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  • 1
    Online Resource
    Online Resource
    Cham :Springer International Publishing AG,
    Keywords: Natural gas-Hydrates. ; Electronic books.
    Type of Medium: Online Resource
    Pages: 1 online resource (501 pages)
    Edition: 1st ed.
    ISBN: 9783030811860
    DDC: 553.285
    Language: English
    Note: Intro -- Preface -- Contents -- Editors and Contributors -- A History of Gas Hydrate Research -- 1 Gas Hydrate Research: From the Laboratory to the Pipeline -- Abstract -- 1.1 General Aspects -- 1.2 Experimental Hydrate Research -- 1.2.1 Multiscale Approach -- 1.2.2 Overview of Experimental Techniques -- 1.2.2.1 Small (Laboratory) Scale -- 1.2.2.2 Pilot Scale -- 1.3 Final Considerations -- Acknowledgements -- References -- 2 Shallow Gas Hydrates Near 64° N, Off Mid-Norway: Concerns Regarding Drilling and Production Technologies -- Abstract -- 2.1 Introduction -- 2.2 The Nyegga Gas Hydrate Location -- 2.2.1 General -- 2.2.2 The BSR -- 2.2.2.1 BSR-Related Drilling and Engineering Concerns -- 2.2.3 Complex Pockmarks -- 2.2.4 Hydrate Pingoes -- 2.2.4.1 A Qualitative Model for Hydrate Pingo Formation -- 2.2.5 Carbonate Rubble -- 2.2.6 Pockmark-, Carbonate Rubble-, and Pingo-Related Engineering Concerns -- 2.2.7 Unique Fauna -- 2.2.8 Fauna-Related Drilling and Engineering Concerns -- 2.2.9 Gas Chimneys -- 2.2.10 Gas-Chimney Related Drilling, Production, and Engineering Concerns -- 2.3 Husmus Geological Setting -- 2.3.1 General -- 2.3.2 The Shallow BSR at Husmus -- 2.3.3 Husmus-Related Drilling and Engineering Concerns -- 2.4 Ormen Lange Gas Seeping Event -- 2.4.1 Gas Seepage-Related Drilling and Engineering Concerns -- 2.5 Conclusions -- Acknowledgements -- References -- 3 Finding and Using the World's Gas Hydrates -- Abstract -- 3.1 Introduction-The Location of Gas Hydrates Beneath the Seabed -- 3.2 History of Gas Hydrate Exploration and Global Assessments of Distribution -- 3.3 The Importance of Natural Gas Hydrates -- 3.3.1 The Role of Gas Hydrates in Climate Change -- 3.3.2 Hydrates as a Control on Benthic Ecosystems -- 3.3.3 The Role of Gas Hydrates in Slope Stability -- 3.3.4 Hydrates as a Future Energy Source. , 3.3.5 Carbon Capture and Storage (CCS) in Gas Hydrate Reservoirs -- 3.4 Evidence of Submarine Gas Hydrates -- 3.4.1 Geophysical Evidence -- 3.4.2 Quantifying Hydrates Through Chemical Measurements of Cores -- 3.4.3 Borehole Logging -- 3.5 Gas Hydrates in the Solar System: Applying Lessons from Earth -- 3.6 Summary -- References -- Gas Hydrate Fundamentals -- 4 Seismic Rock Physics of Gas-Hydrate Bearing Sediments -- Abstract -- 4.1 Introduction -- 4.2 Dry-Rock Moduli -- 4.2.1 Elastic Moduli from Theoretical Models -- 4.2.2 Dry-Rock Elastic Moduli from Calibration -- 4.3 Effective-Fluid Model for Partial Saturation -- 4.4 Permeability -- 4.5 Attenuation -- 4.6 Seismic Velocities -- 4.7 Estimation of the Seismic Velocities and Attenuation -- 4.8 Conclusions -- References -- 5 Estimation of Gas Hydrates in the Pore Space of Sediments Using Inversion Methods -- Abstract -- 5.1 Introduction -- 5.2 Methods, Physical Properties and Microstructures Used for Hydrate Quantification -- 5.3 Strategy for Gas Hydrate Exploration and Quantification -- 5.4 Conclusions -- References -- 6 Electromagnetic Applications in Methane Hydrate Reservoirs -- Abstract -- 6.1 Introduction -- 6.2 Electrical Properties of Gas Hydrates -- 