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  • AGU (American Geophysical Union)  (26)
  • Blackwell Publishing Ltd  (3)
  • Universität Göttingen  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Magnetostratigraphic Data From Late Quaternary Sediments From the Yermak Plateau, Arctic Ocean: Evidence For Four Geomagnetic Polarity Events Within the Last 170 Ka of the Brunhes Chron (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 117 (1994), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Palaeomagnetic investigations of two sediment cores recovered from RV Polarstern near the eastern slope of the Yermak Plateau (sites PS 1533 and PS 2212) reveal convincing evidence for four polarity events of the Earth's magnetic field during the last 170 Ka. A comprehensive rock magnetic study of the sediments proved that fine-grained magnetite is the principal carrier of the remanent magnetization. No changes in magneto-mineralogy across the polarity transitions in the sediments investigated were found. Calcareous nannofossil biostratigraphy, AMS-14C (accelerated mass spectrometry) and oxygen isotope data, and 10Be and 230Th stratigraphies yielded age ranges of 24–29 Ka for the Mono Lake event, 34–43 Ka for the Laschamp event, 72–86 Ka for the Norwegian-Greenland Sea event and 118–128 Ka for the Blake event. Two reverse polarity samples at the base of core PS 2212–3 KAL are interpreted as the termination of the Biwa I event (171-181 Ka). the events exhibit full inversion of inclination in both cores. the data suggest that the transition process of the Earth's magnetic field during such polarity events requires some 1 Ka.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1994.tb03944.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A Reflection on Mg, Cd, Ca, Li and Si Isotopic Measurements and Related Reference Materials (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Geostandards and geoanalytical research 28 (2004), S. 0 
    Details
    ISSN: 1751-908X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: This contribution aims to report the reflections we had with the scientific community during two international workshops on reference materials for stable isotopes in Davos (2002) and Nice (2003). After evaluating the isotopic homogeneity of some existing reference materials, based on either certificates, literature data or specific inter-laboratory rounds, we confirm these as primary reference materials or propose new ones relative to which stable isotope compositions should be reported. We propose DSM-3 for Mg, NIST SRM 915a for Ca, L-SVEC for Li and NBS28 for Si. Cadmium does not yet have a well identified delta zero material, although three commercial mono-elemental Cd solutions have yielded the same isotopic composition relative to one another. In order to scale the linearity of any mass spectrometer, some secondary reference materials are also proposed: Cambridge-1 solution for Mg, the “Münster-Cd” and JEPPIM Cd solutions for Cd and the “Big Batch” silicate for Si. The team from Nancy propose to prepare a mixed spike solution for Li isotopes. Well-characterised natural samples such as ocean or continental waters, diatoms, sponges, rocks and minerals are needed to validate the entire analytical procedure, particularly to take into account the effect of sample mineralisation and of chemical manipulations for elemental separation prior to analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1751-908X.2004.tb01050.x
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  • 3
    Electronic Resource
    Electronic Resource
    Proposal for International Agreement on Ca Notation Resulting from Discussions at Workshops on Stable Isotope Measurements Held in Davos (Goldschmidt 2002) and Nice (EGS-AGU-EUG 2003) (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Geostandards and geoanalytical research 28 (2004), S. 0 
    Details
    ISSN: 1751-908X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A proposal is made to standardise the reporting of Ca isotope data to the δ44Ca/40Ca notation (or δ44Ca/42Ca) and to adopt NIST SRM 915a as the reference standard.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1751-908X.2004.tb01051.x
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  • 4
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    Coral and reef growth in the Western Indian Ocean (La Réunion, Mayotte, and Seychelles) (1996)
    Universität Göttingen
    In:  In: Global and regional controls on biogenic sedimentation. I. Reef evolution. Research reports. , ed. by Reitner, J., Neuweiler, F. and Gunkel, F. Göttinger Arbeiten zur Geologie und Paläontologie, Sb 2 . Universität Göttingen, Göttingen, pp. 23-27.
    Details
    Publication Date: 2019-09-23
    Type: Book chapter , NonPeerReviewed
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  • 5
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    Intra-annual variations in the stable oxygen and carbon and trace element composition of scelerosponges (2002)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 17 (3). p. 1045.
