• Journal of the Korean Geophysical Society
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• v.9 no.3
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• pp.263-272
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• 2006

Since the paleomagnetic study was introduced in Korea about 40 years ago, its scientific findings contributed to the understanding of geologic settings and tectonic processes of the Korean Peninsula and eventually to the escalation of geology and geophysics in Korea. It is worth summarizing and introducing the up-to-date paleomagnetic results produced by the representative paleomagnetic working groups in Korea, such as K. D. Min, I. S. Kim, S. J. Doh, Y. S. Lee, D. W. Suk, the late K. H. Kim and others.

• Ocean and Polar Research
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• v.24 no.3
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• pp.197-205
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• 2002

Total magnetic field and high-resolution bathymetric data were collected over nine seamounts to the northwest of the Marshall Islands in the western Pacific. Magnetic parameters including inclination and declination were calculated from the magnetic anomalies using inversion algorithm of Plouff (1976), and a corresponding paleomagnetic pole was determined with the magnetic parameters. The paleomagnetic poles determined in this study were compared with the previous apparent polar wander path (APWP) of Pacific plate. Most seamounts of the study area have normal polarity. The study reveals that all nine seamounts in the study area formed in the southern hemisphere during the Cretaceous based on their comparison with the APWP of Pacific plate. The ages estimated from paleomagnetic poles can be divided by age into three groups: the oldest (OSM1 and OSM3), middle age (OSM2, OSM4, and 6-2), and the youngest (OSM5-1, 5-2, 5-3, and 6-1). The fermer two groups and the latter seem to be coincident with two distinct pulses of Cretaceous volcanic activity (115-90 Ma and 83-65 Ma). As a whole the seamounts at southwest of the study area are older than at those northeast.

• Economic and Environmental Geology
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• v.25 no.1
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• pp.87-96
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• 1992

Paleomagnetic study on the sedimentary rocks in the Choongnam Coal Field has been carried out to determine the direction of declination and inclination of NRM and position of paleomagnetic pole, and to investigate the geotectonism and geomagnetic stratigraphy of the sedimentary rocks in the Daedong Group. As a result of paleomagnetic study, the study area can be divided tectonically into two blocks by Baegunsa fault, namely northwestern and southeastern blocks. Site mean declination and inclination of Baegunsa and Seoungjuri Formations in the northwestern block are $23.2^{\circ}$ and $54.9^{\circ}$, respectively. Those of Amisan, Jogyeri, Baegunsa and Seoungjuri Formations in the southeastern block show normal direction with declination and inclination of $-22.1^{\circ}$ and $11.2^{\circ}$, and reversed direction with those of $158.5^{\circ}$ and $-12.6^{\circ}$, respectively. Average paleomagnetic pole position in the northwestern block is located at $212.9^{\circ}E$ and $71.1^{\circ}N$, and that in the southeastern block at $345.7^{\circ}E$ and $53.3^{\circ}N$. This difference suggests relative rotation of about $45^{\circ}$ between two blocks. The paleolatitude of Daedong Group at the time of sedimentation is $5.6^{\circ}N$ much lower than present latitude of $37.7^{\circ}N$. Compared with worldwide Mesozoic paleomagnetic polarity stratigraphy, Amisan Formation is correlated with the lower boundary of Nuanetsi reversal zone in Graham interval, and Baegunsa and Seoungjuri Formations are correlated with just upper part of the upper boundary of Nuanetsi reversal zone, and their geologic ages are Late Triassic to Early Jurassic. The position of paleomagnetic pole acquired from Daedong Group in the study area is different from those in other places. This may be attributed to the different tectonic movement by Daebo Orogeny occurred after the deposition of Daedong Group.

• Economic and Environmental Geology
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• v.27 no.1
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• pp.49-63
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• 1994

Paleomagnetic study of Tertiary rocks in Pohang area has been carried out to determine the characteristic directon of natural remanent magnetization, the position of paleomagnetic pole, the stratigraphic correlation, and the tectonic movement. A total of 196 specimens was collected from 5 sites in the Pohang Basin, 19 sites in the Janggi Basin, and 10 sites in the Eoil Basin, respectively. The mean declination and inclination of 4 sites (3 sites in the Yonil Group and 1 site in the Yonil Basalt) are $-3.2^{\circ}$ and $54.3^{\circ}$, and yield the paleomagnetic pole position $86.9^{\circ}N$ and $7.7^{\circ}E$. These are the characteristic direction and pole position of Miocene Epoch by comparison with contemporary Eurasian and Chinese data. The characteristic direction and pole position of remaining 30 sites are $47.6^{\circ}$ and $57.5^{\circ}$, and $52.3^{\circ}N$ and $201.5^{\circ}E$, respectively. These show clockwise rotation of $50.8^{\circ}$ with respect to the Miocene ones resulted by a tectonic movement before the deposition of the Hakjeon Formation of the Yonil Group about 15~16 Ma in the study area. The mechanism of the clockwise rotation is considered to be the dextral movement of the Yangsan Fault presumably caused by the opening of the East Sea. The Yonil Basalt is reclassified into pre- and post-deposition of the Yonil Group, i.e. the former is early Miocene and the latter late Miocene.

