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A long title for a
research topic, but what is it all about? The geomagnetic field behaviour
can be studied using the Natural Remanent Magnetization (NRM) of rocks
and sediments.
"
The NRM signal is
a composite, however, of the geomagnetic field during deposition or formation
of the rock, the grain size and concentration of the magnetic material,
and the type of magnetic minerals. Moreover, the magnetic minerals can
be altered after deposition through diagenesis. This does not only
change the magnetic minerals, but also the magnetic signal they are carrying. |
A marine sedimentary
core from the Azores (North Atlantic Ocean),
spanning the last 270.000 years. This core was used to determine a paleo-intensity
record with the pseudo-Thellier method.
We find that the record
is still slightly contaminated by climatically induced changes. A combined
rock-magnetic/ geochemical fuzzy c-means cluster analysis shows remarkable
agreement between clusters and the climate signal d18O.
In this core there was no evidence for diagenesis. |
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A red bed sequence
from Dôme de Barrot (Southern France)
of Permian age. The patterns of natural remanent magnetisation (NRM) of
this rock resemble those of present day's secular variation. This suggests
that during Kiaman Superchron secular variation was not suppressed, and
is comparable to present-day SV seen in low latitude lavas. However, to
verify secular variation during a Superchron, a precise time control is
required. We found that we could confirm the precessional origin of the
cyclicity in the Permian redbeds. |
Figure
2 from Kruiver et al. (2000)
|
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The
La
Gloria section (Spain). In this section there
are several reversals. The different magnetic minerals recorded the reversals
at different times. Timing of the different components, using the clearly
astronomically induced sedimentary cycles, may reveal the extent and timing
of diagenesis and the NRM acquisition mechanism.
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Mark
Dekkers (right) helps with drilling the continental sediments of the La
Gloria section.
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The
Librilla
section in Southern Spain (left). This is
a beautiful continental section with cyclic patterns of red clay, a paleosol,
dark grey clay, red or light grey clay and dark grey clay again.
The largest part of
the section has normal polarity. The grey layers are an exception: they
have reversed polarity. Diagenesis changed the normal polarity recorded
by the sediments during deposition to the reversed polarity after the reversal,
which is located near the top of the section.
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2004
-
Vlag, P.A., Kruiver, P.P
and Dekkers, M.J. (2004). Evaluating climate change by multivariate statistical
techniques on magnetic and chemical properties of marine sediments (Azores
region), Palaeogeogr. Palaeoclimatol. Palaeoecol., 212, 23-44.
2003
-
Grygar T., Dedecek J.,
Kruiver P.P., Dekkers M.J., Bezdicka P., and Schneeweis, O. (2003). Iron
oxide mineralogy in late Miocene red beds from La Gloria, Spain: rock-magnetic,
voltammetric and Vis spectroscopy analyses, Catena, 53, 115-132.
[PDF]
-
Kruiver, P.P., Langereis,
C.G., Dekkers, M.J. and Krijgsman, W. (2003). Rock magnetic properties
of multi-component natural remanent magnetisation in alluvial red beds
(NE Spain), Geophys. J. Int., 153, 317-332 [PDF]
2002
-
Heslop, D., Dekkers, M.J.,
Kruiver, P.P. and Van Oorschot, I.H.M. (2002). Analysis of isothermal remanent
magnetisation acquisition curves using the expectation-maximisation algorithm.
Geophys.
J. Int., 148, 58-64. [PDF]
[SOFTWARE]
-
Kruiver, P.P., Langereis,
C.G., Dekkers, M.J., Davies, G.R. and Smeets, R.J (2002a). The implications
of non-suppressed geomagnetic secular variation during the Permo-Carboniferous
Superchron,
Phys. Earth Planet. Inter.,
131, 225-235.
[PDF]
-
Kruiver, P.P., Krijgsman,
W., Langereis, C.G. and Dekkers, M.J. (2002b). Cyclostratigraphy and rock-magnetic
investigation of the NRM signal in late Miocene palustrine-alluvial deposits
of the Librilla section (SE Spain), J. Geophys. Res., 107, B12,
2334, doi:10.1029/2001JB000945 [PDF]
2001
-
Kruiver, P.P. (2001).
Unravelling the magnetic record in marine and continental sediments : climatic
versus geomagnetic signals (PhD Thesis Utrecht University), Geologica
Ultraiectina,
210, 207 pp. [PDF
entire thesis or link
to individual chapters]
-
Kruiver, P.P., Dekkers,
M.J., and Heslop, D. Quantification of magnetic coercivity components by
the analysis of acquisition curves of isothermal remanent magnetisation,
Earth
Planet. Sci. Lett.,
189, 269-276. [PDF]
-
Kruiver, P.P. and Passier,
H.F. (2001). Coercivity analysis of magnetic phases in sapropel S1 related
to variations in redox conditions, including an investigation of the S-ratio.
Geochem.
Geophys. Geosyst., 14 December 2001, Paper number 2001GC000181
[PDF]
[link
to G-cubed]
2000
-
Kruiver, P.P., Dekkers,
M.J. and Langereis, C.G. (2000). Secular variation in Permian red beds
from Dôme de Barrot, SE France, Earth Planet. Sci. Lett., 179,
205-217.
[PDF]
1999
-
Kruiver, P.P., Kok, Y.S.,
Dekkers, M.J., Langereis, C.G. and Laj, C. (1999). 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.
Geophys. J. Int., 136 (3): 757-770. [PDF]
[DATA]
1998
-
Kruiver, P.P., Kok, Y.S.,
Dekkers, M.J. and Langereis, C.G. (1998). Rock-magnetic and geochemical
parameters in relation to climate, using fuzzy c-means cluster and spectral
analyses, In: A. Buccianti, G. Nardi and R. Potenza (Eds.), Proceedings
of IAMG'98, Isola d’Ischia, Naples (Italy), 1998, Part 1, 427-432.
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