Records of the Laschamps geomagnetic polarity excursion from Black Sea sediments: magnetite versus greigite, discrete sample versus U-channel data
SUMMARY Magnetostratigraphic investigation of sediment cores from two different water depths in the SE Black Sea based on discrete samples, and parallel U-channels in one of the cores, yielded high-resolution records of geomagnetic field variations from the past about 68 ka. Age constrains are provi...
Published in: | Geophysical Journal International |
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Oxford University Press (OUP)
2020
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Online Access: | http://dx.doi.org/10.1093/gji/ggaa506 http://academic.oup.com/gji/advance-article-pdf/doi/10.1093/gji/ggaa506/33993635/ggaa506.pdf http://academic.oup.com/gji/article-pdf/224/2/1079/34446117/ggaa506.pdf |
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croxfordunivpr:10.1093/gji/ggaa506 2024-06-23T07:53:25+00:00 Records of the Laschamps geomagnetic polarity excursion from Black Sea sediments: magnetite versus greigite, discrete sample versus U-channel data Nowaczyk, Norbert R Liu, Jiabo Arz, Helge W Deutsche Forschungsgemeinschaft INTERDYNAMIC Gary Comer Science and Education Foundation Chinese Scholarship Council 2020 http://dx.doi.org/10.1093/gji/ggaa506 http://academic.oup.com/gji/advance-article-pdf/doi/10.1093/gji/ggaa506/33993635/ggaa506.pdf http://academic.oup.com/gji/article-pdf/224/2/1079/34446117/ggaa506.pdf en eng Oxford University Press (OUP) http://creativecommons.org/licenses/by/4.0/ Geophysical Journal International volume 224, issue 2, page 1079-1095 ISSN 0956-540X 1365-246X journal-article 2020 croxfordunivpr https://doi.org/10.1093/gji/ggaa506 2024-06-11T04:21:36Z SUMMARY Magnetostratigraphic investigation of sediment cores from two different water depths in the SE Black Sea based on discrete samples, and parallel U-channels in one of the cores, yielded high-resolution records of geomagnetic field variations from the past about 68 ka. Age constrains are provided by three tephra layers of known age, accelerator mass spectrometry 14C dating, and by tuning element ratios obtained from X-ray fluorescence scanning to the oxygen isotope record from Greenland ice cores. Sedimentation rates vary from a minimum of ∼5 cm ka−1 in the Holocene to a maximum of ∼50 cm ka−1 in glacial marine isotope stage 4. Completely reversed inclinations and declinations as well as pronounced lows in relative palaeointensity around 41 ka provide evidence for the Laschamps geomagnetic polarity excursion. In one of the investigated cores also a fragmentary record of the Mono Lake excursion at 34.5 ka could be revealed. However, the palaeomagnetic records are more or less affected by greigite, a diagenetically formed magnetic iron sulphide. By definition of an exclusion criterion based on the ratio of saturation magnetization over volume susceptibility, greigite-bearing samples were removed from the palaeomagnetic data. Thus, only 25–55 per cent of the samples were left in the palaeomagnetic records obtained from sediments from the shallower coring site. The palaeomagnetic record from the deeper site, based on both discrete samples and U-channels, is much less affected by greigite. The comparison of palaeomagnetic data shows that the major features of the Laschamps polarity excursion were similarly recovered by both sampling techniques. However, several intervals had to be removed from the U-channel record due to the presence of greigite, carrying anomalous directions. By comparison to discrete sample data, also some directional artefacts in the U-channel record, caused by low-pass filtering of the broad magnetometer response functions, averaging across fast directional and large amplitude changes, can ... Article in Journal/Newspaper Greenland Greenland ice cores Oxford University Press Greenland Geophysical Journal International 224 2 1079 1095 |
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Open Polar |
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Oxford University Press |
op_collection_id |
croxfordunivpr |
language |
English |
description |
