• The Korean Journal of Petroleum Geology
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• v.10 no.1_2 s.11
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• pp.1-9
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• 2004

A total of 17 exploratory wells were drilled from the Block VI-1 and recently commercial gas field was discovered in the Ulleung Basin. Thermal maturity of organic matter in the sediments from the drilling wells were evaluated for the characterization of the petroleum system of the basin. Level of thermal maturation of organic matter is different depending on the area to area. The top of oil window is located at about 800 m in the Dolgorae 5 area, and it is relatively deeper in both western and northern areas. It seems that thermal maturity of organic matter reached present stage before tectonism in the deformed zone 2, whereas thermal maturation continued after tectonism in other zones.

• Journal of the Korean association of regional geographers
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• v.22 no.3
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• pp.703-713
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• 2016

This study documents the altitude of paleo-shoreline and formation age of the $1^{st}$ marine terrace emerged around Heunghae-eup Pohang City (South Korea). As a result, the $1^{st}$ terrace representing 10 m of the paleo-shoreline was formed at MIS 5c around 100,000 BP and was influenced repetitive sedimentation of sea-wave till regression of MIS 5a. The result is recognized as a definite truth for the $1^{st}$ terrace in the eastern coast of the Korean peninsula based on synthetic reviews of previous studies and cross-validation of absolute age data. Furthermore, this study deduces a sea stand at MIS 5c from the geomorphological contrast method, but precise determination of paleo-shoreline of the $2^{nd}$ terrace should be required to estimate that of MIS 5c.

• Economic and Environmental Geology
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• v.24 no.2
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• pp.167-176
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• 1991

The Yeongweol - Yemi area, in the area between the Kagdong thrust fault and Samcheog Coalfield, comprises Paleozoic and Mesozoic sedimentary and igneous rocks. Geologic structures related with thrust movements are dominant in the area. These are thrust faults, imbricate structures and hanging-wall anticline. Thrust sheets were transported from NW to SE and these differ from the Cretaceous Bulkuksa Orogeny of which thrust sheets were transported from N to S. NE - trending folds are dominant, but NW - trending folds and refolded folds are also found. NW - trending folds are only found in the Cambro-Ordovician sedimentary rocks. It might be an indication of the presence of late Paleozoic tectonism in the Korean Peninsula.

• Economic and Environmental Geology
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• v.28 no.5
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• pp.493-501
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• 1995

Carboniferous and Cretaceous rock samples were collected from 3 and 12 sites respectively in the vicinity of the Okcheon Zone. Mean directions of characteristic component magnetizations from Carboniferous rocks along the Honam Shearzone reveal that the Okcheon zone was considerably rotated and deformed during Triassic. The amount of rotations were clockwisely $80.3^{\circ}$ in Mungyeong and $42.4^{\circ}$ in Hwasun areas. Mean directions of characteristic component magnetizations obtained from Cretaceous Yeongdong and Neungju Basin were identical to those from the Gyeongsang Basin in the Yeongnam Block indicating no relative motion between them since Cretaceous. Cretaceous paleopole position from 4 locations, $204.9^{\circ}E$ in longitude and $65.1^{\circ}N $ in latitude.

• Economic and Environmental Geology
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• v.4 no.1
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• pp.39-43
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• 1971

The Korean Peninsula is located between the tectonically stable Asian Continent and the tectonically active Japanese islands. The east coast of Korea shows evidence of uplift whereas the west coast shows evidence of submergence. However, radiocarbon dates indicate that the rate of submergence of the west coast of Korea is slower than the tectonically stable east coast of North America. Therefore, both east and west coasts of Korea might have been uplifted during the last post-glacial period. This uplift may result the spreading line of the from compressional strain produced along East Sea of Korea (Japan Sea) and/or the conversion hinge line of the Pacific mantle convection current plunging beneath the Asian continent. This downturn is supposed to be located in the Japan Trench. High heat flow near the east coast of Korea produces the differential strain. This strain accelerates the compressional strain of the peninsula. The Sea Floor Spreading Theory can explain the tectonism of the Korean Peninsula in Recent time. Baek-Doo Mt. and Han-Ra Mt., dormant volcanoes, may be an evidence of westward movement of the Korean Peninsula.

• Journal of The Geomorphological Association of Korea
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• v.25 no.3
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• pp.57-70
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• 2018

This study restores onshore paleo-shoreline records and establishes the nature and strain rate of neotectonism by investigating the existence and formative age of paleo-coastal sediments emerged around Sacheon-si in the Southern part of the Korean peninsula. As a result, paleo-sand bars representing 5m of the paleo-shoreline from high tide level are formed in Sacheon-si, and the formation age of these is confirmed as MIS 5c at approximately 100,000 year BP through rock surface luminescence dating to rounded gravels in paleo-sand bars. Although it is difficult to establish the uplift rate of crust precisely due to incomplete restoration of sea level records during the last interglacial stage, the uplift rate along the Southern coast of the peninsula was assumed approximately 0.72 lower than the Eastern coast during the late Quaternary in comparison to the 1st marine terrace along the Eastern coast.

