• Geophysics and Geophysical Exploration
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• v.18 no.2
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• pp.39-53
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• 2015

Analysis of multi-channel seismic reflection profiles acquired from the southwestern margin of Ulleung Basin reveals that the cut and fill structures, which show U-shaped or V-shaped morphology, occur on variable size. The cut and fill structure mostly consists of fine-grained sediments on the well data and is characterized by transparent or semitransparent seismic facies on the seismic section. Such cut and fill structures dominantly occur in the syn-compressional megasequence (MSQ3), which was deposited during basin deformation of late Miocene, among the four megasequences of the study area. These cut and fill structures can be divided into three groups based on their size and formation time. The cut and fill structures of Group I were formed when Dolgorae structure was active, and occurred on a small scale. The cut and fill structures of group II were formed when both Dolgorae structure and Gorae V structure were active, and the number and size of those increased compared with group I. The cut and fill structures of group III were formed when Dolgorae structure was weaken gradually but Gorae V structure kept active, and the number and size of those decreased in comparison with group II. Consequently the cut and fill structures in the southwestern margin of Ulleung basin are interpreted as submarine canyon based on spatial distribution, size and fill sediment. They were controlled by the tectonic movement in response to basin closure and tectonic-induced sediment supply variation.

• Journal of Environmental Science International
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• v.2 no.1
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• pp.43-49
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• 1993

Concentrations of sulfate and 6-values of sulfate, $({\delta}^{34}SO_4_){pw}$, dissolved In pore waters were measured from the sediment cores of the two different marine environments : deep northeast Pacific (57-1) and coastal Kyunggi Bay of Yellow Sea (57-2) . Sulfate concentration in pore waters decreases with depth at both cores, reflecting sulfate reduction in the sediment columns. However, much higher gradient of pore water sulfate at 57-2 than 57-1 indicates more rapid sulfate reduction at 57-2, because of high sedimentation rate at the coastal area compared to the deep-sea. The measured 6-values, $({\delta}^{34}SO_4_){pw}$, follow extremely well the predicted trend of the Rayleigh fractionation equation. The range of 26.756 to 61.35% at the coastal core 57-2 is not so great as that of 32.4$\textperthousand$ to 97.8$\textperthousand$ at the deep-sea core 57-1. Despite greater graclient of pore water sulfate at 57-2, the 6-values become lower than those of the deep- sea core 57-1. This inverse relation between the 6-values and the gradients of pore water sulfate could be explained by the combination of the two subsequent factors : the kinetic effect by which the residual pore water sulfate becomes progressively enriched with respect to the heavy isotope of $^{34}S$ as sulfate reduction proceeds, and the intrinsic formulation effect of the Rayleigh fractionation equation in which the greater becomes the fractionation factor, the more diminished values of $({\delta}^{34}SO_4_){pw}$ are predicted.

• Journal of the Korean earth science society
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• v.35 no.2
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• pp.131-146
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• 2014

Multi-beam echosounder data and grain size analysis data of surface sediment were acquired and analyzed in order to investigate the shelf-to-slope morphology, geological character, and their geological controlling factors in the southwestern margin of the Ulleung Basin. According to the morphological character, the continental shelf can be divided into two parts: (1) shallow (~100 m) and steep ($0.5^{\circ}$) inner shelf, (2) deep (100-300 m) and gentle ($0.2^{\circ}$) outer shelf. The continental slope is featured with eight distinct topographic depressions of various spatial dimension (~121 $km^2$ in area) and head wall gradient (${\sim}24.3^{\circ}$). They are developed adjacent to each other and presumably formed by submarine landslides which have recurred under the strong influences of earthquakes and eustatic sea-level change. The inner continental shelf and the continental slope are dominated by fine-grained sediment, whereas the outer continental shelf is dominated by coarse-grained sediment. The surface sediment distribution seems dominantly influenced by eustatic sea-level change. The outer continental shelf is mostly covered by coarse relict sediment deposited during lowstand sea-level, while the inner shelf is covered with recent sediment during highstand sea-level. The surface of the continental slope is covered with fine-grained sediments which were supplied by hemipelagic advection process.