• Economic and Environmental Geology
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• v.19 no.2
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• pp.153-163
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• 1986

Paleomagnetic and geological studies of volcanic and sedimentary rocks of Jeju Island have been carried out to determine the position of virtual geomagnetic pole(VGP), and to estimate the geological sequence and their age. As a result of paleomagnetic studies, the reversal polarities are measured in the Sanbangsan trachyte and Hwasun formation, and the normal are the rest. In case of normal polarity, the mean values of declination and inclination are $2.3^{\circ}$ and $48.4^{\circ}$, respectively, and the average value of VGP is $85.4^{\circ}N$ and $79.9^{\circ}W$. The locations of VGP's are coincident with those obtained from world-wide Plio-Pleistocene rocks. The Hwasun formation and Seongsan formation which have been known to be sedimented in the similar time in the 2nd-stage of volcanic eruption, possess reversal and normal polarities, respectively. This fact brings about the result that two formations should be separated in a sense of geological sequence. Consequently, the geological sequence of the 2nd-stage of volcanic eruption is Pyoseonri basalt-Seoguipo hawaiite-Hwasun formation-Seongsan formation-Jungmun hawaiite-Sanbangsan trachyte. Referring to the paleomagnetic studies and the previous and present geological studies, Seoguipo formation corresponds to the Gauss normal epoch, the 2nd-stage of volcanic eruption to Matuyama reversed epoch, and the 3rd-, 4th-, and 5th-stages to Brunhes normal epoch. Therefore, the Seoguipo formation is mostly sedimented during late Pliocene and/or presumably extended to the early Pleistocene. The rocks of the 2nd- to 5th-stage are formed later than this.

• Economic and Environmental Geology
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• v.27 no.3
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• pp.263-279
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• 1994

Paleomagnetic and rock-magnetic data of Cretaceous sedimentary and volcanic rocks from the Euiseong area indicate that the stable components of remanence are carried by single and pseudo-single domain magnetite, with the exception of the Shinyangdong Formation which has been remagnetized. The Hayang Group, except for the remagnetized Shinyangdong Formation, yields the mean characteristic direction of $D/I=22.5^{\circ}/57.2^{\circ}$ (${\alpha}_{95}=4.6^{\circ}$, N=14 sites) and the pole position is $72.0^{\circ}N$, $206.4^{\circ}E$ ($dp/dm=4.9^{\circ}/6.7^{\circ}$). The Yucheon Group shows two polarities and the mean characteristic direction of $D/I=351.2^{\circ}/60.5^{\circ}$ (${\alpha}_{95}=11.2^{\circ}$, N= 19 sites) and the pole position is $81.3^{\circ}N$, $79.0^{\circ}E$ ($dp/dm=13.0^{\circ}/17.0^{\circ}$). The mean directions of both the Hayang and the Yucheon Groups are supported by the McElhinny's fold test at the 99% confidence level and that of the Yucheon Group by a reversal test at the 95% confidence level. A magnetostratigraphic correlation between polarities of the study formations and the Geomagnetic Time Scale indicates that the Hayang Group can be correlated to the Cretaceous Long Normal Superchron (CLNS), and the Yucheon Group to the boundary between the CLNS and the Polarity Chron 33R or later boundaries between normal and reverse polarities. Comparison of the paleopoles from this study with those from the surrounding areas both within the Gyeongsang basin and in the northeastern Asia indicates that the study area was not undergone significant tectonic rotations with respect to the other parts of the Gyeongsang basin and that the Korean Peninsula was the part of the single terrane of the northeastern Asia at least since the CLNS. The Yucheon Group can be divided into four sub-groups based on the paleomagnetic data, suggesting that there were at least four times of volcanic activities in the study area.

• Economic and Environmental Geology
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• v.32 no.2
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• pp.189-201
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• 1999

Paleomagnetic and rock magnetic investigations have been carried out for the Cretaceous Hanyang Group, exposed in the Yongyang Sub-Basins within the Kyeongsang Basin, eastern South Korea. A total of 452 oriented core samples was drilled from 31 sits for the study. The in-situ site mean direction is more dispersed than the mean direction after bedding correction, indicating that the fold test is positive at 95% confidence level. In addition, the stepwise unfolding of the characteristic remanent magfold test is positive at 95% confidence level. In addition, the stepwise unfolding of the characteristic remanent magnetization reveals that a maximum value of k is observed at 90% unfolding. Furthermore, the rock magnetic investigations and electron microscope observations of the representative samples show that the main magnetic carrier of the Hayang Group is the detrital specular hematite of single and pseudo-single domain sizes with negligible contribution of pigmentary hematite grains. These results collectively imply that the ChRM direction is the primary component acquired at the time of the formation of the strata. Provided the primary nature of the ChRM, a magnetostratigraphic correlation between polarities of the studied formation and the Geomagnetic Time Scale indicates that the Hayang Group in the Yongyang Sub-Basin can be correlated to the Cretaceous Long Normal superchron. The paleomagnetic pole position from this study is significantly different from those of the Hayang group in the Euiseong the Milyang sub-Basins. Rather the paleomagnetic pole position of the Hayang Group of the study area is closer to that of the Quaternary period or present time of the Korean Peninsula. It is hypothesized that the study area might be rotated about 25$^{\circ}$ aticlockwise with respect to the Euiseong and Milyang Sub-Basins after the formation of the strata and aquisition of the ChRM, although there is not enough geologic evidence supporting the rotation hypothesis.

