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  • 1
    Book
    Book
    Submarine mass movements and their consequences : 6th International Symposium (2014)
    Cham : Springer
    Details Availability
    Keywords: Geography ; Oceanography ; Sedimentology ; Physical geography ; Konferenzschrift ; Aufsatzsammlung ; Meereskunde ; Massenbewegung
    Description / Table of Contents: Submarine mass movements are a hidden geohazard with large destructive potential for submarine installations and coastal areas. This hazard and associated risk is growing in proportion with increasing population of coastal urban agglomerations, industrial infrastructure, and coastal tourism. Also, the intensified use of the seafloor for natural resource production, and deep sea cables constitutes an increasing risk. Submarine slides may alter the coastline and bear a high tsunamogenic potential. There is a potential link of submarine mass wasting with climate change, as submarine landslides can uncover and release large amounts greenhouse gases, mainly methane, that are now stored in marine sediments. The factors that govern the stability of submarine slopes against failure, the processes that lead to slope collapses and the collapse processes by themselves need to be better understood in order to foresee and prepare society for potentially hazardous events. This book volume consists of a collection of cutting edge scientific research by international experts in the field, covering geological, geophysical, engineering and environmental aspects of submarine slope failures. The focus is on understanding the full spectrum of challenges presented by this major coastal and offshore geohazard
    Type of Medium: Book
    Pages: XVI, 683 S. , Ill., graph. Darst., Kt.
    ISBN: 9783319009711
    Series Statement: Advances in natural and technological hazards research 37
    URL: https://swbplus.bsz-bw.de/bsz39818478xcov.jpg
    DDC: 551.46
    Language: English
    Note: Literaturangaben , Physical properties of sedimentsGas hydrates and role of interstitial fluids in submarine slope failure -- Slope stability and risk assessment -- Monitoring, observation and repeated surveys of active slope failure processes -- Understanding failure processes from submarine landslide geomorphology -- Interaction between ocean circulation and MTDs -- Landslide generated tsunamis -- Long-term record of submarine landslides and MTD paleoseismology -- Outcrops of ancient submarine landslides.
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  • 2
    Book
    Book
    World atlas of submarine gas hydrates in continental margins (2022)
    Cham : Springer
    Details Availability
    Keywords: Oceanography ; Water ; Hydrology ; Cogeneration of electric power and heat ; Fossil fuels ; Physical geography ; Business ; Management science ; Gashydrate ; Simulation ; Sediment ; Kontinentalrand ; Methanhydrate
    Type of Medium: Book
    Pages: XXI, 514, C3 Seiten , Illustrationen, Karten
    Edition: Corrected Publication 2022
    ISBN: 3030811859 , 9783030811853
    URL: https://www.gbv.de/dms/tib-ub-hannover/1820177041.pdf
    DDC: 551.46
    Language: English
    Note: Literaturangaben
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  • 3
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    On the formation of hydrothermal vents and cold seeps in the Guaymas Basin, Gulf of California (2018)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 15 (18). pp. 5715-5731.
    Details
    Publication Date: 2021-03-18
    Description: Magmatic sill intrusions into organic-rich sediments cause the release of thermogenic CH4 and CO2. Pore fluids from the Guaymas Basin (Gulf of California), a sedimentary basin with recent magmatic activity, were investigated to constrain the link between sill intrusions and fluid seepage as well as the timing of sill-induced hydrothermal activity. Sampling sites were close to a hydrothermal vent field at the northern rift axis and at cold seeps located up to 30km away from the rift. Pore fluids close to the active hydrothermal vent field showed a slight imprint by hydrothermal fluids and indicated a shallow circulation system transporting seawater to the hydrothermal catchment area. Geochemical data of pore fluids at cold seeps showed a mainly ambient diagenetic fluid composition without any imprint related to high temperature processes at greater depth. Seep communities at the seafloor were mainly sustained by microbial methane, which rose along pathways formed earlier by hydrothermal activity, driving the anaerobic oxidation of methane (AOM) and the formation of authigenic carbonates. Overall, our data from the cold seep sites suggest that at present, sill-induced hydrothermalism is not active away from the ridge axis, and the vigorous venting of hydrothermal fluids is restricted to the ridge axis. Using the sediment thickness above extinct conduits and carbonate dating, we calculated that deep fluid and thermogenic gas flow ceased 28 to 7kyr ago. These findings imply a short lifetime of hydrothermal systems, limiting the time of unhindered carbon release as suggested in previous modeling studies. Consequently, activation and deactivation mechanisms of these systems need to be better constrained for the use in climate modeling approaches.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.5194/bg-15-5715-2018
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Rifting under steam – how rift magmatism triggers methane venting from sedimentary basins (2016)
    GSA (Geological Society of America)
    In:  Geology, 44 (9). pp. 767-770.
