Reliable paleointensity determinations from Late Cretaceous volcanic rocks in Korea with constraint of thermochemical alteration

Wonnyon Kim, Seong-Jae Doh, Yongjae Yu

Research output: Contribution to journalArticle

Abstract

Paleointensity determinations were carried out from Late Cretaceous (∼77 Ma) volcanic rocks in Korea using a Thellier-type IZZI experimental protocol with systematic partial thermal remanent magnetization (pTRM) checks. Various data selection criteria were used to estimate reliable paleointensities. We set stringent threshold values for each parameter to ensure that there was: (1) a linear relationship between natural remanent magnetization (NRM) lost and TRM gained; (2) negligible thermal alteration of magnetic minerals; and (3) uni-vectorial decay of NRM towards the origin. From the 336 samples, ∼88% were rejected because of an insufficient extrapolated NRM fraction in the best-fit line (fvds < 0.6), highlighting that fvds is the most stringent selection criterion in this study. For the 31 accepted samples, paleointensities range from 6.4 to 30.4 µT. Among the 31 samples, eight samples yielded extremely low paleointensities. Although single-domain (titano)magnetite was identified as the stable paleointensity recorder, oxidation of superparamagnetic fractions upon repeated heating probably caused enhancement of pTRM acquisition and yielded a low paleointensity estimate. Apart from these low paleointensities (n = 8) as screened by a newly proposed data selection criterion of Δk < 0.2, the remaining 23 samples have a mean paleointensity of 23.1 ± 4.8 µT, corresponding to a virtual axial dipole moment (VADM) of 40.8 ± 8.5 ZAm2, which is ∼50% of the present-day VADM.

Original languageEnglish
Pages (from-to)47-56
Number of pages10
JournalPhysics of the Earth and Planetary Interiors
Volume279
DOIs
Publication statusPublished - 2018 Jun 1

Fingerprint

natural remanent magnetization
Korea
volcanology
volcanic rock
remanent magnetization
rocks
Cretaceous
magnetization
thermal alteration
magnetic mineral
dipole moments
magnetite
recorders
heating
oxidation
estimates
acquisition
minerals
thresholds
augmentation

Keywords

  • Late Cretaceous
  • Paleointensity
  • single-domain (SD)
  • superparamagnetic (SP)
  • virtual axial dipole moment (VADM)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Geophysics
  • Physics and Astronomy (miscellaneous)
  • Space and Planetary Science

Cite this

@article{822668b14656437e86fe42ef8ae8318a,
title = "Reliable paleointensity determinations from Late Cretaceous volcanic rocks in Korea with constraint of thermochemical alteration",
abstract = "Paleointensity determinations were carried out from Late Cretaceous (∼77 Ma) volcanic rocks in Korea using a Thellier-type IZZI experimental protocol with systematic partial thermal remanent magnetization (pTRM) checks. Various data selection criteria were used to estimate reliable paleointensities. We set stringent threshold values for each parameter to ensure that there was: (1) a linear relationship between natural remanent magnetization (NRM) lost and TRM gained; (2) negligible thermal alteration of magnetic minerals; and (3) uni-vectorial decay of NRM towards the origin. From the 336 samples, ∼88{\%} were rejected because of an insufficient extrapolated NRM fraction in the best-fit line (fvds < 0.6), highlighting that fvds is the most stringent selection criterion in this study. For the 31 accepted samples, paleointensities range from 6.4 to 30.4 µT. Among the 31 samples, eight samples yielded extremely low paleointensities. Although single-domain (titano)magnetite was identified as the stable paleointensity recorder, oxidation of superparamagnetic fractions upon repeated heating probably caused enhancement of pTRM acquisition and yielded a low paleointensity estimate. Apart from these low paleointensities (n = 8) as screened by a newly proposed data selection criterion of Δk < 0.2, the remaining 23 samples have a mean paleointensity of 23.1 ± 4.8 µT, corresponding to a virtual axial dipole moment (VADM) of 40.8 ± 8.5 ZAm2, which is ∼50{\%} of the present-day VADM.",
keywords = "Late Cretaceous, Paleointensity, single-domain (SD), superparamagnetic (SP), virtual axial dipole moment (VADM)",
author = "Wonnyon Kim and Seong-Jae Doh and Yongjae Yu",
year = "2018",
month = "6",
day = "1",
doi = "10.1016/j.pepi.2018.04.004",
language = "English",
volume = "279",
pages = "47--56",
journal = "Physics of the Earth and Planetary Interiors",
issn = "0031-9201",
publisher = "Elsevier",

