• Ocean and Polar Research
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• v.30 no.4
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• pp.497-507
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• 2008

With the reduction of tidal currents by the closing of the Saemangeun 4th dyke, sedimentary environments on the Gunsan tidal flat, the nearest inner flat from the 4th dyke, has been severely changed, which might affect macrobenthic assemblages on the habitats. In order to investigate changes in macrobenthic community structure on Gunsan tidal flat, field surveys were seasonally conducted at seven stations from April 2002 to November, 2005. Sedimentary facies on the study area were shifted into muddominant facies. The fine sediment has been greatly deposited on the tidal flat with accumulation of organic materials after closing the water passage of 4th dyke section. These drastic variations in environments gave rise to change in macrobenthic community structure. Since the closure of the 4th dyke, the number of species of macrobenthos has gradually decreased. And the filter feeders and sand-favored species such as Urothoe convexa, Macrophthalmus dilatatus, Umbonium thomasi, and Mactra veneriformis have been replaced by the deposit feeders such as Macrophthalmus japonicus and Ilyoplax pingi. MDS ordination based on Bray-Curtis similarity from forth-root transformed species abundance data showed that the macrobenthic communities have passed through three succession stages from 2002 to 2005. During the third stage of 2005 opportunistic species such as Prionospio japonica, Heteromastus filiformis and Sinocorophium sinensis increased in population on the tidal flat.

• Journal of the Korean earth science society
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• v.28 no.7
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• pp.747-761
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• 2007

This study is to develop teaching aids and materials for geological fieldwork and to maximize their effects in educating high school students in Korea. The site of geological fieldwork, Kyokpo Chaeseokgang area, is located in Byunsan national park in Jeonbuk Province. The sedimentary succession of Chaeseokgang developed in the era of Cretaceous shows large-scale and distinct sedimentary structures on sea cliffs. In this study, teaching aids and materials of earth science for secondary-level students were developed based on the sedimentary structures of Chaeseokgang. A 5-step teaching model of earth science fieldwork was applied to a group of 13 students, who had been involved in clubs related to earth science in a science high school, using teaching aids and materials developed in this study. The teaching aids and fieldwork-related materials were also presented to a group of 37 students, who did not take fieldwork or fieldwork-related classes during the period of the study. The results of this study showed that the use of fieldwork-related aids and materials was effective in helping the students in both groups improve their self-directed teaming and practical understanding of earth science.

• 한국석유지질학회:학술대회논문집
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• spring
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• pp.1-11
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• 1997

Thirty one samples from Late Cretaceous and Tertiary interval sections (468-783m) of the Kachi-I Well in Block II, Yellow Sea Basin, have been analysed for their terrestrially derived palynofloras. The systematic study of the palynomorphs recovered has yielded one hundred and fifty-five taxa; forty-three species of spores belonging to twenty-eight genera, seventy-seven pollen assignable to forty-three genera, and twenty-seven species assignable to fifteen genera and eight fungal remains. The results of both qualitative and quantitative analysis propose a succession of eight terrestrial palynomorph associations. Seven associations are erected in Late Maastrichtian and one in Early to Middle Miocene. Age determinations are on the basis of palynomorph taxa alone for the all associations. The Late Cretaceous/Tertiary unconformity is recognised at between 603 and 613m, based on the palynological data. The sedimentary basin during the Late Cretaceous seem to be lowland shallow marginal lacustrine with stagnant, mesotrophic conditions. On the other hand, the basin during the Early-Middle Miocene is considered to have been characterised by lowland swamp areas. The palaeoclimatic conditions during the Late Cretaceous are considered to be humid tropical to subtropical, while during the Early to Middle Miocene they are considered to be warm temperate with humid conditions. A comparison of palynomorph assemblages between the present study and the previous studies of Late Cretaceous in Circum-Pacific Northern Hemisphere is made, These assemblages reveal that lower sections (612-783m) of the Kachi-I well belong to the Late Cretaceous Aquilapollenites province of Herngreen and Chlonova (1981) and Srivastava (1981, 1994).

