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  • 1
    Call number: MOP Per 287/B
    Type of Medium: Monograph available for loan
    Pages: 100 S.
    Series Statement: Veröffentlichungen des Königlich Preußischen Meteorologischen Instituts 232
    Location: MOP - must be ordered
    Branch Library: GFZ Library
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  • 2
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract Based on sediment physical property data from DSDP/ ODP Legs 78A and 110 (Barbados Ridge Complex), a simple palinspastic reconstruction scheme was employed to study porosity changes during accretion. Undoing the compactional effects caused by imbricate stacking of wedge slices, a synthetic pre-accretion porosity depth profile was developed, which bears strong resemblence to a characteristic profile from a reference drillhole in front of the Barbados accretionary complex. Differences between synthetic and reference profile are interpreted in terms of a semiquantitative estimate of the relative impact of the horizontal stress component on gravitational compaction in accretionary wedge environments. An exponential relationship between depth and porosity divergence for distinct lithologic units is evident. The defined relationship facilitates the analysis of deformational behavior of accreted sediments in general.
    Abstract: Résumé Les propriétés physiques des sédiments fournies par les Legs 78A et 110 du programme DSDP/ODP (Barbados Ridge Complex) ont servi de base à une reconstitution palynspastique: celle-ci a été utilisée à son tour pour l'étude des changements de porosité au cours de l'accrétion. Par élimination des effets de compaction dûs à l'empilement des écailles de sédiments, il a été possible d'établir un profil de la porosité selon la profondeur; ce profil présente de grande similitudes avec le profil caractéristique d'un forage de référence situé en avant du complexe d'accrétion des Barbades. La comparaison du profil reconstitué avec ce profil de référence montre, pour des unités lithologiques déterminées, une relation exponentielle entre la profondeur et les écarts de porosités. On peut de là estimer l'influence de la composante horizontale des contraintes sur la compaction gravifique dans cette partie du prisme d'accrétion. Ces relations sont de nature à faciliter, d'une manière gènérale, l'analyse du processus déformatif dans les sédiments accrétionnés.
    Notes: Zusammenfassung Auf der Grundlage sedimentphysikalischer Daten der DSDP/ODP — Legs 78A und 110 (Barbados Ridge Komplex) wurde ein einfaches palinspastisches Rekonstruktionsverfahren zur Untersuchung der Porositätsentwicklung unter den Bedingungen der initialen Akkretion entwickelt. Durch rechnerische Umkehrung der durch imbrikierte Schuppung von Sedimentpaketen bedingten Kompaktionseffekte konnte ein synthetisches prä-akkretionäres Porositäts-Tiefen-Profil modelliert werden, welches weitgehende Übereinstimmung mit dem vor dem Barbados Akkretions-system erbohrten Referenzprofil aufweist. Der Vergleich von synthetischem und Referenz-Profil zeigt für einzelne lithologische Einheiten eine exponentielle Beziehung zwischen Tiefe und Porositätsdifferenz. Dies kann als ein relatives Maß für den Einfluß der horizontalen Streßkomponente auf die effektive Kompaktionsrate in diesem Teil des Akkretionskeils angesehen werden. Darüber hinaus läßt sich durch diese Beziehung das Deformationsverhalten akkretierter Sedimente generell beschreiben.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2014-09-17
    Description: Cold seep ecosystems can support enormous biomasses of free-living and symbiotic chemoautotrophic organisms that get their energy from the oxidation of methane or sulfide. Most of this biomass derives from animals that are associated with bacterial symbionts, which are able to metabolize the chemical resources provided by the seeping fluids. Often these systems also harbor dense accumulations of non-symbiotic megafauna, which can be relevant in exporting chemosynthetically fixed carbon from seeps to the surrounding deep sea. Here we investigated the carbon sources of lithodid crabs (Paralomis sp.) feeding on thiotrophic bacterial mats at an active mud volcano at the Costa Rica subduction zone. To evaluate the dietary carbon source of the crabs, we compared the microbial community in stomach contents with surface sediments covered by microbial mats. The stomach content analyses revealed a dominance of epsilonproteobacterial 16S rRNA gene sequences related to the free-living and epibiotic sulfur oxidiser Sulfurovum sp. We also found Sulfurovum sp. as well as members of the genera Arcobacter and Sulfurimonas in mat-covered surface sediments where Epsilonproteobacteria were highly abundant constituting 10% of total cells. Furthermore, we detected substantial amounts of bacterial fatty acids such as i-C15:0 and C17:1ω6c with stable carbon isotope compositions as low as −53‰ in the stomach and muscle tissue. These results indicate that the white microbial mats at Mound 12 are comprised of Epsilonproteobacteria and that microbial mat-derived carbon provides an important contribution to the crab's nutrition. In addition, our lipid analyses also suggest that the crabs feed on other 13C-depleted organic matter sources, possibly symbiotic megafauna as well as on photosynthetic carbon sources such as sedimentary detritus.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 4