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TY - JOUR

T1 - Reliable paleointensity determinations from Late Cretaceous volcanic rocks in Korea with constraint of thermochemical alteration

AU - Kim, Wonnyon

AU - Doh, Seong-Jae

AU - Yu, Yongjae

PY - 2018/6/1

Y1 - 2018/6/1

N2 - Paleointensity determinations were carried out from Late Cretaceous (∼77 Ma) volcanic rocks in Korea using a Thellier-type IZZI experimental protocol with systematic partial thermal remanent magnetization (pTRM) checks. Various data selection criteria were used to estimate reliable paleointensities. We set stringent threshold values for each parameter to ensure that there was: (1) a linear relationship between natural remanent magnetization (NRM) lost and TRM gained; (2) negligible thermal alteration of magnetic minerals; and (3) uni-vectorial decay of NRM towards the origin. From the 336 samples, ∼88% were rejected because of an insufficient extrapolated NRM fraction in the best-fit line (fvds < 0.6), highlighting that fvds is the most stringent selection criterion in this study. For the 31 accepted samples, paleointensities range from 6.4 to 30.4 µT. Among the 31 samples, eight samples yielded extremely low paleointensities. Although single-domain (titano)magnetite was identified as the stable paleointensity recorder, oxidation of superparamagnetic fractions upon repeated heating probably caused enhancement of pTRM acquisition and yielded a low paleointensity estimate. Apart from these low paleointensities (n = 8) as screened by a newly proposed data selection criterion of Δk < 0.2, the remaining 23 samples have a mean paleointensity of 23.1 ± 4.8 µT, corresponding to a virtual axial dipole moment (VADM) of 40.8 ± 8.5 ZAm2, which is ∼50% of the present-day VADM.

AB - Paleointensity determinations were carried out from Late Cretaceous (∼77 Ma) volcanic rocks in Korea using a Thellier-type IZZI experimental protocol with systematic partial thermal remanent magnetization (pTRM) checks. Various data selection criteria were used to estimate reliable paleointensities. We set stringent threshold values for each parameter to ensure that there was: (1) a linear relationship between natural remanent magnetization (NRM) lost and TRM gained; (2) negligible thermal alteration of magnetic minerals; and (3) uni-vectorial decay of NRM towards the origin. From the 336 samples, ∼88% were rejected because of an insufficient extrapolated NRM fraction in the best-fit line (fvds < 0.6), highlighting that fvds is the most stringent selection criterion in this study. For the 31 accepted samples, paleointensities range from 6.4 to 30.4 µT. Among the 31 samples, eight samples yielded extremely low paleointensities. Although single-domain (titano)magnetite was identified as the stable paleointensity recorder, oxidation of superparamagnetic fractions upon repeated heating probably caused enhancement of pTRM acquisition and yielded a low paleointensity estimate. Apart from these low paleointensities (n = 8) as screened by a newly proposed data selection criterion of Δk < 0.2, the remaining 23 samples have a mean paleointensity of 23.1 ± 4.8 µT, corresponding to a virtual axial dipole moment (VADM) of 40.8 ± 8.5 ZAm2, which is ∼50% of the present-day VADM.

KW - Late Cretaceous

KW - Paleointensity

KW - single-domain (SD)

KW - superparamagnetic (SP)

KW - virtual axial dipole moment (VADM)

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U2 - 10.1016/j.pepi.2018.04.004

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VL - 279

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EP - 56

JO - Physics of the Earth and Planetary Interiors

JF - Physics of the Earth and Planetary Interiors

SN - 0031-9201

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