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  • 1
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    The Character and Formation of Elongated Depressions on the Upper Bulgarian Slope (2018)
    Springer
    In:  Journal of Ocean University of China, 17 (3). pp. 555-562.
    Details
    Publication Date: 2021-02-08
    Description: Seafloor elongated depressions are indicators of gas seepage or slope instability. Here we report a sequence of slope-parallel elongated depressions that link to headwalls of sediment slides on upper slope. The depressions of about 250 m in width and several kilometers in length are areas of focused gas discharge indicated by bubble-release into the water column and methane enriched pore waters. Sparker seismic profiles running perpendicular and parallel to the coast, show gas migration pathways and trapped gas underneath these depressions with bright spots and seismic blanking. The data indicate that upward gas migration is the initial reason for fracturing sedimentary layers. In the top sediment where two young stages of landslides can be detected, the slope-parallel sediment weakening lengthens and deepens the surficial fractures, creating the elongated depressions in the seafloor supported by sediment erosion due to slope-parallel water currents.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    DOI: 10.1007/s11802-018-3460-7
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Sidescan backscatter variations of cold seeps on the Hikurangi Margin (New Zealand): indications for different stages in seep development (2014)
    Springer
    In:  Geo-Marine Letters, 34 (2/3). pp. 169-184.
    Details
    Publication Date: 2017-05-19
    Description: Cold seeps on the Hikurangi Margin off New Zealand exhibit various seabed morphologies producing different intensity patterns in backscatter images. Acoustic backscatter characteristics of 25 investigated seep sites do not show a continuous range of patterns between two end members, but fall into four distinct types characterised by variations in backscatter intensity, distribution and inferred structural heights. The types reflect different carbonate morphologies including up to 20 m high structures (type 1), low-relief crusts (type 2), scattered blocks (type 3) and carbonate free sites (type 4). Each seep corresponds to a single type; ntermediates were not observed. Although the observed morphologies and backscatter patterns may have been caused by variations in sediment burial of seep carbonates or differential exhumation by erosion, they probably epresent varying onsets of authigenic carbonate precipitation. Precipitation of carbonate is episodic, which is likely the result of internal forcing. Blocking and subsequent reorganisation of the seep plumbing system lead to abandonment of old seeps and formation of new sites.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00367-014-0361-7
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Gas migration through Opouawe Bank at the Hikurangi margin offshore New Zealand (2016)
    Springer
    In:  Geo-Marine Letters, 36 (3). pp. 187-196.
    Details
    Publication Date: 2019-09-23
    Description: This study presents 2D seismic reflection data, seismic velocity analysis, as well as geochemical and isotopic porewater compositions from Opouawe Bank on New Zealand’s Hikurangi subduction margin, providing evidence for essentially pure methane gas seepage. The combination of geochemical information and seismic reflection images is an effective way to investigate the nature of gas migration beneath the seafloor, and to distinguish between water advection and gas ascent. The maximum source depth of the methane that migrates to the seep sites on Opouawe Bank is 1,500–2,100 m below seafloor, generated by low-temperature degradation of organic matter via microbial CO2 reduction. Seismic velocity analysis enabled identifying a zone of gas accumulation underneath the base of gas hydrate stability (BGHS) below the bank. Besides structurally controlled gas migration along conduits, gas migration also takes place along dipping strata across the BGHS. Gas migration on Opouawe Bank is influenced by anticlinal focusing and by several focusing levels within the gas hydrate stability zone.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    DOI: 10.1007/s00367-016-0441-y
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Ocean bottom seismics (2011)
    Springer
    In:  In: Encyclopedia of Solid Earth Geophysics, Vol. 1-2. , ed. by Gupta, H. K. Encyclopedia of Earth Sciences Series . Springer, Heidelberg, Germany, pp. 901-918. 1. ed. ISBN 978-90-481-8701-0
    Details
    Publication Date: 2020-08-03
    Type: Book chapter , NonPeerReviewed
    Format: text
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    OceanRep: Book chapter
  • 5
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    The BGR Slide off Costa Rica: preconditioning factors, trigger and slide dynamics (2012)
    Springer
    In:  In: Submarine Mass Movements and Their Consequences. Advances in Natural and Technological Hazards Research, 31 . Springer, Dordrecht, pp. 289-298. ISBN 978-94-007-2161-6
    Details
    Publication Date: 2019-09-23
    Type: Book chapter , NonPeerReviewed
    DOI: 10.1007/978-94-007-2162-3_26
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    OceanRep: Book chapter
  • 6
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    Sidescan sonar imagery of widespread fossil and active cold seeps along the central Chilean continental margin (2012)
    Springer
    In:  Geo-Marine Letters, 32 . pp. 489-499.
    Details
    Publication Date: 2019-09-23
    Description: The central Chilean subduction zone between 35°S and 37°S was investigated in order to identify, document and possibly understand fluid flow and fluid venting within the forearc region. Several areas were mapped using multibeam bathymetry and backscatter, high-resolution sidescan sonar, chirp subbottom profiling and reflection seismic data. On a subsequent cruise ground-truthing observations were made using a video sled. In general, this dataset shows surprisingly little evidence of fluid venting along the mid-slope region, in contrast to other subduction zones such as Central America and New Zealand. There were abundant indications of active and predominantly fossil fluid venting along the upper slope between 36.5°S and 36.8°S at the seaward margin of an intraslope basin. Here, backscatter anomalies suggest widespread authigenic carbonate deposits, likely the result of methane-rich fluid expulsion. There is unpublished evidence that these fluids are of biogenic origin and generated within the slope sediments, similar to other accretionary margins but in contrast to the erosional margin off Central America, where fluids have geochemical signals indicating an origin from the subducting plate.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00367-012-0283-1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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