• The Korean Journal of Petroleum Geology
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• v.2 no.2 s.3
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• pp.43-50
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• 1994

The geologic structure of Gongju Basin, which is a Cretaceous sedimentary basin located on the boundary of Gyeonggi Massif and Ogcheon Belt, is modeled by using gravity data and interpreted in relation with basin forming tectonism. The electrical survey with dipole-dipole array was also conducted to uncover the development of fractures in the two fault zones which form the boundaries of the basin. In the process of gravity data reduction, the terrain correction was performed by using the conic prism model, which showed better results specially for topography having a steep slope. The gravity model of the geologic structure of Gongju basin is obtained by forward modeling based on the surface geology and density inversion. It reveals that the width of the basin at its central part is about $4{\cal}km$ and about $2.5{\cal}km$ at the southern part. The depth of crystalline basement beneath sedimentary rocks of the basin is about $700{\~}400{\cal}m$ below the sea level and it is thinner in the center than in margin. The fault of the southeastern boundary appears more clearly than that of the northwestern boundary, and its fracture zone may extended to the depth of more than $1{\cal}km$. Therefore, it is thought that the tectonic movement along the fault in the southeastern boundary was much stronger. These results coincide with the appearance of broad low resistivity anomaly at the southeastern boundary of the basin in the resistivity section. The fracture zones having low density are also recognized inside the basin from the gravity model. The swelling feature of basement and the fractures in sedimentary rocks of the basin suggest that the compressional tectonic stress had also involved after the deposition of the Cretaceous sediments.

• 한국석유지질학회:학술대회논문집
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• autumn
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• pp.7-7
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• 2000

• Economic and Environmental Geology
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• v.52 no.5
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• pp.427-448
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• 2019

This study reconstructed the paleoenvironments and paleogeography of the Taebaeksan Basin, through a review of the previous researches on sedimentology, paleontology and stratigraphy. This study also carried out a sequence stratigraphic analysis on regional tectonism and sea-level fluctuations on the basin during the Early Paleozoic. The basin broadly occur in the Taebaek, Yeongweol-Jecheon, Jeongseon-Pyeongchang, and Mungyeong areas, Gangwon province, South Korea. The basin-fills are composed mainly of mixed carbonates and siliciclastics, divided into the Taebaek, Yeongweol, Yongtan, Pyeongchang and Mungyeong groups according to lithologies and stratigraphic characteristics. Recently, there are a lot of studies on the provenance and depositional ages of the siliciclastic sequences of the basin. The detrital sediments of the basin would be derived from two separated provenances of the core-Gondwana and Sino-Korean cratons. In the Early Cambrian, the Taebaek and Jeongseon-Pyeongchang platforms have most likely received detrital sediments from the provenance of the Sino-Korean craton. On the other hand, the detrital sediments of the Yeongweol-Jecheon platform was probably sourced by those of the core-Gondwana craton. This separation of provenance can be interpreted as the result of the paleogeographic and paleotopographic separation of the Yeongweol-Jecheon platform from the Taebaek and Jeongseon-Pyeongchang platforms. The analyses on detrital zircons additionally reveal that the separation of provenance was ceased by the eustatic rise of sea-level during the Middle Cambrian, and the detrital sediments of the Taebaeksan Basin were entirely supplied from those of the core-Gondwana craton. During that period, sediment supply from the Sino-Korean craton would be restricted due to inundation of the provenance area of the craton. On the other hand, the Jeongseon-Pyeongchang platform sequences show the unconformable relationship between the Early Cambrian siliciclastic and the Early Ordovician carbonate strata. It is indicative of presence of regional uplift movements around the platform which would be to the extent offset of the effects of the Middle to Late Cambrian eustatic sealevel rise. These movements expanded and were reinforced across the basin in the latest Cambrian and earliest Ordovician. After the earliest Ordovician, the basin was tectonically stabilized, and the shallow marine carbonate environments were developed on the whole-platform by the Early Ordovician global eustatic sea-level rise, forming very thick carbonate strata in the basin. In the Late Ordovician, the Early Paleozoic sedimentation on the basin was terminated by the large-scale tectonic uplift across the Sino-Korean platform including the Taebaeksan Basin.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.679-684
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• 2011

