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  • 1
    Online Resource
    Online Resource
    Cham : Springer
    Keywords: Earth sciences ; Earth Sciences ; Geology ; Oceanography ; Geomorphology ; Meereskunde ; Meeresboden ; Meeresgeologie ; Meeressediment ; Geomorphologie ; Meeresboden ; Sonar ; Topografie ; Hydroakustik ; Relief ; Geomorphographie
    Description / Table of Contents: This book on the current state of knowledge of submarine geomorphology aims to achieve the goals of the Submarine Geomorphology working group, set up in 2013, by establishing submarine geomorphology as a field of research, disseminating its concepts and techniques among earth scientists and professionals, and encouraging students to develop their skills and knowledge in this field. Editors have invited 30 experts from around the world to contribute chapters to this book, which is divided into 4 sections - (i) Introduction & history, (ii) Data & methods, (ii) Submarine landforms & processes and (iv) Conclusions & future directions. Each chapter provides a review of a topic, establishes the state-of-the-art, identifies the key research questions that need to be addressed, and delineates a strategy on how to achieve this. Submarine geomorphology is a priority for many research institutions, government authorities and industries globally. The book is useful for undergraduate and graduate students, and professionals with limited training in this field
    Type of Medium: Online Resource
    Pages: Online-Ressource (XIII, 556 p. 195 illus., 55 illus. in color, online resource)
    ISBN: 9783319578521
    Series Statement: Springer Geology
    Language: English
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  • 2
    Keywords: Earth sciences ; Earth Sciences ; Sedimentology ; Oceanography ; Natural disasters ; Geotechnical engineering ; Physical geography ; Earth sciences ; Sedimentology ; Oceanography ; Natural disasters ; Geotechnical engineering ; Physical geography ; Konferenzschrift 2015 ; Submarine Gleitung ; Meeresgeologie ; Submarine Gleitung ; Massenbewegung ; Meeresgeologie ; Meeresboden ; Suspensionsströmung ; Submarine Gleitung ; Turbidit
    Description / Table of Contents: 1. Submarine Mass Movements and Their Consequences: Progress and Challenges -- Part I Submarine Mass Movement in Margin Construction and Economic Significance2. The Role of Submarine Landslides in the Law of the Sea -- 3. Fabric Development and Pore-Throat Reduction in a Mass-Transport Deposit in the Jubilee Gas Field, Eastern Gulf of Mexico: Consequences for the Sealing Capacity of MTDs -- 4. Seismic geomorphology of the Israel Slump Complex in the central Levant Basin (SE Mediterranean) -- 5. Multiple Megaslide Complexes and their Significance for the Miocene stratigraphic evolution of the offshore Amazon Basin -- 6. Kinematics of submarine slope failures in the deepwater Taranaki Basin, New Zealand -- Part II Failure dynamics from landslide geomorphology -- 7. Postglacial Mass Failures in the Inner Hardangerfjorden System, Western Norway -- 8. Onshore and offshore geomorphological features of the El Golfo debris avalanche (El Hierro, Canary Islands) -- 9. New insights on failure and post-failure dynamics of submarine landslides on the intra-slope Palmarola ridge (Central Tyrrhenian Sea) -- 10. Assessment of Canyon Wall Failure Process from Multibeam Bathymetry and Remotely Operated Vehicle (ROV) Observations, U.S. Atlantic Continental Margin -- 11. The Chuí Megaslide Complex: regional-scale submarine landslides on the Southern Brazilian Margin -- 12. Submarine landslides and incised canyons of the southeast Queensland continental margin -- 13. Novel method to map the morphology of submarine landslide headwall scarps using Remotely Operated Vehicles -- 14. Flow behaviour of a giant landslide and debris flow entering Agadir Canyon, NW Africa -- 15. Fine-Scale Morphology of Tubeworm Slump, Monterey Canyon -- 16. Submarine slide topography and the Distribution of Vulnerable Marine Ecosystems: A Case Study in the Ionian Sea (Eastern Mediterranean) -- Part III Geotechnical aspects of mass movement -- 17. Shear Strength of Siliciclastic Sediments from Passive and Active Margins (0-100 meters below seafloor): Insights into Seismic Strengthening -- 18. A small volume calibration chamber for cone penetration testing (CPT) on submarine soils -- 19. Underwater Mass Movements in Lake Mjøsa, Norway -- 20. In situ cyclic softening of marine silts by vibratory CPTU at Orkdalsfjord test site, mid Norway -- 21. First results of the geotechnical in situ investigation for soil characterisation along the upper slope off Vesterålen - Northern Norway -- 22. A novel micro-shear tester for failure analysis of fine and cohesive granular matter -- 23. Knickpoint migration induced by landslide: Evidence from laboratory to field observations in Wabush Lake -- 24. Multiple flow slide experiment in the Westerschelde Estuary, The Netherlands -- Part IV Multidisciplinary case studies -- 25. Submarine mass wasting on Hovgaard Ridge, Fram Strait, European Arctic -- 26. 