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Conference paperWilliams W, Nagy L, Fabian K, et al., 2016,
The Hunting of the ‘Psark' - 40 Years On (invited)
, AGU Fall 2016 -
Conference paperNagy L, Williams W, Fabian K, et al., 2016,
Thermomagnetic Stability in Pseudo-Single Domain Grains
, AGU Fall 2016 -
Conference paperMuxworthy AR, 2016,
Recovering ancient magnetic field intensities from rocks and meteorites using FORC Measurements (invited)
, 2nd FORC Workshop -
Conference paperMaidment S, Muxworthy AR, 2016,
A chronostratigraphic framework for the Morrison Formation and the latitudinal biodiversity gradient in Morrison dinosaurs (poster)
, 76th Annual Meeting Society of Vertebrate Paleontology -
Journal articleDøssing A, Muxworthy AR, Supakulopas R, et al., 2016,
High northern geomagnetic field behavior and new constraints on the Gilsá event: Paleomagnetic and 40Ar/39Ar results of ∼0.5–3.1Ma basalts from Jökuldalur, Iceland
, Earth and Planetary Science Letters, Vol: 456, Pages: 98-111, ISSN: 0012-821XRecent paleomagnetic results of extrusive rocks from high southern latitudes (>60°S) and high northern latitudes (>60°N) have been suggested to reflect a hemispheric asymmetry of the geomagnetic field on time-scales of 105 to 106 yrs, with higher and more stable fields in the north. This interpretation, however, is based on only a few modern-standard paleodirectional data sets and on high northern stable field paleointensity data of rocks that are mainly younger than 100 kyr. The sparsity of modern-standard data questions the validity (and age range) of this potential geomagnetic asymmetry. In 2013 and 2014, we sampled basaltic lava flows in Jökuldalur, north-eastern Iceland, to obtain high-standard paleodirectional and paleointensity data at relatively high-northern latitudes (65.2°N). On average, we sampled >15 cores per site at 51 sites of predominantly Matuyama age. Complete demagnetization was carried out on all samples using AF or thermal demagnetization. We present 45 distinct paleomagnetic directions based on overall N>10 ChRMs per site and α95<3.5°. We obtain a mean direction of D=355.7°, I=76.3°, and α95=3.2 for N=45 sites that is not significantly different from a GAD field. The resulting 45 VGPs distribute around the North Pole, and the global mean paleomagnetic pole (View the MathML source, View the MathML source) is coincident with the North Pole within the α 95 confidence limit. We calculate a VGP dispersion View the MathML source and an average inclination anomaly View the MathML source for our 38 Matuyama age data. The dispersion SB overall supports the interpretation of a dependence of SB on latitude during the Matuyama, while the negligible ΔI suggests little deviation from a GAD field. Based on relatively strict cut-off criteria we also present six new field strength estimates from the time interval ∼1.2–1.83 Ma, thus filling a large data gap of the high-northern sta
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Conference paperPenny C, Muxworthy AR, Fabian K, 2016,
The Curie temperature of magnetite nanoparticles (poster)
, EMRS Fall 2016 -
Conference paperMuxworthy AR, Almeida TP, Williams W, et al., 2016,
Imaging magnetic stability of PSD magnetite
, 15th Castle Meeting -
Conference paperShah J, Bates H, Muxworthy AR, et al., 2016,
A micro-CT conglomerate test (poster)
, 15th Castle Meeting -
Conference paperValdez-Grijalva MA, Nagy L, Muxworthy AR, et al., 2016,
Domain structure of greigite (Fe3S4) in the SD to PSD regime
, 15th Castle Meeting -
Conference paperNagy L, Williams W, Fabian K, et al., 2016,
Thermoremanent magnetization in pseudo-Single domain grains
, 15th Castle Meeting -
Conference paperShah J, Muxworthy AR, Almeida TP, et al., 2016,
Determining the magnetic recording fidelity of chondrule dusty olivine
, 15th Castle Meeting -
Conference paperSupakulopas R, Muxworthy AR, Riishuus MS, et al., 2016,
High-latitude palaeomagnetic field behaviour during 3-7 Ma in Northern Iceland
, 15th Castle Meeting -
Conference paperWilliams W, Nagy L, Ó Conbhuí P, et al., 2016,
The Hunting of the ‘Psark' - 40 Years On
, 15th Castle Meeting -
Conference paperPenny C, Muxworthy AR, Fabian K, 2016,
The Curie temperature of magnetite nanoparticles (poster)
, 15th Castle Meeting -
Journal articleAlmeida TP, Muxworthy AR, Kovacs A, et al., 2016,
Direct observation of the thermal demagnetization of magnetic vortex structures in non-ideal magnetite recorders
, Geophysical Research Letters, Vol: 43, Pages: 8426-8434, ISSN: 1944-8007The thermal demagnetization of pseudo-single-domain (PSD) magnetite (Fe3O4) particles, which govern the magnetic signal in many igneous rocks, is examined using off-axis electron holography. Visualization of a vortex structure held by an individual Fe3O4 particle (~ 250 nm in diameter) during in situ heating is achieved through the construction and examination of magnetic-induction maps. Step-wise demagnetization of the remanence-induced Fe3O4 particle upon heating to above the Curie temperature, performed in a similar fashion to bulk thermal demagnetization measurements, revealed its vortex state remains stable under heating close to its unblocking temperature, and is recovered upon cooling with the same or reversed vorticity. Hence, the PSD Fe3O4 particle exhibits thermomagnetic behavior comparable to a single-domain carrier, and thus vortex-states are considered reliable magnetic recorders for paleomagnetic investigations.
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