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  • 1995-1999  (80)
  • 1980-1984  (27)
  • 1970-1974  (9)
  • 1
    Electronic Resource
    Electronic Resource
    Sedimentation rate variations and anthropogenic metal fluxes into Lake Constance sediments (1983)
    Springer
    Environmental geology 5 (1983), S. 151-157 
    Details
    ISSN: 1432-0495
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Sedimentation rates were determined by210Pb in three sediment cores from the main basin of Lake Constance. Rates vary from 0.094 to 0.133 g cm−2y−1, in agreement with previous determinations. A constant radionuclide flux (CR) model reveals long-term, quasi-synchronous fluctuations of sedimentation rate on the basin-wide scale. On average, the rate of sedimentation remains much the same from the beginning of this century indicating little effect of human activity in the watershed on fine-silt sediment supply. The anthropogenic fluxes of Zn, Pb, and Cd in the three cores are compared and the application of210Pb as a heavy metal tracer in Lake Constance is examined. It seems to be a very good tracer for Pb, moderately good for Zn and Cu, and not useful for Cd.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02381273
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  • 2
    Electronic Resource
    Electronic Resource
    Coral provides way to age deep water (1998)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 392 (1998), S. 347-348 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We propose a new method for computing the ratio of the isotopes carbon-14 to carbon-12 in deep water from the past, and for testing the results derived from the normal method of age difference between benthic and planktic foraminifera in deep-sea sediments. Our method involves measuring ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/32804
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of recent deposition rates in Lake Constance with radioisotopic methods (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 28 (1981), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Sedimentation rates were determined with the 210Pb method in eight sediment cores from Lake Constance. The rate of deposition in the main basin (Obersee) varies from about 0.06 g cm−2 y−1 in the central part to 0.13 g cm−2 y−1 in the eastern part of the lake and then increases rapidly towards the Rhine delta.In the central lake area the rate of deposition has been approximately constant since 1900, and dating with the 210Pb method is in good agreement with sedimentological observations. In the Konstanzer Trichter area, the deposition rate has been increasing since about 1955 as a result of eutrophication and subsequent high carbonate production.Dating with 137Cs is fairly accurate for sediments deposited at a high rate, but is questionable for slowly accumulating ones.A positive correlation of 210Pb fluxes and sedimentation rates indicates that 210Pb flux into sediments follows the distribution pattern of solids. 210Pb profiles in four sediment cores interpreted in terms of a constant flux model display synchronous fluctuations of the sedimentation rate; however, their relation to long-range particulate input variations remains to be proved.Sedimentation rates determined with the 210Pb method were used to calculate recent nutrient and heavy metal fluxes. Anthropogenic fluxes of Zn and Pb are in the same range of magnitude as in other polluted areas in Europe and America.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.1981.tb01927.x
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  • 4
    Electronic Resource
    Electronic Resource
    Co-fluxes and growth rates in ferromanganese deposits from central Pacific seamount areas (1983)
    [s.l.] : Nature Publishing Group
    Nature 304 (1983), S. 716-719 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In early diagenetic and mixed type nodules Co displays a positive correlation with Fe (r = 0.77)3 and no correlation to Mn, whereas in hydrogenetic nodules Co correlates to Mn (r = 0.79)3. Hydrogenetic nodules and crusts show generally higher Co contents than diagenetically formed nodules. This ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/304716a0
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  • 5
    Electronic Resource
    Electronic Resource
    Geochemistry of a piston core from Ontong Java Plateau (western equatorial Pacific): evidence for sediment redistribution and changes in paleoproductivity (1996)
    Springer
    International journal of earth sciences 85 (1996), S. 536-545 
    Details
    ISSN: 1437-3262
    Keywords: Ontong Java Plateau ; Thorium-230 ; Barium ; Productivity ; Lysocline ; Sediment focusing ; Vertical mass accumulation rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract We discuss geochemical proxies, reflecting processes of primary productivity, CaCO3 dissolution, and sediment redistribution in a piston core (RNDB 74P) from the Ontong Java Plateau. Due to the shallow water depth, biogenic carbonate is well preserved and a very goodδ 18O stratigraphy is available down to isotopic stage 11.230Thex gives evidence that the sediment accumulation pattern is driven mainly by processes of sediment focusing or winnowing. Due to the constant production of230Th in the water column, the bulk sediment accumulation rates could be corrected for the particle rain deriving from the water column above. The230Thex 0/CaCO3 ratio reflects the well-known Pacific CaCO3 preservation pattern with ice growth dissolution spikes and deglacial