• Journal of architectural history
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• v.25 no.4
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• pp.57-64
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• 2016

It was believed that Jeongnimsa temple was built after the capital was moved from Gongju to Buyeo. It was confirmed that it was built A.D. $625{\pm}20$ by conducting a paleomagnetic analysis on the fireplace, which was recently found at the bottom of Jungmunji(middle gate). Consequently, it is assumed that the temple was built in the early 7th century unlike the previous point of view. Therefore, this study evaluated if the fireplace at the bottom of Jungmunji was found at the geological stratum representing the Jeongnimsa temple. Moreover, the study examined when the fireplace at the bottom of Jungmunji was constructed on the soil stratum. It is possible that the fireplace was built in the early 7th century as shown in the paleomagnetic analysis. However, when we compared the soil strata of the Jungmunji and the existing five-story stone pagoda, it showed that the ground was prepared differently and they were built over a fairly long period of time. Furthermore, I discovered that there was a wooden pagoda under the five-story stone pagoda by examining the soil strata map. Therefore, previous studies evaluated the arrangement of auxiliary buildings of Jeongnimsa temple and concluded that it was built in the early 7th century. It is hard to determine when the temple was built based on the arrangement of auxiliary buildings, because it takes a long time to build a temple and auxiliary buildings can be relocated during this long construction period. Rather, we have to admit that there are various arrangement patterns through minor changes in buildings from the one pagoda and one main building(Geumdang) arrangement.

• Economic and Environmental Geology
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• v.26 no.4
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• pp.507-518
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• 1993

Paleomagnetic investigations have been carried out on the Tertiary sedimentary formations (Yeonil Group) in Pohang basin, southeastern Korea. A total of 215 samples were collected from 26 sites. Progressive thermal demagnetization indicates that many samples have unstable magnetization and do not reveal a characteristic direction. However, some samples from the lower and upper Duho Formation show a characteristic direction $D/I=7.8^{\circ}/48.3^{\circ}$ (${\alpha}_{95}=3.7^{\circ}$, k=174.1). Stepwise thermal demagnetization data show that some samples from the Hagjeon and middle Duho Formations reveal great-circle distributions moving from the present to a reversed direction of geomagnetic field. The mean of intersection points of the great-circles is nearly antipodal to the characteristic normal direction of the lower and upper Duho Formation. We infer that the Hagjeon Formation was formed during the reversed polarity chron C5B (16.2~14.7 Ma) and the Duho Formation 14.7~11.6 Ma based on our results and previous paleontologic and age dating data. Paleomagnetic direction for the Middle Miocene of Korea, analysed from the combined results of stable endpoints and great circles, is $D/I=8.7^{\circ}/53.9^{\circ}$ (${\alpha}_{95}=4.2^{\circ}$, k=74.8), and the corresponding paleopole is Lat./Long.=$82.7^{\circ}/230.2^{\circ}$ (${\delta}p=2.8^{\circ}$, ${\delta}m=5.9^{\circ}$). On the basis of this, we interpret that the opening of the East sea (Japan sea) or the synchronous clockwise rotation of the Southwest Japan exerted no structural influence on the Yeonil Group in the Middle Miocene.

• Economic and Environmental Geology
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• v.31 no.1
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• pp.45-52
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• 1998

Paleomagnetic data have been obtained from the Lower Triassic Tonggo Formation which is exposed in Tanyang area comprising the Pyeongan Supergroup in eastern Korea. Mean characteristic direction of the Tonggo Formation is declination/inclination=$121.4^{\circ}/-26.4^{\circ}$ (k=52.7, ${\alpha}_{95}=7.2^{\circ}$, N=9 Sites) and paleopole at longitude/latitude=$30.7^{\circ}E/33.3^{\circ}N$ ($dp/dm=4.2^{\circ}/7.8^{\circ}$). The mean direction passes reversal test and fold test at 99% confidence level. Therefore, it is inferred to be a pre-folding component. The paleopole position of this study is close to the Triassic pole positions of the North China Block; it is far from those of the South China Block. Therefore, a first order correlation between the Korean Peninsula and North China at least since Lower Triassic times is identified in this study.