3D seismic investigations of Pleistocene Mass Transport Deposits and Glacigenic Debris Flows on the North Sea Fan, NE Atlantic Margin -- 27. Do embedded volcaniclastic layers serve as potential glide planes? – An integrated analysis from the Gela Basin offshore southern Sicily -- 28. Sediment failure affecting muddy contourites on the continental slope offshore northern Norway – lessons learned and some outstanding issues -- 29. Mass Wasting History within Lake Ohrid Basin (Albania/Macedonia) over the last 600ka -- 30. Implications of Sediment Dynamics in Mass Transport along the Pianosa Ridge (Northern Tyrrhenian Sea) -- 31. Late-Holocene Mass Movements in High Arctic East Lake, Melville Island (Western Canadian Arctic Archipelago) -- 32. Pleistocene Mass Transport Complexes off Barbados accretionary prism (Lesser Antilles) -- 33. Exploring the Influence of Deepwater Currents as Potential Triggers for Slope Instability -- Part V Tectonics and mass movements -- 34. French alpine foreland Holocene paleoseismicity revealed by coeval mass wasting deposits in glacial lakes -- 35. Spatial and temporal relation of submarine landslides and faults along the Israeli continental slope, eastern Mediterranean -- 36. Earthquake induced landslides in Lake Éternité, Québec, Canada -- 37. Large Mass Transport Deposits in Kumano Basin, Nankai Trough, Japan -- 38. Insights into Effectiveness of Simplified Seismic Displacement Procedures to Evaluate Earthquake Behavior of a Deepwater Slope -- Part VI Fluid flow and gas hydrates -- 39. Deriving the Rate of Salt Rise at the Cape Fear Slide Using New Seismic Data -- 40. Submarine slope instabilities coincident with shallow gas hydrate systems: insights from New Zealand examples -- 41. Eel Canyon Slump Scar and Associated Fluid Venting -- 42. Shallow gas and the development of a weak layer in submarine spreading, Hikurangi margin (New Zealand) -- 43. Stability of fine-grained sediments subject to gas hydrate dissociation in the Arctic continental margin -- Part VII Mass transport deposits in modern and outcrop sedimentology -- 44. Soft-sediment deformation associated with mass transport deposits of the aAnsa basin (Spanish Pyrenees) -- 45. Synsedimentary tectonics and mass wasting along the Alpine margin in Liassic time -- 46. Meso-scale kinematic indicators in exhumed mass transport deposits: definitions and implications -- 47. Morphodynamics of supercritical turbidity currents in the channel-lobe transition zone -- 48. Tiny fossils, big impact: the role of foraminifera-enriched condensed section in arresting the movement of a large retrogressive submarine landslide in the Gulf of Mexico -- 49. Inclusion of substrate blocks within a mass transport deposit: A case study from Cerro Bola, Argentina -- Part VIII Numerical and statistical analysis -- 50. GIS catalogue of submarine landslides in the Spanish Continental Shelf: potential and difficulties for susceptibility assessment -- 51. Tempo and triggering of large submarine landslides – Statistical analysis for hazard assessment -- 52. Morphological controls on submarine slab failures -- 53. Incorporating Correlated Variables into GIS-Based Probabilistic Submarine Slope Stability Assessments -- 54. Quantifying the key role of slope material peak strength – using Discrete Element simulations -- 55. Correction Factors for 1-D Runout Analyses of Selected Submarine Slides -- Part IX Tsunami generation from slope failure -- 56. Volcanic generation of tsunamis: Two New Zealand palaeo-events -- 57. Tsunami-genesis due to retrogressive landslides on an inclined seabed -- 58. Geothermal System as the Cause of the 1979 Landslide Tsunami in Lembata Island, Indonesia -- 59. Towards a spatial probabilistic submarine landslide hazard model for submarine canyons -- 60. Coupled modelling of the failure and tsunami of a submarine debris avalanche offshore central New Zealand -- 61. Observations of coastal landslide-generated tsunami under an ice cover: the case of Lac-des-Seize-Îles, Québec, Canada -- Index.
