• The Journal of the Petrological Society of Korea
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• v.12 no.4
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• pp.155-169
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• 2003

In the northwest Okcheon metamorphic belt, the metaigneous rocks in the Gyemyeongsan Formation have wider chemical ranges for major, trace and REE elements compared with metaigneous rocks in the Munjuri Formation and do not represent bimodal igneous activity which is characteristic for a continental rifting. The metaigneous rocks in the Munjuri Formation are regarded as products of single magmatic evolution, whereas those in the Gyemyeongsan Formation may be formed through multiple magmatic episodes. The felsic metavolcanic rocks in the Gyemyeongsan Formation show weaker Eu negative anomalies compared with those in the Munjuri Formation but those in both formations show similar degrees of enrichment from LREE to HREE. The metabasites in the Munjuri Formation do not show Eu anomalies but those in the Gyemyeongsan Formation show both positive and negative Eu anomalies(0.59

• Korean Journal of Organic Agriculture
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• v.25 no.2
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• pp.373-386
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• 2017

The study was conducted to investigate seasonal nutrient dynamics in rice-cultivated soils collected from farmhouses of three large-scale environment-friendly agricultural districts (LEAD), Jangheung, Suncheon, and Okcheon in which environmental-friendly agriculture has been exemplarily practiced in Korea. Among three districts, Crop- livestock cycling organic farming system had been introduced only in Jangheung. pH and EC of farmhouse soils of three LEADs were ranged between 5.5 - 6.7 and $0.4-1.0dS\;m^{-1}$ from March to September, respectively. T-N was observed to be high on the farmhouse soil in Suncheon and K was observed to be lowest on farmhouse soil in Okcheon. Concentration of $NH_4-N$ in soil was observed to be highest on June, in particular on the farmhouse in Jangheung, but rapidly decreased due to the loss of fertilizer applied in Spring. Yield and harvest index were the highest on the farmhouse in Okcheon in which total annual gross production $ha^{-1}$ was nearly three time higher than those of other two farmhouses. Farmhouse soil of Okcheon was maintained the highest seasonal nutrient balance due to the high input of fertilizer. It was estimated that K balance in the farmhouse soil in Suncheon dropped to $-60kg\;ha^{-1}$ on September, and it might have some effect on the less rice productivity due to K deficiency. Farmhouse soil in Jangheung was maintained low seasonal balance of T-N and P but showed the highest N use efficiency in the rice grain. Based on above-mentioned results, we think Jangheung farmhouse can be recommended as a model farmhouse of LEADs.

• The Journal of the Petrological Society of Korea
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• v.23 no.1
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• pp.17-30
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• 2014

In this study we carried out SHRIMP U-Pb age dating of detrital zircons from age-unknown meta-sedimentary formations distributed around the NNE-SSW trending Gwangju Shear Zone, a branch of Honam Shear Zone, in the southwestern region of the Korean Peninsula. The meta-sedimentary formations from the west (Yeonggwang) and east (Jangseong) areas of the Gwangju Shear Zone have different patterns of zircon age distributions. Zircons of quartzites from the Yeonggwang area yield clusters at Neoarchean (ca. 2,500 Ma), Paleoproterozoic (ca. 1,860 Ma), Neoproterozoic (ca. 960 Ma) and Paleozoic (ca. 380 Ma) ages, but those of the Jangseong area yield clusters at only Neoarchean (ca. 2,500Ma) and Paleoproterozoic (ca. 1,880 Ma) ages. The contrastive patterns in age indicate that the meta-sedimentary formations from the west and east areas correspond to the meta-sedimentary formations of the Okcheon Metamorphic Belt and the sedimentary formations overlying on the Yeongnam Massif, respectively. The results imply that the Gwangju Shear Zone is the tectonic boundary between the Okcheon Metamorphic Belt and the Yeongnam Massif.

• Economic and Environmental Geology
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• v.42 no.1
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• pp.9-25
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• 2009

The Northwestern Okcheon Metamorphic Belt in the Chungju area consists of the Munjuri Formation, the Daehyangsan Quartzite, the Hyangsanri Dolomite, and the Gyemyeongsan Formation, but the stratigraphy is still controversial. For a stratigraphic study, detailed stratigraphic sections were measured in two locations and mapping was carried out in the study area. The Munjuri Formation and the Daehyangsan Quartzite changed gradually in north and south section, but bedding parallel faults have developed in the boundary between two formations. The Daehyangsan Quartzite and the Hyangsanri Dolomite are conformable. Fault have developed in boundary between the Hyangsanri Dolomite and the Gyemyeongsan Formation. As a result of mapping in the study area, folding was recognized with $41^{\circ}/280^{\circ}$ plunging axis in the north part of the study area. Therefore, the bedding-parallel faults in the boundary might have occurred resulting from a layer parallel slip during the folding as well as the thrust. These results from this study and previous studies indicate that bedding-parallel faults in boundary between the Munjuri Formation and the Daehyangsan Quartzite are caused by a layer parallel slip during the folding. The fault between the Hyangsanri Dolomite and the Gyemyeongsan Formation is considered as a thrust fault, thereby the uppermost Gyemyeongsan Formation is placed under the Munjuri Formation. However the Gyemyeongsan Formation and the Munjuri Formation have similar age and rock composition. Hence, the Gyemyeongsan Formation is considered as an equivalent one with the Munjuri Formation. Therefore, the stratigraphy of Northwestern Okcheon Metamorphic Belt consists of the Gyemyeongsan/ Munjuri formations, the Daehyangsan Quartzite, and the Hyangsanri Dolomite in ascending order.

