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  • 1
    Online Resource
    Online Resource
    The Håkon Mosby mud volcano : 330 000 years of focused fluid flow activity at the SW Barents Sea slope (2009)
    Associated volumes
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    In: Marine geology, Amsterdam [u.a.] : Elsevier Science, 1964, 262(2009), Seite 105-115, 1872-6151
    In: volume:262
    In: year:2009
    In: pages:105-115
    Description / Table of Contents: Studying the morphology and subsurface geometry of mud volcanoes provides insights into their activity. This paper describes the internal structure of the Håkon Mosby mud volcano (HMMV) in the southwestern Barents Sea and presents a conceptual model of its evolution. The lack of a mud edifice and the profuse gas flares suggest that in the recent past the mud volcano evolution was predominantly controlled by venting of gas-rich fluids and free gas. However, the analysis of high-resolution single-channel seismic (SCS) data reveals for the first time the existence of a pseudo-mud chamber at the top of the 3 km deep central conduit. It was once created at the seabed and is now a buried expression that acts as mud chamber. The pseudo-mud chamber is situated approximately 300 m below the seafloor, directly above the 330 ka Bear Island Slide (BIS) scar reflection and below glacigenic debris flow deposits that constitute the sediment on top. The sediment profiler data indicates a younger mud deposit above the debris flows, which points to a reactivation of the mud volcano. The reactivation was most likely triggered by the contrast in density between the gas-rich mud chamber and the high-density debris flow deposits. Three stages, i.e. initiation, sealing and reactivation, and a second active period define the evolution of this young mud volcano. Both, the morphology and size of the conduit as well as in-situ temperature gradients point towards a focused and rapid fluid flow.
    Type of Medium: Online Resource
    Pages: graph. Darst
    ISSN: 1872-6151
    DOI: 10.1016/j.margeo.2009.03.022
    Language: English
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  • 2
    Online Resource
    Online Resource
    The thermal structure of the Dvurechenskii mud volcano and its implications for gas hydrate stability and eruption dynamics (2009)
    Associated volumes
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    In: Marine and petroleum geology, Amsterdam [u.a.] : Elsevier Science, 1984, 26(2009), 9, Seite 1812-1823, 0264-8172
    In: volume:26
    In: year:2009
    In: number:9
    In: pages:1812-1823
    Description / Table of Contents: The sediment temperature distribution at mud volcanoes provides insights into their activity and into the occurrence of gas hydrates. If ambient pressure and temperature conditions are close to the limits of the gas hydrate stability field, the sediment temperature distribution not only limits the occurrence of gas hydrates, but is itself influenced by heat production and consumption related to the formation and dissociation of gas hydrates. Located in the Sorokin Trough in the northern Black Sea, the Dvurechenskii mud volcano (DMV) was in the focus of detailed investigations during the M72/2 and M73/3a cruises of the German R/V Meteor and the ROV Quest 4000 m in February and March 2007. A large number of in-situ sediment temperature measurements were conducted from the ROV and with a sensor-equipped gravity corer. Gas hydrates were sampled in pressurized cores using a dynamic autoclave piston corer (DAPC). The thermal structure of the DMV suggests a regime of fluid flow at rates decreasing from the summit towards the edges of the mud volcano, accompanied by intermittent mud expulsion at the summit. Modeled gas hydrate dissociation temperatures reveal that the gas hydrates at the DMV are very close to the stability limits. Changes in heat flow due to variable seepage rates probably do not result in changes in sediment temperature but are compensated by gas hydrate dissociation and formation.
