Yongjae Yu

Chungnam National University

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Wonnyon Kim

Korea Institute of Ocean Science and Technology

Qingsong Liu

Southern University of Science and Technology

David J. Dunlop

Czech Academy of Sciences, Institute of Organic Chemistry and Biochemistry

Seong‐Jae Doh

Korea University

Lisa Tauxe

Scripps Institution of Oceanography

J. Torrent

University of Córdoba

ÖÖ

Özden Özdemir

University of Toronto

Rixiang Zhu

Institute of Geology and Geophysics

Sung Hi Choi

Chungnam National University

Chenglong Deng

Chinese Academy of Sciences

Cooperative Institutions

Seoul National University

Chinese Academy of Sciences

Korea University

Chungnam National University

University of Chinese Academy of Sciences

Korea Institute of Ocean Science and Technology

Institute of Geology and Geophysics

National Research Institute of Cultural Heritage

Scripps Institution of Oceanography

University of California, San Diego

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Archeomagnetism of Ontario potsherds from the last 2000 years

Journal of Geophysical Research Atmospheres (2000)

Yongjae Yu David J. Dunlop L. A. Pavlish Martin Cooper

An archeomagnetic study was carried out on potsherds samples from sites in Ontario with ages ranging from A.D. 90 to A.D. 1640 as determined by 14 C dating. Thellier double‐heating paleointensity experiments were performed in air on 65 specimens of 52 samples from seven sample sets. Reliable paleointensity estimates were obtained for 49 specimens. Alternating field and thermal demagnetization, temperature dependence of weak‐field susceptibility, and hysteresis measurements indicate that magnetite of pseudo‐single‐domain grain size is the carrier of natural remanent magnetization. The paleointensity results follow a half‐cycle sine curve, with a steady decrease from 54.0±5.9 μT to 37.6±5.7 μT between A.D. 90 and A.D. 885 and a monotonic increase from 52.0±6.1 μT to 59.4±1.7 μT between A.D. 1200 and A.D. 1900. The paleointensities determined yield virtual axial dipole moments (VADMs) of the Earth's magnetic field that agree well with those from other parts of North America, except between A.D. 900 and A.D. 1400, when they are systematically lower. This discrepancy is probably caused by a substantial non‐dipole field in southwestern North America from the tenth to the fifteenth century, since secular variation studies using potsherds from Arizona and lake sediments from Minnesota show different inclination variations during that period.

Natural remanent magnetization

Secular Variation

10.1029/2000jb900177

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Magnetic Properties of Deep‐Sea Sediments From the North Pacific: A Proxy of Glacial Deep‐Water Ventilation

Geochemistry Geophysics Geosystems (2018)

Ji Young Shin Yongjae Yu Inah Seo Kiseong Hyeong Dhongil Lim

Abstract The magnetic properties of deep‐sea sediments in the North Pacific vary in sync with glacial‐interglacial climatic changes and have thus been considered as a paleoclimate indicator. However, the causes of these variations in magnetic properties, including the concentration, grain size, and mineralogy of magnetic minerals, remain poorly understood. Here we investigate the magnetic properties of deep‐sea sediments recovered from the Shatsky Rise in the North Pacific to investigate the cause of the variability associated with glacial‐interglacial cycles. Compared to the potential sediment provenances, the interglacial‐stage and more than half of the glacial‐stage sediments reveal magnetic mineralogical properties (S ratio and L ratio) of the Gobi and Taklimakan deserts, probably indicating dust from the both sources. During glacials, an abrupt decrease in the concentration of magnetic minerals is associated with increases in the average grain size and in the proportion of hematite relative to magnetite. The changes during glacials are mostly a result of dissolutions of magnetite by exposure to ambient ocean environments after deposition. Both magnetic and geochemical proxies validate that poor ventilation of the glacial deep waters in the North Pacific possibly induced iron‐reducing conditions. With comprehensive compilation with the S‐ratio data in the North Pacific sediments, our result indicates that the poorly ventilated deep waters reached up to water depths of ~2,500 m during glacials.

