• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.1
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• pp.35-43
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• 2003

Recent geomorphological changes and late Quaternary depositional sequences of Gwangyang Bay are studied based on bathymetric maps, surface sediments, and seismic profiles. As a result of the reclamation of coastal area for an industrial complex construction, the coastline of Gwangyang Bay has rapidly been changed and the area of it has now been reduced by about 25 ％ in the last 30 years. In addition, the bottom topography is actively modified by dredging for navigation channels. In surfical sediment distribution, the western part of Gwangyang Bay is dominated by mud facies, whereas the eastern part of the Bay is dominated by sand-mud mixing facies. Depositional sequences above the basement are divided into two units: Unit I in upper layer and Unit II in lower one. These depositional units are unconformably bounded by middle reflector-M. Unit II, mostly occupying the channel areas, is interpreted as fluvial-origin deposits during sea-level lowstand. Unit I typically shows a progradational pattern from the Seomjin River mouth to the Yeosu Strait, which is interpreted as deltaic deposits supplied from the Seomjin River during the Holocene sea-level highstand. The shallow gas within the sediments Is widely distributed in most area, and locally exposed onto the sea-bed due to dredging.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.1
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• pp.50-62
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• 1999

Sediment core samples recovered from the Korea Deep Ocean Study (KODOS)-97 area were divided into two or three units according to their distinct changes in sediment colors and chemical and physical properties. Analyses of radiolarian faunas in the sediments and $^{10}Be$ ratios in each unit were performed to reveal stratigraphic and paleoceanographic history of the study area. In the upper part of the sediments, Tertiary radiolarians were mixed at various proportions with Quaternary assemblages probably by reworking process of bottom current and benthic animals. Dissolution of radiolarians was severe in deeper depth and in the Unit III, only few of the fragments of corroded Tertiary radiolarians were detectable. The mid layer of the Unit I belonged to Collosphaera invaginata Zone, the time period of 0.21 Ma. The Unit II belonged to Collosphaera tuberosa Zone with the time period younger than 0.42 Ma which was observed above the Stylatractus universus Zone. The Unit III is assigned to Tertiary, which is younger than the Late Eocene. Composition analyses of radiolarian assemblage and $^{10}Be$ ratio data indicated hiatus periods of more than 3 My between late of Middle Miocene and Pliocene resulting from erosion and dissolution caused by Antarctic Bottom Water. Stratigraphic evidence from radiolaria was well correlated with $^{10}Be$ data. Sedimentation rate during Quaternary can be suggested as 0.15-0.5 mm per 1000 years. Dominance of warm-water radiolaria species and the results reflected minimum climatic changes of tropical conditions.

• Journal of the Korean earth science society
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• v.23 no.5
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• pp.442-453
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• 2002

A total of 64 species belonging to 23 genera of diatom fossils are identified from the Core GC 98-06 in the southern Drake Passage, Antarctica. The diatom assemblages are dominated by Actinocyclus actinochilus, Coscinodiscus asteromphalus, Eucampia antarctica, Fragilariopsis kerguelensis, Thalassiosira lentiginosa, T. ritscheri and T. anguste-lineata, which are about 73% of the assemblage. Open water species are more abundant than sea ice species in the diatom assemblages of the core. Fragilariopsis. kerguelensis and Thalassiosira lentiginosa are valuable indicators of the habitats. Especially, F. kerguelensis represent the influence of waters from the Antarctic Circumpolar Current. Sea ice taxa represents the influence of cold waters from Bransfield Strait Water and melt water from the sea-ice at during warm periods. The reworked diatoms such as Denticulopsis dimopha (Miocene) and D. hustedtii (Pliocene) are occurred with Quaternary species (Actinocyclus actinochilus, Fragilariopsis kerguelensis, Thalassiosira lentiginosa, and T. glacilis). The presence of reworked diatoms indicates the transportation of the older diatoms into the Drake passage from the circumference sediments, due to strong bottom current activity of Antarctic circumpolar deep water.