6.2.1 Saturation Estimates -- 6.3 Marine CSEM Principle -- 6.4 CSEM Data Interpretation -- 6.5 CSEM Instrumentation and Exploration History -- 6.5.1 Seafloor-Towed Systems -- 6.5.2 Deep-Towed Systems -- 6.5.3 Other Systems -- 6.6 Global Case Studies -- 6.7 Discussion and Conclusions -- References -- Gas Hydrate Drilling for Research and Natural Resources -- 7 Hydrate Ridge-A Gas Hydrate System in a Subduction Zone Setting -- Abstract -- 7.1 Introduction -- 7.2 Tectonic Setting -- 7.3 Stratigraphy and Structure -- 7.4 The Bottom Simulating Reflection Across Hydrate Ridge -- 7.5 Hydrate Occurrence and Distribution Within Hydrate Ridge. , 7.5.1 Hydrate Concentrations from Drilling -- 7.5.2 Inferred Hydrates and Free Gas Regionally Across Hydrate Ridge -- 7.6 Conclusions -- References -- 8 Northern Cascadia Margin Gas Hydrates-Regional Geophysical Surveying, IODP Drilling Leg 311 and Cabled Observatory Monitoring -- Abstract -- 8.1 Introduction -- 8.2 Regional Occurrences of Gas Hydrate Inferred from Remote Sensing Data -- 8.3 The Gas Hydrate Petroleum System for the Northern Cascadia Margin -- 8.4 Gas Hydrate Saturation Estimates -- 8.5 Gas Vents, Focused Fluid Flow and Shallow Gas Hydrates -- 8.6 Long-Term Observations -- 8.6.1 Gas Emissions at the Seafloor -- 8.6.2 Controlled-Source EM and Seafloor Compliance -- 8.6.3 Borehole In Situ Monitoring -- 8.7 Summary and Conclusions -- Acknowledgements -- References -- 9 Accretionary Wedge Tectonics and Gas Hydrate Distribution in the Cascadia Forearc -- Abstract -- 9.1 Introduction -- 9.2 Data -- 9.3 Results -- 9.4 Summary -- Acknowledgements -- References -- 10 Bottom Simulating Reflections Below the Blake Ridge, Western North Atlantic Margin -- Abstract -- 10.1 Geologic Setting -- 10.2 A Brief History of Blake Ridge Gas Hydrate Research -- 10.3 Blake Ridge BSR Distribution, Character and Dynamics -- 10.3.1 A Dynamic BSR on the Eastern Flank of Blake Ridge -- 10.3.2 Gas Chimneys Extending from BSRs -- 10.3.3 The Role of Sediment Waves in Gas Migration from the BSR -- 10.3.4 The Blake Ridge Diapir -- 10.4 Unanswered Questions and Future Research -- References -- 11 A Review of the Exploration, Discovery and Characterization of Highly Concentrated Gas Hydrate Accumulations in Coarse-Grained Reservoir Systems Along the Eastern Continental Margin of India -- Abstract -- 11.1 Introduction -- 11.2 India National Gas Hydrate Program-Scientific Drilling Expeditions -- 11.3 Representative Gas Hydrate Systems-Krishna-Godavari Basin. , 11.3.1 Krishna-Godavari Basin Geologic Setting -- 11.3.2 NGHP-02 Area C Gas Hydrate System -- 11.3.3 NGHP-02 Area B Gas Hydrate System -- 11.4 Summary -- Acknowledgements -- References -- 12 Ulleung Basin Gas Hydrate Drilling Expeditions, Korea: Lithologic Characteristics of Gas Hydrate-Bearing Sediments -- Abstract -- 12.1 Introduction -- 12.2 Geological Setting of the Ulleung Basin -- 12.3 Overview of the First and Second Ulleung Basin Gas Hydrate Drilling Expeditions (UBGH1 and 2) -- 12.4 Lithologic Characteristics of Gas Hydrate-Bearing Sediments in the Ulleung Basin -- 12.5 Summary -- References -- 13 Bottom Simulating Reflections in the South China Sea -- Abstract -- 13.1 Introduction -- 13.2 Geological Setting and Gas Hydrate Drilling Expeditions -- 13.3 The Characteristics of BSRs Within Various Sediment Environments -- 13.3.1 BSR and Cold Seeps in Taixinan Basin -- 13.3.2 BSRs in the Pearl River Mouth Basin -- 