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Geomagnetic palaeosecular variation around 15 ka ago from NW Barents Sea cores (south of Svalbard)
Language
English
Obiettivo Specifico
1A. Geomagnetismo e Paleomagnetismo
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
/204(2016)
Pages (printed)
785-797
Issued date
February 2, 2016
Alternative Location
Keywords
Abstract
The sedimentary sequence deposited during the deglaciation phase following the last glacial
maximum in the Storfjorden trough, on the northwestern Barents Sea south of Svalbard, was
sampled with 10 piston and gravity cores during the SVAIS and EGLACOM cruises. Three
cores (SV-02, SV-03 and SV-05) collected on the upper continental slope are characterized by
a thin (20–40 cm) Holocene interval and a thick (up to 4.5 m in core SV-03) late Pleistocene
sequence of finely laminated fine-grained sediments that have been interpreted as plumites
deposited during the Melt Water Pulse 1a (MWP-1a). Radiocarbon ages obtained at the top
and bottom of this stratigraphic interval revealed that deposition occurred during less than
two centuries at around 15 ka ago, with a very high sedimentary rate exceeding 3 cm a−1. We
studied the palaeomagnetic and rock magnetic properties of this interval, by taking magnetic
measurements at 1 cm spacing on u-channel samples collected from the three cores. The
data show that this sequence is characterized by good palaeomagnetic properties and the
palaeomagnetic and rock magnetic trends may be correlated at high resolution from core to
core. The obtained palaeomagnetic data therefore offer the unique opportunity to investigate
in detail the rate of geomagnetic palaeosecular variation (PSV) in the high northern latitudes at
a decadal scale. Notwithstanding the palaeomagnetic trends of the three cores may be closely
matched, the amplitude of directional PSV and the consequent virtual geomagnetic pole (VGP)
scatter (S) is distinctly higher in one core (SV-05) than in the other two cores (SV-02 andSV-03).
This might result from a variable proportion of two distinct populations of magnetic minerals
in core SV-05, as suggested by the variable tendency to acquire a gyromagnetic remanent
magnetization at high fields during the AF demagnetization treatment. For the plumite interval
of cores SV-02 and SV-03, where the magnetic mineralogy is uniform and magnetite is the
main magnetic carrier, a S value of about 9◦ is obtained. We consider this value as a reliable
approximation of palaeomagnetic secular variation at a latitude of 75◦N over a time interval
spanning a couple of centuries around 15 ka ago.
maximum in the Storfjorden trough, on the northwestern Barents Sea south of Svalbard, was
sampled with 10 piston and gravity cores during the SVAIS and EGLACOM cruises. Three
cores (SV-02, SV-03 and SV-05) collected on the upper continental slope are characterized by
a thin (20–40 cm) Holocene interval and a thick (up to 4.5 m in core SV-03) late Pleistocene
sequence of finely laminated fine-grained sediments that have been interpreted as plumites
deposited during the Melt Water Pulse 1a (MWP-1a). Radiocarbon ages obtained at the top
and bottom of this stratigraphic interval revealed that deposition occurred during less than
two centuries at around 15 ka ago, with a very high sedimentary rate exceeding 3 cm a−1. We
studied the palaeomagnetic and rock magnetic properties of this interval, by taking magnetic
measurements at 1 cm spacing on u-channel samples collected from the three cores. The
data show that this sequence is characterized by good palaeomagnetic properties and the
palaeomagnetic and rock magnetic trends may be correlated at high resolution from core to
core. The obtained palaeomagnetic data therefore offer the unique opportunity to investigate
in detail the rate of geomagnetic palaeosecular variation (PSV) in the high northern latitudes at
a decadal scale. Notwithstanding the palaeomagnetic trends of the three cores may be closely
matched, the amplitude of directional PSV and the consequent virtual geomagnetic pole (VGP)
scatter (S) is distinctly higher in one core (SV-05) than in the other two cores (SV-02 andSV-03).
This might result from a variable proportion of two distinct populations of magnetic minerals
in core SV-05, as suggested by the variable tendency to acquire a gyromagnetic remanent
magnetization at high fields during the AF demagnetization treatment. For the plumite interval
of cores SV-02 and SV-03, where the magnetic mineralogy is uniform and magnetite is the
main magnetic carrier, a S value of about 9◦ is obtained. We consider this value as a reliable
approximation of palaeomagnetic secular variation at a latitude of 75◦N over a time interval
spanning a couple of centuries around 15 ka ago.
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