Branched polypropylenes (LCB-PP) with a long chain branch were prepared by the solid-state and molt-state reaction. Divinylbenzene (DVB), 1,4-benzenediol (RES), and furfuryl sulphide (FS) were used as branching agents of fabricate LCB-PP/silicate composites. Chemical structures, thermal properties, and rheological properties of the LCB-PP were determined by FT-IR, DSC, TGA, and dynamic rheometer (ARES). The chemical structure of the LCB-PP was confirmed by the existence of =C-H stretching peak of the branching agent at $3100cm^{-1}$. From DSC and TGA results, the melting reaction was more effective than the solid state reaction in the manufacture of LCB-PP, which was additionally certified by rheological properties. Based on rheological properties, FS was the best for branching efficiency of PP. Compared to PP, LCB-PPs indicated an increase of complex viscosity in the low frequency and shear thinning tendency, and G'-G" plot represented an increase in elasticity and the heterogeneousness in a melt state. Rheological properties of LCB-PP/silicate composites were observed with the silicate content. When 5 wt% silicate was added in LCB-PP, distinct changes in the shear thinning and the slope of G'-G" plots were observed.

• Journal of the Korean earth science society
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• v.39 no.6
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• pp.545-554
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• 2018

The Cretaceous Eumsung (Eumseong) Basin is a pull-apart basin, formed along a series of the Gongju strike-slip faults trending NE-SW. The Nongdari-Meer forest of the Gugokri area in the southwestern part of the basin is comprised of thick purple mudstone, intercalating conglomerate, pebbly sandstone, and green mudstone beds. The succession mainly consists of seven sedimentary facies: stratified conglomerate (C2), conglomerate encased in siltstone (CE), stratified pebbly sandstone encased in siltstone (PSE2), purple sandy siltstone (Zp), green sandy siltstone (Zg), purple mudstone (Mp), and green mudstone (Mg). Sedimentary environment is mainly indicative of alluvial-plain setting in an alluvial-to-lacustrine sedimentary system, developed in the southwestern part of the basin. Geological survey was fulfilled in succession of the Gugokri sedimentary system using 1:5000 topographic map, which resulted in a geological route map. This study newly suggested that there be fluvial systems showing ENE and NNE trends in the study area, based on data of palaeocurrent direction and sedimentary characteristics in new outcrops of the forest. The study also revised the precedent sedimentation model of the Gugokri system.

• Economic and Environmental Geology
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• v.37 no.2
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• pp.195-206
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• 2004

Paleomagnetic and rock-magnetic investigations have been carried out for the Cretaceous sedimentary rocks in the Poongam (also called Gapcheon) Basin in the eastern South Korea. A total of 128 independently oriented core samples were drilled from 13 sites for this study. The mean direction after bedding correction (D/I=353.1$^{\circ}$/55.6$^{\circ}$, k=21.5, =$$\alpha$_{95}$=10.1$^{\circ}$) is more dispersed than the mean direction before bedding correction (D/I=10.5$^{\circ}$/56.9$^{\circ}$, k=73.9, =$$\alpha$_{95}$=5.3$^{\circ}$), and the stepwise unfolding of the characteristic remanent magnetization (ChRM) reveals a maximum value of k at 20% unfolding. Secondary authigenic hematite accompanied by altered clays such as chlorite was identified by the electron microscope observations. These results collectively imply that the ChRM is remagnetized due to the formation of the secondary authigenic hematite after tilting of the strata. It is interpreted that the chemical remagnetization was connected to the introduction of mixed magmatic-meteoric fluids, which formed hydrothermal vein deposits near the study area. The paleomagnetic pole position (214.3$^{\circ}$E, 81.6$^{\circ}$N, =$A_{95}$=7.4$^{\circ}$) of the Cretaceous sedimentary rocks calculated from remagnetized directions is close to those of the Late Cretaceous and Tertiary poles of the Korean Peninsula. This Late Cretaceous to Tertiary remagnetization seems to be widespread over the Okcheon Belt because the chemical remagnetization is previously reported to be found in rocks from other Cretaceous small basins (e.g., Eumseong, Gongju and Youngdong basins) along the Okcheon Belt and some Paleozoic strata from the Okcheon unmetamorphosed zone.

