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  • 1
    Keywords: Dissertation ; Hochschulschrift
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource ( 165Seiten = 23MB) , Ill., graph. Darst., Kt
    Language: English , German
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  • 2
    Keywords: Dissertation ; Report ; Forschungsbericht ; Hochschulschrift
    Type of Medium: Book
    Pages: 159 S , graph. Darst., Kt
    Series Statement: GEOMAR-Report 47
    Language: English , German
    Note: Zugl.: Kiel, Univ., Diss., 1995
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  • 3
    Keywords: Dissertation ; Hochschulschrift
    Type of Medium: Book
    Pages: 159 S , Ill., graph. Darst., Kt
    Language: English , German
    Note: Kiel, Univ., Diss. : 1995
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  • 4
    In: Marine geology, Amsterdam [u.a.] : Elsevier Science, 1964, (2009), 1872-6151
    In: year:2009
    In: extent:10
    Description / Table of Contents: Porangahau Ridge, located offshore the Wairarapa on the Hikurangi Margin, is an active ocean-continent collision region in northeastern New Zealand coastal waters. Bottom simulating reflections (BSRs) in seismic data indicate the potential for significant gas hydrate deposits across this part of the margin. Beneath Porangahau Ridge a prominent high-amplitude reflection band has been observed to extend from a deep BSR towards the seafloor. Review of the seismic data suggest that this high-amplitude band is caused by local shoaling of the base of gas hydrate stability due to advective heat flow and it may constitute the location of elevated gas hydrate concentrations. During R/V Tangaroa cruise TAN0607 in 2006 heat flow probing for measurements of vertical fluid migration, sediment coring for methane concentrations, and additional seismic profiles were obtained across the ridge. In a subsequent 2007 expedition, on R/V Sonne cruise SO191, a controlled source electromagnetic (CSEM) experiment was conducted along the same seismic, geochemical, and heat flow transect to reveal the electrical resistivity distribution. CSEM data highlight a remarkable coincidence of anomalously high resistivity along the western, landward flank of the ridge which point to locally higher gas hydrate concentration above the high amplitude reflection band. Measured sediment temperature profiles, also along the western flank, consistently show non-linear and concave geothermal gradients typical of advective heat flow. Geochemical data reveal elevated methane concentrations in surface sediments concomitant with a rapid decline in sulfate concentrations indicating elevated methane flux and oxidation of methane in conjunction with sulfate reduction at the landward ridge base. Together, these data sets suggest that the western rim of Porangahau Ridge is a tectonically driven zone of rising fluids that transport methane and cause an upward inflection of the base of gas hydrate stability and the formation of locally enriched gas hydrate above the reflective zone.
    Type of Medium: Online Resource
    Pages: 10 , graph. Darst
    ISSN: 1872-6151
    Language: English
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 420 (2002), S. 622-623 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Gas hydrates are an ice-like form of water that has cavities containing gas — usually methane. They exist in vast quantities beneath the ocean floor in certain areas, especially continental margins, where the methane is generated mostly from the bacterial breakdown of organic matter, and they ...
    Type of Medium: Electronic Resource
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  • 6
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    PANGAEA
    In:  Supplement to: Pecher, Ingo A; Villinger, Heinrich; Kaul, Norbert; Crutchley, Gareth J; Mountjoy, Joshu J; Huhn, Katrin; Kukowski, Nina; Henrys, Stuart A; Rose, Paula S; Coffin, R B (2017): A Fluid Pulse on the Hikurangi Subduction Margin: Evidence From a Heat Flux Transect Across the Upper Limit of Gas Hydrate Stability. Geophysical Research Letters, 44(24), 12,385-12,395, https://doi.org/10.1002/2017GL076368
    Publication Date: 2023-11-18
    Description: A transect of seafloor heat probe measurements on the Hikurangi Margin shows a significant increase of thermal gradients upslope of the pinchout of the base of gas hydrate stability. We attribute these anomalously high thermal gradients to a fluid pulse leading to advective heat flow while endothermic cooling from gas hydrate dissociation may arrest temperature gradients in the hydrate stability field. Double-bottom simulating reflections in the study area are likely to be caused by uplift based on gas hydrate phase boundary considerations. Previous studies predict a seamount on the subducting Pacific Plate to cause significant overpressure beneath our study area, which may be the source of the fluid pulse. We suggest this seamount may also cause the inferred uplift. Transient expulsion of warm fluids may lead to gas hydrate dissociation with potential implications for seafloor stability.
    Type: Dataset
    Format: application/zip, 15 datasets
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  • 7
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    PANGAEA
    In:  Supplement to: Shao, Jun; Stott, Lowell D; Gray, William Robert; Greenop, Rosanna; Pecher, Ingo A; Neil, Helen L; Coffin, R B; Davy, Bryan; Rae, James W B (2019): Atmosphere‐Ocean CO₂ Exchange Across the Last Deglaciation From the Boron Isotope Proxy. Paleoceanography and Paleoclimatology, 34(10), 1650-1670, https://doi.org/10.1029/2018PA003498
    Publication Date: 2023-11-18
    Description: 2 new deglacial planktic boron isotope records from the Southwest Pacific. pH/pCO2 calculated from 12 boron isotope records from the global ocean were compiled to determine the history of air-sea exchange of CO2 since the glacial (last 25ka).