    Details
    Publication Date: 2019-10-24
    Description: During opening of a new ocean magma intrudes into the surrounding sedimentary basins. Heat provided by the intrusions matures the host rock creating metamorphic aureoles potentially releasing large amounts of hydrocarbons. These hydrocarbons may migrate to the seafloor in hydrothermal vent complexes in sufficient volumes to trigger global warming, e.g. during the Paleocene Eocene Thermal Maximum (PETM). Mound structures at the top of buried hydrothermal vent complexes observed in seismic data off Norway were previously interpreted as mud volcanoes and the amount of released hydrocarbon was estimated based on this interpretation. Here, we present new geophysical and geochemical data from the Gulf of California suggesting that such mound structures could in fact be edifices constructed by the growth of black-smoker type chimneys rather than mud volcanoes. We have evidence for two buried and one active hydrothermal vent system outside the rift axis. The vent releases several hundred degrees Celsius hot fluids containing abundant methane, mid-ocean-ridge-basalt (MORB)-type helium, and precipitating solids up to 300 m high into the water column. Our observations challenge the idea that methane is emitted slowly from rift-related vents. The association of large amounts of methane with hydrothermal fluids that enter the water column at high pressure and temperature provides an efficient mechanism to transport hydrocarbons into the water column and atmosphere, lending support to the hypothesis that rapid climate change such as during the PETM can be triggered by magmatic intrusions into organic-rich sedimentary basins.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1130/G38049.1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Drivers of focused fluid flow and methane seepage at South Hydrate Ridge, offshore Oregon, USA (2013)
    GSA (Geological Society of America)
    In:  Geology, 41 (5). pp. 551-554.
    Details
    Publication Date: 2019-10-24
    Description: Methane seepage at south Hydrate Ridge (offshore Oregon, United States), one of the best-studied examples of gas venting through gas hydrates, is the seafloor expression of a vigorous fluid flow system at depth. The seeps host chemosynthetic ecosystems and release significant amounts of carbon into the ocean. With new three-dimensional seismic data, we image strata and structures beneath the ridge in unprecedented detail to determine the geological processes controlling the style of focused fluid flow. Numerical fluid flow simulations reveal the influence of free gas within a stratigraphic unit known as Horizon A, beneath the base of gas hydrate stability (BGHS). Free gas within Horizon A increases the total mobility of the composite water-gas fluid, resulting in high fluid flux that accumulates at the intersection between Horizon A and the BGHS. This intersection controls the development of fluid overpressure at the BGHS, and together with a well-defined network of faults, reveals the link between the gas hydrate system at depth and methane seepage at the surface.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1130/G34057.1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Gas-controlled seafloor doming (2015)
    GSA (Geological Society of America)
    In:  Geology, 43 (7). pp. 571-574.
    Details
    Publication Date: 2019-10-24
    Description: The upward migration of gas through marine sediments typically manifests itself as gas chimneys or pipes in seismic images and can lead to the formation of cold seeps. Gas seepage is often linked to morphological features like seabed domes, pockmarks, and carbonate build-ups. In this context, sediment doming is discussed to be a precursor of pockmark formation. Here, we present parametric echosounder, sidescan sonar, and two-dimensional seismic data from Opouawe Bank, offshore New Zealand, providing field evidence for sediment doming. Geomechanical quantification of the stresses required for doming show that the calculated gas column heights are geologically feasible and consistent with the observed geophysical data. The progression from channeled gas flow to gas trapping results in overpressure build-up in the shallow sediment. Our results suggest that by breaching of domed seafloor sediments a new seep site can develop, but contrary to ongoing discussion this does not necessarily lead to the formation of pockmarks.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1130/G36596.1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Northeast Atlantic breakup volcanism and consequences for Paleogene climate change - MagellanPlus Workshop report (2019)
    Copernicus Publications (EGU)
    In:  Scientific Drilling, 26 . pp. 69-85.