• Economic and Environmental Geology
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• v.46 no.1
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• pp.39-50
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• 2013

The study area is located on the western coastal region of Korea, partly had been reclaimed lands. Groundwaters of the coastal area show lower Eh and DO values (Eh: 0.57 V ${\rightarrow}$ 0.13 V, DO; 9.7 mg/l ${\rightarrow}$ 1.3 mg/l), and higher Fe concentrations (> 20 mg/l) than those of the inner land (< 0.3 mg/l), indicating that the redox condition of groundwater changes from oxic into suboxic/anoxic conditions as it flows from the inland toward the coastal area. In addition, Fe speciation of groundwater from the coastal area demonstrates that the most dissolved Fe exist as $Fe^{2+}$, reflecting that groundwater is under the anoxic condition to sufficiently occur Fe reduction. According to the result of Fe extraction with the sediment samples from three wells (A, B, C), the sediments provide enough $Fe^{3+}$ to occur the Fe reduction in the groundwater. Integrated all results of the groundwater and sediment, we infer that the Fe reduction to occur in groundwater is associated with the reclamation processes of the study area.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.24 no.3
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• pp.400-421
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• 2019

This study was conducted to find out the seasonal distribution characteristics of meiobenthic communities to understand the benthic ecosystem of Gwangyang Bay, one of the representative bays in the southern coast of Korea. The faunal sampling was conducted eight times seasonally at 20 stations from 2010 to 2011. Among the meiobenthic fauna that appeared during the study period, the nematodes and harpacticoids were the most dominant. In the summer of 2011, the lowest density ($13ind.10m^{-2}$) was seen at station 10 on the inner part of the bay. In the winter of 2011, the highest density ($3,109ind.10m^{-2}$) was seen at station 4 on the inner part of the bay. Although the trend of seasonal changes in density was not clear, the meiobenthic community was seen to be affected more by the environmental factors in each season. Particularly, while the density of the harpacticoids, a dominant faunal group, showed negative correlations with the organic content and average particle size in the summer sediments (p<0.05, p<0.01), the density of the nematodes showed no significant correlation with the environmental factors except with the winter average particle size and the bottom layer's water temperature. The density change of meiobenthos showed irregular changes in Gwangyang Bay, instead of a general trend showing a low density in winter due to low water temperature but an increased density in spring and summer when the water temperature rises and a decreased one again in fall. Considering such a seasonal trend, it seems that the benthic ecosystem of Gwangyang Bay is affected more by artificial environmental factors than by natural environmental ones.

• Journal of the Korean earth science society
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• v.42 no.6
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• pp.677-687
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• 2021

In this study, we analyzed diatoms from core RS15-GC41 collected in Iselin Bank, Ross Sea. A total of 24 genera and 35 species of diatoms are identified, and the having valve abundance of diatoms varies from 0.2 to 28.6×10⁶/g. Four diatom assemblage zones are established by the vertical distribution of diatoms, and changed with a cycle of 100 kyrs. RS15-GC41 were deposited over the last 400 kyrs (corresponding to Marine Isotope Stages 1-11). The open-water species Fragilariopsis kerguelensis, Rhizosolenia styliformis, and Thalassionema nitzschioides abundantly occurred in interglacial periods. Whereas, Actinocyclus actinochilus abundantly dominant during the glacial periods. The distribution of these diatoms indicated, it can be seen that the sea-ice extent was larger and lasted longer during MIS 7, 9, and 11 than that of MIS 1, 3, and 5. Moreover, Paralia sulcata was abundantly predominant in MIS 7, 9, and 11; this finding suggests likely indicating that P. sulcata was transported from the coastal/inner shelf area to the study site, during accumulated in the sediments, reworked with the influx of ice-rafted debris by the currents

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.27 no.1
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• pp.33-47
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• 2022

In this study, distribution of submarine sand ridges in the coastal waters of Korea was surveyed using multibeam echo sounder data, and the topographic characteristics of each region were identified. For this purpose, the DEM (Digital Elevation Model) data was generated using depth data obtained from the Yellow Sea and the South Sea by Korea Hydrographic and Oceanographic Agency, and then applied the TPI (Topographic Position Index) technique to precisely extract the boundary of the sand ridges. As a result, a total of 200 sand ridges distributed in the coastal waters were identified, and the characteristics of each region of the sedimentary sediments were analyzed by performing statistical analysis on the scale (width, length, perimeter, area, height) and shape (width/length ratio, height/width ratio, linear·branch type, exposure·non-exposure type). The results of this study are expected to be used not only for coastal navigational safety, but also for marine naming support, marine aggregate resource identification, and fisheries resource management.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.6 no.3
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• pp.383-391
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• 2016