    Type: Dataset
    Format: application/zip, 11 datasets
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  • 8
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    PANGAEA
    In:  Supplement to: Stott, Lowell D; Davy, Bryan; Shao, Jun; Coffin, Richard C; Pecher, Ingo A; Neil, Helen L; Rose, Paula S; Bialas, Jörg (2019): CO2 Release From Pockmarks on the Chatham Rise‐Bounty Trough at the Glacial Termination. Paleoceanography and Paleoclimatology, https://doi.org/10.1029/2019PA003674
    Publication Date: 2023-11-18
    Description: Seafloor pockmarks of varying size occur over an area of 50,000 km² on the Chatham Rise, Canterbury Shelf and Inner Bounty Trough, New Zealand. The pockmarks are concentrated above the flat-subducted Hikurangi Plateau. Echosounder data identifies recurrent episodes of pockmark formation at ~100,000yr frequency coinciding with Pleistocene glacial terminations. Here we show that there are structural conduits beneath the larger pockmarks through which fluids flowed upward toward the seafloor. Large negative Δ¹⁴C excursions are documented in marine sediments deposited next to these subseafloor conduits and pockmarks at the last glacial termination. Modern pore waters contain no methane and there is no negative δ¹³C excursion at the glacial termination that would be indicative of methane or mantle-derived carbon at the time the Δ¹⁴C excursion and pockmarks were produced. An ocean general circulation model equipped with isotope tracers is unable to simulate these large Δ¹⁴C excursions on the Chatham Rise by transport of hydrothermal carbon released from the East Pacific Rise as previous studies suggested. Here we attribute the Δ¹⁴C anomalies and pockmarks to release of ¹⁴C-dead CO2 and carbon-rich fluids from subsurface reservoirs, the most likely being dissociated Mesozoic carbonates that subducted beneath the Rise during the Late Cretaceous. Because of the large number of pockmarks and duration of the Δ¹⁴C anomaly, the pockmarks may collectively represent an important source of ¹⁴C-dead carbon to the ocean during glacial terminations.
    Keywords: carbon isotope composition of DIC; Dissolved inorganic carbon; pore water; sulfate
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 9
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    PANGAEA
    In:  Supplement to: Herbozo, Gery; Hübscher, Christian; Kaul, Norbert; Wagner, M; Pecher, Ingo A; Kukowski, Nina (2013): Influence of recent depositional and tectonic controls on marine gas hydrates in Trujillo Basin, Peru Margin. Marine Geology, 340, 30-48, https://doi.org/10.1016/j.margeo.2013.04.010
    Publication Date: 2023-11-18
    Description: The development of bottom simulating reflectors (BSRs) and the gas hydrate stability zone (GHSZ) in continental margins is related to recent depositional and tectonic processes. This interrelation is important for understanding the potential resource of gas hydrate deposits. The purpose of this study is to understand the influence of such activity on the marine gas hydrate system of the seaward extension of the Trujillo Basin, Peru Margin. Here, we analyze near-seafloor heat flow probe data, high-resolution multichannel seismic (MCS) profiles, swath bathymetry and ocean floor observation system (OFOS) images. Based on our results, we identify three main physiographical subregions in the study area: (1) an area with turbidites, continuous BSRs and low-to-moderate near-seafloor heat flow (7-33 mW/m**2), (2) an area with sediment waves of turbidity origin, a mix of continuous and patchy BSRs, and moderate near-seafloor heat flow (26-39 mW/m**2), (3) an area with extensional faulting, patchy BSRs and moderate-to-high near-seafloor heat flow (52-110 mW/m**2). We conclude that sediment flow processes are the result of recent depositional controls, and faulting is the result of recent tectonic activity. Near-seafloor heat flow around chemoherms is moderate. Estimates of BSR-derived heat flow show differences to near-seafloor heat flow. This difference points to advection of fluids occurring at the seafloor. Alive Calyptogena and tube worms were observed in these venting zones. Based on our analysis, we conclude that: (1) recent depositional processes control the development of continuous BSRs and may restrict heat transfer through the GHSZ in the form of fluid venting at the seafloor, (2) recent tectonic processes control the development of patchy BSRs and allow heat transfer through the GHSZ along faults, which is manifested as fluid venting at the seafloor.
    Keywords: Conductivity, thermal; DEPTH, water; Event label; GeoB; GEOPECO; Geosciences, University of Bremen; Heat flow; Heat-Flow probe; HF; HF020P01; HF020P02; HF020P03; HF020P04; HF020P05; HF020P06; HF020P07; HF020P08; HF020P09; HF020P10; HF020P11; HF020P12; HF020P13; HF021P01; HF021P02; HF021P03; HF021P04; HF021P05; HF021P06; HF021P07; HF021P08; HF021P09; HF022P01; HF022P02; HF022P03; HF022P04; HF022P05; HF022P06; HF022P07; HF022P08; HF022P09; HF023P01; HF023P02; HF023P03; HF023P04; HF023P05; HF023P06; HF023P07; HF023P08; HF023P09; HF023P10; HF023P11; HF024P01; HF024P02; HF024P03; HF024P04; HF024P05; HF025P01; HF025P02; HF025P03; HF025P04; HF025P05; HF025P06; HF025P07; HF025P08; HF025P09; HF025P10; HF026P01; HF026P02; HF026P03; HF026P04; HF026P05; HF026P06; HF026P07; HF026P08; Latitude of event; Longitude of event; Number; Number of shots; Root mean square error; see reference(s); SO146/2; Sonne; Temperature, technical; Tilt angle
    Type: Dataset
    Format: text/tab-separated-values, 412 data points
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  • 10
    Publication Date: 2023-11-18
    Keywords: Calculated; Calendar age; Carbon dioxide, partial pressure; DEPTH, sediment/rock; Gas chromatography; Globigerina bulloides, Magnesium/Calcium ratio; Globigerina bulloides, δ11B; Globigerina bulloides, δ11B, standard deviation; Partial pressure of carbon dioxide, standard deviation; PC; PC75-2; pH; pH, standard deviation; Piston corer; Sea surface temperature; Sea surface temperature, standard deviation; Southwest Pacific
    Type: Dataset
    Format: text/tab-separated-values, 100 data points
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