13.3.3 BSRs in the Qiongdongnan Basin -- 13.4 Well Log Anomalies of Different Types of Gas Hydrate -- 13.5 BSR Dynamics and Response to Fluid Migration -- 13.6 Summary -- Acknowledgements -- References -- 14 Gas Hydrate and Fluid-Related Seismic Indicators Across the Passive and Active Margins off SW Taiwan -- Abstract -- 14.1 Introduction -- 14.2 Geological Setting -- 14.3 Seismic Observations -- 14.3.1 Gas Accumulation -- 14.3.2 Fluid Migration -- 14.3.3 Presence of Gas Hydrate -- 14.4 Distribution of the Seismic Indicators and Implications for Understanding the Hydrate System -- 14.5 Summary -- References -- 15 Gas Hydrate Drilling in the Nankai Trough, Japan -- Abstract -- 15.1 Introduction -- 15.2 Discovery of Gas Hydrates and Early Expeditions in the Nankai Trough Area -- 15.3 MITI Exploratory Test Well: Nankai Trough (1999-2000) -- 15.4 METI Multi-well Exploratory Drilling Campaign and Resource Assessments. , 15.4.1 Drilling Operations and Achievements -- 15.4.2 Discovery of the Methane Hydrate Concentration Zone and Resource Assessments -- 15.5 Tests for Gas Production Undertaken in 2013 and 2017 -- 15.5.1 Gas Production Techniques and Site Selection -- 15.5.2 Drilled Boreholes and Data/Sample Acquisitions -- 15.5.3 Production Test Results and Findings -- 15.6 Other Gas Hydrate Occurrences and Resource Evaluation Results -- 15.7 Summary -- Acknowledgements -- References -- 16 Alaska North Slope Terrestrial Gas Hydrate Systems: Insights from Scientific Drilling -- Abstract -- 16.1 Introduction -- 16.2 Alaska North Slope Gas Hydrate Accumulations -- 16.3 Alaska North Slope Gas Hydrate Research Drilling Programs -- 16.3.1 Mount Elbert Gas Hydrate Stratigraphic Test Well -- 16.3.2 Iġnik Sikumi Gas Hydrate Production Test Well -- 16.3.3 Hydrate-01 Stratigraphic Test Well -- 16.4 Alaska North Slope Gas Hydrate Energy Assessments -- 16.5 Summary -- Acknowledgements -- References -- Arctic -- 17 Gas Hydrates on Alaskan Marine Margins -- Abstract -- 17.1 Introduction -- 17.2 Southeastern Alaskan Margin -- 17.3 Aleutian Arc -- 17.3.1 Eastern Aleutian Arc -- 17.3.2 Central Aleutian Arc -- 17.3.3 Western Aleutian Arc -- 17.3.4 Bering Sea -- 17.4 US Beaufort Sea -- 17.5 Summary -- Acknowledgements -- References -- 18 Gas Hydrate Related Bottom-Simulating Reflections Along the West-Svalbard Margin, Fram Strait -- Abstract -- 18.1 Introduction -- 18.2 Geological and Oceanographic Settings -- 18.2.1 Regional Tectonic Setting -- 18.2.2 Sedimentary Setting -- 18.2.3 Oceanographic Setting -- 18.3 BSR Distribution and Characteristics Within Various Sediment Types -- 18.3.1 Regional Extent of the BSRs -- 18.4 Evidence for Gas Migration from Deep and Shallow Sources -- 18.4.1 The Gas Sources -- 18.4.2 Vertical Fluid Migration Features -- 18.5 Inferred Gas Hydrate Distribution. , 18.6 BSR Dynamics and Response to Natural Changes in the Environment.
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  • 2
    Online Resource
    Online Resource
    Cham :Springer International Publishing AG,
    Keywords: Mass-wasting. ; Electronic books.
    Description / Table of Contents: This book covers the geological, geophysical, engineering and environmental aspects of submarine slope failures. It focuses on understanding the full spectrum of challenges presented by this major coastal and offshore geohazard.
    Type of Medium: Online Resource
    Pages: 1 online resource (664 pages)
    Edition: 1st ed.
