The effect of remanence anisotropy on paleointensity estimates: a case study from the Archean Stillwater Complex

Selkin, P.A.; Gee, Jeffrey S.; Tauxe, Lisa; Meurer, W. P.; Newell, Andrew J.

doi:10.1016/s0012-821x(00)00292-2

Cited by 144 publications

(121 citation statements)

References 38 publications

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“…Selkin et al (2000) reported that the anisotropy of ARM imparted with a high peak AF field reasonably approximated the anisotropy of the total TRM. Because the Shaw method uses only the high coercivity part of NRM and TRM, the anisotropy of the partial ARM of the corresponding coercivity window was used.…”

Section: Methodsmentioning

confidence: 87%

“…To correct for the effect of anisotropy on paleointensity estimates (Selkin et al, 2000), the anisotropy of partial ARM was measured on samples that were successful in the paleointensity experiments. Selkin et al (2000) reported that the anisotropy of ARM imparted with a high peak AF field reasonably approximated the anisotropy of the total TRM.…”

Section: Methodsmentioning

confidence: 99%

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Paleointensity estimates from oceanic gabbros: Effects of hydrothermal alteration and cooling rate

Usui

2013

Earth Planet Sp

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Gabbros recovered by previous ocean drillings were investigated in paleointensity and rock magnetic experiments. The young ages of the samples (ca. 0.78-1.3 Ma) enable a direct comparison between the plutonic paleointensity and volcanic data. Microscopic observations revealed two kinds of magnetite: needle-shaped exsolution in plagioclase and aggregate associated with the hydrothermal alteration of olivine. In Shaw paleointensity experiments, some samples revealed reasonable estimates, while some others showed an anomalously low ratio of natural remanent magnetization (NRM) versus thermoremanent magnetization (TRM). First-order reversal curve (FORC) diagrams indicated that the reasonable NRM/TRM were from non-interacting single domain magnetite exsolved in plagioclase, while the anomalously low NRM/TRM were from secondary magnetite associated with olivine. From the paleointensity results, the mean virtual axial dipole moment (VADM) was calculated to be 8.2 ± 2.1 10 22 Am 2 . Volcanic records in the PINT database for 0.78-1.3 Ma revealed a mean virtual dipole moment (VDM) of 6.3 ± 0.73 10 22 Am 2 . The difference between them is consistent with the theoretical prediction of the cooling rate effect on paleointensity. These results indicate that oceanic gabbros are reliable paleointensity recorders.

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Section: Methodsmentioning

confidence: 87%

Section: Methodsmentioning

confidence: 99%

Paleointensity estimates from oceanic gabbros: Effects of hydrothermal alteration and cooling rate

Usui

2013

Earth Planet Sp

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“…DRAT and DRATS are two important parameters representing the quality of pTRM checks, which are affected by measurement noise or alteration. DRAT is the maximum difference between pTRM and the pTRM check at a given temperature step normalized by the length of the best fit line (Selkin et al, 2000) while DRATs is the difference sum between pTRM and relative pTRM check normalized by the pTRM acquired by cooling from maximum temperature of the best fit line to room temperature (Kissel and Laj, 2004;Tauxe and Staudigel, 2004). Both are limited to be 10% here.…”

Section: Paleointensity Resultsmentioning

confidence: 99%

“…TRM anisotropy is sometimes observed in geological samples, but occurs frequently in archaeological artifacts because of manufacturing procedures, which makes the anisotropy correction in archaeological study non-trivial. The bias in paleointensity caused by ATRM can be corrected by determining the anisotropy tensor of each specimen (Selkin et al, 2000;Veitch et al, 1984). This can be determined by anisotropy of magnetic susceptibility (AMS) or anisotropy of anhysteretic remanent magnetization (AARM) or ATRM.…”