preservation spikes. The record of the grain size fraction 〉63 µm supports these results. The downcore concentrations and accumulation rates of barium (Ba) are on a higher level during interglacials and show several peaks. Normalization of Ba with230Thex 0 delivers a more uniform level of the Ba accumulation rates throughout the core. This pattern suggests a constantly higher biological productivity (nearly tenfold) in this area throughout the past 200 kyr compared with an open ocean environment. Barium peaks observed at the climatic transitions 2/1 and 6/5 and in stage 5 are in contrast to a predicted reduction of interglacial productivity at this location. A possible explanation might be the onset of the modern circulation pattern. The transition from Ba-enriched deep water to lower contents in the Atlantic might have resulted in an enhanced deposition of Ba in the Pacific.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02369008
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  • 6
    Electronic Resource
    Electronic Resource
    Late Quaternary sediment dating and quantification of lateral sediment redistribution applying230Thex: a study from the eastern Atlantic sector of the Southern Ocean (1996)
    Springer
    International journal of earth sciences 85 (1996), S. 554-566 
    Details
    ISSN: 1437-3262
    Keywords: High-resolution dating ; 230Thex constant flux models ; Sediment focusing ; Sediment winnowing ; Particle flux reconstruction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract High-resolution records of the natural radionuclide230Th were measured in sediments from the eastern Atlantic sector of the Antarctic circumpolar current to obtain a detailed reconstruction of the sedimentation history of this key area for global climate change during the late Quaternary. High-resolution dating rests on the assumption that the230Thex flux to the sediments is constant. Short periods of drastically increased sediment accumulation rates (up to a factor of 8) were determined in the sediments of the Antarctic zone during the climate optima at the beginning of the Holocene and the isotope stage 5e. By comparing expected and measured accumulation rate of230Thex, lateral sediment redistribution was quantified and vertical particle rain rates originating from the surface water above were calculated. We show that lateral contributions locally were up to 6.5 times higher than the vertical particle rain rates. At other locations only 15% of the expected vertical particle rain rate were deposited.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02369010
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  • 7
    Electronic Resource
    Electronic Resource
    Ferromanganese crusts as indicators for paleoceanographic events in the NE Atlantic (1996)
    Springer
    International journal of earth sciences 85 (1996), S. 567-576 
    Details
    ISSN: 1437-3262
    Keywords: Ferromanganese crusts ; Phosphatization ; Paleoceanographic events ; NE Atlantic ; Mediterranean outflow water ; Messinian salinity crisis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Hydrogenetic ferromanganese crusts reflect the chemical conditions of the sewater from which they formed. Fine-scale geochemical analysis of crust layers in combination with age determinations can therefore be used to investigate paleoceanographic changes which are recorded in geochemical gradients in the crusts. At Tropic seamount (off northwest Africa), uniform crust growth influenced by terrigenous input from the African continent occurred during approximately the past 12 Ma. Phosphatization of these crusts is minor. In contrast, crusts from Lion seamount, located between Madeira and the Portuguese coast, display a much more variable growth history. A pronounced increase in Ni, Cu, and Zn is observed in some intervals of the crusts, which probably reflects increased surface productivity. A thick older phosphatized generation occurs in many samples. Hydrographic profiles indicate that Mediterranean outflow water (MOW) may play an important role in the composition of these crusts.10Be dating of one sample confirms that the interruption of the MOW during the Messinian salinity crisis (6.2–5 Ma ago) resulted in changes in element composition. Sr-isotope dating of the apatite phase of the old crust generation has been carried out to obtain a minimum age for the older generation of Atlantic crusts and to determine whether crust phosphatization in the Atlantic can be related to phosphatization episodes recorded in Pacific crusts. The preliminary data show that the old phosphatized crust generation might be as old as approximately 30–40 Ma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02369011
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  • 8
    Electronic Resource
    Electronic Resource
    Thorium and uranium isotopes in a manganese nodule from the Peru basin determined by alpha spectrometry and thermal ionization mass spectrometry (TIMS): Are manganese supply and growth related to climate? (1996)
    Springer
    International journal of earth sciences 85 (1996), S. 577-585 
    Details
    ISSN: 1437-3262