• Geosciences Journal
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• v.22 no.6
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• pp.903-919
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• 2018

This paper focuses on the depositional processes and environmental changes during initial marine flooding recorded in the lower Cambrian succession of the North China Platform in Shandong Province, China. In order to understand imbalance of accommodation and sediment supply in the initial stage of basin-fill, a detailed analysis of sedimentary facies was made for the lowermost siliciclastic deposits of the Liguan Formation. It reveals ten siliciclastic lithofacies in three large-scale outcrops (Jinhe, Anqianzhuang, and Zhangjiapo sections). These facies are grouped into four facies associations, representing siliciclastic foreshoreshoreface (S1), siliciclastic offshore (S2), distributary mouth bars (S3), and coastal plain (S4). The siliciclastic components occur in a linear belt, emanating from a major drainage system in the northeastern part of the platform. Deposition of siliciclastic sediments was largely controlled by regional topography of the unconformable surface and shoreline configuration as well as strong effect of waves and currents. With ensued rise in sea level and decrease in siliciclastic sediment supply, carbonate sediments prevailed, filling the accommodation created by epeirogenic subsidence and sediment loading.

• Journal of the Korean earth science society
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• v.43 no.4
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• pp.520-531
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• 2022

The Yellow Sea experienced glacio-eustasy sea-level fluctuations during the Quaternary period. In the middle part of the Yellow Sea, the Quaternary successions were accumulated by alternating terrestrial, paralic, and shallow marine deposits that reflected the fluctuating sea levels. A long core of 69.2 m was acquired at the YMGR-102 site (33°50.1782'N and 123°48.3019'E) at a depth of 72.5 m in the middle of the Yellow Sea. A four-layered geoacoustic model was reconstructed for the sedimentary succession. It was based on seismic characteristics from 3.5 kHz SBP and air-gun seismic profiles and 96 grain-size properties in the core sample from YMGR-102. For the underwater simulation and experiments, the in-situ P-wave speeds were calculated using the sound speed ratio of the Hamilton method. The geoacoustic model of YMGR-102 can contribute to the reconstruction of geoacoustic models, reflecting the vertical and lateral variability of the acoustic properties in the continental shelf of the middle Yellow Sea.

• Journal of the Korean earth science society
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• v.33 no.7
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• pp.658-671
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• 2012

This study is to develop teaching materials for the geological fieldwork of Jeokbyeokgang area located in the national park of the Byeonsan-bando National Park, Buangun, Jeonbuk, Korea. The developed teaching materials are used in middle school science to effectively teach the fieldwork of the area. The sedimentary succession of Jeokbyeokgang area in the Cretaceous age, Mesozoic, represents the large-scale and distinctive sedimentary structures on sea cliffs, which are worth developing as teaching materials for the earth science fieldwork. The area of Jeokbyeokgang also comprises various geological structures related to the advanced learning programs as well as those within the curriculum of earth science in middle school level. A five-step fieldwork model was applied to 20 students in middle school earth science. This study quantitatively analyzed students' responses to the process of the fieldwork activity. Results indicated that the fieldwork activity using the developed teaching materials was effective in helping the students to improve their self-directed learning and practical understanding of earth science.

• Journal of the Korean earth science society
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• v.24 no.1
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• pp.46-60
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• 2003

In Namyang Bay of western Korea, macrotidal-flat deposits are divisible into three late Quaternary units: Unit M1 of upper marine mud, Unit T1 of middle siderite-bearing terrestrial clay, and Unit M2 of lower marine mud. Unit M1 represents typical Holocene intertidal mudflat deposits, showing a coarsening-upward textural trend. It probably resulted from the continual retrogradation of tidal flat during the mid-to-late Holocene sea-level rise. Reddish brown-color Unit T1 consists of homogeneous clay with abundant freshwater siderite grains and plant remains. Unit T1 is clearly separated from the overlying Unit M1 by a sharp lithologic boundary. Radiocarbon age, siderite grains and lithologic features indicate that Unit T1 is originated from freshwater bog or swamp deposition infilling the localized topographic lows during the early Holocene age. Overlain unconformably by early Holocene swamp clay, Unit M2 is orange to yellow in color and mottled, suggesting significant degree of weathering during the sea-level lowstand. Such subaerial oxidation is confirmed in the vertical profiles of geotechnical properties, clay mineral assemblages and magnetic susceptibility. Unit M2 appears to be correlated with the upper part of the late Pleistocene tidal deposits developed along the western Korean coast. The sedimentary succession of the Namyang-Bay tidal-flat deposit provides stratigraphic information for the Holocene-late Pleistocene unconformity and also permits an assessment of the preservation potential of the late Pleistocene marginal marine deposit along the western coast of Korea.

