A pseudo-Thellier relative palaeointensity record, and rock magnetic and geochemical parameters in relation to climate during the last 276 kyr in the Azores region
In the pseudo-Thellier method for relative palaeointensity determinations (Tauxe et al. 1995) the slope of the NRM intensity left after AF demagnetization versus ARM intensity gained at the same peak field is used as a palaeointensity measure. We tested this method on a marine core from the Azores,...
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1999
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fthighwire:oai:open-archive.highwire.org:gji:136/3/757 2023-05-15T16:51:33+02:00 A pseudo-Thellier relative palaeointensity record, and rock magnetic and geochemical parameters in relation to climate during the last 276 kyr in the Azores region Kruiver, P. P. Kok, Y. S. Dekkers, M. J. Langereis, C. G. Laj, C. 1999-03-01 00:00:00.0 text/html http://gji.oxfordjournals.org/cgi/content/short/136/3/757 https://doi.org/10.1046/j.1365-246x.1999.00777.x en eng Oxford University Press http://gji.oxfordjournals.org/cgi/content/short/136/3/757 http://dx.doi.org/10.1046/j.1365-246x.1999.00777.x Copyright (C) 1999, Oxford University Press Articles TEXT 1999 fthighwire https://doi.org/10.1046/j.1365-246x.1999.00777.x 2015-02-28T22:01:29Z In the pseudo-Thellier method for relative palaeointensity determinations (Tauxe et al. 1995) the slope of the NRM intensity left after AF demagnetization versus ARM intensity gained at the same peak field is used as a palaeointensity measure. We tested this method on a marine core from the Azores, spanning the last 276 kyr. We compared the pseudo-Thellier palaeointensity record with the conventional record obtained earlier by Lehman et al . (1996), who normalized NRM by SIRM. The two records show similar features: intensity lows with deviating palaeomagnetic directions at 40–45 ka and at 180–190 ka. The first interval is associated with the Laschamps excursion, while the 180–190 ka low represents the Iceland Basin excursion (Channell et al. 1997). The pseudo-Thellier method, in combination with a jackknife resampling scheme, provides error estimates on the palaeointensity. Spectral analysis of the rock magnetic parameters and the palaeointensity estimates shows orbitally forced periods, particularly 23 kyr for climatic precession. This suggests that palaeointensity is still slightly contaminated by climate. Fuzzy c -means cluster analysis of rock magnetic and geochemical parameters yields a seven-cluster model of predominantly calcareous clusters and detrital clusters. The clusters show a strong correlation with climate, for example samples from detrital clusters predominantly appear during rapid warming. Although both the pseudo-Thellier palaeointensity m a and fuzzy clusters show climatic influences, we have not been able to find an unambiguous connection between the clusters and m a . Text Iceland HighWire Press (Stanford University) Geophysical Journal International 136 3 757 770 |
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Articles Kruiver, P. P. Kok, Y. S. Dekkers, M. J. Langereis, C. G. Laj, C. A pseudo-Thellier relative palaeointensity record, and rock magnetic and geochemical parameters in relation to climate during the last 276 kyr in the Azores region |
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In the pseudo-Thellier method for relative palaeointensity determinations (Tauxe et al. 1995) the slope of the NRM intensity left after AF demagnetization versus ARM intensity gained at the same peak field is used as a palaeointensity measure. We tested this method on a marine core from the Azores, spanning the last 276 kyr. We compared the pseudo-Thellier palaeointensity record with the conventional record obtained earlier by Lehman et al . (1996), who normalized NRM by SIRM. The two records show similar features: intensity lows with deviating palaeomagnetic directions at 40–45 ka and at 180–190 ka. The first interval is associated with the Laschamps excursion, while the 180–190 ka low represents the Iceland Basin excursion (Channell et al. 1997). The pseudo-Thellier method, in combination with a jackknife resampling scheme, provides error estimates on the palaeointensity. Spectral analysis of the rock magnetic parameters and the palaeointensity estimates shows orbitally forced periods, particularly 23 kyr for climatic precession. This suggests that palaeointensity is still slightly contaminated by climate. Fuzzy c -means cluster analysis of rock magnetic and geochemical parameters yields a seven-cluster model of predominantly calcareous clusters and detrital clusters. The clusters show a strong correlation with climate, for example samples from detrital clusters predominantly appear during rapid warming. Although both the pseudo-Thellier palaeointensity m a and fuzzy clusters show climatic influences, we have not been able to find an unambiguous connection between the clusters and m a . |
format |
Text |
author |
Kruiver, P. P. Kok, Y. S. Dekkers, M. J. Langereis, C. G. Laj, C. |
author_facet |
Kruiver, P. P. Kok, Y. S. Dekkers, M. J. Langereis, C. G. Laj, C. |
author_sort |
Kruiver, P. P. |
title |
A pseudo-Thellier relative palaeointensity record, and rock magnetic and geochemical parameters in relation to climate during the last 276 kyr in the Azores region |
title_short |
A pseudo-Thellier relative palaeointensity record, and rock magnetic and geochemical parameters in relation to climate during the last 276 kyr in the Azores region |
title_full |
A pseudo-Thellier relative palaeointensity record, and rock magnetic and geochemical parameters in relation to climate during the last 276 kyr in the Azores region |
title_fullStr |
A pseudo-Thellier relative palaeointensity record, and rock magnetic and geochemical parameters in relation to climate during the last 276 kyr in the Azores region |
title_full_unstemmed |
A pseudo-Thellier relative palaeointensity record, and rock magnetic and geochemical parameters in relation to climate during the last 276 kyr in the Azores region |
title_sort |
pseudo-thellier relative palaeointensity record, and rock magnetic and geochemical parameters in relation to climate during the last 276 kyr in the azores region |
publisher |
Oxford University Press |
publishDate |
1999 |
url |
http://gji.oxfordjournals.org/cgi/content/short/136/3/757 https://doi.org/10.1046/j.1365-246x.1999.00777.x |
genre |
Iceland |
genre_facet |
Iceland |
op_relation |
http://gji.oxfordjournals.org/cgi/content/short/136/3/757 http://dx.doi.org/10.1046/j.1365-246x.1999.00777.x |
op_rights |
Copyright (C) 1999, Oxford University Press |
op_doi |
https://doi.org/10.1046/j.1365-246x.1999.00777.x |
container_title |
Geophysical Journal International |
container_volume |
136 |
container_issue |
3 |
container_start_page |
757 |
op_container_end_page |
770 |
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1766041673351036928 |