    ISBN: 9783319009728
    Series Statement: Advances in Natural and Technological Hazards Research Series ; v.37
    DDC: 551.468
    Language: English
    Note: Intro -- Preface -- Contents -- Part I Physical Properties of Sediments -- Chapter 1: Weak Layers: Their Definition and Classification from a Geotechnical Perspective -- 1.1 Introduction -- 1.2 Weak Layer Definition -- 1.3 Weak Layer Observations -- 1.4 Classification System from a Geotechnical Approach -- 1.5 Concluding Remarks -- References -- Chapter 2: Field Measurements to Investigate Submerged Slope Failures -- 2.1 Introduction -- 2.2 Interpretation Methods of Field Measurements -- 2.2.1 Relative Density -- 2.2.2 State Parameter -- 2.3 Application on Test Locations -- 2.4 Discussion -- 2.5 Conclusions and Recommendations -- References -- Chapter 3: Elemental Distribution and Microfabric Characterization Across a Buried Slump Scar: New Insights on the Long-Term Development and Reactivation of Scar Surfaces from a Microscopic Perspective -- 3.1 Introduction -- 3.2 Geological Setting -- 3.3 Investigation of Remineralization at the Unconformity -- 3.3.1 X-ray Computed Tomography (X-CT) -- 3.3.2 X-ray Fluorescence Spectroscopy (XRF) -- 3.3.3 Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDX) -- 3.4 Discussion and Conclusion -- References -- Chapter 4: Evidence for Mass Transport Deposits at the IODP JFAST-Site in the Japan Trench -- 4.1 Introduction -- 4.2 Background and Geological Setting -- 4.3 Material and Methods -- 4.3.1 Bathymetric Mapping -- 4.3.2 Sediment Core -- 4.3.2.1 Physical Properties -- 4.3.2.2 Pore-Water Analyses -- 4.4 Results -- 4.5 Discussion -- 4.5.1 Evidencing Mass Transport Deposits at the JFAST-Site -- 4.5.2 Estimating the Age of the MTD Formation -- 4.6 Conclusions -- References -- Chapter 5: Preliminary Investigations of Rheological Properties of Busan Clays and Possible Implications for DebrisFlow Modelling -- 5.1 Introduction -- 5.2 Materials and Methods -- 5.3 Results. , 5.3.1 Rheological Behaviour of the Busan Clays -- 5.4 Discussion -- 5.5 Conclusions -- References -- Chapter 6: Utilizing Cone Penetration Tests for Landslide Evaluation -- 6.1 Introduction -- 6.2 Site Characterization -- 6.3 Methods -- 6.3.1 In-Situ CPT Measurements -- 6.3.2 Physical and Mechanical Properties -- 6.4 Results and Discussion -- 6.4.1 Static CPT -- 6.4.2 Vibratory CPT -- 6.4.3 Dissipation Test -- 6.4.4 Liquefaction Analysis with CLiq Software -- 6.5 Summary and Conclusion -- References -- Chapter 7: Geomechanical Characterization of Submarine Volcano-Flank Sediments, Martinique, Lesser Antilles Arc -- 7.1 Introduction -- 7.2 Geomechanical Characterization -- 7.3 Results -- 7.3.1 Summary of Hole Stratigraphy -- 7.3.2 Consolidation State -- 7.3.3 Hydraulic Conductivity -- 7.4 Discussion and Conclusion -- References -- Part II Gas Hydrates and Role of Interstitial Fluids in Submarine Slope Failure -- Chapter 8: Interrelationship Between Sediment Fabric, Pore Volume Variations as Indicator for Pore Pressure Changes, and Sediment Shear Strength -- 8.1 Introduction -- 8.2 Method -- 8.3 Results -- 8.4 Discussion -- 8.4.1 Interplay: Sediment Strength and Pore Volume Changes -- 8.4.1.1 Effect of Grain Shape Complexity -- 8.4.2 Local Pore Volume Changes -- 8.5 Conclusions -- References -- Chapter 9: Slope Instability of Glaciated Continental Margins: Constraints from Permeability-Compressibility Tests and Hydrogeological Modeling Off Storfjorden, NW Barents Sea -- 9.1 Introduction -- 9.2 Data and Methods -- 9.3 Results -- 9.4 Discussion -- 9.5 Conclusions -- References -- Chapter 10: Baiyun Slide and Its Relation to Fluid Migration in the Northern Slope of Southern China Sea -- 10.1 Introduction -- 10.2 Geological Setting -- 10.3 Data and Methods -- 10.4 Results -- 10.4.1 Morphology and Distribution of Baiyun Slide. , 10.4.2 Seismic Indications of Gas and