High-resolution record of the Laschamp geomagnetic excursion at the Blake-Bahama Outer Ridge
Geomagnetic excursions are brief deviations of the geomagnetic field from behaviour expected during ‘normal secular’ variation. The Laschamp excursion at ∼41 ka was one such deviation. Previously published records suggest rapid changes in field direction and a concurrent substantial decrease in fiel...
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fthighwire:oai:open-archive.highwire.org:gji:195/3/1519 2023-05-15T16:30:02+02:00 High-resolution record of the Laschamp geomagnetic excursion at the Blake-Bahama Outer Ridge Bourne, Mark D. Mac Niocaill, Conall Thomas, Alex L. Henderson, Gideon M. 2013-12-01 00:00:00.0 text/html http://gji.oxfordjournals.org/cgi/content/short/195/3/1519 https://doi.org/10.1093/gji/ggt327 en eng Oxford University Press http://gji.oxfordjournals.org/cgi/content/short/195/3/1519 http://dx.doi.org/10.1093/gji/ggt327 Copyright (C) 2013, Oxford University Press Geomagnetism rock magnetism and palaeomagnetism TEXT 2013 fthighwire https://doi.org/10.1093/gji/ggt327 2018-04-07T06:27:59Z Geomagnetic excursions are brief deviations of the geomagnetic field from behaviour expected during ‘normal secular’ variation. The Laschamp excursion at ∼41 ka was one such deviation. Previously published records suggest rapid changes in field direction and a concurrent substantial decrease in field intensity associated with this excursion. Accurate dating of excursions, and determination of their durations from multiple locations, is vital to our understanding of global field behaviour during these deviations. We present here high-resolution palaeomagnetic records of the Laschamp excursion obtained from two Ocean Drilling Program (ODP) Sites, 1061 and 1062 on the Blake-Bahama Outer Ridge (ODP Leg 172). High sedimentation rates (∼30–40 cm kyr−1) at these locations allow determination of transitional field behaviour during the excursion. Palaeomagnetic measurements of discrete samples from four cores reveal a single excursional feature, across an interval of 30 cm, associated with a broader palaeointensity low. We determine the age and duration of the Laschamp excursion using a stratigraphy linked to the δ18O record from the Greenland ice cores. This chronology dates the Laschamp excursion at the Blake Ridge to 41.3 ka. The excursion is characterized by rapid transitions (less than 200 yr) between stable normal polarity and a partially reversed polarity state. The palaeointensity record is in good agreement between the two sites, revealing two prominent minima. The first minimum is associated with the Laschamp excursion at 41 ka and the second corresponds to the Mono Lake excursion at ∼35.5 ka. We determine that the directional excursion during the Laschamp at this location was no longer than ∼400 yr, occurring within a palaeointensity minimum that lasted 2000 yr. The Laschamp excursion at this location is much shorter in duration than the Blake and Iceland Basin excursions. Text Greenland Greenland ice cores Iceland HighWire Press (Stanford University) Greenland Geophysical Journal International 195 3 1519 1533 |
institution |
Open Polar |
collection |
HighWire Press (Stanford University) |
op_collection_id |
fthighwire |
language |
English |
topic |
Geomagnetism rock magnetism and palaeomagnetism |
spellingShingle |
Geomagnetism rock magnetism and palaeomagnetism Bourne, Mark D. Mac Niocaill, Conall Thomas, Alex L. Henderson, Gideon M. High-resolution record of the Laschamp geomagnetic excursion at the Blake-Bahama Outer Ridge |
topic_facet |
Geomagnetism rock magnetism and palaeomagnetism |
description |
Geomagnetic excursions are brief deviations of the geomagnetic field from behaviour expected during ‘normal secular’ variation. The Laschamp excursion at ∼41 ka was one such deviation. Previously published records suggest rapid changes in field direction and a concurrent substantial decrease in field intensity associated with this excursion. Accurate dating of excursions, and determination of their durations from multiple locations, is vital to our understanding of global field behaviour during these deviations. We present here high-resolution palaeomagnetic records of the Laschamp excursion obtained from two Ocean Drilling Program (ODP) Sites, 1061 and 1062 on the Blake-Bahama Outer Ridge (ODP Leg 172). High sedimentation rates (∼30–40 cm kyr−1) at these locations allow determination of transitional field behaviour during the excursion. Palaeomagnetic measurements of discrete samples from four cores reveal a single excursional feature, across an interval of 30 cm, associated with a broader palaeointensity low. We determine the age and duration of the Laschamp excursion using a stratigraphy linked to the δ18O record from the Greenland ice cores. This chronology dates the Laschamp excursion at the Blake Ridge to 41.3 ka. The excursion is characterized by rapid transitions (less than 200 yr) between stable normal polarity and a partially reversed polarity state. The palaeointensity record is in good agreement between the two sites, revealing two prominent minima. The first minimum is associated with the Laschamp excursion at 41 ka and the second corresponds to the Mono Lake excursion at ∼35.5 ka. We determine that the directional excursion during the Laschamp at this location was no longer than ∼400 yr, occurring within a palaeointensity minimum that lasted 2000 yr. The Laschamp excursion at this location is much shorter in duration than the Blake and Iceland Basin excursions. |
format |
Text |
author |
Bourne, Mark D. Mac Niocaill, Conall Thomas, Alex L. Henderson, Gideon M. |
author_facet |
Bourne, Mark D. Mac Niocaill, Conall Thomas, Alex L. Henderson, Gideon M. |
author_sort |
Bourne, Mark D. |
title |
High-resolution record of the Laschamp geomagnetic excursion at the Blake-Bahama Outer Ridge |
title_short |
High-resolution record of the Laschamp geomagnetic excursion at the Blake-Bahama Outer Ridge |
title_full |
High-resolution record of the Laschamp geomagnetic excursion at the Blake-Bahama Outer Ridge |
title_fullStr |
High-resolution record of the Laschamp geomagnetic excursion at the Blake-Bahama Outer Ridge |
title_full_unstemmed |
High-resolution record of the Laschamp geomagnetic excursion at the Blake-Bahama Outer Ridge |
title_sort |
high-resolution record of the laschamp geomagnetic excursion at the blake-bahama outer ridge |
publisher |
Oxford University Press |
publishDate |
2013 |
url |
http://gji.oxfordjournals.org/cgi/content/short/195/3/1519 https://doi.org/10.1093/gji/ggt327 |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland Greenland ice cores Iceland |
genre_facet |
Greenland Greenland ice cores Iceland |
op_relation |
http://gji.oxfordjournals.org/cgi/content/short/195/3/1519 http://dx.doi.org/10.1093/gji/ggt327 |
op_rights |
Copyright (C) 2013, Oxford University Press |
op_doi |
https://doi.org/10.1093/gji/ggt327 |
container_title |
Geophysical Journal International |
container_volume |
195 |
container_issue |
3 |
container_start_page |
1519 |
op_container_end_page |
1533 |
_version_ |
1766019742227759104 |