    Type of Medium: Online Resource
    Pages: graph. Darst
    ISSN: 0264-8172
    DOI: 10.1016/j.marpetgeo.2009.01.021
    Language: English
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  • 3
    Online Resource
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    In-situ sediment temperature measurements and geochemical porewater data suggest highly dynamic fluid flow at Isis mud volcano, eastern Mediterranean Sea (2009)
    Associated volumes
    Details Availability
    In: Marine geology, Amsterdam [u.a.] : Elsevier Science, 1964, 261(2009), 1/4, Seite 128-137, 1872-6151
    In: volume:261
    In: year:2009
    In: number:1/4
    In: pages:128-137
    Description / Table of Contents: Isis mud volcano is located on the upper slope of the Nile deep-sea fan and has been described as the surface expression of a deep-seated gas chimney [Loncke, L., Gaullier, V., Mascle, J., Vendeville, B., 2002. Shallow structure of the Nile deep-sea fan: interactions between structural heritage and salt tectonics; consequences on sedimentary dispersal. In: CIESM (Ed.), Turbidite systems and deep-sea fans of the Mediterranean and the Black seas. CIESM Workshop Series. vol. 17. Monaco]. Detailed geothermal and geochemical investigations of Isis MV have been carried out during the NAUTINIL (2003) and MIMES (2004) cruises within the framework of the Euro-margins/Mediflux project. Sediment temperatures of more than 40°C at 10 m below the seafloor at the center of the mud volcano indicate an exceptionally high level of activity. Rapidly decreasing temperature gradients away from the center support the hypothesis of a dominantly axisymmetric functioning of Isis MV. The microbathymetry along dive tracks of the submersible Nautile reveals the presence of terraces and shows that the temperature gradients at shallow sediment depth follow the morphology. At the center, porewater profiles are characterized by a rapid decrease of chlorinity within the uppermost meter of the sediments, whereas the chlorinity of cores taken at short distances away is equal to bottom water values. Applying simple analytical models to the data provides evidence of recent mud volcano activity but no straightforward explanation of the observed anomalies, which points to a transient regime of variable fluid flow, possibly accompanied by episodic mud eruptions. Numerical modeling suggests that rapid cooling of the sediment column and downward progression of the sharp decrease in porewater chlorinity observed between the two cruises is related to episodic infiltration of bottom seawater into the mud.
    Type of Medium: Online Resource
    Pages: graph. Darst
    ISSN: 1872-6151
    DOI: 10.1016/j.margeo.2008.09.003
    Language: English
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  • 4
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    Geological controls on the gas hydrate system of Formosa Ridge, South China Sea (2014)
    IEEE
    In:  In: OCEANS 2014 - TAIPEI. IEEE, Taipei, pp. 1-4. ISBN 978-1-4799-3645-8
    Details
    Publication Date: 2017-05-29
    Description: Formosa Ridge is one of many topographic ridges created by canyon incision into the eastern South China Sea margin. The northwestern termination of the ridge is caused by beheading of the ridge due to a westward shift of the canyon that originally formed to the eastern flank of Formosa Ridge. Below Formosa Ridge a bottom simulating reflector (BSR) exists. Its depth below sea floor coincides with the theoretical base of the gas hydrate stability zone and the reflection has reverse polarity suggesting that it is caused by free gas below gas hydrate accumulations. The BSR is ubiquitous but shows significant variations in depth below sea floor ranging from 150 ms TWT (or approximately 180 m) underneath the incised canyon in the north to up to 500 ms (or approximately 460 m) underneath the crest of Formosa Ridge. Predominantly this depth variation is the result of topography on subsurface temperature, but comparison with the average BSR depth underneath the surrounding canyons suggests that recent canyon incision in the north has perturbed the thermal state of the sediments. Formosa Ridge consists of a northern half that is dominated by refilled older canyons and a southern half that consists mainly of contourite deposits. However, judging by the reflection seismic data this difference in origin seems to have little effect on the distribution of gas hydrate.
    Type: Book chapter , NonPeerReviewed
    Format: text
    DOI: 10.1109/OCEANS-TAIPEI.2014.6964481
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  • 5
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    Tectonic Controls on Gas Hydrate Distribution off SW Taiwan (2019)
    Wiley | AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Solid Earth, 124 (2). pp. 1164-1184.