Fluid Migration -- 10.4.2.1 Active Faults Related to Gas and Fluid Migration -- 10.4.2.2 Gas Chimneys -- 10.5 Discussion -- 10.5.1 Relationship Between Fluid Migration and Slope Stability -- 10.5.2 Possible Trigger Mechanisms -- 10.6 Conclusions -- References -- Chapter 11: Post-failure Processes on the Continental Slope of the Central Nile Deep-Sea Fan: Interactions Between Fluid Seepage, Sediment Deformation and Sediment-Wave Construction -- 11.1 Introduction -- 11.2 Methods -- 11.3 Results -- 11.3.1 Architecture and Age of MTDs and Slope Deposits -- 11.3.2 Seabed Sediment Undulations -- 11.3.3 Sediment Pathways -- 11.4 Discussion -- 11.4.1 End-Members: Sediment Waves Versus Deformation Structures -- 11.4.2 Post-failure Slope Evolution -- 11.5 Conclusion -- References -- Chapter 12: Fluid Seepage in Relation to Seabed Deformation on the Central Nile Deep-Sea Fan, Part 1: Evidence from Sidescan Sonar Data -- 12.1 Introduction -- 12.2 Methods -- 12.3 Results -- 12.3.1 Erosional Furrows -- 12.3.2 Sediment Cracks -- 12.3.3 Carbonate Pavements -- 12.3.4 Hydroacoustic Flares -- 12.4 Discussion -- 12.4.1 Mid-slope Domain: Focused Fluid Flow Through MTDs -- 12.4.2 Western Undulations: Fluid Flow Along Faults Rooted in MTDs -- 12.4.3 Eastern Undulations: Exhumation of Fossil Carbonates -- 12.5 Conclusions -- References -- Chapter 13: Fluid Seepage in Relation to Seabed Deformation on the Central Nile Deep-Sea Fan, Part 2: Evidence from Multibeam and Sidescan Imagery -- 13.1 Introduction -- 13.2 Methods -- 13.3 Results -- 13.3.1 Faults and Fluid Indicators on Sub-bottom Profiles -- 13.3.2 Seabed Backscatter Anomalies at Differing Frequencies -- 13.3.3 Water Column Gas Flares -- 13.4 Discussion -- 13.4.1 Growth and Burial of Carbonate Pavements -- 13.4.2 Fluid Migration Along Fault Planes -- 13.5 Conclusions -- References. , Part III Slope Stability and Risk Assessment -- Chapter 14: Advances in Offshore Seismic Slope Stability: A Case History -- 14.1 Introduction -- 14.2 Geomorphological and Geotechnical Data -- 14.2.1 Site Investigations -- 14.2.2 Geomorphological Setting -- 14.2.3 Geotechnical and Geophysical Data Integration -- 14.2.4 Soil Sampling -- 14.2.5 Advanced Laboratory Testing -- 14.3 Stability Analyses -- 14.3.1 Conventional Approach -- 14.3.2 Dynamic Approach -- 14.4 Conclusions -- References -- Chapter 15: Size-Frequency Relationship of Submarine Landslides at Convergent Plate Margins: Implications for Hazard and Risk Assessment -- 15.1 Introduction -- 15.2 Tectonic Setting of the MA and CC Convergent Margins -- 15.3 MA and CC Slumps and Slides: Observations and Data -- 15.4 Size-Frequency Relationships -- 15.5 Discussion and Conclusion -- References -- Chapter 16: A Numerical Investigation of Sediment Destructuring as a Potential Globally Widespread Trigger for Large Submarine Landslides on Low Gradients -- 16.1 Introduction -- 16.1.1 Destructuring of Cemented Hemipelagic Clay as a Source of Overpressure -- 16.1.2 Aims and Approach -- 16.2 Methodology -- 16.2.1 Material Model -- 16.2.2 Model Description -- 16.2.3 Assumptions and Limitations -- 16.3 Results -- 16.4 Discussion -- 16.5 Conclusion -- References -- Chapter 17: How Stable Is the Nice Slope? - An Analysis Based on Strength and Cohesion from Ring Shear Experiments -- 17.1 Introduction and Geological Setting -- 17.2 Methods -- 17.2.1 Coring and Sedimentological Analysis -- 17.2.2 Shear Experiments with the Ring Shear Apparatus -- 17.2.3 Stability Assessment of the Nice Slope Sediments -- 17.3 Results -- 17.3.1 Sedimentological Analysis and Physical Properties -- 17.3.2 Frictional Behavior of the Nice Slope Sediments -- 17.3.3 Stability Assessment of the Nice Slope Sediments -- 17.4 Discussion. , References -- Chapter 18: Regional Slope Stability Assessment Along the Caucasian Shelf of the Black Sea -- 18.1 Introduction -- 18.2 Geological Engineering