Paleointensity on volcanic glass of varying hydration states

Ferk, A.; Denton, Joanna S.; Leonhardt, Roman; Tuffen, Hugh; Koch, Stephan; Hess, Kai‐Uwe; Dingwell, Donald B.

doi:10.1016/j.pepi.2012.06.004

Cited by 11 publications

(9 citation statements)

References 36 publications

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“…These data are not present in the T+ data set. This result is consistent with reports of low field bias from SBG [e.g., Smirnov and Tarduno , ; Ferk et al , ]. For the WRSBG mean model over the period 202 to 10 Ma, taking into account the small amplitude of the changepoint at 92 Ma, GFI can be interpreted to have had an effectively constant value of 5.46±0.28×10 22 A/m 2 at the 95% confidence level.…”

Section: Inferences From Bdmcmc Mean Modelssupporting

confidence: 91%

Is there a link between geomagnetic reversal frequency and paleointensity? A Bayesian approach

et al. 2014

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Over the last 25 years, several studies have tested for a link between geomagnetic field intensity and reversal frequency. However, despite a large increase in the number of absolute paleointensity determinations, and improved methods for obtaining such data, two competing models have arisen. Here we employ a new tool for objectively analyzing paleomagnetic time series to investigate the possibility of a link between reversal frequency and paleointensity. Transdimensional Markov chain Monte Carlo techniques are applied to a quality-filtered version of the global paleointensity (PINT) database for the last 202 Myr to model long-term paleointensity behavior. A large ensemble of models is sampled, from which a final representative mean model is extracted. The resulting paleointensity model confirms published conclusions that the single-silicate crystal method gives significantly different results from more conventional whole rock paleointensity methods; this makes it difficult to jointly model the two data types in the same analysis. When the much larger whole rock data set is considered, a stable paleointensity of 5.46 ± 0.28 × 10 22 A/m 2 for the last 202 Myr is consistent with the 95% confidence interval of the paleointensity model. Statistical tests indicate no significant correlation between reversal frequency and field intensity at the 0.05 level. However, this result is likely due to the characteristics of the PINT database rather than being a genuine, physically representative conclusion. Given the paucity of data and general state of the global paleointensity database, concerted efforts to increase the number of high-quality, well-dated paleointensity data are required before conclusions about a link between geomagnetic field intensity and reversal frequency can be confidently drawn.

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Section: Inferences From Bdmcmc Mean Modelssupporting

confidence: 91%

Is there a link between geomagnetic reversal frequency and paleointensity? A Bayesian approach

et al. 2014

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“…Geochemistry, Geophysics, Geosystems 10.1002/2015GC005910 variation in paleointensity is a red flag. Ferk et al [2012] find a similar pattern in rhyolitic obsidian, where lower paleointensities are associated with greater hydration. In that case, however, the most hydrated samples had lower coercivity, whereas the most altered samples from NV site 4 have elevated coercivity.…”

Section: Discussionsupporting

confidence: 58%

Geomagnetic paleointensity in historical pyroclastic density currents: Testing the effects of emplacement temperature and postemplacement alteration

Bowles

Gee

Jackson

et al. 2015

Geochem Geophys Geosyst

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Thellier‐type paleointensity experiments were conducted on welded ash matrix or pumice from the 1912 Novarupta (NV) and 1980 Mt. St. Helens (MSH) pyroclastic density currents (PDCs) with the intention of evaluating their suitability for geomagnetic paleointensity studies. PDCs are common worldwide, but can have complicated thermal and alteration histories. We attempt to address the role that emplacement temperature and postemplacement hydrothermal alteration may play in nonideal paleointensity behavior of PDCs. Results demonstrate two types of nonideal behavior: unstable remanence in multidomain (MD) titanomagnetite, and nonideal behavior linked to fumarolic and vapor phase alteration. Emplacement temperature indirectly influences MSH results by controlling the fraction of homogenous MD versus oxyexsolved pseudo‐single domain titanomagnetite. NV samples are more directly influenced by vapor phase alteration. The majority of NV samples show distinct two‐slope behavior in the natural remanent magnetization—partial thermal remanent magnetization plots. We interpret this to arise from a (thermo)chemical remanent magnetization associated with vapor phase alteration, and samples with high water content (>0.75% loss on ignition) generate paleointensities that deviate most strongly from the true value. We find that PDCs can be productively used for paleointensity, but that—as with all paleointensity studies—care should be taken in identifying potential postemplacement alteration below the Curie temperature, and that large, welded flows may be more alteration‐prone. One advantage in using PDCs is that they typically have greater areal (spatial) exposure than a basalt flow, allowing for more extensive sampling and better assessment of errors and uncertainty.

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“…Subaerial rhyolitic volcanic glass has been tested as a suitable recorder of paleointensity (e.g., Leonhardt et al, 2006;Ferk et al, 2012) in relation to laboratory (Ferk et al, 2010) and ancient (Ferk et al, 2011) magnetic fields. Here, we explore the viability of glassy margins of subaerial lava flows as recorders of magnetic field strength.…”

Section: Physics Of the Earth And Planetary Interiorsmentioning

confidence: 99%

Paleointensity estimates from historic and modern Hawaiian lava flows using glassy basalt as a primary source material

Cromwell

Tauxe

Staudigel

et al. 2015

Physics of the Earth and Planetary Interiors

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Paleointensity on volcanic glass of varying hydration states

Cited by 11 publications

References 36 publications

Is there a link between geomagnetic reversal frequency and paleointensity? A Bayesian approach

Is there a link between geomagnetic reversal frequency and paleointensity? A Bayesian approach

Geomagnetic paleointensity in historical pyroclastic density currents: Testing the effects of emplacement temperature and postemplacement alteration

Paleointensity estimates from historic and modern Hawaiian lava flows using glassy basalt as a primary source material

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