SUMMARY Magnetostratigraphic investigation of sediment cores from two different water depths in the SE Black Sea based on discrete samples, and parallel U-channels in one of the cores, yielded high-resolution records of geomagnetic field variations from the past about 68 ka. Age constrains are provided by three tephra layers of known age, accelerator mass spectrometry 14C dating, and by tuning element ratios obtained from X-ray fluorescence scanning to the oxygen isotope record from Greenland ice cores. Sedimentation rates vary from a minimum of ∼5 cm ka−1 in the Holocene to a maximum of ∼50 cm ka−1 in glacial marine isotope stage 4. Completely reversed inclinations and declinations as well as pronounced lows in relative palaeointensity around 41 ka provide evidence for the Laschamps geomagnetic polarity excursion. In one of the investigated cores also a fragmentary record of the Mono Lake excursion at 34.5 ka could be revealed. However, the palaeomagnetic records are more or less affected by greigite, a diagenetically formed magnetic iron sulphide. By definition of an exclusion criterion based on the ratio of saturation magnetization over volume susceptibility, greigite-bearing samples were removed from the palaeomagnetic data. Thus, only 25–55 per cent of the samples were left in the palaeomagnetic records obtained from sediments from the shallower coring site. The palaeomagnetic record from the deeper site, based on both discrete samples and U-channels, is much less affected by greigite. The comparison of palaeomagnetic data shows that the major features of the Laschamps polarity excursion were similarly recovered by both sampling techniques. However, several intervals had to be removed from the U-channel record due to the presence of greigite, carrying anomalous directions. By comparison to discrete sample data, also some directional artefacts in the U-channel record, caused by low-pass filtering of the broad magnetometer response functions, averaging across fast directional and large amplitude changes, can ... |
author2 |
Deutsche Forschungsgemeinschaft INTERDYNAMIC Gary Comer Science and Education Foundation Chinese Scholarship Council |
format |
Article in Journal/Newspaper |
author |
Nowaczyk, Norbert R Liu, Jiabo Arz, Helge W |
spellingShingle |
Nowaczyk, Norbert R Liu, Jiabo Arz, Helge W Records of the Laschamps geomagnetic polarity excursion from Black Sea sediments: magnetite versus greigite, discrete sample versus U-channel data |
author_facet |
Nowaczyk, Norbert R Liu, Jiabo Arz, Helge W |
author_sort |
Nowaczyk, Norbert R |
title |
Records of the Laschamps geomagnetic polarity excursion from Black Sea sediments: magnetite versus greigite, discrete sample versus U-channel data |
title_short |
Records of the Laschamps geomagnetic polarity excursion from Black Sea sediments: magnetite versus greigite, discrete sample versus U-channel data |
title_full |
Records of the Laschamps geomagnetic polarity excursion from Black Sea sediments: magnetite versus greigite, discrete sample versus U-channel data |
title_fullStr |
Records of the Laschamps geomagnetic polarity excursion from Black Sea sediments: magnetite versus greigite, discrete sample versus U-channel data |
title_full_unstemmed |
Records of the Laschamps geomagnetic polarity excursion from Black Sea sediments: magnetite versus greigite, discrete sample versus U-channel data |
title_sort |
records of the laschamps geomagnetic polarity excursion from black sea sediments: magnetite versus greigite, discrete sample versus u-channel data |
publisher |
Oxford University Press (OUP) |
publishDate |
2020 |
url |
http://dx.doi.org/10.1093/gji/ggaa506 http://academic.oup.com/gji/advance-article-pdf/doi/10.1093/gji/ggaa506/33993635/ggaa506.pdf http://academic.oup.com/gji/article-pdf/224/2/1079/34446117/ggaa506.pdf |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland Greenland ice cores |
genre_facet |
Greenland Greenland ice cores |
op_source |
Geophysical Journal International volume 224, issue 2, page 1079-1095 ISSN 0956-540X 1365-246X |
op_rights |
http://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.1093/gji/ggaa506 |
container_title |
Geophysical Journal International |
container_volume |
224 |
container_issue |
2 |
container_start_page |
1079 |
op_container_end_page |
1095 |
_version_ |
1802645032752119808 |