    Type of Medium: Online Resource
    Pages: Online-Ressource (XIII, 621 p. 256 illus., 219 illus. in color, online resource)
    Edition: 1st ed. 2016
    ISBN: 9783319209791
    Series Statement: Advances in Natural and Technological Hazards Research 41
    RVK:
    Language: English
    Note: 1. Submarine Mass Movements and Their Consequences: Progress and ChallengesPart  I Submarine Mass Movement in Margin Construction and Economic Significance2. The Role of Submarine Landslides in the Law of the Sea -- 3. Fabric Development and Pore-Throat Reduction in a Mass-Transport Deposit in the Jubilee Gas Field, Eastern Gulf of Mexico: Consequences for the Sealing Capacity of MTDs -- 4. Seismic geomorphology of the Israel Slump Complex in the central Levant Basin (SE Mediterranean) -- 5. Multiple Megaslide Complexes and their Significance for the Miocene stratigraphic evolution of the offshore Amazon Basin -- 6. Kinematics of submarine slope failures in the deepwater Taranaki Basin, New Zealand -- Part II Failure dynamics from landslide geomorphology -- 7. Postglacial Mass Failures in the Inner Hardangerfjorden System, Western Norway -- 8. Onshore and offshore geomorphological features of the El Golfo debris avalanche (El Hierro, Canary Islands) -- 9. New insights on failure and post-failure dynamics of submarine landslides on the intra-slope Palmarola ridge (Central Tyrrhenian Sea) -- 10. Assessment of Canyon Wall Failure Process from Multibeam Bathymetry and Remotely Operated Vehicle (ROV) Observations, U.S. Atlantic Continental Margin -- 11. The Chuí Megaslide Complex: regional-scale submarine landslides on the Southern Brazilian Margin -- 12. Submarine landslides and incised canyons of the southeast Queensland continental margin -- 13. Novel method to map the morphology of submarine landslide headwall scarps using Remotely Operated Vehicles -- 14. Flow behaviour of a giant landslide and debris flow entering Agadir Canyon, NW Africa -- 15. Fine-Scale Morphology of Tubeworm Slump, Monterey Canyon -- 16. Submarine slide topography and the Distribution of Vulnerable Marine Ecosystems: A Case Study in the Ionian Sea (Eastern Mediterranean) -- Part III Geotechnical aspects of mass movement -- 17. Shear Strength of Siliciclastic Sediments from Passive and Active Margins (0-100 meters below seafloor): Insights into Seismic Strengthening -- 18. A small volume calibration chamber for cone penetration testing (CPT) on submarine soils -- 19. Underwater Mass Movements in Lake Mjøsa, Norway -- 20. In situ cyclic softening of marine silts by vibratory CPTU at Orkdalsfjord test site, mid Norway -- 21. First results of the geotechnical in situ investigation for soil characterisation along the upper slope off Vesterålen - Northern Norway -- 22. A novel micro-shear tester for failure analysis of fine and cohesive granular matter -- 23. Knickpoint migration induced by landslide: Evidence from laboratory to field observations in Wabush Lake -- 24. Multiple flow slide experiment in the Westerschelde Estuary, The Netherlands -- Part IV Multidisciplinary case studies -- 25. Submarine mass wasting on Hovgaard Ridge, Fram Strait, European Arctic -- 26. 