Conditions Along the Caucasian Shelf of the Black Sea -- 18.3 Methods -- 18.4 Regional Submarine Slope Stability Assessment Based on 1D Modelling -- 18.5 Local Submarine Slope Stability Assessment Based on 1D Modelling -- 18.5.1 Dzhubga -- 18.5.2 Novomikhailovsky -- 18.5.3 Tuapse -- 18.5.4 Ashe -- 18.5.5 Shahe -- 18.5.6 Dagomis -- 18.5.7 Kudepsta -- 18.6 Discussion and Conclusion -- References -- Chapter 19: A Semi-empirical Method to Assess Flow-Slide Probability -- 19.1 Introduction -- 19.2 Failure Mechanisms -- 19.2.1 Static Liquefaction -- 19.2.2 Breach Flow-Slide -- 19.3 Physical-Based Models -- 19.3.1 Static Liquefaction -- 19.3.2 Breach Flow-Slide -- 19.3.3 Applicability of Physical-Based Models -- 19.4 Empirical Method -- 19.4.1 Basic Information and Mean Flow-Slide Frequency -- 19.4.2 General Applicability to Other Regions in the Netherlands -- 19.4.3 Influence of Local Soil Characteristics and Slope Geometry -- 19.5 Semi-empirical Method -- 19.5.1 Determination of P(ZVliquefaction) -- 19.5.2 Determination of P(ZVbreachflow) -- 19.6 Concluding Remarks -- References -- Chapter 20: Submarine Slope Stability Assessment of the Central Mediterranean Continental Margin: The Gela Basin -- 20.1 Introduction -- 20.2 Geological Setting -- 20.3 Material and Methods -- 20.3.1 Shipboard and Laboratory Analysis -- 20.3.2 Overpressure Estimation -- 20.3.3 Slope Stability Analysis -- 20.4 Results -- 20.4.1 Physical and Geotechnical Properties -- 20.4.2 Slope Stability Analysis -- 20.5 Discussion -- 20.5.1 Preconditioning Factors -- 20.5.2 Triggering Factors -- 20.6 Conclusions -- References -- Part IV Monitoring, Observation and Repeated Surveys of Active Slope Failure Processes. , Chapter 21: The 1930 Landslide in Orkdalsfjorden: Morphology and Failure Mechanism.
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  • 3
    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
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  • 4
    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
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  • 5
    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
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  • 6
    Publication Date: 2024-02-07
    Description: The continental margin of the northern South China Sea is considered to be a magma-poor rifted margin. This work uses new seismic, bathymetric, gravity, and magnetic data to reveal how extensively magmatic processes have reshaped the latter continental margin. Widespread hydrothermal vent complexes and magmatic edifices such as volcanoes, igneous sills, lava flows, and associated domes are confirmed in the broader area of the northern South China Sea. Newly identified hydrothermal vents have crater- and mound-shaped surface expressions, and occur chiefly above igneous sills and volcanic edifices. Detailed stratigraphic analyses of volcanoes and hydrothermal vents suggest that magmatic activity took place in discrete phases between the early Miocene and the Quaternary. Importantly, the occurrence of hydrothermal vents close to the present seafloor, when accompanied by shallow igneous sills, suggest that fluid seepage is still active, well after main phases of volcanism previously documented in the literature. After combining geophysical and geochemical data, this study postulates that the extensive post-rift magmatism in the northern South China Sea is linked to the effect of a mantle plume over a long time interval. We propose that prolonged magmatism resulted in contact metamorphism in carbon-rich sediments, producing large amounts of hydrothermal fluid along the northern South China Sea. Similar processes are expected in parts of magma-poor margins in association with CO2/CH4 and heat flow release into sea water and underlying strata.
    Type: Article , PeerReviewed
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