• Economic and Environmental Geology
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• v.32 no.3
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• pp.293-306
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• 1999

The lower Permian jungseong Formation, Taebaegsan basin (Baegunsan Syncline), represents a coal-bearing siliciclastic succession which was later modified by the Songrim or Dabo orogeny. Sandstone perography and clay mineralogy were studied to understand the thermal history of the Jangseong Formation during basin evolution. Petrographic study indicates the Jangseong sandstones are composed of quartz, feldspar, lithic fragments (metamorphic and sedimetary), and varying proportions of matrix and cement. The dominance of quartz(<97%) over feldspar (<1%) and lithic fragments (<2%) classifies most Jangseong sandstones as quartz arenotes or quartzwackes, but lithic graywackes and sublithic arenite locally occur. The diagentic features of these sandstones include mechanical compaction, cemenation by quartz and clay minerals indentified in the Jangseong Formation by X-ray diffraction analysis are late-stage clay pore-filling. Clay minerals isdentified in the Jangseong Formation by X-ray diffaction analysis are illite, kaolinte, and pyrophyllite with a minor amount of chlorite and micas. The illite, kaolinite, and pyrophyllite appear to be largely autjigenic based on their well-crystallinity forms. There authigenic clay minerals form clay minerals form clay coats/rims and late-stage pore-filling cements, Illitecrystallinity shows that the Jangseong formation has been in late-diagenetic zone to early-epizone, which ranges in temperature from $200^{\circ}C$ to $300^{\circ}C$. In assition, kaolinite-pyrophyllite transition suggests that paleotemperature of the formation has reached at least $265^{\circ}C$. Such temperatureis likely to be consistent with homogenixation temperatures of fluid inclusions in quartz veins in the formation. Thus, the Jangseong Formation has been subjected to paleotemperature of about $265^{\circ}C$. The major heat source responsible for paleotemperature may be hydrothermal solutions. The passage of hydrothermal solutions was probably assisted by fractures created during the basin-modifying tectonism of the taebaegsan basin.

• Economic and Environmental Geology
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• v.16 no.2
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• pp.111-123
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• 1983

The studied area is situated in tho southern part of the Ogcheon fold belt, where the "Ogcheon Group" is widespread with Jurassic and Cretaceous intrusions. The regional stratigraphy may be divided into three formations, the lower pebble bearing phyllitic, the middle dark grey phyllitic, and the upper black phyllitic formations. For the purposes of the present study, the area has been partitioned to three structural subareas based on major fold axes and fault line. The main subjects of the research have been discussed from two different points, multiple deformation and minor-micro fold styles. The former is analyzed by pebble elongation, folding and lineation in a pebbly formation as well as schistosity, crenulation cleavage and crenulated lineation in the phyllitic formation. The later describes the characteristic features of fold style in each formation and structural subarea. Although minor fold axes within broad pelitic rocks usually tend to trend northeast and to plunge northward, most of these were probably formed by two stages, first a similar fold phase and second a kink fold phase. Measured structural elements indicate that crenulation cleavage in phyllite formed parallel to fold axes of folded pebble followed a NE phase of first deformation and a fold axes of pebbles diagonal to bedding of phyllite are represented by a NW phase of a second deformation. Microscopically, quartz and mica grains form a micro fold enabling one to establish tectonic levels which occur in different deformation modes in each stratigraphic sequence. Microtextures such as crenulation cleavage, kink band, aggregate band of mica and pressure shadows of porphyroblast of quartz related to qarnet and staurolite may suggest the time relation of crystallization and tectonism. The result of this study may conform that three deformation phase, NE first phase-NE second phase-NW phase, occurred in the area.

• Geophysics and Geophysical Exploration
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• v.12 no.2
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• pp.199-207
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• 2009

From 329 earthquake data in the Korean Peninsula, we separated the intrinsic and scattering quality factor ($Q_i^{-1}$ and $Q_s^{-1}$) using the Multiple Lapse Time Window Analysis (MLTW) method. For the homogeneous velocity structure, $Q_i^{-1}$ reduces the amplitudes of both direct and coda waves; $Q_s^{-1}$ diminishes the direct wave amplitude but enlarges the coda wave amplitude. Based on this phenomenon, MLTW method analytically derives theoretical curves and obtains $Q_i^{-1}$ and $Q_s^{-1}$ by least square fit with observation curves. This study is the first approach for the seismic stable region by MLTW method, and show that $Q_i^{-1}$ and $Q_s^{-1}$ in the Korean Peninsula are very low at lower than frequencies of 5 Hz. This low value seems to be related to the inactive tectonism of the Korean Peninsula.

• The Journal of the Petrological Society of Korea
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• v.2 no.2
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• pp.122-129
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• 1993

We report Rb-Sr whole rock, K-Ar and fission track mineral ages for the Chuncheon granite in the Precambrian Gyeonggi massif. The Rb-Sr whole rock define an age of $196{\pm}9$ Ma with an initial ratio of $0.7159{\pm}0.0006$, suggesting that the granitic magma might have been generated from crustal sources (S-type), or probably mixed mantle and crustal materials, and emplaced into the massif in the late Triassic or the early Jurassic. K-Ar mineral ages of hornblende, muscovite and biotite are ~210 Ma, ~180 Ma and 166-170 Ma respectively, and fission track zircon and apatite ages are 65-70 Ma, ~35 Ma respectively. These ages indicate that the granitic magma might have been emplaced at about 7 to 9 km from the paleosurface, and rapidly cooled down up to $300^{\circ}C$ until middle Jurassic (~170 Ma) with a rate of about $10^{\circ}C$/Ma, due to thermal difference between the magma and the wall rock. During middle Jurassic to late Cretaceous (about 170-70 Ma), the granite pluton is assumed to have uplifted to 4 to 6 km level under the paleosurface with a rate of 30 m/Ma and slowly cooled down with a rate of about $1^{\circ}C$/Ma owing to relatively slow denudation of the massif. In late Cretaceous to the present, the pluton might have more rapidly uplifted to the present level with a rate of 85 m/Ma and rapidly cooled down with a rate of about $3^{\circ}C$/Ma compared to those of middle Jurassic to late Cretaceous time because of extensive igneous activities accompanied by tectonism in the Gyeonggi massif.