Multiple-specimen absolute paleointensity determination: An optimal protocol including pTRM normalization, domain-state correction, and alteration test

Fabian, Karl; Leonhardt, Roman

doi:10.1016/j.epsl.2010.06.006

Cited by 86 publications

(215 citation statements)

References 14 publications

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“…We selected 250°C as a temperature typically exploited in palaeointensity experiments for these samples: Thellier 7,8 palaeointensity experiments were interpreted between 100 and 280°C (ref. 26) while multi specimen style (MSP) experiments 9,10 were done at 250°C (ref. 26).…”

Section: Resultsmentioning

confidence: 99%

“…Directional information is generally straightforward to obtain from various recorders, including well-dated lavas and (lake) sediments for shorter timescales and sedimentary sequences for reconstructions going further back into geological history. Despite recent methodological progress [3][4][5][6][7][8][9][10][11][12] , however, acquiring reliable absolute palaeointensity data remains a formidable task. Only materials that acquired their remanent magnetization by cooling in the Earth's ambient magnetic field are suited for absolute palaeointensity determinations.…”

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confidence: 99%

“…Over the past decades, various tests and protocols have been proposed to identify and (partially) overcome the MD effects during palaeointensity experiments [3][4][5][6][7][8][9][10][11][12] , but success rates of such experiments are still notoriously low [17][18][19][20] . It is even more disturbing that-in spite of extensive testing-palaeointensity experiments sometimes yield technically successful estimates of the palaeofield that actually over-or underestimate the palaeofield by tens of percent 6,21 .…”

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confidence: 99%

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Magnetic force microscopy reveals meta-stable magnetic domain states that prevent reliable absolute palaeointensity experiments

et al. 2014

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Obtaining reliable estimates of the absolute palaeointensity of the Earth's magnetic field is notoriously difficult. The heating of samples in most methods induces magnetic alteration-a process that is still poorly understood, but prevents obtaining correct field values. Here we show induced changes in magnetic domain state directly by imaging the domain configurations of titanomagnetite particles in samples that systematically fail to produce truthful estimates. Magnetic force microscope images were taken before and after a heating step typically used in absolute palaeointensity experiments. For a critical temperature (250°C), we observe major changes: distinct, blocky domains before heating change into curvier, wavy domains thereafter. These structures appeared unstable over time: after 1-year of storage in a magnetic-field-free environment, the domain states evolved into a viscous remanent magnetization state. Our observations qualitatively explain reported underestimates from otherwise (technically) successful experiments and therefore have major implications for all palaeointensity methods involving heating.

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Section: Resultsmentioning

confidence: 99%

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Magnetic force microscopy reveals meta-stable magnetic domain states that prevent reliable absolute palaeointensity experiments

et al. 2014

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“…To this end Fabian & Leonhardt (2010) improved the MSP-DB protocol by adding three extra heating steps to identify and correct for these potential domain state effects, resulting in the MSP-DSC (domain state corrected) method. Furthermore, a check for potential alteration was added Table 3.…”

Section: Multispecimen Techniquementioning

confidence: 99%

“…Taking a different thermal approach, Dekkers & Böhnel (2006) proposed a method exploiting multiple sister specimens and reducing the number of heating steps compared to Thellier-style protocols. This multispecimen method (MSP) was later refined by Fabian & Leonhardt (2010) to account for potential changes in the magnetic domain state during the experiment. To avoid thermally induced alteration altogether, a relative palaeointensity technique frequently used on sediments, the pseudo-Thellier method, was recently calibrated to provide absolute estimates of the palaeofield's intensity from volcanic samples and proved to be a valuable addition to the palaeointensity toolbox (de Groot et al 2013).…”

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The multimethod palaeointensity approach applied to volcanics from Terceira: full-vector geomagnetic data for the past 50 kyr

Groot¹,

Pimentel

Chiara

2016

Geophys. J. Int.

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S U M M A R YThe island of Terceira (38.5 • N, 27.2 • W) in the Azores Archipelago boasts a wealth of welldated recent volcanic products; it is therefore the ideal location to improve the resolution of the full-vector geomagnetic field record for the Mid-Atlantic Ocean. We investigated 21 (sub-)sites sampled from 10 different cooling units; six of these cooling units are from the Holocene, the other four are approximately coeval with the age of known geomagnetic excursions. After successfully determining the palaeodirections from all but one site, we applied the multimethod palaeointensity approach to all sites. Here, we used three different palaeointensity methods: the IZZI-Thellier protocol, the Multispecimen technique, and the calibrated pseudo-Thellier method. For the Holocene sites four robust palaeointensity estimates were obtained, they mostly agree with data from the nearby island of São Miguel and data from the Iberian Peninsula and West Africa. Two older sites, dated at 25.7 and 46.3 ka, produced low palaeointensities: 24.4 and 24.1 µT, respectively. As both the IZZI-Thellier and pseudo-Thellier methods yielded technically acceptable results for these sites we used them to improve the pseudo-Thellier calibration relation and establish its applicability to lower palaeointensities. Sixty per cent of all sampled cooling units/ages in our study yielded a technically successful palaeointensity estimate; this unusually high success rate is attributed both to our sampling strategy and the implementation of the multimethod approach.

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Magnetic properties and paleointensities as function of depth in a Hawaiian lava flow

Groot

Dekkers

Visscher

et al. 2014

Geochem. Geophys. Geosyst.

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The outcome of paleointensity experiments largely depends on the rock-magnetic properties of the samples. To assess the relation between volcanic emplacement processes and rock-magnetic properties, we sampled a vertical transect in a 6 m thick inflated lava flow at Hawaii, emplaced in 588 AD. Its rock-magnetic properties vary as function of distance from the flow top; the observations can be correlated to the typical cooling rate profile for such a flow. The top and to a lesser extent the bottom parts of the flow cooled faster and reveal a composition of TM60 in which the magnetic remanence is carried by finegrained titanomagnetites, relatively rich in titanium, with associated low Curie and unblocking temperatures. The titanomagnetite in the slower cooled central part of the flow is unmixed into the magnetite and € ulvospinel end-members as evidenced by scanning electron microscope observation. The remanence is carried by coarse-grained magnetite lamella ( TM0) with high Curie and unblocking temperatures. The calibrated pseudo-Thellier results that can be accepted yield an average paleointensity of 44.1 6 2.4 lT. This is in good agreement with the paleointensity results obtained using the thermal IZZI-Thellier technique (41.6 6 7.4 lT) and a recently proposed record for Hawaii. We therefore suggest that the chance of obtaining a reliable paleointensity from a particular cooling unit can be increased by sampling lavas at multiple levels at different distances from the top of the flow combined with careful preliminary testing of the rockmagnetic properties.

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Multiple-specimen absolute paleointensity determination: An optimal protocol including pTRM normalization, domain-state correction, and alteration test

Cited by 86 publications

References 14 publications

Magnetic force microscopy reveals meta-stable magnetic domain states that prevent reliable absolute palaeointensity experiments

Magnetic force microscopy reveals meta-stable magnetic domain states that prevent reliable absolute palaeointensity experiments

The multimethod palaeointensity approach applied to volcanics from Terceira: full-vector geomagnetic data for the past 50 kyr

Magnetic properties and paleointensities as function of depth in a Hawaiian lava flow

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