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High-resolution evidence for dynamic transitional geomagnetic field behaviour from a Miocene reversal, McMurdo Sound, Ross Sea, Antarctica
Author(s)
Language
English
Obiettivo Specifico
2.2. Laboratorio di paleomagnetismo
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
/ 59(2007)
Publisher
Terra Pub
Pages (printed)
815-824
Issued date
2007
Abstract
We report a high-resolution record of a Miocene polarity transition (probably the Chron C6r-C6n transition)
from glacimarine sediments in McMurdo Sound, Ross Sea, Antarctica, which is the first transition record reported
from high southern latitudes. The transition is recorded in two parallel cores through a 10.7 m stratigraphic
thickness. The sediments are interpreted as having been deposited in a marine environment under the influence of
floating ice or seaward of a glacier terminus from which a large sediment load was delivered to the drill site. The
core was recovered using rotary drilling, which precludes azimuthal orientation of the core and determination
of a vector record of the field during the transition. However, constraints on transitional field behaviour are
provided by the exceptional resolution of this record. Large-scale paleomagnetic inclination fluctuations in the
two cores can be independently correlated with each other using magnetic susceptibility data, which suggests
that the sediments are reliable recorders of geomagnetic field variations. Agreement between the two parallel
transition records provides evidence for highly dynamic field behaviour, as suggested by numerous large-scale
inclination changes (∼90◦) throughout the transition. These large-scale changes occur across stratigraphically
narrow intervals, which is consistent with the suggestion of rapid field changes during transitions. In one
intact portion of the core, where there is no apparent relative core rotation between samples, declinations and
inclinations are consistent with the presence of a stable cluster of virtual geomagnetic poles within the transition
(although the possibility that this cluster represents a rapid depositional event cannot be precluded). These
observations are consistent with those from other high-resolution records and provide a rare detailed view of
transitional field behaviour compared to most sedimentary records, which are not as thick and which appear to
have been smoothed by sedimentary remanence acquisition processes.
from glacimarine sediments in McMurdo Sound, Ross Sea, Antarctica, which is the first transition record reported
from high southern latitudes. The transition is recorded in two parallel cores through a 10.7 m stratigraphic
thickness. The sediments are interpreted as having been deposited in a marine environment under the influence of
floating ice or seaward of a glacier terminus from which a large sediment load was delivered to the drill site. The
core was recovered using rotary drilling, which precludes azimuthal orientation of the core and determination
of a vector record of the field during the transition. However, constraints on transitional field behaviour are
provided by the exceptional resolution of this record. Large-scale paleomagnetic inclination fluctuations in the
two cores can be independently correlated with each other using magnetic susceptibility data, which suggests
that the sediments are reliable recorders of geomagnetic field variations. Agreement between the two parallel
transition records provides evidence for highly dynamic field behaviour, as suggested by numerous large-scale
inclination changes (∼90◦) throughout the transition. These large-scale changes occur across stratigraphically
narrow intervals, which is consistent with the suggestion of rapid field changes during transitions. In one
intact portion of the core, where there is no apparent relative core rotation between samples, declinations and
inclinations are consistent with the presence of a stable cluster of virtual geomagnetic poles within the transition
(although the possibility that this cluster represents a rapid depositional event cannot be precluded). These
observations are consistent with those from other high-resolution records and provide a rare detailed view of
transitional field behaviour compared to most sedimentary records, which are not as thick and which appear to
have been smoothed by sedimentary remanence acquisition processes.
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article
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