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Bohrmann, Horst (2013): Radioisotope stratigraphy, sedimentology and geochemistry of Late Quaternary sediments from the Eastern Arctic Ocean [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.809032

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Abstract:
To reconstruct Recent and past sedimentary environments, marine sediments of Upper Pleistocene and Holocene ages from the eastern Arctic Ocean and especially from the Nansen-Gakkel Ridge (NGR) were investigated by means of radioisotopic, geochemical and sedimentological methods. In combination with mass physical property data and lithological analysis these investigations allow clearly to characterize the depositional environments.
Age dating by using the radioisotope 230Th gives evidence that the investigated sediments from the NGR are younger than 250,000 years.
Identical lithological sediment sequences within and between sediment cores from the NGR can be related to sedimentary processes which are clearly controlled by palaeoclimate. The sediments consist predominantly of siliciclastic, terrigenous ice-rafted detritus (IRD) deriving from assorted and redeposited sediments from the Siberian shelfs. By their geochemical composition the sediments are similar to mudstone, graywacke and arcose. Sea-ice as well as icebergs play a major roll in marine arctic sedimentation.
In the NGR area rapid change in sedimentary conditions can be detected 128,000 years ago. This was due to drastic change in the kind of ice cover, resulting from rapid climatic change within only hundreds of years. So icebergs, deriving mostly from Siberian shelfs, vanished and sea-ice became dominant in the eastern Arctic Ocean.
At least three short-period retreats of the shelf ice between 186,000 and 128,000 years are responsible for the change of coarse to fine-grained sediments in the NGR area. These warmer stages lasted between 1,000 and 3,000 years.
By monitoring and comparing the distribution patterns of sedimentologic, mass physical and geochemical properties with 230Th ex activity distribution patterns in the sediment cores from the NGR, there is clear evidence that sediment dilution is responsible for high 230Th ex activity variations. Thus sedimentation rate is the controlling factor of 230Th ex activity variations. The 230Th flux density in sediments from the NGR seems to be highly dependent On topographic Position. The distribution patterns of chemical elements in sediment cores are in general governed by lithology.
The derivation of a method for dry bulk density determination gave the opportunity to establish a high resolution stratigraphy on sediment cores from the eastern Arctic Ocean, based on 230Thex activity analyses. For the first time sedimentation and accumulation rates were determined for recent sediments in the eastern Arctic Ocean by 230Th ex analyses. Bulk accumulation rates are highly variable in space and time, ranging between 0.2 and 30 g/cm**2/ka. In the sediments from the NGR highly variable accumulation rates are related to the kind of ice cover.
There is evidence for hydrothermal input into the sediments of the NGR. Hydrothermal activity probably also influences surficial sediments in the Sofia Basin. High contents of As are typical for surficial sediments from the NGR. In particular SL 370-20 from the bottom of the rift valley has As contents exceeding in parts 300 ppm. Hydrothermal activity can be traced back to at least 130,000 years.
Recent to subrecent tectonic activity is documented by the rock debris in KAL 370 from the NGR. In four other sediment cores from the NGR rift valley area tectonically induced movements can be dated to about 130,000 years ago, related most probably to the rapid climate change.
Processes of early diagenesis in sediments from the NGR caused the aobilization and redeposition of Fe, Mn and Mo. These diagenetic processes probably took place during the last 130,000 years.
In sediment cores from the NGR high amounts of kaolinite are related to coarse grained siliciclastic material, probably indicating reworking and redeposition of siberian sandstones with kaolinitic binding material. In contrast to kaolinite, illite is correlated to total clay and 232Th contents.
Aragonite, associated with serpentinites in the rift valley area of the NGR, was precipitated under cold bottom-water conditions. Preliminary data result in a time of formation about 60 - 80 ka ago. Manganese precipitates with high Ni contents, which can be related to the ultrabasic rocks, are of similar age.
Related to:
Bohrmann, Horst (1991): Radioisotopenstratigraphie, Sedimentologie und Geochemie jungquartärer Sedimente des östlichen Arktischen Ozeans (Radioisotope Stratigraphy, Sedimentology and Geochemistry of Late Quaternary Sediments from the Eastern Arctic Ocean). Berichte zur Polarforschung = Reports on Polar Research, 95, 133 pp, https://doi.org/10.2312/BzP_0095_1991
Project(s):
Paleoenvironmental Reconstructions from Marine Sediments @ AWI (AWI_Paleo)
Coverage:
Median Latitude: 84.915980 * Median Longitude: 23.699315 * South-bound Latitude: 78.750000 * West-bound Longitude: 1.775000 * North-bound Latitude: 86.135000 * East-bound Longitude: 32.058333
Date/Time Start: 1987-06-08T00:00:00 * Date/Time End: 1987-10-08T00:00:00
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
24 datasets