• Ocean and Polar Research
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• v.36 no.1
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• pp.25-37
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• 2014

To understand the degradation processes of organic matter related to sulfate reduction by Sulfate Reduction Bacteria (SRB) in the tidal flat sediments of Hwang-do and Sogeun-ri, Tae-an Peninsula in Chungnam-do, biogeochemical characteristics were analyzed and highlighted using specific microbial biomarkers. The organic geochemical parameters (TOC, ${\delta}^{13}C_{org}$, C/N ratio, long-chain-n-alkane) indicate that most of the organic matter has been derived from marine phytoplankton and bacteria in the fine-grained sediment of Sogeun-ri, although terrestrial plant components have occasionally been incorporated to a significant degree in the coarse-grained sediment of Hwang-do. The concentration of sulfate in pore water is a constant tendency with regard to depth profile, while methane concentration appears to be slightly different with regard to depth profile at the two sites. Especially, the sum of bacteria fatty acid (a-C15:0 + i-C15:0 + C16:1w5) confirms that the these concentrations in Sogeun-ri are related to the degradation of Benzene, Toluene, Ethylbenzene and Xylene (BTEX) compounds from the crude oil retained in the sediments as a result of the Hebei Spirit oil-spill accident in 2007. The methane-related microbial communities as shown by lipid biomarkers (crocetane, PMI) are larger in some sedimentary sections of Hwang-do than in the Sogeunri tidal flat. These findings suggest that methane production by microbiological processes is clearly governed by SRB activity along the vertical succession in organic-enriched tidal flats.

• Economic and Environmental Geology
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• v.52 no.5
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• pp.357-366
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• 2019

Deposition of the Daedong Supergroup has been considered to be related with the Triassic Songrim and Jurassic Daebo orogenies. The Chungnam Basin fills is an important sedimentary succession to understand the geological evolution of the Early to Middle Mesozoic Korean Peninsula. Previous paleontological and paleomagnetic studies have suggested the Late Triassic to Early Jurassic sedimentation of the Chungnam Basin fills. However, the orogenic model of the basin development has remained controversial because recently reported zircon U-Pb isotopic ages are not harmonious with the previous studies. This paper aims to review the stratigraphy, depositional age, and composition of the Chungnam Basin fills, together with test of the basin development models.

• 한국해양학회지
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• v.25 no.2
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• pp.74-83
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• 1990

The similarity in Mesozoic geology between the Antarctic Peninsula and South America indicates the possibility that they had situated along the same tectonics line before the separation of southwestern Gondwanaland. The igneous activity around the Antarctic Peninsula, including the South Shetland islands, can be correlated with the South American Cordillera Orogeny due to the subduction of Farallon/Phoenix plate until late Mesozoic. However igneous activity in Tertiary correlates with the tectonics movement accompanying the formations of Drake passage and Scotian sea. The south Shetland islands form a Jurassic-Quaternary miasmatic island arc on the sialic basement of schist and deformed sedimentary rocks. Forming of the South Shetland Islands arc began during the latest Jurassic or earliest Cretaceous from the southwestern part of the archipelago. The igneous activity migrated northeasterly and continued in most areas until late Tertiary. The entire arc-forming period, between late Jurassic and late tertiary times, was characterized by emplacement and eruption of magmas of intermediate between island-arc tholeiite and calc-alkaline types. However, Quaternary volcanic rocks show strong alkaline affinities which corresponds to the switch from compressional to intra: plate tensional tectonics. The rocks of late Cretaceous to Tertiary, mainly found in King George Island, consist of lava of basalt to andesite and intercalated pyroclastic rocks. Some of the volcanic rocks, which ofter called quartz-pyrite lodes'are severely altered and include much content of calcite,silica and pyrite.The stratographic succession of King George Island can be divided into two formation:Fields formation and Hennequin formation.The Fildes formation crops out at the west side of Admiralty Bay n King George Island,while the Hennequin formation at the east side of the bay.These two formtions are thought to be formed contempiranceously.The Fildes formation consists of altered olivine-basalt and basaltic andestie, whereas the Hennequin formation consists of fine-grained hypersthene-augite-andesite.Both formations interclate pyroclastic rocks.