    Details
    Publication Date: 2017-05-10
    Description: This paper presents data to support the presence of (1) intra-annual signals in the chemical composition (δ18O and Sr/Ca) of the skeletons of sclerosponges from the Bahamas and (2) variable rates of skeletal accretion. These conclusions are based on data obtained by using a microsampling method for the stable oxygen and carbon isotopes in which material was extracted at a resolution of one sample every 34 μm and a laser microprobe which obtained trace element data every 20 μm (Sr, Mg, and Pb). An age model was established using a combination of changes in the concentration of Pb, the change in the δ13C of the skeleton of the sclerosponges, and U/Th isotopic measurements. These methods yield a mean growth rate of 220 μm/yr but suggest that the growth rate in this particular sclerosponge was not constant. The calculated growth rate is within error identical to that determined by U/Th methods. The variable growth rate was confirmed through spectral analysis of the δ18O and Sr/Ca data that showed peaks corresponding to the annual cycle in these parameters as well as peaks corresponding to growth rates of approximately 128, 212, 270, and 400 μm/yr. The presence of these additional frequencies suggests a growth rate between approximately 100 and 300 μm/yr. These conclusions were supported by modeling of oxygen isotopic data measured on a scleractinian coral as well as model isotope data generated on synthetic time series. These findings have important implications for the use of sclerosponges as proxies of paleoclimate because they emphasize the need for a precise yearly chronology in order that proxy data can be compared with climatic variables.
    Type: Article , PeerReviewed
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  • 6
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    Disentangling the Biological and Environmental Control of M. edulis Shell Chemistry (2011)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 12 (3). Q03009.
    Details
    Publication Date: 2020-10-16
    Description: Blue mussel individuals (Mytilus edulis) were cultured at four different salinities (17, 20, 29, and 34). During the course of the experiment, temperature was gradually increased from 6°C to 14°C. Mg/Ca and Sr/Ca ratios of the shell calcite portions produced during the 9 weeks of experimental treatment as well parts that were precipitated before the treatment phase were measured by laser ablation–multicollector–inductively coupled plasma–mass spectrometry. Mg/Ca ratios show a positive correlation with temperature for individuals cultured at salinity 29 and 34 (Mg/Ca (mmol/mol) ∼ (0.2–0.3)*T (°C)), while for individuals cultured at low salinities (17, 20) no trend was observed. Sr/Ca ratios were not affected by temperature but strongly by salinity. The data show very strong biological influence (“individual differences” and “physiological variability”) on elemental ratios (79% on Mg/Ca and 41% on Sr/Ca) in M. edulis calcite. The results challenge the use of blue mussel shell data as environmental proxies.
    Type: Article , PeerReviewed
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  • 7
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    Beryllium-10, thorium-231 and protactium-231 in Galapagos Microplate Sediments: implications of hydrothermal activity and paleoproductivity changes during the last 100.000 years (1994)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 9 (4). pp. 559-578.
    Details
    Publication Date: 2017-01-18
    Description: Biogenic particle fluxes from highly productive surface waters, boundary scavenging, and hydrothermal activity are the main factors influencing the deposition of radionuclides in the area of the Galapagos microplate, eastern Equatorial Pacific. In order to evaluate the importance of these three processes throughout the last 100 kyr, concentrations of the radionuclides 10Be, 230Th, and 231Pa, and of Mn and Fe were measured at high resolution in sediment samples from two gravity cores KLH 068 and KLH 093. High biological productivity in the surface waters overlying the investigated area has led to 10Be and 231Pa fluxes exceeding production during at least the last 30 kyr and probably the last 100 kyr. However, during periods of high productivity at the up welling centers off Peru and extension of the equatorial high-productivity zone, a relative loss of 10Be and 231Pa may have occurred in these sediment cores because of boundary scavenging. The effects of hydrothermal activity were investigated by comparing the 230Thex concentrations to the Mn/Fe ratios and by comparing the fluxes of 230Th and 10Be which exceed production. The results suggest an enhanced hydrothermal influence during isotope stages 4 and 5 and to a lesser extent during isotope stage 1 in core KLH 093. During isotope stages 2 and 3, the hydrothermal supply of Mn was deposited elsewhere, probably because of changes in current regime or deep water oxygenation. A strong increase of the Mn/Fe ratio at the beginning of climatic stage 1 which is not accompanied by an increase of the 230Thex concentration is interpreted to be an effect of Mn remobilization and reprecipitation in the sediment.
    Type: Article , PeerReviewed
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  • 8
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    Modification of Ca isotope and trace metal composition of the major matrices involved in shell formation of Mytilus edulis (2008)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 9 (Q01006).