• The Korean Journal of Quaternary Research
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• v.24 no.2
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• pp.1-11
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• 2010

Energy Balance Model (EBM) was used to experiment the distribution of surface equilibrium temperature which responds to external forcing associated with the surface characteristics. Surface equilibrium temperature is calculated as sum of incoming solar radiation and latitudinal transport is balanced with outgoing infrared radiation. To treat incoming solar radiation, the source of the earth energy, significantly for energy balance, the experiment for surface equilibrium temperature distribution was performed considering the energy balance with the latitudinal albedo change as well as land and sea distribution. In addition, linear albedo change experiment, arctic albedo 5%, 10%, 15% change experiments and the opposite albedo change experiments between arctic and mid-latitudes were performed using incoming solar radiation as an external forcing. Moreover, with and without ice-albedo feedback experiments were performed. Increasing of arctic albedo is blocked out the incoming solar radiation so that it induces decreasing of latitudinal heat transport. It is strengthened energy transport from low latitudes by keeping arctic low energy states. Therefore the temperature change in the mid-latitudes exhibits larger response than that of arctic due to the difference of transport. The land which has lower heat capacity than sea can be reach to equilibrium temperature shortly. Also land is more sensitive to temperature change with respects to albedo. Thus it induces the thermal difference between land and sea. As a result, the equilibrium temperature exhibits differently as the difference of albedo and heat capacity which are the one of surface characteristics. Surface equilibrium temperature decreases as albedo increase and the ratio of temperature change is large as heat capacity is small. The decreasing of surface equilibrium temperature with respects to increasing of linear albedo is accelerated by ice-albedo feedback. However local change of surface equilibrium temperature decreases non-linearly.

• The Korean Journal of Quaternary Research
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• v.18 no.2 s.23
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• pp.103-104
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• 2004

This paper discuss some results of observed changes of meteorological elements as temperature, precipitation and some extreme indexes in Mongolia. Mongolia is one of the largest landlocked countries in the world. The climate is characterized by a long lasting cold winter, dry and hot summer, low precipitation, high temperature fluctuation and relatively high number of sunny days per year. During last 60 years the annual mean air temperature has risen $1.66^{\circ}C$. Intensive warming of > $2^{\circ}C$ was observed at higher altitudes of high mountains when warming of < $1^{\circ}C$ was observed the Domod steppe and the Gobi Desert. Heat Wave Duration have statistically significant risen trend with increaded number of days by 8-18 at significance level of 95-99.9% depending on geography and Cold Wave Duration have shortened by 13.3 days significance level of 95-99%. In general, by the amount of precipitation, Mongolia falls in semi-arid and arid region. It is 300-350 mm in the high mountain regions while it is only 50-150 mm in Gobi Desert regions. The changes of annual precipitation have very localized character i.e.decreasing at one site and increasing at a sit nearby. Annual precipitation decreased by 30-90 mm in the northern-central region and increased by 2-60 mm in the western and eastern region. The magnitude of alteration changes in precipitation regardless increasing or decreasing is 5-25%. A trends, significant at the level of 90%, found where changes are more than 40 mm or more than 15% of annual mean value. Moreover, the soil moisture resources was decreased in the last 40 years. Specially, moisture contents of the top soil have decreased 2 times(N. Natsagsuren, 2002). Months of June and July in Mongolia is the year that moisture is not inhibiting vegetation growth. Unfortunately, its also found that moisture in this time tends to decrease. Increased temperature, decreased precipitation and soil moisture are most likely resulted in occurences of more intense drought spells that have taken place during the recent years. Intimately, these changes have considerable impact on livestock in Mongolia.

• Economic and Environmental Geology
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• v.38 no.3 s.172
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• pp.335-346
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• 2005

In this study, core sediments and pore water were analysed to identify the origin of organic matter and Bas in late Quaternary sediments from the northwestern Ulleung Basin of the East Sea. C/N and C/S ratios in the sediments show that the organic matter in the study area originated predominantly from marine algae. However, the results of Rock-Eval pyrolysis indicate that the organic matter has an origin of the land-plant (Type III), locating in the immature stage. These different results might be due to the heavy oxidizing of the organic matter during sinking down to the seafloor or after deposition in the sediments. Concentration of sulfate in the pore water decreases gradually with core depth, while concentration of $CH_4$ increases gradually with core depth. This indicates that sulfate reduction and methanogenesis occurred actively in the sediments. Also, it is likely that the compositions of $CH_4$ are characterized as a more biogenic origin, mostly caused by microbial activity, rather than a thermogenic one.

