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  • 2000-2004  (3)
  • 1995-1999  (3)
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Year
  • 1
    Book
    Book
    Mathematical models of early diagenetic processes : impacts on the biogeochemical environment of the deep-sea floor (1999)
    Details Availability
    Keywords: Tiefseeboden ; Dissertation ; Diagenese ; Tiefseesediment ; Peru-Becken ; Hochschulschrift
    Type of Medium: Book
    Pages: 147 S , graph. Darst., Kt
    Language: English
    Note: Kiel, Univ., Diss., 2000
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  • 2
    Online Resource
    Online Resource
    Mathematical models of early diagenetic processes : impacts on the biogeochemical environment of the deep-sea floor (1999)
    Kiel
    Details Availability
    Keywords: Tiefseeboden ; Dissertation ; Diagenese ; Tiefseesediment ; Peru-Becken ; Hochschulschrift
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource ( 160Seiten = 14MB) , graph. Darst., Kt
    URL: https://oceanrep.geomar.de/id/eprint/49626/
    Language: English
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  • 3
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    Mathematical models of early diagenetic processes: Impacts on the biogeochemical environment of the deep-sea floor (2000)
    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 147 pp
    Details
    Publication Date: 2020-06-24
    Description: In this work, multicomponent transport-reaction models were successfully applied to analyse and assess the effects of human interventions and natural, large-scale perturbations of the deep-sea floor. In particular, two scenarios were studied that are suitable as case studies for a variety of possible impacts. Firstly, the removal of the uppermost bioturbated sediment layer due to deepsea mining of manganese nodules in the Peru Basin is considered, and secondly, the disposal of highly reactive material on the deep-sea floor of the South China Sea, i.e. the Mount Pinatubo ash fallout of 1991, is evaluated. In addition, the current theoretical background for equilibrium calculations is expanded, and by this a mathematical tool is provided that, for example, may allow an evaluation of the influence of calcite dissolution and precipitation at the sea floor on the global C02 budget.
    Type: Thesis , NonPeerReviewed
    Format: text
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    OceanRep: Thesis - not published by a publisher
  • 4
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    Unknown
    A geochemical model of the Peru Basin deep-sea floor and the response of the system to technical impacts (2001)
    Pergamon Press
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 48 . pp. 3737-3756.
    Details
    Publication Date: 2020-08-05
    Description: A geochemical model of the Peru Basin deep-sea floor, based on an extensive set of field data as well as on numerical simulations, is presented. The model takes into account the vertical oscillations of the redox zonation that occur in response to both long-term (glacial/interglacial) and short-term (El Niño Southern Oscillation (ENSO) time scale) variations in the depositional flux of organic matter. Field evidence of reaction between the pore water NO3− and an oxidizable fraction of the structural Fe(II) in the clay mineral content of the deep-sea sediments is provided. The conditions of formation and destruction of reactive clay Fe(II) layers in the sea floor are defined, whereby a new paleo-redox proxy is established. Transitional NO3− profile shapes are explained by periodic contractions and expansions of the oxic zone (ocean bottom respiration) on the ENSO time scale. The near-surface oscillations of the oxic–suboxic boundary constitute a redox pump mechanism of major importance with respect to diagenetic trace metal enrichments and manganese nodule formation, which may account for the particularly high nodule growth rates in this ocean basin. These conditions are due to the similar depth ranges of both the O2 penetration in the sea floor and the bioturbated high reactivity surface layer (HRSL), all against the background of ENSO-related large variations in depositional Corg flux. Removal of the HRSL in the course of deep-sea mining would result in a massive expansion of the oxic surface layer and, thus, the shut down of the near-surface redox pump for centuries, which is demonstrated by numerical modeling.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0967-0645(01)00065-0
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Unknown
    Rising methane gas bubbles form massive hydrate layers at the seafloor (2004)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 68 (21). pp. 4335-4354.
    Details
    Publication Date: 2017-09-08
    Description: Extensive methane hydrate layers are formed in the near-surface sediments of the Cascadia margin. An undissociated section of such a layer was recovered at the base of a gravity core (i.e. at a sediment depth of 120 cm) at the southern summit of Hydrate Ridge. As a result of salt exclusion during methane hydrate formation, the associated pore waters show a highly elevated chloride concentration of 809 mM. In comparison, the average background value is 543 mM. A simple transport-reaction model was developed to reproduce the Cl- observations and quantify processes such as hydrate formation, methane demand, and fluid flow. From this first field observation of a positive Cl- anomaly, high hydrate formation rates (0.15–1.08 mol cm-2 a-1) were calculated. Our model results also suggest that the fluid flow rate at the Cascadia accretionary margin is constrained to 45–300 cm a-1. The amount of methane needed to build up enough methane hydrate to produce the observed chloride enrichment exceeds the methane solubility in pore water. Thus, most of the gas hydrate was most likely formed from ascending methane gas bubbles rather than solely from CH4 dissolved in the pore water.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.gca.2004.01.018
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Reactive Fe (II) layers in deep-sea sediments (1999)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 63 (10). pp. 1517-1526.
    Details
    Publication Date: 2017-08-25
    Description: The percentage of the structural Fe(II) in clay minerals that is readily oxidized to Fe(III) upon contact with atmospheric oxygen was determined across the downcore tan–green color change in Peru Basin sediments. This latent fraction of reactive Fe(II) was only found in the green strata, where it proved to be large enough to constitute a deep reaction layer with respect to the pore water O2 and NO3−. Large variations were detected in the proportion of the reactive Fe(II) concentration to the organic matter content along core profiles. Hence, the commonly observed tan–green color change in marine sediments marks the top of a reactive Fe(II) layer, which may represent the major barrier to the movement of oxidation fronts in pelagic subsurface sediments. This is also demonstrated by numerical model simulations. The findings imply that geochemical barriers to pore water oxidation fronts form diagenetically in the sea floor wherever the stage of iron reduction is reached, provided that the sediments contain a significant amount of structural iron in clay minerals.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0016-7037(99)00104-0
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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