Section: Anisotropy Correctionmentioning

confidence: 99%

“…When calculating the ATRM tensor, we prefer the original method proposed by Veitch et al (1984) to the modified version by Selkin et al (2000) because the latter might change paleointensity parameters which are critical to data selection (Paterson, 2013). Following the six ATRM measurements, we include an additional step, which is a repeat of the first measurement position to test for possible alteration during the heatings required to measure the tensor.…”

Section: Anisotropy Correctionmentioning

confidence: 99%

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Geomagnetic intensity variations for the past 8 kyr: New archaeointensity results from Eastern China

Cai

Tauxe

Deng

et al. 2014

Earth and Planetary Science Letters

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In this study, we have carried out paleointensity experiments on 918 specimens spanning the last ∼7 kyr, including pottery fragments, baked clay and slag, collected from Shandong, Liaoning, Zhejiang and Hebei Provinces in China. Approximately half of the specimens yielded results that passed strict data selection criteria and give high-fidelity paleointensities. The virtual axial dipole moments (VADMs) of our sites range from ∼2 × 10 22 to ∼13 × 10 22 Am 2 . At ∼2250 BCE our results suggest a paleointensity low of ∼2 × 10 22 Am 2 , which increases to a high of ∼13 × 10 22 Am 2 by ∼1300 BCE. This rapid (less than 1000 yrs) six-fold change in the paleointensity may have important implications for the dynamics of core flow at this time. Our data from the last ∼3 kyr are generally in good agreement with the ARCH3k.1 model, but deviate significantly at certain time periods from the CALS3k.4 and CALS10k.1b model, which is likely due to differences in the data used to constrain these models. At ages older than ∼3 ka, where only the CALS10k.1b model is available for comparison, our data deviate significantly from the model. Combining our new results with the published data from China and Japan, we provide greatly improved constraints for the regional model of Eastern Asia. When comparing the variations of geomagnetic field in three global representative areas of Eastern Asia, the Middle East and Southern Europe, a common general trend of sinusoidal variations since ∼8 ka is shown, likely dominated by the dipole component. However, significant disparities are revealed as well, which we attribute to non-dipolar components caused by movement of magnetic flux patches at the core-mantle boundary.

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On improving the selection of Thellier-type paleointensity data

Paterson

Tauxe

Biggin

et al. 2014

Geochem. Geophys. Geosyst.

186

268

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The selection of paleointensity data is a challenging, but essential step for establishing data reliability. There is, however, no consensus as to how best to quantify paleointensity data and which data selection processes are most effective. To address these issues, we begin to lay the foundations for a more unified and theoretically justified approach to the selection of paleointensity data. We present a new compilation of standard definitions for paleointensity statistics to help remove ambiguities in their calculation. We also compile the largest-to-date data set of raw paleointensity data from historical locations and laboratory control experiments with which to test the effectiveness of commonly used sets of selection criteria. Although most currently used criteria are capable of increasing the proportion of accurate results accepted, criteria that are better at excluding inaccurate results tend to perform poorly at including accurate results and vice versa. In the extreme case, one widely used set of criteria, which is used by default in the ThellierTool software (v4.22), excludes so many accurate results that it is often statistically indistinguishable from randomly selecting data. We demonstrate that, when modified according to recent single domain paleointensity predictions, criteria sets that are no better than a random selector can produce statistically significant increases in the acceptance of accurate results and represent effective selection criteria. The use of such theoretically derived modifications places the selection of paleointensity data on a more justifiable theoretical foundation and we encourage the use of the modified criteria over their original forms.

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The effect of remanence anisotropy on paleointensity estimates: a case study from the Archean Stillwater Complex

Cited by 144 publications

References 38 publications

Paleointensity estimates from oceanic gabbros: Effects of hydrothermal alteration and cooling rate

Paleointensity estimates from oceanic gabbros: Effects of hydrothermal alteration and cooling rate

Geomagnetic intensity variations for the past 8 kyr: New archaeointensity results from Eastern China

On improving the selection of Thellier-type paleointensity data

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