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  • 1
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    Sidescan Sonar (2017)
    Springer
    In:  In: Submarine Geomorphology. , ed. by Micallef, A., Krastel, S. and Savini, A. Springer, Cham, pp. 13-24. ISBN 978-3-319-57851-4
    Details
    Publication Date: 2017-12-13
    Description: Sidescan sonar allows obtaining an acoustic image of the seafloor at high resolution, wide swath and relatively low cost. For that purpose the backscattered signal of an acoustic pulse sent out sideways from an instrument carrier is registered. At low incident angles small-scale relief is well imaged and the length of shadows allows calculation of the height of seafloor features but sidescan sonar is particularly useful in mapping compositional differences of the seafloor. Sidescan sonar images are, however, mostly uncalibrated and need some form of ground-truthing for meaningful geological interpretation. Interferometric sidescan sonar systems now also provide bathymetric information together with backscatter strength.
    Type: Book chapter , NonPeerReviewed
    Format: text
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  • 2
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    Mud volcanoes and gas hydrates in the Black Sea: new data from Dvurechenskii and Odessa mud volcanoes (2003)
    Springer
    In:  Geo-Marine Letters, 23 (3-4). pp. 239-249.
    Details
    Publication Date: 2017-05-22
    Type: Article , PeerReviewed
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  • 3
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    Fluid venting and seepage at accretionary ridges: the Four Way Closure Ridge offshore SW Taiwan (2016)
    Springer
    In:  Geo-Marine Letters, 36 (3). pp. 165-174.
    Details
    Publication Date: 2019-02-01
    Description: Within the accretionary prism offshore SW Taiwan, widespread gas hydrate accumulations are postulated to occur based on the presence of a bottom simulating reflection. Methane seepage, however, is also widespread at accretionary ridges offshore SW Taiwan and may indicate a significant loss of methane bypassing the gas hydrate system. Four Way Closure Ridge, located in 1,500 m water depth, is an anticlinal ridge that would constitute an ideal trap for methane and consequently represents a site with good potential for gas hydrate accumulations. The analysis of high-resolution bathymetry, deep-towed sidescan sonar imagery, high-resolution seismic profiling and towed video observations of the seafloor shows that Four Way Closure Ridge is and has been a site of intensive methane seepage. Continuous seepage is mainly evidenced by large accumulations of authigenic carbonate precipitates, which appear to be controlled by the creation of fluid pathways through faulting. Consequently, Four Way Closure Ridge is not a closed system in terms of fluid migration and seepage. A conceptual model of the evolution of gas hydrates and seepage at accretionary ridges suggests that seepage is common and may be a standard feature during the geological development of ridges in accretionary prisms. The observation of seafloor seepage alone is therefore not a reliable indicator of exploitable gas hydrate accumulations at depth.
    Type: Article , PeerReviewed
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  • 4
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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
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  • 5
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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
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  • 6
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    Glacimarine Drainage Systems in Deep-sea: The NAMOC System of the Labrador Sea and its Sibling (1997)
    Springer
    Details
    Publication Date: 2022-05-30
    Description: The continental Pleistocene Laurentide Ice Sheet (LIS) had far-reaching marine influence in shaping the ocean-floor adjacent to ice margin. The basinwide submarine-canyon and deep-sea channel system of the Northwest Atlantic Mid-Ocean Channel (NAMOC) of the Labrador Sea is the submarine continuation of the drainge system of the LIS on land, forming an interconnected land/sea drainage system 6,000 km long, one of the word’s longest drainage systems of Pleistocene age. The submarine portion forms a dual system, consisting of the mud-dominated NAMOC with its tributaries and a submarine sandy braid-plain.
    Type: Book chapter , NonPeerReviewed
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  • 7
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    Discovery of numerous pingos and comet-shaped depressions offshore southwestern Taiwan (2020)
    Springer
    Details
    Publication Date: 2023-02-08
    Description: High-resolution bathymetry collected with an autonomous underwater vehicle (AUV) along the flanks of three ridges of the accretionary prism offshore southwestern (SW) Taiwan revealed more than 650 elongated depressions in water depths ranging from 1155 to 1420 m. The depressions are between 12 and 129 m long, 5 to 70 m wide, and up 9 m deep at their center and shallowing downslope to about 1-m depth. Due to their shape in downslope cross section, they are termed comet-shaped depressions (CSD). The CSD occur in patches of more than 100 with densities of 53 to 98 CSD/km2. In addition, seven topographic mounds were mapped and interpreted as pingos, which remotely operate vehicle (ROV) observations and sampling show to be covered with authigenic carbonate. These features overlie areas where multichannel seismic reflection (MCS) profiles show bottom simulating reflectors (BSR) and dipping strata extending from below the BSR to near the seafloor. We consider comet-shaped depression, a new type of pockmark, forms on a sloping seafloor where fluids expulsion occurred. We also suggest that the two types of distinctive geomorphic features are attributed to fluid venting which occurs at different rates, with the mounds developing slowly over time, but the CSD forming in discrete events perhaps associated with large earthquakes.
    Type: Article , PeerReviewed
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  • 8
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    Seismic and geoacoustic evidence for subsurface fluid flow and seepage offshore Akçakoca, Southwestern Black Sea, Turkey (2022)
    Springer
    Details
    Publication Date: 2024-02-07
    Description: Widespread indications of free and hydrate gas accumulations and mud volcanoes were imaged using multichannel seismic reflection, chirp sub-bottom profiler, multibeam bathymetry, and deep-towed side-scan sonar data collected along the Southwestern Black Sea margin, offshore Akçakoca. These indications are typically associated with sedimentary ridges along the continental slope and rise, particularly with the “Ereğli Plateau” (850–1350 m water depth), where 20 mud volcanoes were found. Two types of bottom-simulating reflections (BSR) were identified, both mimicking the seafloor relief: Type-1 crosscuts the sedimentary reflections with amplitudes similar to the surrounding strata, while Type-2 shows higher amplitudes that terminate against the base of the gas hydrate stability zone. These types were observed over large portions of the continental rise, indicating the base of gas hydrate accumulations. Analyses of the BSR depth indicate that thermogenic gas is possibly present in the gas hydrates. A fault-driven hypothetical model was then developed to describe the formation of gas hydrate and mud volcanoes and the effect of submarine fluid flow in the area. According to this model, Type-1 BSRs form through biogenic gas accumulations. The presence of fault regions with Type-2 BSRs suggests active fluid transfer between permeable and impermeable units, where the fault surfaces act as possible conduits for thermogenic gases produced in the deeper sediments and transported into the shallower subsurface where then thermogenic biogenic gases coexist.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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