    Details
    Publication Date: 2021-03-26
    Description: The northeast Atlantic encompasses archetypal examples of volcanic rifted margins. Twenty-five years after the last ODP (Ocean Drilling Program) leg on these volcanic margins, the reasons for excess melting are still disputed with at least three competing hypotheses being discussed. We are proposing a new drilling campaign that will constrain the timing, rates of volcanism, and vertical movements of rifted margins. This will allow us to parameterise geodynamic models that can distinguish between the hypotheses. Furthermore, the drilling-derived data will help us to understand the role of breakup magmatism as a potential driver for the Palaeocene–Eocene thermal maximum (PETM) and its influence on the oceanographic circulation in the earliest phase of the northeast Atlantic Ocean formation. Tackling these questions with a new drilling campaign in the northeast Atlantic region will advance our understanding of the long-term interactions between tectonics, volcanism, oceanography, and climate and the functioning of subpolar northern ecosystems and climate during intervals of extreme warmth.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.5194/sd-26-69-2019
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Ideas and perspectives: Land-ocean connectivity through groundwater (2022)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2023-02-10
    Description: For millennia humans have gravitated towards coastlines for their resource potential and as geopolitical centres for global trade. A basic requirement ensuring water security for coastal communities relies on a delicate balance between the supply and demand of potable water. The interaction between freshwater and saltwater in coastal settings is, therefore, complicated by both natural and human-driven environmental changes at the land-sea interface. In particular, ongoing sea level rise, warming and deoxygenation might exacerbate such perturbations. In this context, an improved understanding of the nature and variability of groundwater fluxes across the land-sea continuum is timely, yet remains out of reach. The flow of terrestrial groundwater across the coastal transition zone as well as the extent of freshened groundwater below the present-day seafloor are receiving increased attention in marine and coastal sciences because they likely represent a significant, yet highly uncertain component of (bio)geochemical budgets, and because of the emerging interest in the potential use of offshore freshened groundwater as a resource. At the same time, “reverse” groundwater flux from offshore to onshore is of prevalent socio-economic interest as terrestrial groundwater resources are continuously pressured by overpumping and seawater intrusion in many coastal regions worldwide. An accurate assessment of the land-ocean connectivity through groundwater and its potential responses to future anthropogenic activities and climate change will require a multidisciplinary approach combining the expertise of geophysicists, hydrogeologists, (bio)geochemists and modellers. Such joint activities will lay the scientific basis for better understanding the role of groundwater in societal-relevant issues such as climate change, pollution and the environmental status of the coastal oceans within the framework of the United Nations Sustainable Development Goals. Here, we present our perspectives on future research directions to better understand land-ocean connectivity through groundwater, including the spatial distributions of the essential hydrogeological parameters, highlighting technical and scientific developments, and briefly discussing its societal relevance in rapidly changing coastal oceans.
    Type: Article , NonPeerReviewed , info:eu-repo/semantics/article
    Format: text
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    OceanRep: Article in a Scientific Journal - without review
  • 9
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    Formation and geophysical character of transitional crust at the passive continental margin around Walvis Ridge, Namibia (2022)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2023-02-09
    Description: When interpreting geophysical models, we need to establish a link between the models’ physical parameters and geological units. To define these connections, it is crucial to consider and compare geophysical models with multiple, independent parameters. Particularly in complex geological scenarios, such as the rifted passive margin offshore Namibia, multi-parameter analysis and joint inversion are key techniques for comprehensive geological inferences. The models resulting from joint inversion enable the definition of specific parameter combinations, which can then be ascribed to geological units. Here we perform a user-unbiased clustering analysis of the parameters electrical resistivity and density from two models derived in a joint inversion along the Namibian passive margin. We link the resulting parameter combinations to break-up related lithology, and infer the history of margin formation. This analysis enables us to clearly differentiate two types of sediment cover. Namely, one of near-shore, thick, clastic sediments, and a second one of further offshore located, more biogenic, marine sediments. Furthermore, we clearly identify areas of interlayered massive, and weathered volcanic flows, which are usually only identified in reflection seismic studies as seaward dipping reflectors. Lastly, we find a distinct difference in the signature of the transitional crust south of- and along the supposed hot-spot track Walvis Ridge. We ascribe this contrast to an increase in magmatic activity above the volcanic centre along Walvis Ridge, and potentially a change in melt sources or depth of melting. This characterizes a rift-related southern complex, and a plume-driven Walvis Ridge regime. All of these observations demonstrate the importance of multi-parameter geophysical analysis for large-scale geological interpretations. Furthermore, our results may improve future joint inversions using direct parameter coupling, by providing a guideline for the complex passive margins parameter correlations.
    Type: Article , NonPeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - without review
  • 10
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    Correlation of core and downhole seismic velocities in high-pressure metamorphic rocks: a case study for the COSC-1 borehole, Sweden (2020)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2023-02-08
    Description: Deeply rooted thrust zones are key features of tectonic processes and the evolution of mountain belts. Exhumed and deeply-eroded orogens like the Scandinavian Caledonides allow to study such systems from the surface. Previous seismic investigations of the Seve Nappe Complex have shown indications for a strong but discontinuous reflectivity of this thrust zone, which is only poorly understood. The correlation of seismic properties measured on borehole cores with surface seismic data constrains the origin of this reflectivity. In this study, we compare seismic velocities measured on cores to in situ velocities measured in the borehole. The core and downhole velocities deviate by up to 2 km/s. However, velocities of mafic rocks are generally in close agreement. Seismic anisotropy increases from about 5 to 26 % at depth, indicating a transition from gneissic to schistose foliation. We suggest that differences in the core and downhole velocities are most likely the result of microcracks mainly due to depressurization. Thus, seismic velocity can help to identify mafic rocks on different scales whereas the velocity signature of other lithologies is obscured in core-derived velocities. Metamorphic foliation on the other hand has a clear expression in seismic anisotropy. These results will aid in the evaluation of core-derived seismic properties of high-grade metamorphic rocks at the COSC-1 borehole and elsewhere. In particular, they show that core log seismic integration via synthetic seismograms requires wireline logging data in any but mafic lithologies.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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