    Details
    Publication Date: 2022-01-31
    Description: The northern part of the South China Sea is characterized by widespread occurrence of bottom simulating reflectors (BSR) indicating the presence of marine gas hydrate. Because the area covers both a tectonically inactive passive margin and the termination of a subduction zone, the influence of tectonism on the dynamics of gas hydrate systems can be studied in this region. Geophysical data show that there are multiple thrust faults on the active margin while much fewer and smaller faults exist in the passive margin. This tectonic difference matches with a difference in the geophysical characteristics of the gas hydrate systems. High hydrate saturation derived from ocean bottom seismometer data and controlled source electromagnetic data and conspicuous high‐amplitude reflections in P‐Cable 3D seismic data above the BSR are found in the anticlinal ridges of the active margin. In contrast all geophysical evidence for the passive margin points to normal to low hydrate saturations. Geochemical analyses of gas samples collected at seep sites on the active margin show methane with heavy δ13C isotope composition, while gas collected at the passive margin shows light carbon isotope composition. Thus, we interpret the passive margin as a typical gas hydrate province fuelled by biogenic production of methane and the active margin gas hydrate system as a system that is fuelled not only by biogenic gas production but also by additional advection of thermogenic methane from the subduction system.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1029/2018JB016213
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  • 6
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    Biogeochemical consequences of nonvertical methane transport in sediment offshore northwestern Svalbard (2020)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2023-02-08
    Description: A site at the gas hydrate stability limit was investigated offshore northwestern Svalbard to study methane transport in sediment. The site was characterized by chemosynthetic communities (sulfur bacteria mats, tubeworms) and gas venting. Sediments were sampled with in‐situ porewater collectors and by gravity coring followed by analyses of porewater constituents, sediment and carbonate geochemistry, and microbial activity, taxonomy, and lipid biomarkers. Sulfide and alkalinity concentrations showed concentration maxima in near‐surface sediments at the bacterial mat and deeper maxima at the gas vent site. Sediments at the periphery of the chemosynthetic field were characterized by two sulfate‐methane transition zones (SMTZ) at ~204 and 45 cm depth, where activity maxima of microbial anaerobic oxidation of methane (AOM) with sulfate were found. Amplicon sequencing and lipid biomarker indicate that AOM at the SMTZs was mediated by ANME‐1 archaea. A 1D numerical transport reaction model suggests that the deeper SMTZ‐1 formed on centennial scale by vertical advection of methane, while the shallower SMTZ‐2 could only be reproduced by non‐vertical methane injections starting on decadal scale. Model results were supported by age distribution of authigenic carbonates, showing youngest carbonates within SMTZ‐2. We propose that non‐vertical methane injection was induced by increasing blockage of vertical transport or formation of sediment fractures. Our study further suggests that the methanotrophic response to the non‐vertical methane injection was commensurate with new methane supply. This finding provides new information about for the response time and efficiency of the benthic methane filter in environments with fluctuating methane transport.
    Type: Article , PeerReviewed
    Format: text
    Format: video
    Format: text
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  • 7
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    Deep-biosphere methane production stimulated by geofluids in the Nankai accretionary complex (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2018-06-14
    Description: Microbial life inhabiting subseafloor sediments plays an important role in Earth’s carbon cycle. However, the impact of geodynamic processes on the distributions and carbon-cycling activities of subseafloor life remains poorly constrained. We explore a submarine mud volcano of the Nankai accretionary complex by drilling down to 200 m below the summit. Stable isotopic compositions of water and carbon compounds, including clumped methane isotopologues, suggest that ~90% of methane is microbially produced at 16° to 30°C and 300 to 900 m below seafloor, corresponding to the basin bottom, where fluids in the accretionary prism are supplied via megasplay faults. Radiotracer experiments showed that relatively small microbial populations in deep mud volcano sediments (10 2 to 10 3 cells cm –3 ) include highly active hydrogenotrophic methanogens and acetogens. Our findings indicate that subduction-associated fluid migration has stimulated microbial activity in the mud reservoir and that mud volcanoes may contribute more substantially to the methane budget than previously estimated.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
