Assessing Holocene and late Pleistocene geomagnetic dipole field variability
Palaeomagnetic studies of continuous geological archives and archaeological artefacts are required to reconstruct geomagnetic field changes beyond the range of historical observations. In this thesis I assess the reliability of sedimentary palaeomagnetic data and Holocene dipole field reconstruction...
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Department of Earth and Ecosystem Sciences, Lund University
2011
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Online Access: | https://lup.lub.lu.se/record/1962850 https://portal.research.lu.se/files/3607470/1962870.pdf |
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ftulundlup:oai:lup.lub.lu.se:cff8d825-7aa2-4ea8-9a23-131a5bd19d22 2023-05-15T16:19:41+02:00 Assessing Holocene and late Pleistocene geomagnetic dipole field variability Nilsson, Andreas 2011 application/pdf https://lup.lub.lu.se/record/1962850 https://portal.research.lu.se/files/3607470/1962870.pdf eng eng Department of Earth and Ecosystem Sciences, Lund University https://lup.lub.lu.se/record/1962850 urn:isbn:978-91-86746-69-8 https://portal.research.lu.se/files/3607470/1962870.pdf scopus:84856183196 info:eu-repo/semantics/openAccess Lundqua thesis; (64) (2011) ISSN: 0281-3033 Geology Geomagnetic field palaeomagnetism the Holocene dipole tilt dipole moment cosmogenic radionuclides thesis/doccomp info:eu-repo/semantics/doctoralThesis text 2011 ftulundlup 2023-02-01T23:35:23Z Palaeomagnetic studies of continuous geological archives and archaeological artefacts are required to reconstruct geomagnetic field changes beyond the range of historical observations. In this thesis I assess the reliability of sedimentary palaeomagnetic data and Holocene dipole field reconstructions. New palaeomagnetic records are presented from a maar crater lake in New Zealand and a post-glacial lake in Sweden. The fidelity of the data is evaluated through comparisons with sediment parameters sensitive to environmental change and measurement of cosmogenic radionuclides. The results are used to date the sediments and to study regional and global geomagnetic field variations over the past 50,000 years. The Holocene dipole tilt variation is reconstructed by averaging virtual geomagnetic poles from five sedimentary palaeomagnetic records. The data are selected based on palaeomagnetic quality, chronologic constraint and location, with an emphasis on attaining a globally well-distributed data set. The results indicate a cyclical behaviour of the dipole tilt with a period of c. 1350 years. In addition, two preferred states of the dipole axis are identified with north geomagnetic pole longitudes confined to c. 120° West or 30° East. The performance of the dipole tilt reconstruction is compared to more complex geomagnetic field models. The comparison highlights inconsistencies within the sedimentary palaeomagnetic database that may smooth out variations of the dipole component and potentially shift power to higher degree components of the more complex field models. Independent geomagnetic field intensity data from western Eurasia and North America are shown to be consistent with the dipole tilt reconstruction. The cyclical tilt variation and the two preferred states of the dipole axis are interpreted in terms of displacement and/or distortions of high latitude flux lobes on the core mantle boundary. Based on palaeomagnetic directions and palaeointensity data, the two tilt maxima at 2650 and 1200 years BP are ... Doctoral or Postdoctoral Thesis Geomagnetic Pole Lund University Publications (LUP) Crater Lake ENVELOPE(-60.667,-60.667,-62.983,-62.983) Glacial Lake ENVELOPE(-129.463,-129.463,58.259,58.259) New Zealand |
institution |
Open Polar |
collection |
Lund University Publications (LUP) |
op_collection_id |
ftulundlup |
language |
English |
topic |
Geology Geomagnetic field palaeomagnetism the Holocene dipole tilt dipole moment cosmogenic radionuclides |
spellingShingle |
Geology Geomagnetic field palaeomagnetism the Holocene dipole tilt dipole moment cosmogenic radionuclides Nilsson, Andreas Assessing Holocene and late Pleistocene geomagnetic dipole field variability |
topic_facet |
Geology Geomagnetic field palaeomagnetism the Holocene dipole tilt dipole moment cosmogenic radionuclides |
description |
Palaeomagnetic studies of continuous geological archives and archaeological artefacts are required to reconstruct geomagnetic field changes beyond the range of historical observations. In this thesis I assess the reliability of sedimentary palaeomagnetic data and Holocene dipole field reconstructions. New palaeomagnetic records are presented from a maar crater lake in New Zealand and a post-glacial lake in Sweden. The fidelity of the data is evaluated through comparisons with sediment parameters sensitive to environmental change and measurement of cosmogenic radionuclides. The results are used to date the sediments and to study regional and global geomagnetic field variations over the past 50,000 years. The Holocene dipole tilt variation is reconstructed by averaging virtual geomagnetic poles from five sedimentary palaeomagnetic records. The data are selected based on palaeomagnetic quality, chronologic constraint and location, with an emphasis on attaining a globally well-distributed data set. The results indicate a cyclical behaviour of the dipole tilt with a period of c. 1350 years. In addition, two preferred states of the dipole axis are identified with north geomagnetic pole longitudes confined to c. 120° West or 30° East. The performance of the dipole tilt reconstruction is compared to more complex geomagnetic field models. The comparison highlights inconsistencies within the sedimentary palaeomagnetic database that may smooth out variations of the dipole component and potentially shift power to higher degree components of the more complex field models. Independent geomagnetic field intensity data from western Eurasia and North America are shown to be consistent with the dipole tilt reconstruction. The cyclical tilt variation and the two preferred states of the dipole axis are interpreted in terms of displacement and/or distortions of high latitude flux lobes on the core mantle boundary. Based on palaeomagnetic directions and palaeointensity data, the two tilt maxima at 2650 and 1200 years BP are ... |
format |
Doctoral or Postdoctoral Thesis |
author |
Nilsson, Andreas |
author_facet |
Nilsson, Andreas |
author_sort |
Nilsson, Andreas |
title |
Assessing Holocene and late Pleistocene geomagnetic dipole field variability |
title_short |
Assessing Holocene and late Pleistocene geomagnetic dipole field variability |
title_full |
Assessing Holocene and late Pleistocene geomagnetic dipole field variability |
title_fullStr |
Assessing Holocene and late Pleistocene geomagnetic dipole field variability |
title_full_unstemmed |
Assessing Holocene and late Pleistocene geomagnetic dipole field variability |
title_sort |
assessing holocene and late pleistocene geomagnetic dipole field variability |
publisher |
Department of Earth and Ecosystem Sciences, Lund University |
publishDate |
2011 |
url |
https://lup.lub.lu.se/record/1962850 https://portal.research.lu.se/files/3607470/1962870.pdf |
long_lat |
ENVELOPE(-60.667,-60.667,-62.983,-62.983) ENVELOPE(-129.463,-129.463,58.259,58.259) |
geographic |
Crater Lake Glacial Lake New Zealand |
geographic_facet |
Crater Lake Glacial Lake New Zealand |
genre |
Geomagnetic Pole |
genre_facet |
Geomagnetic Pole |
op_source |
Lundqua thesis; (64) (2011) ISSN: 0281-3033 |
op_relation |
https://lup.lub.lu.se/record/1962850 urn:isbn:978-91-86746-69-8 https://portal.research.lu.se/files/3607470/1962870.pdf scopus:84856183196 |
op_rights |
info:eu-repo/semantics/openAccess |
_version_ |
1766006089928671232 |