When and why sediments fail to record the geomagnetic field during polarity reversals
We present four new records of the Matuyama–Brunhes (M–B) reversal from sediments of the Equatorial Indian Ocean, West Equatorial Pacific and North Atlantic Oceans with deposition rates between 2 cm/kyr and 4.5 cm/kyr. The magnetic measurements were performed using 8 cc cubic samples and provided we...
Published in: | Earth and Planetary Science Letters |
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Main Authors: | , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Elsevier Science Bv
2016
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Subjects: | |
Online Access: | https://archimer.ifremer.fr/doc/00347/45868/45561.pdf https://archimer.ifremer.fr/doc/00347/45868/45562.pdf https://archimer.ifremer.fr/doc/00347/45868/45564.pdf https://archimer.ifremer.fr/doc/00347/45868/45565.pdf https://archimer.ifremer.fr/doc/00347/45868/45567.pdf https://doi.org/10.1016/j.epsl.2016.07.055 https://archimer.ifremer.fr/doc/00347/45868/ |
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ftarchimer:oai:archimer.ifremer.fr:45868 |
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openpolar |
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Open Polar |
collection |
Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) |
op_collection_id |
ftarchimer |
language |
English |
topic |
geomagnetic reversals magnetization acquisition rock magnetism sediment demagnetization |
spellingShingle |
geomagnetic reversals magnetization acquisition rock magnetism sediment demagnetization Valet, Jean-pierre Meynadier, Laure Simon, Quentin Thouveny, Nicolas When and why sediments fail to record the geomagnetic field during polarity reversals |
topic_facet |
geomagnetic reversals magnetization acquisition rock magnetism sediment demagnetization |
description |
We present four new records of the Matuyama–Brunhes (M–B) reversal from sediments of the Equatorial Indian Ocean, West Equatorial Pacific and North Atlantic Oceans with deposition rates between 2 cm/kyr and 4.5 cm/kyr. The magnetic measurements were performed using 8 cc cubic samples and provided well-defined reverse and normal polarity directions prior and after the last reversal. In three records stepwise demagnetization of the transitional samples revealed a succession of scattered directions instead of a well-defined characteristic component of magnetization. There is no relationship with changes in magnetic mineralogy, magnetic concentration and magnetic grain sizes. This behavior could be caused by weakly magnetized sediment. However the transitional samples of two cores have almost three orders of magnitude stronger magnetizations than the non-transitional samples that yielded unambiguous primary directions in the other two cores. Moreover a similar proportion of magnetic grains was aligned in all records. Therefore, the large amount of magnetic grains oriented by the weak transitional field did not contribute to improve the definition of the characteristic component. We infer that the weakness of the field might not be only responsible. Assuming that the transitional period is dominated by a multipolar field, it is likely that the rapidly moving non-dipole components generated different directions that were recorded over the 2 cm stratigraphic thickness of each sample. These components are carried by grains with similar magnetic properties yielding scattered directions during demagnetization. In contrast, the strongly magnetized sediments of the fourth core from the West Equatorial Pacific Ocean were exempt of problems during demagnetization. The declinations rotate smoothly between the two polarities while the inclinations remain close to zero. This scenario results from post-depositional realignment that integrated various amounts of pre- and post-transitional magnetic directions within each sample. The present results point out the impossibility of extracting reliable information on geomagnetic reversals from low-medium deposition rate sediments with the current sampling techniques. Among other features, they put in question the relationship between reversal duration and site latitude. |
format |
Article in Journal/Newspaper |
author |
Valet, Jean-pierre Meynadier, Laure Simon, Quentin Thouveny, Nicolas |
author_facet |
Valet, Jean-pierre Meynadier, Laure Simon, Quentin Thouveny, Nicolas |
author_sort |
Valet, Jean-pierre |
title |
When and why sediments fail to record the geomagnetic field during polarity reversals |
title_short |
When and why sediments fail to record the geomagnetic field during polarity reversals |
title_full |
When and why sediments fail to record the geomagnetic field during polarity reversals |
title_fullStr |
When and why sediments fail to record the geomagnetic field during polarity reversals |
title_full_unstemmed |
When and why sediments fail to record the geomagnetic field during polarity reversals |
title_sort |
when and why sediments fail to record the geomagnetic field during polarity reversals |
publisher |
Elsevier Science Bv |
publishDate |
2016 |
url |