Ballast water provides stability and manoeuvrability to a ship. Foreign harmful aquatic organisms, which were transferred by ballast water, cause disturbing ecosystem. In order to minimize transference of foreign harmful aquatic organisms, IMO(International Maritime Organization) adopted the International Convention for the Control and Management of Ship's Ballast Water and Sediments in 2004. If the convention take effect, a port authority might need to check that ballast water is properly disposed of. In this paper, we propose a method of counting harmful aquatic organisms in ballast water thorough image processing. We extracted three samples from the ballast water that had been collected at Busan port in Korea. Then we made three grey-scale images from each sample as experimental data. We made a comparison between the proposed method and CellProfiler which is a well known cell-counting program based on image processing. Setting of CellProfiler is empirically chosen from the result of cell count by an expert. After finding a proper threshold for each image at which the result is similar to that of CellProfiler, we used the average value as the final threshold. Our experimental results showed that the proposed method is simple but about ten times faster than CellProfiler without loss of the output quality.

• The Korean Journal of Quaternary Research
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• v.33 no.1_2
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• pp.59-68
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• 2021

The maximum upper limit of seawater inflow can be recognized by the acid-resistant dinoflagellate cysts and salt-marsh pollen encountered from surface samples in the lower reach of Jujin Stream facing Gomso Bay. Based on their relative yield ratio, the downstream area of Jujin Stream could be further subdivided into coastal marine, brackish-upper limit brackish, and freshwater environments. The abundance of dinoflagellate cysts from JJR-41 to JJR-36 sites reflects that this area is a coastal marine. In the section between JJR-35 and JJR-5 sites, dinoflagellate cysts associated with pollen derived from riparian or salt-marsh (e.g., reeds and sedges) appear to reflect the brackish environments. It may be indicated that dinoflagellate cysts appear up to the JJR-4 site, which is the maximum upper limit where seawater flows up to this point at high tide. This analysis is relatively well corresponding to the hypothetical inundation map showing the maximum flooding area where seawater can flow at high tide.

• Economic and Environmental Geology
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• v.25 no.3
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• pp.337-349
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• 1992