Magnetic mineralogy

10.1029/2018gc007735

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Citations (8)

Mesozoic lithospheric mantle of the Central North China craton: Evidence from peridotite xenoliths

Geochimica et Cosmochimica Acta Supplement (2008)

Wenliang Xu De‐Ping Yang Shunbao Gao Yongjae Yu F. Pei

Peridotite

Xenolith

Source

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Spinel in Martian meteorite SaU 008: implications for Martian magnetism

Earth and Planetary Science Letters (2005)

Yongjae Yu J. S. Gee

Achondrite

10.1016/j.epsl.2004.12.015

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Citations (25)

How accurately can NRM/SIRM determine the ancient planetary magnetic field intensity?

Earth and Planetary Science Letters (2006)

Yongjae Yu

Thermoremanent magnetization

Natural remanent magnetization

Single domain

Saturation (graph theory)

Environmental Magnetism

Rock magnetism

10.1016/j.epsl.2006.07.027

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Citations (29)

Extreme Conditions Modeling Workshop Report

Ryan G. Coe Vincent S. Neary Michael Lawson Yongjae Yu Johannes Weber

Sandia National Laboratories (SNL) and the National Renewable Energy Laboratory (NREL) hosted the Wave Energy Converter (WEC) Extreme Conditions Modeling (ECM) Workshop in Albuquerque, NM on May 13th-14th, 2014. The objective of the workshop was to review the current state of knowledge on how to model WECs in extreme conditions (e.g. hurricanes and other large storms) and to suggest how U.S. Department of Energy (DOE) and national laboratory resources could be used to improve ECM methods for the benefit of the wave energy industry.

National laboratory

Energy Modeling

10.2172/1149224

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Citations (12)

On the resolution of multivectorial remanences

Earth and Planetary Science Letters (2003)

Yongjae Yu David J. Dunlop Özden Özdemir

10.1016/s0012-821x(02)01149-4

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Magnetic evaluation of sediment provenance in the northern East China Sea using fuzzy c-means cluster analysis

Marine Geology (2013)

Wonnyon Kim Seong‐Jae Doh Yongjae Yu Yong Il Lee

Environmental Magnetism

Single domain

10.1016/j.margeo.2013.01.001

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Citations (38)

Magnetic Fabrics and Source Implications of Chisulryoung Ignimbrites, South Korea

Frontiers in Earth Science (2016)

Hoabin Hong Yongjae Yu Seong‐Jae Doh Dongwoo Suk Jeongmin Kim

The anisotropy of magnetic susceptibility (AMS) of late Cretaceous ash-flow tuffs in Chisulryoung Volcanic Formation, southeastern Korea was studied to define the primary pyroclastic flow azimuth. AMS data revealed a dominant oblate fabric with a tight clustering of k3 (minimum axis of magnetic susceptibility) and shallow dispersal of k1 (maximum axis of magnetic susceptibility) and k2 (intermediate axis of magnetic susceptibility). Dominance of oblate fabrics indicates clast imbrications imposed by compaction and welding. Flow azimuth inferred from AMS data indicates the nearby intrusive welded tuff (IWT) as the source of calderas for ignimbrites. Such an inference is supported by geologic investigations, in which the IWT displays eutaxitic textures nearly parallel to its subvertical contacts. The results are compatible with a unique prolate fabric and an anomalously high inclination observed for the IWT, possibly produced by rheomorphic flows as the welded tuff is squeezed along the rough-surfaced dyke walls due to agglutination.

10.3389/feart.2016.00079

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Citations (2)

Effect of multi-cycle heat treatment and pre-history dependence on partial thermoremanence (pTRM) and pTRM tails

Physics of The Earth and Planetary Interiors (2006)

Yongjae Yu Lisa Tauxe

Thermoremanent magnetization

10.1016/j.pepi.2006.04.006

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Citations (12)