https://archimer.ifremer.fr/doc/00347/45868/45561.pdf https://archimer.ifremer.fr/doc/00347/45868/45562.pdf https://archimer.ifremer.fr/doc/00347/45868/45564.pdf https://archimer.ifremer.fr/doc/00347/45868/45565.pdf https://archimer.ifremer.fr/doc/00347/45868/45567.pdf https://doi.org/10.1016/j.epsl.2016.07.055 https://archimer.ifremer.fr/doc/00347/45868/ |
geographic |
Indian Pacific |
geographic_facet |
Indian Pacific |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
Earth And Planetary Science Letters (0012-821X) (Elsevier Science Bv), 2016-11 , Vol. 453 , P. 96-107 |
op_relation |
info:eu-repo/grantAgreement/EC/FP7/339899/EU//EDIFICE https://archimer.ifremer.fr/doc/00347/45868/45561.pdf https://archimer.ifremer.fr/doc/00347/45868/45562.pdf https://archimer.ifremer.fr/doc/00347/45868/45564.pdf https://archimer.ifremer.fr/doc/00347/45868/45565.pdf https://archimer.ifremer.fr/doc/00347/45868/45567.pdf doi:10.1016/j.epsl.2016.07.055 https://archimer.ifremer.fr/doc/00347/45868/ |
op_rights |
2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). info:eu-repo/semantics/openAccess restricted use |
op_rightsnorm |
CC-BY-NC-ND |
op_doi |
https://doi.org/10.1016/j.epsl.2016.07.055 |
container_title |
Earth and Planetary Science Letters |
container_volume |
453 |
container_start_page |
96 |
op_container_end_page |
107 |
_version_ |
1766136357434949632 |
spelling |
ftarchimer:oai:archimer.ifremer.fr:45868 2023-05-15T17:36:46+02:00 When and why sediments fail to record the geomagnetic field during polarity reversals Valet, Jean-pierre Meynadier, Laure Simon, Quentin Thouveny, Nicolas 2016-11 application/pdf https://archimer.ifremer.fr/doc/00347/45868/45561.pdf https://archimer.ifremer.fr/doc/00347/45868/45562.pdf https://archimer.ifremer.fr/doc/00347/45868/45564.pdf https://archimer.ifremer.fr/doc/00347/45868/45565.pdf https://archimer.ifremer.fr/doc/00347/45868/45567.pdf https://doi.org/10.1016/j.epsl.2016.07.055 https://archimer.ifremer.fr/doc/00347/45868/ eng eng Elsevier Science Bv info:eu-repo/grantAgreement/EC/FP7/339899/EU//EDIFICE https://archimer.ifremer.fr/doc/00347/45868/45561.pdf https://archimer.ifremer.fr/doc/00347/45868/45562.pdf https://archimer.ifremer.fr/doc/00347/45868/45564.pdf https://archimer.ifremer.fr/doc/00347/45868/45565.pdf https://archimer.ifremer.fr/doc/00347/45868/45567.pdf doi:10.1016/j.epsl.2016.07.055 https://archimer.ifremer.fr/doc/00347/45868/ 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). info:eu-repo/semantics/openAccess restricted use CC-BY-NC-ND Earth And Planetary Science Letters (0012-821X) (Elsevier Science Bv), 2016-11 , Vol. 453 , P. 96-107 geomagnetic reversals magnetization acquisition rock magnetism sediment demagnetization text Publication info:eu-repo/semantics/article 2016 ftarchimer https://doi.org/10.1016/j.epsl.2016.07.055 2021-09-23T20:28:42Z We present four new records of the Matuyama–Brunhes (M–B) reversal from sediments of the Equatorial Indian Ocean, West Equatorial Pacific and North Atlantic Oceans with deposition rates between 2 cm/kyr and 4.5 cm/kyr. The magnetic measurements were performed using 8 cc cubic samples and provided well-defined reverse and normal polarity directions prior and after the last reversal. In three records stepwise demagnetization of the transitional samples revealed a succession of scattered directions instead of a well-defined characteristic component of magnetization. There is no relationship with changes in magnetic mineralogy, magnetic concentration and magnetic grain sizes. This behavior could be caused by weakly magnetized sediment. However the transitional samples of two cores have almost three orders of magnitude stronger magnetizations than the non-transitional samples that yielded unambiguous primary directions in the other two cores. Moreover a similar proportion of magnetic grains was aligned in all records. Therefore, the large amount of magnetic grains oriented by the weak transitional field did not contribute to improve the definition of the characteristic component. We infer that the weakness of the field might not be only responsible. Assuming that the transitional period is dominated by a multipolar field, it is likely that the rapidly moving non-dipole components generated different directions that were recorded over the 2 cm stratigraphic thickness of each sample. These components are carried by grains with similar magnetic properties yielding scattered directions during demagnetization. In contrast, the strongly magnetized sediments of the fourth core from the West Equatorial Pacific Ocean were exempt of problems during demagnetization. The declinations rotate smoothly between the two polarities while the inclinations remain close to zero. This scenario results from post-depositional realignment that integrated various amounts of pre- and post-transitional magnetic directions within each sample. The present results point out the impossibility of extracting reliable information on geomagnetic reversals from low-medium deposition rate sediments with the current sampling techniques. Among other features, they put in question the relationship between reversal duration and site latitude. Article in Journal/Newspaper North Atlantic Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) Indian Pacific Earth and Planetary Science Letters 453 96 107 |