3D seismic investigations of Pleistocene Mass Transport Deposits and Glacigenic Debris Flows on the North Sea Fan, NE Atlantic Margin -- 27. Do embedded volcaniclastic layers serve as potential glide planes? - An integrated analysis from the Gela Basin offshore southern Sicily -- 28. Sediment failure affecting muddy contourites on the continental slope offshore northern Norway - lessons learned and some outstanding issues -- 29. Mass Wasting History within Lake Ohrid Basin (Albania/Macedonia) over the last 600ka -- 30. Implications of Sediment Dynamics in Mass Transport along the Pianosa Ridge (Northern Tyrrhenian Sea) -- 31. Late-Holocene Mass Movements in High Arctic East Lake, Melville Island (Western Canadian Arctic Archipelago) -- 32. Pleistocene Mass Transport Complexes off Barbados accretionary prism (Lesser Antilles) -- 33. Exploring the Influence of Deepwater Currents as Potential Triggers for Slope Instability -- Part V Tectonics and mass movements -- 34. French alpine foreland Holocene paleoseismicity revealed by coeval mass wasting deposits in glacial lakes -- 35. Spatial and temporal relation of submarine landslides and faults along the Israeli continental slope, eastern Mediterranean -- 36. Earthquake induced landslides in Lake Éternité, Québec, Canada -- 37. Large Mass Transport Deposits in Kumano Basin, Nankai Trough, Japan -- 38. Insights into Effectiveness of Simplified Seismic Displacement Procedures to Evaluate Earthquake Behavior of a Deepwater Slope -- Part VI Fluid flow and gas hydrates -- 39. Deriving the Rate of Salt Rise at the Cape Fear Slide Using New Seismic Data -- 40. Submarine slope instabilities coincident with shallow gas hydrate systems: insights from New Zealand examples -- 41. Eel Canyon Slump Scar and Associated Fluid Venting -- 42. Shallow gas and the development of a weak layer in submarine spreading, Hikurangi margin (New Zealand) -- 43. Stability of fine-grained sediments subject to gas hydrate dissociation in the Arctic continental margin -- Part VII Mass transport deposits in modern and outcrop sedimentology -- 44. Soft-sediment deformation associated with mass transport deposits of the aAnsa basin (Spanish Pyrenees) -- 45. Synsedimentary tectonics and mass wasting along the Alpine margin in Liassic time -- 46. Meso-scale kinematic indicators in exhumed mass transport deposits: definitions and implications -- 47. Morphodynamics of supercritical turbidity currents in the channel-lobe transition zone -- 48. Tiny fossils, big impact: the role of foraminifera-enriched condensed section in arresting the movement of a large retrogressive submarine landslide in the Gulf of Mexico -- 49. Inclusion of substrate blocks within a mass transport deposit: A case study from Cerro Bola, Argentina -- Part VIII Numerical and statistical analysis -- 50. GIS catalogue of submarine landslides in the Spanish Continental Shelf: potential and difficulties for susceptibility assessment -- 51. Tempo and triggering of large submarine landslides - Statistical analysis for hazard assessment -- 52. Morphological controls on submarine slab failures -- 53. Incorporating Correlated Variables into GIS-Based Probabilistic Submarine Slope Stability Assessments -- 54. Quantifying the key role of slope material peak strength - using Discrete Element simulations -- 55. Correction Factors for 1-D Runout Analyses of Selected Submarine Slides -- Part IX Tsunami generation from slope failure -- 56. Volcanic generation of tsunamis: Two New Zealand palaeo-events -- 57. Tsunami-genesis due to retrogressive landslides on an inclined seabed -- 58. Geothermal System as the Cause of the 1979 Landslide Tsunami in Lembata Island, Indonesia -- 59. Towards a spatial probabilistic submarine landslide hazard model for submarine canyons -- 60. Coupled modelling of the failure and tsunami of a submarine debris avalanche offshore central New Zealand -- 61. Observations of coastal landslide-generated tsunami under an ice cover: the case of Lac-des-Seize-Îles, Québec, Canada -- Index.