• The Korean Journal of Quaternary Research
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• v.25 no.2
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• pp.17-24
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• 2011

We investigated the variation of $CaCO_3$ contents in cores PC1 and PC2 recovered from the continental slope area of the Ulleung Basin in the East Sea. $CaCO_3$ contents of cores PC1 and PC2 varied between 0.6 and 17.2% and between 0.3 and 43.0%, respectively. $CaCO_3$ contents in the upper part of core PC1 corresponding to MIS 1 are less than 5%, whereas those in the lower part of MIS 2 are more than 10%. Such variation of $CaCO_3$ contents in core PC1 confirms the previous results of $CaCO_3$ studies in the East Sea. In core PC2, $CaCO_3$ contents of the upper part are similar to those of core PC1. However, $CaCO_3$ contents in the lower part of core PC2 are more than 40%. According to XRD operation and SEM examination, the high $CaCO_3$ contents in the lower part of core PC2 are more attributable to the authigenic carbonate minerals rather than the biogenic carbonate composition. Such abundant authigenic carbonate minerals are closely related to the dissociation of methan hydrates which were observed in the Ulleung Basin.

• Economic and Environmental Geology
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• v.48 no.6
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• pp.501-508
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• 2015

The purpose of this study is to provide an inquiry into paleovegetation (paleoenvironment), eruption age and inferred emplacement temperature of pyroclastic deposit using charcoal occurred in the Quaternary Nari Caldera, Ulleung Island. In order to obtain the data, we carried out species identification and tree-ring analysis, radiocarbon dating for the charcoal. This sample was collected from pumiceous deposit in lowermost member(Member N-5) of the Nari Tephra Formation, which corresponds to the wood branch that has well preserved the tree-ring structure. Speciation and outermost tree-ring of wood reveal Picea spp. and $263+{\alpha}$ years. The calibrated ages from the center(pith) to the outermost tree-ring are $20,260{\pm}230$, $19,995{\pm}245$, and $19,975{\pm}265cal\;BP$, respectively, which are accordant with the tree-ring position. The youngest age, <19,710 cal BP would have implications for the eruptive age of Member N-5. Our results indicate that Picea spp. is the paleovegetation representing that Nari Caldera was under cold and wet climate conditions during the late Pleistocene. Based on the silky luster, brittleness, color, and streak of charcoal, etc., the lowest emplacement temperatures of pyroclastic flow are interpreted to have been at least as high as $350{\sim}500^{\circ}C$.

• The Korean Journal of Quaternary Research
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• v.24 no.2
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• pp.23-34
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• 2010

The purpose of this study is to clarify the characteristics of geomorphic surfaces and investigate their geomorphological development at Sinsong-ri archaeological sites by the classification of geomorphic surfaces. The sedimentary facies of trench 1, 2 and 3 were identified and pollen analysis was performed at site 3. The geomorphic surfaces are classified by hillslope, valley plain, alluvial fan and river terrace. Most of the study area is located on low hillsides and valley plains are connected with tidal flats extended from small river valley. Also, alluvial fans are distributed over the piedmont and narrow, long river terraces are developed downstream along the Sojeong-stream flowing between valley plain and hillsides. River valleys were deeply eroded during the Last Glacial Maximum (LGM) periods, responded to the lowest sea level among the hillslopes and valley plains are formed during the Holocene. The sedimentary facies are identified composed of basal gravel layers with coarse gravels and sands, relatively thick culture layer of the Bronze Age and thin layer during the early Iron Age in upper part study area. Thus, land uses during the Bronze Age people was performed more intensively comparing to the early Iron Age by deforestation for habitation.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.4
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• pp.414-421
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• 2018

In this study, Gram-positive bacilli (GPB) were identified by MALDI-TOF MS and analyzed according to the quaternary and microbial strains in the blood culture medium over a two year period at a university hospital. The results were as follows. The overall positive rate of blood culture was 9.97%. In 713 isolated GPB, 410 strains (57.5%) were identified using a microflex MALDI Biotyper. The positive rate of GPB among the blood culture positive bacteria was 8.2%, and the quarterly isolation rate was 9.8% in the third quarter of 2015, 8.7% in the second quarter of 2016, 8.1% in the third quarter of 2016, 8.1% in the first quarter of 2015, 7.9% in the first quarter of 2015, 7.9% in the second quarter of 2015, 6.8% in the first quarter of 2016, and 6.7% in the fourth quarter of 2015. The isolates were Corynebacterium striatum 89 (12.4%), Bacillus cereus 60 (8.4%), Bacillus subtilis 30 (4.2%), Paenibacillus urinalis 29 (4.1%), and Listeria monocytogenes 25 (3.5%). The results of 16S rRNA sequencing of 43 isolates (86.0%) were consistent with those of the other 50 isolates. Five out of the seven unmatched weeks were not identified by MALDI-TOF MS.