    Keywords: Manganese nodules ; Thorium dating ; Uranium isotopes ; Peru basin ; TIMS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Thorium- and uranium isotopes were measured in a diagenetic manganese nodule from the Peru basin applying alpha- and thermal ionization mass spectrometry (TIMS). Alpha-counting of 62 samples was carried out with a depth resolution of 0.4 mm to gain a high-resolution230Thexcess profile. In addition, 17 samples were measured with TIMS to obtain precise isotope concentrations and isotope ratios. We got values of 0.06–0.59 ppb (230Th), 0.43–1.40 ppm (232Th), 0.09–0.49 ppb (234U) and 1.66–8.24 ppm (238U). The uranium activity ratio in the uppermost samples (1–6 mm) and in two further sections in the nodule at 12.5±1.0 mm and 27.3–33.5 mm comes close to the present ocean water value of 1.144±0.004. In two other sections of the nodule, this ratio is significantly higher, probably reflecting incorporation of diagenetic uranium. The upper 25 mm section of the Mn nodule shows a relatively smooth exponential decrease in the230Thexcess concentration (TIMS). The slope of the best fit yields a growth rate of 110 mm/Ma up to 24.5 mm depth. The section from 25 to 30.3 mm depth shows constant230Thexcess concentrations probably due to growth rates even faster than those in the top section of the nodule. From 33 to 50 mm depth, the growth rate is approximately 60 mm/Ma. Two layers in the nodule with distinct laminations (11–15 and 28–33 mm depth) probably formed during the transition from isotopic stage 8 to 7 and in stage 5e, respectively. The Mn/Fe ratio shows higher values during interglacials 5 and 7, and lower ones during glacials 4 and 6. A comparison of our data with data from adjacent sediment cores suggests (a) a variable supply of hydrothermal Mn to sediments and Mn nodules of the Peru basin or (b) suboxic conditions at the water sediment interface during periods with lower Mn/Fe ratios.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02369012
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  • 9
    Electronic Resource
    Electronic Resource
    Geochemistry of a piston core from Ontong Java Plateau (western equatorial Pacific): evidence for sediment redistribution and changes in paleoproductivity (1996)
    Springer
    Geologische Rundschau 85 (1996), S. 536-545 
    Details
    ISSN: 0016-7835
    Keywords: Key words Ontong Java Plateau ; Thorium-230 ; Barium ; Productivity ; Lysocline ; Sediment focusing ; Vertical mass accumulation rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  We discuss geochemical proxies, reflecting processes of primary productivity, CaCO3 dissolution, and sediment redistribution in a piston core (RNDB 74P) from the Ontong Java Plateau. Due to the shallow water depth, biogenic carbonate is well preserved and a very good δ18O stratigraphy is available down to isotopic stage 11. 230Thex gives evidence that the sediment accumulation pattern is driven mainly by processes of sediment focusing or winnowing. Due to the constant production of 230Th in the water column, the bulk sediment accumulation rates could be corrected for the particle rain deriving from the water column above. The 230Thex 0/CaCO3 ratio reflects the well-known Pacific CaCO3 preservation pattern with ice growth dissolution spikes and deglacial preservation spikes. The record of the grain size fraction 〉63 μm supports these results. The downcore concentrations and accumulation rates of barium (Ba) are on a higher level during interglacials and show several peaks. Normalization of Ba with 230Thex 0 delivers a more uniform level of the Ba accumulation rates throughout the core. This pattern suggests a constantly higher biological productivity (nearly tenfold) in this area throughout the past 200 kyr compared with an open ocean environment. Barium peaks observed at the climatic transitions 2/1 and 6/5 and in stage 5 are in contrast to a predicted reduction of interglacial productivity at this location. A possible explanation might be the onset of the modern circulation pattern. The transition from Ba-enriched deep water to lower contents in the Atlantic might have resulted in an enhanced deposition of Ba in the Pacific.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310050094
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  • 10
    Electronic Resource
    Electronic Resource
    Late Quaternary sediment dating and quantification of lateral sediment redistribution applying 230Thex: a study from the eastern Atlantic sector of the Southern Ocean (1996)
    Springer
    Geologische Rundschau 85 (1996), S. 554-566 
    Details
    ISSN: 0016-7835
    Keywords: Key words High-resolution dating ; 230Thex constant flux models ; Sediment focusing ; Sediment winnowing ; Particle flux reconstruction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  High-resolution records of the natural radionuclide 230Th were measured in sediments from the eastern Atlantic sector of the Antarctic circumpolar current to obtain a detailed reconstruction of the sedimentation history of this key area for global climate change during the late Quaternary. High-resolution dating rests on the assumption that the 230Thex flux to the sediments is constant. Short periods of drastically increased sediment accumulation rates (up to a factor of 8) were determined in the sediments of the Antarctic zone during the climate optima at the beginning of the Holocene and the isotope stage 5e. By comparing expected and measured accumulation rate of 230Thex, lateral sediment redistribution was quantified and vertical particle rain rates originating from the surface water above were calculated. We show that lateral contributions locally were up to 6.5 times higher than the vertical particle rain rates. At other locations only 15% of the expected vertical particle rain rate were deposited.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310050096
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