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  • 3
    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
    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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  • 4
    Publication Date: 2021-02-08
    Description: A newly identified large-scale submarine landslide on the NW African margin (Agadir Slide) is investigated in terms of its morphology, internal architecture, timing, and emplacement processes using high-resolution multibeam bathymetry data, 2D seismic profiles, and gravity cores. The Agadir Slide is located south of the Agadir Canyon at a water depth ranging from 500 m to 3,500 m, showing an estimated affected area of approximately 5,500 km2. The analysis of the Agadir Slide's complex morphology reveals the presence of two headwall areas and two slide fairways (the Western and Central slide fairways). Volume calculations indicate that ∼340 km3 of sediment were accumulated downslope along the slide fairways (∼270 km3) and inside the Agadir Canyon (∼70 km3). Stratigraphic correlations based on five gravity cores indicate an emplacement age of 142±1 ka for the Agadir Slide. However, its emplacement dynamics suggest that the slide was developed in two distinct, successive stages. The presence of two weak layers (glide planes) is a major preconditioning factor for the occurrence of slope instability in the study area, and local seismicity related to fault activity and halokinesis likely triggered the Agadir Slide. Importantly, the Agadir Slide neither disintegrated into sediment blocks nor was transformed into turbidity currents. The emplacement timing of the Agadir Slide does not correlate with any turbidites cored downslope across the Moroccan Turbidite System.
    Type: Article , PeerReviewed
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  • 5
    Publication Date: 2021-05-10
    Description: Highlights • 3D seismic imaging of an entire landslide complex. • Shallow gas accumulation within and underneath Tuaheni Landslide Complex. • Imaging of a basal shear zone within a subaqueous landslide complex. Abstract The Hikurangi margin is an active continental margin east of New Zealand's North Island. It is well recognized as a seismically active zone and is known for the occurrence of free gas and gas hydrates within the shallow sediments. A variety of subaqueous landslides can be observed at the margin, including the Tuaheni Landslide Complex off Poverty Bay. This slide complex has been interpreted previously as a slowly creeping landform, as its morphology and internal deformation is comparable to terrestrial earthflows and rock glaciers. In 2014, we acquired a high-resolution 3D seismic volume covering major parts of the Tuaheni South landslide. The 3D data show a variety of fluid migration indicators, free gas accumulations and manifestations of the base of gas hydrate stability in the pre-slide sedimentary units and the lower unit of the landslide system. The data also show that the landslide system is composed of an upper and lower unit that are separated by an intra-debris negative-polarity reflection. Free gas accumulations directly beneath the landslide units suggest that the debris acts as a boundary for rising fluids and only few migration pathways to the intra-debris reflector are observed in the distal parts of the landslide. Deformation within the landslide's debris is focused in the upper landslide unit, and we interpret the intra-debris reflector as a basal shear zone or ‘glide plane’ upon which the debris has been remobilized. The origin of the intra-debris reflector is unclear, but we suggest it could be a relatively coarse-grained horizon that would be prone to fluid flow focusing and the development of excess fluid pressure. Our seismic study provides one of the most detailed examples of a subaqueous landslide system and reveals insights into the fluid flow system and potential basal shear zone development of the Tuaheni Landslide Complex.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 6
    Publication Date: 2019-09-23
    Description: Bottom currents and their margin-shaping character became a central aspect in the research field of sediment dynamics and paleoceanography during the last decades due to their potential to form large contourite depositional systems (CDS), consisting of both erosive and depositional features. A major CDS at the northern Argentine continental margin was studied off the Rio de la Plata River by means of seismo- and hydro-acoustic methods including conventional and high-resolution seismic, parametric echosounder and single and swath bathymetry. Additionally, hydrographic data were considered allowing jointly interpretation of morphosedimentary features and the oceanographic framework, which is dominated by the presence of the dynamic and highly variable Brazil-Malvinas Confluence. We focus on three regional contouritic terraces identified on the slope in the vicinity of the Mar del Plata Canyon. The shallowest one, the La Plata Terrace (similar to 500 m), is located at the Brazil Current/Antarctic Intermediate Water interface characterized by its deep and distinct thermocline. In similar to 1200 m water depth the Ewing Terrace correlates with the Antarctic Intermediate Water/Upper Circumpolar Deep Water interface. At the foot of the slope in similar to 3500 m the Necochea Terrace marks the transition between Lower Circumpolar Deep Water and Antarctic Bottom Water during glacial times. Based on these correlations, a comprehensive conceptual model is proposed, in which the onset and evolution of contourite terraces is controlled by short- and long-term variations of water mass interfaces. We suggest that the terrace genesis is strongly connected to the turbulent current pattern typical for water mass interfaces. Furthermore, the erosive processes necessary for terrace formation are probably enhanced due to internal waves, which are generated along strong density gradients typical for water mass interfaces. The terraces widen through time due to locally focused, partly helical currents along the steep landward slopes and more tabular conditions seaward along the terrace surface. Considering this scheme of contourite terrace development, lateral variations of the morphosedimentary features off northern Argentina can be used to derive the evolution of the Brazil-Malvinas Confluence on geological time scales. We propose that the Brazil-Malvinas Confluence in modern times is located close to its southernmost position in the Quaternary, while its center was shifted northward during cold periods
    Type: Article , PeerReviewed
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  • 7
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    Elsevier
    In:  Marine and Petroleum Geology, 48 . pp. 341-353.