• Journal of The Geomorphological Association of Korea
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• v.19 no.2
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• pp.99-111
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• 2012

The purpose of this study is to identify the change of geographical (or geomorphological) location environment of the dwelling site and its cause in Daejon Basin during transition from the Bronze Age to the Proto Three Kingdoms Period. In order to achieve this goal, it was divided into (1) 'comparison of the total number of dwelling sites of a group of remains (or high-density dwelling remains)' and (2) 'comparison of the total number of dwelling sites in certain remains including locations of dwelling of two periods' and location environment was compared to each other in aspects of altitude, gradient, 'distance from the river of water available for use' and 'the difference between the highest altitude and lowest altitude of river bed of water available for use' based on change of period. The results were as follows: 1. looking at a change of individual factors, the altitude was elevated and the gradient was increased. The distance from the river of water available for use was decreased or increased in case of 'small scale river' and it was very little difference or increased in case of 'medium scale river'. The difference between the highest altitude and lowest altitude of river bed of water available for use was increased in case of 'small scale river' and it was increased or decreased in case of 'medium scale river'. If comparing the individual factors to each other, the increase and decrease of altitude, gradient and the difference between the highest altitude and lowest altitude of river bed of water available for use have the similar pattern. Especially, it was shown that the increase of gradient affected the increase of altitude and the difference between the highest altitude and lowest altitude of river bed of water available for use. In addition, it was shown that the increase and decrease of distance from the river of water available for use had the different pattern from those of altitude, gradient and 'the difference between the highest altitude and lowest altitude of river bed of water available for use'. 3. With above results, it was thought that combination of micro landform characteristics (eg. Characteristics of gradient) of low hills distributed within Daejeon Basin and rich aquatic environment surrounding the low hills affected the selection of location of dwelling sites at the time. Especially, it was shown that 'gradient and distance from the river of water available for use' were relatively more important factors for the inhabitants at the time to select the location of dwelling sites compared to 'altitude and difference between the highest altitude and lowest altitude of river bed of water available for use' upon selecting the location of dwelling.

• Economic and Environmental Geology
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• v.52 no.5
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• pp.323-336
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• 2019

The Mesozoic activity on the Korean Peninsula is mainly represented by the Triassic post-collisional, Jurassic orogenic, and Cretaceous post-orogenic igneous activities. The diversity of mineralization by each geological period came from various geothermal systems derived from the geochemical characteristics of magma with different emplacement depth. The Cretaceous metallic mineralization has been carried out over a wide range of time periods from ca. 115 to 45 Ma (main stage; ca. 100 to 60 Ma) related to post-orogenic igneous activity, and spatial distribution patterns of most metal deposits are concentrated along small granitic stocks. The late Cretaceous metal deposits in the Gyeonggi and Yeongnam massifs are generally distributed along the boundary among the Gongju-Eumseong fault system and the Yeongdong-Gwangju fault system and the Gyeongsang Basin, most of them are in the form of a distal epithermal~mesothermal Au-Ag vein or a transitional mesothermal Zn-Pb-Cu vein. On the other hand, diverse metal commodities in the Taebaeg Basin, the Okcheon metamorphic belt and the Gyeongsang Basin are produced from various deposit types such as skarn, carbonate-replacement, vein, porphyry, breccia pipe, and Carlin type. In the late Cretaceous metallic mineralization, various mineral deposits and commodities were induced not only by the pathway of the hydrothermal solution, but also by the diversity of precipitation environment in the proximity difference of the granitic rocks. The diversity of these types of Cretaceous deposits is fundamentally dependent on the geochemical characteristics such as degree of differentiation and oxidation state of related igneous rocks, and ore-forming fluids generally exhibit the evolutionary characteristics of intermediate- to low-sulfur hydrothermal fluids.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.2
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• pp.298-317
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• 2019

The physical characteristics of the Ulleung Warm Eddy (UWE) and its relationship with the East Korea Warm Current (EKWC) were analyzed using the CMEMS (Copernicus Marine Environment Monitoring Service) satellite altimetry data and the CTD data of the National Institute of Fisheries Science (NIFS) near the Ulleung Basin from 1993 to 2017. The distribution of the UWEs coupled with EKWC accounts for 81% of the total number of the UWEs. Only 7% of the total eddies are completely separated from the EKWC. The UWE has the characteristics of high temperature and high salinity water inside of it when it is formed from the EKWC. However, when the UWE is wintering, its internal structure changes greatly. In the winter, surface homogeneous layer of $10^{\circ}C$ and 34.2 psu inside of the UWE is produced by vertical convection from sea-surface cooling, and deepened to a maximum depth of approximately 250 m in early spring. In summer, the UWE changes into a structure with a stratified structure in the upper layer within a depth of 100 m and a homogeneous layer made in winter in the lower layer. 62 UWEs were produced for 25 years from 1993 to 2017. on average, 2.5 UWEs were formed annually, and the average life span was 259 days (approximately 8.6 months). The average size of the UWEs is 98 km in the east-west direction and 109 km in the north-south direction. The average size of UWE using satellite altimetric data is estimated to be 1~25 km smaller than that using water temperature cross-sectional data.