ; Poás volcano ; REE fractionation ; Geochemistry ; 04.08. Volcanology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    Explosivity of basaltic lava fountains is controlled by magma rheology, ascent rate and outgassing (2020)
    Elsevier
    Details
    Publication Date: 2021-03-30
    Description: The dichotomy between explosive volcanic eruptions, which produce pyroclasts, and effusive eruptions, which produce lava, is defined by the presence or absence of fragmentation during magma ascent. For lava fountains the distinction is unclear, since the liquid phase in the rising magma may remain continuous to the vent, fragment in the fountain, then re-weld on deposition to feed rheomorphic lava flows. Here we use a numerical model to constrain the controls on basaltic eruption style, using Kilauea and Etna as case studies. Based on our results, we propose that lava fountaining is a distinct style, separate from effusive and explosive eruption styles, that is produced when magma ascends rapidly and fragments above the vent, rather than within the conduit. Sensitivity analyses of Kilauea and Etna case studies show that high lava fountains (〉50 m high) occur when the Reynolds number of the bubbly magma is greater than ∼0.1, the bulk viscosity is less than 10^6, and the gas is well-coupled to the melt. Explosive eruptions (Plinian and sub-Plinian) are predicted over a wide region of parameter space for higher viscosity basalts, typical of Etna, but over a much narrower region of parameter space for lower viscosity basalts, typical of Kilauea. Numerical results show also that the magma that feeds high lava fountains ascends more rapidly than the magma that feeds explosive eruptions, owing to its lower viscosity. For the Kilauea case study, waning ascent velocity is predicted to produce a progressive evolution from high to weak fountaining, to ultimate effusion; whereas for the Etna case study, small changes in parameter values lead to transitions to and from explosive activity, suggesting that eruption transitions may occur with little warning.
    Description: RCUK NERC DisEqm project
    Description: Published
    Description: 116658
    Description: 5V. Processi eruttivi e post-eruttivi
    Description: JCR Journal
    Keywords: 04.08. Volcanology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
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    Chemical heterogeneity of Mt. Etna magmas in the last 15 ka. Inferences on their mantle sources (2020)
    Elsevier
    Details
    Publication Date: 2021-03-18
    Description: Primitive basalticmagmas are crucial in the study of the geochemical heterogeneity documented in Etnamagmas and their inferred mantle sources. We undertook a systematic sampling of the less evolved basalts (Mg# N50) erupted over the last 15 ka, a time period which corresponds to the activity of the youngest volcanic edifice of Mt. Etna complex, i.e. Mongibello volcano. We focused on lava flows and pyroclastites emplaced during ‘deepdyke fed’ (DDF) eruptions which were driven by the rapid ascent of deeply-rooted magma intrusions that bypassed the shallow plumbing system of the volcano. All the samples were analyzed by the same laboratory to avoid analytical bias, to build a comprehensive dataset on their major and trace element compositions and to propose a coherent framework for interpreting the geochemical fingerprints of present-day Etna basalts. Trace element modeling, togetherwith literature data for Sr isotopes, gave insight into long-term magmatic processes related to different melting degrees of the heterogeneous mantle beneath Mt Etna. DDF magma batches provide good snapshots of their mantle source heterogeneities that point to the variable involvement of clinopyroxenitic lithology, Rb–87Sr–Cl-rich fluid component(s) possibly controlled by their source mineralogy, and slab-derived fluids selectively enriched in alkalis (Rb, K). The ongoing alkali (Rb, K) enrichment of the present-day magmas, well manifest since the 1970s, is decoupled from that of Sr and Cl. We propose that this process is linked to mantle source composition and is concomitant with changes in both volcanological and seismotectonic patterns of the volcano. There is no time evolution of DDF magma chemistry.
    Description: Published
    Description: 123-134
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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