    Publication Date: 2019-09-23
    Description: Analysis of multi-channel seismic reflection and chirp data from Lake Van (eastern Turkey) reveals various shallow gas indicators including seismic chimneys, enhanced reflections, bright spots, mud volcanoes, pockmarks, and acoustic blanking. The enhanced reflections, suggesting the presence of free gas, are most dominant and observed at more than 200 locations. They are characterized by very-high amplitude reflections and occur in both deep and shallow sedimentary sections. Some enhanced reflections are accompanied by very subtle seafloor expressions such as mounds, which may suggest active venting activity. Seismic chimneys or columnar zones of amplitude blanking have been observed in much of the surveyed area. Seismic chimneys in the study area cannot be associated with any known faults that would act as migration pathways for deep fluids. This suggests that the observed structures in Lake Van sediments allow the preferential emission of gases which might be for a large share of biogenic origin. The acoustic blanking, characterized by transparent or chaotic seismic facies, is seen in the eastern part of the lake. The lakeward edge of the acoustic blanking largely coincides with the 100 m water depth contour, indicating that (past) changes of the hydrostatic pressure may be responsible for the distribution of these anomalies. Mound-like features, interpreted as mud volcanoes, occur in a few locations. The presence of these features may suggest active gas emission. Very strong amplitude anomalies or bright spots with negative polarity, indicating gas-charged zones, are also seen in a number of locations. Pockmarks are observed only in the northeastern part of the study area. The scarce occurrence of pockmarks in the study area might be ascribed to a higher permeability of the lake sediments or to the absence of the substrate/reservoir providing the critical mass of gases necessary to produce such features. Turbidites, tephra layers, and deltaic deposits have the potential to provide ideal conditions to allow the sediments to act as a gas reservoir.
    Type: Article , PeerReviewed
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  • 8
    Publication Date: 2017-03-13
    Description: Highlights • We map out the 3D extent of gas hydrate stability beneath two methane seep sites. • Focused fluid flow has sustained large-scale gas hydrate instability. • The two seeps likely have the same deep fluid source, despite shallow differences. • Fault networks influenced the initiation of advective flow through the hydrate system. • Ongoing flow towards the seeps is likely sustained by networks of hydrofractures. Abstract Fluid flow through marine sediments drives a wide range of processes, from gas hydrate formation and dissociation, to seafloor methane seepage including the development of chemosynthetic ecosystems, and ocean acidification. Here, we present new seismic data that reveal the 3D nature of focused fluid flow beneath two mound structures on the seafloor offshore Costa Rica. These mounds have formed as a result of ongoing seepage of methane-rich fluids. We show the spatial impact of advective heat flow on gas hydrate stability due to the channelled ascent of warm fluids towards the seafloor. The base of gas hydrate stability (BGHS) imaged in the seismic data constrains peak heat flow values to View the MathML source∼60 mWm−2 and View the MathML source∼70 mWm−2 beneath two separate seep sites known as Mound 11 and Mound 12, respectively. The initiation of pronounced fluid flow towards these structures was likely controlled by fault networks that acted as efficient pathways for warm fluids ascending from depth. Through the gas hydrate stability zone, fluid flow has been focused through vertical conduits that we suggest developed as migrating fluids generated their own secondary permeability by fracturing strata as they forced their way upwards towards the seafloor. We show that Mound 11 and Mound 12 (about 1 km apart on the seafloor) are sustained by independent fluid flow systems through the hydrate system, and that fluid flow rates across the BGHS are probably similar beneath both mounds. 2D seismic data suggest that these two flow systems might merge at approximately 1 km depth, i.e. much deeper than the BGHS. This study provides a new level of detail and understanding of how channelled, anomalously-high fluid flow towards the seafloor influences gas hydrate stability. Thus, gas hydrate systems have good potential for quantifying the upward flow of subduction system fluids to seafloor seep sites, since the fluids have to interact with and leave their mark on the hydrate system before reaching the seafloor.