    Details
    Publication Date: 2018-03-07
    Description: In this study we present the first combined investigation into the composition of the major matrices involved in calcification processes (surrounding water, extrapallial fluid, aragonite, and calcite) of Mytilus edulis with respect to their calcium isotope (d44/40Ca) and elemental compositions (Sr/Ca and Mg/Ca). Our aim was to examine the suitability of Mytilus edulis as a proxy archive and to contribute to the understanding of the process of biomineralization. Mytilus edulis specimens were live collected from the Schwentine Estuary, Kiel Fjord, and North Sea (Sylt). d44/40Ca was determined by thermal ionization mass spectrometry (TIMS) accompanied by measurements of Mg/Ca and Sr/Ca using inductively coupled plasma–optical emission spectroscopy (ICP-OES). The elemental and isotopic compositions of the investigated matrices showed systematic offsets. The carbonates are strongly depleted in their magnesium and strontium concentrations and fractionated toward lighter calcium isotope compositions relative to the surrounding Schwentine Estuary water. The opposite is observed for the extrapallial fluid (EPF). Our findings extend the results of previous studies reporting a strong biological control and the interaction of different environmental conditions influencing biomineralization. Future studies should focus on the temporal development of the interrelation between the different matrices.
    Type: Article , PeerReviewed
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  • 9
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    Response of Manganese in the Ocean to the Climate Cycles in the Quaternary (1990)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 5 (5). pp. 811-821.
    Details
    Publication Date: 2017-05-10
    Description: Profiles of the 230Th concentration in Mn crusts from the central Pacific Ocean measured at extremely high depth resolution reveal that the growth rates of Mn crusts are influenced by climate. Based on a “constant flux model” the sections of maximum 230Th concentration correspond to periods of slow growth during glacial stages. Fast growth occurred during interglacial stages 1, 5, and 7, probably due to a larger supply of Mn oxides from the water column. High-resolution profiles of 230Th and 10Be in sediment cores from high biological productivity areas display radioisotope maxima in the interglacial stages and minima during glacial periods, the ratio of the fluxes of 10Be/230Th being ≥4. The only exceptions are observed at 135 and 270 kyr B.P., where the ratio of the fluxes is as low as 0.1 to 0.3. We presume that this “230Th anomaly” reflects short periods of time at the end of glacials when precipitation of MnO2 occurred. This hypothesis is confirmed by peaks of Mn observed in sediment cores mainly at the transitions from glacial to interglacial stages. The standing crops of Mn in these layers suggest release of Mn2+ from the sediments during glacial stages and buildup of Mn in the water column to concentrations of up to 10 µmol/L.
    Type: Article , PeerReviewed
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  • 10
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    Beryllium-10, thorium-231 and protactinium-231 in galapagos Microplate Sedimentes: implications of hydrothermal activity and paleoproductivity changes during the last 100.000 years (1994)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 9 (4). pp. 559-578.
    Details
    Publication Date: 2019-02-27
    Description: Biogenic particle fluxes from highly productive surface waters, boundary scavenging, and hydrothermal activity are the main factors influencing the deposition of radionuclides in the area of the Galapagos microplate, eastern Equatorial Pacific. In order to evaluate the importance of these three processes throughout the last 100 kyr, concentrations of the radionuclides 10Be, 230Th, and 231Pa, and of Mn and Fe were measured at high resolution in sediment samples from two gravity cores KLH 068 and KLH 093. High biological productivity in the surface waters overlying the investigated area has led to 10Be and 231Pa fluxes exceeding production during at least the last 30 kyr and probably the last 100 kyr. However, during periods of high productivity at the up welling centers off Peru and extension of the equatorial high-productivity zone, a relative loss of 10Be and 231Pa may have occurred in these sediment cores because of boundary scavenging. The effects of hydrothermal activity were investigated by comparing the 230Thex concentrations to the Mn/Fe ratios and by comparing the fluxes of 230Th and 10Be which exceed production. The results suggest an enhanced hydrothermal influence during isotope stages 4 and 5 and to a lesser extent during isotope stage 1 in core KLH 093. During isotope stages 2 and 3, the hydrothermal supply of Mn was deposited elsewhere, probably because of changes in current regime or deep water oxygenation. A strong increase of the Mn/Fe ratio at the beginning of climatic stage 1 which is not accompanied by an increase of the 230Thex concentration is interpreted to be an effect of Mn remobilization and reprecipitation in the sediment.
    Type: Article , PeerReviewed
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