The Tertiary basins in Korea have widely been studied by numerous researchers producing individual results in sedimentology, paleontology, stratigraphy, volcanic petrology and structural geology, but interdisciplinary studies, inter-basin analysis and basin-forming process have not been carried out yet. Major work of this study is to elucidate evidences obtained from different parts of a basin as well as different Tertiary basins (Pohang, Changgi, Eoil, Haseo and Ulsan basins) in order to build up the correlation between the basins, and an overall picture of the basin architecture and evolution in Korea. According to the paleontologic evidences the geologic age of the Pohang marine basin is dated to be late Lower Miocence to Middle Miocene, whereas other non-marine basins are older as being either Early Miocene or Oligocene(Lee, 1975, 1978: Bong, 1984: Chun, 1982: Choi et al., 1984: Yun et al., 1990: Yoon, 1982). However, detailed ages of the Tertiary sediments, and their correlations in a basin and between basins are still controversial, since the basins are separated from each other, sedimentary sequence is disturbed and intruded by voncanic rocks, and non-marine sediments are not fossiliferous to be correlated. Therefore, in this work radiometric, magnetostratigraphic, and biostratigraphic data was integrated for the refinement of chronostratigraphy and synopsis of stratigraphy of Tertiary basins of Korea. A total of 21 samples including 10 basaltic, 2 porphyritic, and 9 andesitic rocks from 4 basins were collected for the K-Ar dating of whole rock method. The obtained age can be grouped as follows: $14.8{\pm}0.4{\sim}15.2{\pm}0.4Ma$, $19.9{\pm}0.5{\sim}22.1{\pm}0.7Ma$, $18.0{\pm}1.1{\sim}20.4+0.5Ma$, and $14.6{\pm}0.7{\sim}21.1{\pm}0.5Ma$. Stratigraphically they mostly fall into the range of Lower Miocene to Mid Miocene. The oldest volcanic rock recorded is a basalt (911213-6) with the age of $22.05{\pm}0.67Ma$ near Sangjeong-ri in the Changgi (or Janggi) basin and presumed to be formed in the Early Miocene, when Changgi Conglomerate began to deposit. The youngest one (911214-9) is a basalt of $14.64{\pm}0.66Ma$ in the Haseo basin. This means the intrusive and extrusive rocks are not a product of sudden voncanic activity of short duration as previously accepted but of successive processes lasting relatively long period of 8 or 9 Ma. The radiometric age of the volcanic rocks is not randomly distributed but varies systematically with basins and localities. It becomes generlly younger to the south, namely from the Changgi basin to the Haseo basin. The rocks in the Changgi basin are dated to be from $19.92{\pm}0.47$ to $22.05{\pm}0.67Ma$. With exception of only one locality in the Geumgwangdong they all formed before 20 Ma B.P. The Eoil basalt by Tateiwa in the Eoil basin are dated to be from $20.44{\pm}0.47$ to $18.35{\pm}0.62Ma$ and they are younger than those in the Changgi basin by 2~4 Ma. Specifically, basaltic rocks in the sedimentary and voncanic sequences of the Eoil basin can be well compared to the sequence of associated sedimentary rocks. Generally they become younger to the stratigraphically upper part. Among the basin, the Haseo basin is characterized by the youngest volcanic rocks. The basalt (911214-7) which crops out in Jeongja-ri, Gangdong-myon, Ulsan-gun is $16.22{\pm}0.75Ma$ and the other one (911214-9) in coastal area, Jujon-dong, Ulsan is $14.64{\pm}0.66Ma$ old. The radiometric data are positively collaborated with the results of paleomagnetic study, pull-apart basin model and East Sea spreading theory. Especially, the successively changing age of Eoil basalts are in accordance with successively changing degree of rotation. In detail, following results are discussed. Firstly, the porphyritic rocks previously known as Cretaceous basement (911213-2, 911214-1) show the age of $43.73{\pm}1.05$ 및 $49.58{\pm}1.13Ma$(Eocene) confirms the results of Jin et al. (1988). This means sequential volcanic activity from Cretaceous up to Lower Tertiary. Secondly, intrusive andesitic rocks in the Pohang basin, which are dated to be $21.8{\pm}2.8Ma$ (Jin et al., 1988) are found out to be 15 Ma old in coincindence with the age of host strata of 16.5 Ma. Thirdly, The Quaternary basalt (911213-5 and 911213-6) of Tateiwa(1924) is not homogeneous regarding formation age and petrological characteristics. The basalt in the Changgi basin show the age of $19.92{\pm}0.47$ and $22.05{\pm}0.67$ (Miocene). The basalt (911213-8) in Sangjond-ri, which intruded Nultaeri Trachytic Tuff is dated to be $20.55{\pm}0.50Ma$, which means Changgi Group is older than this age. The Yeonil Basalt, which Tateiwa described as Quaternary one shows different age ranging from Lower Miocene to Upper Miocene(cf. Jin et al., 1988: sample no. 93-33: $10.20{\pm}0.30Ma$). Therefore, the Yeonil Quarterary basalt should be revised and divided into different geologic epochs. Fourthly, Yeonil basalt of Tateiwa (1926) in the Eoil basin is correlated to the Yeonil basalt in the Changgi basin. Yoon (1989) intergrated both basalts as Eoil basaltic andesitic volcanic rocks or Eoil basalt (Yoon et al., 1991), and placed uppermost unit of the Changgi Group. As mentioned above the so-called Quarternary basalt in the Eoil basin are not extruded or intruaed simultaneously, but differentiatedly (14 Ma~25 Ma) so that they can not be classified as one unit. Fifthly, the Yongdong-ri formation of the Pomgogri Group is intruded by the Eoil basalt (911214-3) of 18.35~0.62 Ma age. Therefore, the deposition of the Pomgogri Group is completed before this age. Referring petrological characteristics, occurences, paleomagnetic data, and relationship to other Eoil basalts, it is most provable that this basalt is younger than two others. That means the Pomgogri Group is underlain by the Changgi Group. Sixthly, mineral composition of the basalts and andesitic rocks from the 4 basins show different ground mass and phenocryst. In volcanic rocks in the Pohang basin, phenocrysts are pyroxene and a small amount of biotite. Those of the Changgi basin is predominant by Labradorite, in the Eoil by bytownite-anorthite and a small amount pyroxene.