    Type: Article , PeerReviewed
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  • 9
    Publication Date: 2017-08-08
    Description: Large sedimentary deposits consisting of several major contourite drifts were studied by means of high-resolution multichannel seismic data at the middle slope along the Northern Argentina Continental Margin to determine their evolutionary stages as well as to identify and assess the possible impact of Northern Source Deep Water (NSDW) on the slope architecture. The imaged contouritic sediments allow decoding on the regional paleo-oceanographic setting of the last 32 Ma. Earliest contouritic sedimentation can be observed close to the Eocene/Oligocene boundary based on an aggradational stacking pattern with a complex and wavy seismic facies, pointing toward a hydrodynamically turbulent flow pattern. This facies is most likely related to the opening of the Drake Passage associated with global cooling and a strengthening of surface, intermediate and deep ocean currents in the Southern Ocean. During the Middle Miocene plastered drift sequences with an aggradational reflection pattern were deposited. Their depositional style indicates weak, non-turbulent current conditions, which are interpreted to be related to a vertical shift of water mass interfaces caused by the first formation of NSDW during the Mid-Miocene climatic optimum. On top, the formation of plastered drift sequences led to the modern extent of the Ewing Terrace, which was probably controlled by the continuous strengthening and thickening of NSDW until the final closure of the Central American Seaway (CAS). During the Pliocene and Quaternary, after the complete closure of the CAS and under the influence of the full force of the NSDW, mounded plastered drift sequences are built upon the Ewing Terrace generating the modern slope morphology. Therefore, we suggest that deep-water production in the northern hemisphere plays a significant role by controlling the shape of the continental slopes in the southwestern South Atlantic since the Middle Miocene. Highlights ► Slope of northern Argentine Continental margin is current controlled since 32 Ma. ► Variability of Northern Source Deep Water (NSDW) controls sedimentary processes. ► Sedimentary processes are susceptible to changes of the Brazil-Malvinas Confluence. ► Impact of NSDW on slope processes is underestimated in the southern hemisphere.
    Type: Article , PeerReviewed
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  • 10
    Publication Date: 2017-08-04
    Description: Newly acquired bathymetric and seismic reflection data have revealed mass-transport deposits (MTDs) on the northeastern Cretan margin in the active Hellenic subduction zone. These include a stack of two submarine landslides within the Malia Basin with a total volume of approximately 4.6 km(3) covering an area of about 135 km(2). These two MTDs have different geometry, internal deformations and transport structures. The older and stratigraphic lower MTD is interpreted as a debrite that fills a large part of the Malia Basin, while the second, younger MTD, with an age of at least 12.6 cal. ka B.P., indicate a thick, lens-shaped, partially translational landslide. This MTD comprises multiple slide masses with internal structure varying from highly deformed to nearly undeformed. The reconstructed source area of the older MTD is located in the westernmost Malia Basin. The source area of the younger MTD is identified in multiple headwalls at the slope-basin-transition in 450 m water depth. Numerous faults with an orientation almost parallel to the southwest-northeast-trending basin axis occur along the northern and southern boundaries of the Malia Basin and have caused a partial steepening of the slope-basin-transition. The possible triggers for slope failure and mass-wasting include (i) seismicity and (ii) movement of the uplifting island of Crete from neotectonics of the Hellenic subduction zone, and (iii) slip of clay-mineral-rich or ash-bearing layers during fluid involvement. (c) 2009 Elsevier B.V. All rights reserved.
    Type: Article , PeerReviewed
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