• Korean Journal of Organic Agriculture
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• v.25 no.1
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• pp.203-218
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• 2017

The study was initiated at three rice paddy fields of each large-scale area environment-friendly agricultural district, Suncheon and Jangheung in Jeollanam-do, and Okcheon in Chungcheongbuk-do in 2016 to observe growth and nutrients in soil and rice in a season. Jangheung farm had two observed plots; conventional plots and conventional plots additionally fertilizing of 20% T-N with oil-cake. Soil pH, EC, and K concentration on June in Jangheung farm were significantly higher than those values observed in Suncheon and Okcheon farms. Annual rice T-N contents in the Jangheung farm were more than 80 g but decreased in a season. T-N concentration in rice was high in Jangheung farm but the concentrations of P and K were not significantly different among the three farms at harvest. Plant height was as low as 101 cm in Sunchon farm but high in the dry weight (72 g). Leaf SPAD was higher in Jangheung farm than those of other farms. Okcheon farm, with early cultivar 'Milky queen', produced high head rice of 93%, and high unhulled rice and the brown rice per ha. Therefore, the annual production income was as high as 26.7 million won per ha. However, nutrient (T-N + P + K) balance in Okcheon farm with high amount of fertilizer application were as high as 900 kg per ha. On the other hand, nutrient balance in Jangheung farm resulted in less than 300 kg.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.831-846
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• 2023

The Jucheon-Pyeongchang area in the northwestern Taebaeksan Zone of the Okcheon fold-thrust belt preserved several thrust faults placing the Precambrian basement granite gneisses of the Gyeonggi Massif on top of the Early Paleozoic Joseon Supergroup and the age-unknown Bangrim Group. Especially, the thrust faults in the study area show the closed-loop patterns on the map view, showing older allochthonous strata surrounded by younger autochthonous or para-autochthonous strata. These basement-involved thrusts including Klippes will provide important information on the hinterland portion of the fold-thrust belt. For defining Klippe geometry in the thrust fault terrains of the Jucheon-Pyeongchang area by older on younger relationship, the stratigraphic position of the age-unknown Bangrim Group should be determined. The Middle Cambrian maximum depositional age by the detrital zircon SHRIMP U-Pb method from this study, together with field relations and previous research results suggest that the Bangrim Group overlies the Precambrian basement rocks by nonconformity and underlies the Cambrian Yangdeok Group (Jangsan and Myobong formations). The structural geometric interpretation of the Pyeongchang area based on newly defined stratigraphy indicates that the Wungyori and Barngrim thrusts are the same folded thrust, and can be interpreted as a Klippe, having Precambrian hanging wall granite gneisses surrounded by younger Cambrian strata of the Joseon Supergroup and the Bangrim Group. Further detailed structural studies on the Jucheon-Pyeongchang area can give crucial insights into the basement-involved deformation during the structural evolution of the Okcheon Belt.

• The Journal of the Petrological Society of Korea
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• v.13 no.4
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• pp.244-246
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• 2004

• The Plant Pathology Journal
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• v.17 no.6
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• pp.357-360
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• 2001

Gray mold was observed on leaves of castor bean grown in Woniu and Okcheon in Korea in October 2000. Symptoms developed in the form of spot and blight with sporulation of the causal fungi at the marginal or central parts of the leaves. A total of 25 isolates were obtained from the infected leaves of castor bean. Out of the 25 isolates, 5 isolates which originated from Woniu were identified as Botrytis cinerea, while 20 isolates from Okcheon were identified as Amphobotrys ricini based on morphological and cultural characteristics. Two isolates each of B. cinerea and A. ricini were tested for their pathogenicity to castor bean plants. Gray mold symptoms similar to those observed in the fields were induced on leaves of castor bean by artificial inoculation. This is the first report of gray mold in castor bean caused by B. cinerea and A. ricini in Korea.

• The Journal of the Petrological Society of Korea
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• v.22 no.4
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• pp.291-298
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• 2013

We identified well developed overgrowth rims from several zircon grains separated from the Gyemyeongsan metavolcanics of the Okcheon Metamorphic Belt. Such overgrowth rims reveal generally quite low Th/U ratios indicating formation during the metamorphism. We were able to conduct SHRIMP U-Pb spot analyses from the relatively wide overgrowth rims and determined a concordia age of $259.7{\pm}3.3Ma$ (n=8, $2{\sigma}$), which indicates timing of the regional metamorphism occurred in the Gyemyeongsan Formation.

• Journal of The Geomorphological Association of Korea
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• v.28 no.1
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• pp.1-12
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• 2021

This study tried to reveal relative surface denudation resistance and ranking by geologic types in the Southern Korean Peninsula using an 1:250,000 digital geologic map and ASTER GDEM. Among rock types such as igneous, sedimentary and metamorphic rocks, metamorphic rock showed the greatest resistance to surface denudation. The most resistant rock to surface denudation by geologic periods (e.g., the Precambrian, Paleozoic, Mesozoic and Cenozoic) was found from the Precambrian. Among the major tectonic settings in the Southern Korean Peninsula such as the Gyeonggi massif, Okcheon belt, Yeongnam massif, Gyeongsang basin and Pohang basin, the Okcheon belt indicated the greatest resistance. The most and least resistant rocks from the representative nine rocks in the Southern Korean Peninsula were Paleozoic limestone, and Cretaceous sedimentary rock and Cenozoic sedimentary rock, respectively. This study suggests that Paleozoic limestone, Cretaceous volcanic rock, Paleozoic sedimentary rock and Precambrian gneiss can be regarded as hard rocks with high elevation, steep slope and complicated relief, while soft rocks with low elevation, gentle slope and simple relief are Jurassic granite, Cretaceous sedimentary rock and Cenozoic sedimentary rock.