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Datasets listed in this publication series

  1. Bohrmann, H (2013): (Appendix Table 1) Geochemistry and sedimentology of surface sediment samples from the Arctic Ocean. https://doi.org/10.1594/PANGAEA.809007
  2. Bohrmann, H (2013): (Appendix Table 2) Geochemistry and sedimentology of sediment core PS1526-12. https://doi.org/10.1594/PANGAEA.809008
  3. Bohrmann, H (2013): (Appendix Table 3) Geochemistry and sedimentology of sediment core PS1526-20. https://doi.org/10.1594/PANGAEA.809009
  4. Bohrmann, H (2013): (Appendix Table 4) Geochemistry and sedimentology of sediment core PS1524-2. https://doi.org/10.1594/PANGAEA.809010
  5. Bohrmann, H (2013): (Appendix Table 5) Isotope activity measured in surface sediment samples from the Arctic Ocean. https://doi.org/10.1594/PANGAEA.809011
  6. Bohrmann, H (2013): (Appendix Table 6) Isotope activity of sediment core PS1526-12. https://doi.org/10.1594/PANGAEA.809012
  7. Bohrmann, H (2013): (Appendix Table 7) Isotope activity of sediment core PS1526-20. https://doi.org/10.1594/PANGAEA.809013
  8. Bohrmann, H (2013): (Appendix Table 8) Isotope activity of sediment core PS1524-2. https://doi.org/10.1594/PANGAEA.809014
  9. Bohrmann, H (2013): (Appendix Table 9) Isotope activity of sediment core PS1528-3. https://doi.org/10.1594/PANGAEA.809015
  10. Bohrmann, H (2013): (Appendix Table 10) Isotope activity of sediment core PS1515-10. https://doi.org/10.1594/PANGAEA.809017
  11. Bohrmann, H (2013): (Appendix Table 10) Isotope activity of sediment core PS1521-14. https://doi.org/10.1594/PANGAEA.809018
  12. Bohrmann, H (2013): (Appendix Table 10) Isotope activity of sediment core PS1523-15. https://doi.org/10.1594/PANGAEA.809019
  13. Bohrmann, H (2013): (Appendix Table 10) Isotope activity of sediment core PS1524-1. https://doi.org/10.1594/PANGAEA.809020
  14. Bohrmann, H (2013): (Appendix Table 10) Isotope activity of sediment core PS1527-10. https://doi.org/10.1594/PANGAEA.809021
  15. Bohrmann, H (2013): (Appendix Table 10) Isotope activity of sediment core PS1529-7. https://doi.org/10.1594/PANGAEA.809022
  16. Bohrmann, H (2013): (Appendix Table 10) Isotope activity of sediment core PS1534-6. https://doi.org/10.1594/PANGAEA.809023
  17. Bohrmann, H (2013): (Appendix Table 11) Bulk sediment parameter of sediment core PS1524-2. https://doi.org/10.1594/PANGAEA.809024
  18. Bohrmann, H (2013): (Appendix Table 11) Bulk sediment parameter of sediment core PS1525-7. https://doi.org/10.1594/PANGAEA.809025
  19. Bohrmann, H (2013): (Appendix Table 11) Bulk sediment parameter of sediment core PS1526-12. https://doi.org/10.1594/PANGAEA.809026
  20. Bohrmann, H (2013): (Appendix Table 11) Bulk sediment parameter of sediment core PS1526-20. https://doi.org/10.1594/PANGAEA.809027
  21. Bohrmann, H (2013): (Appendix Table 11) Bulk sediment parameter of sediment core PS1527-12. https://doi.org/10.1594/PANGAEA.809028
  22. Bohrmann, H (2013): (Appendix Table 11) Bulk sediment parameter of sediment core PS1528-3. https://doi.org/10.1594/PANGAEA.809029
  23. Bohrmann, H (2013): (Appendix Table 11) Bulk sediment parameter of sediment core PS1529-8. https://doi.org/10.1594/PANGAEA.809030
  24. Bohrmann, H (2013): (Appendix Table 12) Accumulation rates of sediment core PS1524-2. https://doi.org/10.1594/PANGAEA.809031