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    Near-surface heating of young rift sediment causes mass production and discharge of reactive dissolved organic matter (2017)
    Nature
    In:  EPIC3Scientific Reports, Nature, 7(44864)
    Details
    Publication Date: 2017-04-03
    Description: Ocean margin sediments have been considered as important sources of dissolved organic carbon (DOC) to the deep ocean, yet the contribution from advective settings has just started to be acknowledged. Here we present evidence showing that near-surface heating of sediment in the Guaymas Basin, a young extensional depression, causes mass production and discharge of reactive dissolved organic matter (DOM). In the sediment heated up to ~100 °C, we found unexpectedly low DOC concentrations in the pore waters, reflecting the combined effect of thermal desorption and advective fluid flow. Heating experiments suggested DOC production to be a rapid, abiotic process with the DOC concentration increasing exponentially with temperature. The high proportions of total hydrolyzable amino acids and presence of chemical species affiliated with activated hydrocarbons, carbohydrates and peptides indicate high reactivity of the DOM. Model simulation suggests that at the local scale, near-surface heating of sediment creates short and massive DOC discharge events that elevate the bottom-water DOC concentration. Because of the heterogeneous distribution of high heat flow areas, the expulsion of reactive DOM is spotty at any given time. We conclude that hydrothermal heating of young rift sediments alter deep-ocean budgets of bioavailable DOM, creating organic-rich habitats for benthic life.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
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    Rhizon in situ sampler (RISS) for pore water sampling from aquatic sediments. (2005)
    In:  EPIC3In-situ Methods and Investigations in Environmental Science, 230th Meeting of the American Chemical Society, Division of Geochemistry, 28 Aug. - 1 Sept., Washington, DC, USA.
    Details
    Publication Date: 2019-07-17
    Description: Rhizon soil moisture samplers were successfully used for multi-level pore water sampling from in-situ sediments and sediment cores. By this method, high resolution pore water profiles may be sampled with minimum disturbance of both, the sediment structure and possible flow fields. To investigate biogeochemical cycles, especially at the sediment/water interface, we present a newly developed Rhizon In Situ Sampler (RISS) as a non-destructive tool for in-situ pore water sampling. Field experiments, tracer studies and numerical modeling were combined to assess the suitability of Rhizons for pore water sampling. A combination of a benthic chamber with the RISS allows studies of benthic fluxes and pore water profiles at the exact same location with negligible effect on the incubated sediment/water interface. This allows improved modeling of transport and reaction processes. Long term deployments of the RISS and repetitive pore water sampling will support future studies of the seasonal variation of benthic processes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 10
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    New Rhizon in situ sampler for pore water studies in aquatic sediments: For example nutrient input from submarine groundwater discharge in costal areas. (2005)
    In:  EPIC3EGU General Assembly, 25-29 Apr., Vienna, Austria.
    Details
    Publication Date: 2019-07-17
    Description: To investigate coastal biogeochemical cycles, especially at the sediment/water interface,improved sampling methods are necessary. For this purpose, we developed apore water in situ sampler with miniature sampling devices, so called Rhizons. Rhizonsoil moisture samplers have been used as sampling devices in unsaturated soilsfor the last ten years. In aquatic science they have been rarely used to extract porewater from sediments. This study presents a new developed Rhizon In Situ Sampler(RISS) as a non-destructive and inexpensive tool for in situ pore water sampling. Fieldexperiments, tracer studies and numerical modeling were combined to assess the suitabilityof Rhizons for pore water sampling. Our investigations show that the RISS isa very suitable alternative to classical methods for in situ sampling. Combined withan in situ benthic chamber system the RISS allows studies of benthic fluxes and porewater profiles at the same location with negligible effect on the incubated sedimentwater interface. This allows improved calculation and modeling of transport and reactionprocesses. Results of nutrient and freshwater input into surface water derivedby in situ sampling of tidal flat sediments of the Wadden Sea (Sahlenburg/Cuxhaven,Germany) are presented. Long term deployments of the RISS and repetitive pore watersampling at the same location might support future studies of seasonal variation ofbenthic processes in sediments of the coastal zone and open ocean.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Format: application/pdf
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