Volcanic records of the Laschamp geomagnetic excursion from Mt Ruapehu, New Zealand

Ingham, Elizabeth; Turner, Gillian; Conway, Chris E.; Heslop, David; Roberts, Andrew P.; Leonard, Graham S.; Townsend, Dougal; Calvert, Andrew T.

doi:10.1016/j.epsl.2017.05.023

Cited by 19 publications

(46 citation statements)

References 51 publications

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“…(d–f) SEM images of hexagonal magnetite plates (Li, ) for which FORC diagrams are shown in Figures 5a–5c. (g–i) The same progression of FORC diagrams as in Figures 5a–5c for a typical PSD sample (andesite from Mt Ruapehu, New Zealand; Ingham et al, ). (j–l) The same progression of FORC diagrams as in Figures 5a–5c for a 120 μm natural MD magnetite.…”

Section: Understanding Magnetic Domain States Using Forc Diagramsmentioning

confidence: 86%

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Resolving the Origin of Pseudo‐Single Domain Magnetic Behavior

et al. 2017

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The term “pseudo‐single domain” (PSD) has been used to describe the transitional state in rock magnetism that spans the particle size range between the single domain (SD) and multidomain (MD) states. The particle size range for the stable SD state in the most commonly occurring terrestrial magnetic mineral, magnetite, is so narrow (~20–75 nm) that it is widely considered that much of the paleomagnetic record of interest is carried by PSD rather than stable SD particles. The PSD concept has, thus, become the dominant explanation for the magnetization associated with a major fraction of particles that record paleomagnetic signals throughout geological time. In this paper, we argue that in contrast to the SD and MD states, the term PSD does not describe the relevant physical processes, which have been documented extensively using three‐dimensional micromagnetic modeling and by parallel research in material science and solid‐state physics. We also argue that features attributed to PSD behavior can be explained by nucleation of a single magnetic vortex immediately above the maximum stable SD transition size. With increasing particle size, multiple vortices, antivortices, and domain walls can nucleate, which produce variable cancellation of magnetic moments and a gradual transition into the MD state. Thus, while the term PSD describes a well‐known transitional state, it fails to describe adequately the physics of the relevant processes. We recommend that use of this term should be discontinued in favor of “vortex state,” which spans a range of behaviors associated with magnetic vortices.

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Section: Understanding Magnetic Domain States Using Forc Diagramsmentioning

confidence: 86%

“…A more typical PSD FORC diagram is shown in Figure g for an andesite sample from Mount Ruapehu, New Zealand (Ingham et al, ). This conventional FORC diagram is not obviously representative of single vortex behavior (compare Figures f and g with Figures n and o).…”

Section: Understanding Magnetic Domain States Using Forc Diagramsmentioning

confidence: 99%

Resolving the Origin of Pseudo‐Single Domain Magnetic Behavior

et al. 2017

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“…Lava records of the Laschamp are restricted to the Massif Central in France (e.g., Laj et al, ), the Auckland volcanic field (Cassata et al, ), and New Zealand's Mt. Ruapehu (Ingham et al, ), that just happened to have erupted with high frequency during this brief period.…”

Section: The Geomagnetic Fieldmentioning

confidence: 99%

“…Lava records of the Laschamp are restricted to the Massif Central in France (e.g., Laj et al, 2014), the Auckland volcanic field (Cassata et al, 2008), and New Zealand's Mt. Ruapehu (Ingham et al, 2017), that just happened to have erupted with high frequency during this brief period. Be-based VADM from Greenland ice cores (blue) filtered with cutoffs of 1/3,000 years (dark blue) and 1/500 years (dashed light blue; Channell et al, 2018).…”

Section: Reviews Of Geophysicsmentioning

confidence: 99%

The Role of Geomagnetic Field Intensity in Late Quaternary Evolution of Humans and Large Mammals

Channell

Vigliotti

2019

Reviews of Geophysics

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It has long been speculated that biological evolution was influenced by ultraviolet radiation (UVR) reaching the Earth's surface, despite imprecise knowledge of the timing of both UVR flux and evolutionary events. The past strength of Earth's dipole field provides a proxy for UVR flux because of its role in maintaining stratospheric ozone. The timing of Quaternary evolutionary events has become better constrained by fossil finds, improved radiometric dating, use of dung fungi as proxies for herbivore populations, and improved ages for nodes in human phylogeny from human mitochondrial DNA and Y chromosomes. The demise of Neanderthals at ~41 ka can now be closely tied to the intensity minimum associated with the Laschamp magnetic excursion, and the survival of anatomically modern humans can be attributed to differences in the aryl hydrocarbon receptor that has a key role in the evolutionary response to UVR flux. Fossil occurrences and dung‐fungal proxies in Australia indicate that episodes of Late Quaternary extinction of mammalian megafauna occurred close to the Laschamp and Blake magnetic excursions. Fossil and dung fungal evidence for the age of the Late Quaternary extinction in North America (and Europe) coincide with a prominent decline in geomagnetic field intensity at ~13 ka. Over the last ~200 kyr, phylogeny based on mitochondrial DNA and Y chromosomes in modern humans yields nodes and bifurcations in evolution corresponding to geomagnetic intensity minima, which supports the proposition that UVR reaching Earth's surface influenced mammalian evolution with the loci of extinction controlled by the geometry of stratospheric ozone depletion.

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“…Geomagnetic excursions are short-lived episodes when the Earth's magnetic field is in intermediate polarity (Roberts, 2008). Knowledge of the Laschamp excursion have accumulated regarding its paleointensity minimum and hemispherical scale VGP path (e.g., Ingham et al, 2017;Laj et al, 2006;Lund et al, 2005). Knowledge of the Laschamp excursion have accumulated regarding its paleointensity minimum and hemispherical scale VGP path (e.g., Ingham et al, 2017;Laj et al, 2006;Lund et al, 2005).…”

Section: Possible Geomagnetic Excursions Recorded In Bengal Fan Sedimmentioning

confidence: 99%

Paleomagnetic Secular Variations During the Past 40,000 Years From the Bay of Bengal

Wang

Chang

Xue

et al. 2019

Geochem Geophys Geosyst

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Paleomagnetic secular variations in South Asia are not well understood due to insufficient records. In this study, we produce a new paleomagnetic secular variation curve covering the past 40,000 years by stacking four marine sediment records from the middle portion of Bay of Bengal. Age models are based on radiocarbon dating and core correlation. Stepwise alternating field demagnetization was used to isolate the primary remanent component. Rock magnetic measurements indicate that the primary magnetic remanence carriers are single domain and pseudo‐single domain magnetites with no sign of diagenetic alteration. Our Bengal relative paleointensity stack is broadly consistent with local records and the PISO‐1500 relative paleointensity stack (Channell et al., 2009; https://doi.org/10.1016/j.epsl.2009.03.012). Two geomagnetic excursions presented by paleointensity minima are recognized, which correlate to the Mono Lake (29–32 ka) and Laschamp excursion (38–40 ka), respectively. We conclude that the Mono Lake and Laschamp excursion are two separate events.

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Volcanic records of the Laschamp geomagnetic excursion from Mt Ruapehu, New Zealand

Cited by 19 publications

References 51 publications

Resolving the Origin of Pseudo‐Single Domain Magnetic Behavior

Resolving the Origin of Pseudo‐Single Domain Magnetic Behavior

The Role of Geomagnetic Field Intensity in Late Quaternary Evolution of Humans and Large Mammals

Paleomagnetic Secular Variations During the Past 40,000 Years From the Bay of Bengal

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