    Publication Date: 2019-07-17
    Description: During RV Sonne cruise SO173-1 in the framework of SFB574 (volatiles and fluids in Subduction zones) in July/August 2003, a new area offshore Nicaragua has been surveyed with the IFM-GEOMAR deep-towed multichannel seismic system (DTMCS). In total 13 NW-SE striking profiles running parallel to the continental slope were recorded at water depths between 1000 and 2500 m covering an area of approximately 700 square km. This study presents some new results from the ongoing investigations with these seismic profiles.The continental margin off Nicaragua is dominated by deeply incised canyons and numerous mound structures, as well as two large slides at the lower slope. Most of these mud mounds built positive topographic expressions (up to ca. 130 m) on the seafloor. They are characterized by transparent or semitransparent seismic facies in the cylinder like feeder channel tapering upward to cone shape geometry. The mud mounds are of different size and at different stages of development. The distribution of the mounds shows two distinct orientations (NW-SE and NE-SW) and is controlled by faults. The widespread occurrence of gas hydrate is imaged by a BSR visible in most parts of the survey area. Although the BSR has been identified over the entire area, it is variable along the seismic line in the frequency windows used (50-300 Hz). The BSR presents high to moderate amplitudes near the mud mounds or/and diapir structures and seems to disappear away from them. For the first time, our data show that the BSRs are continued but uplifted beneath some mud mounds.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 5
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 6
    Publication Date: 2019-07-17
    Description: During RV SONNE cruise SO173-1, carried in the framework of the Cooperative Research Center (SFB) 574 (Volatiles and Fluids in Subduction Zones) in July and August 2003, an area offshore Nicaragua has been surveyed with the IFM-GEOMAR deep-towed multichannel seismic system (DTMCS). In total 13 NW-SE striking profiles running parallel to the continental slope were recorded in the water depths between 1000 and 2500 m covering an area of approximately 700 square km. This study presents some new results from the ongoing investigations with these seismic profiles. The continental margin off Nicaragua is dominated by deeply incised canyons and numerous mound structures, as well as slides at the lower slope. Most of these mud mounds built positive topographic expressions (up to ca. 130 m) on the seafloor. They are characterized by transparent or semi-transparent seismic facies in the cylinder-like feeder channel tapering upward to cone shape geometry. The mud mounds are of different size and different stages of development. The distribution of the mounds show two distinct orientations (NW-SE and NE-SW) and are most probably controlled by faults. The widespread occurrence of gas hydrate is imaged by a BSR visible in most parts of the survey area. For the first time, our data show that the BSR is continued but uplifted beneath some mud mounds.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 7
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 8
    Publication Date: 2019-07-17
    Description: Bathymetric and conventional multichannel seismic surveys offshore Nicaragua and Costa Rica have revealed numerous mud mounds beneath which the generally widespread BSR is not well imaged. However, many of the mounds are partially capped by patches of authigenic carbonate crusts, so it was not clear if the semitransparent seismic facies and the apparent gaps in the BSR beneath the mounds are real or due to poor normal-incidence seismic penetration through the cap rocks. To address these problems, a high-resolution seismic survey was carried out over the continental slope of the Nicaraguan Pacific margin using a deep towed multichannel seismic streamer (DTMCS) along with a sidescan sonar system (DTS) to image submarine mud mounds and the associated BSR. The proximity of the very short (39 m active length) but high-resolution 17 channel streamer to the seafloor of the deep towed system allows greatly improved lateral resolution whereas the relatively large sourcereceiver offset allows the undershooting of the cap rocks. For the first time our data show that the BSR in many cases continues but rises beneath the mounds. This is consistent with the advection of deep warm fluids and thus increased heat flow through the mounds. The occurrence of mud mounds seems to be controlled by the locations of faults.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 9
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 10
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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