• Title/Summary/Keyword: continental rise

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Biogenic Opal Production and Paleoclimate Change in the Wilkes Land Continental Rise (East Antarctica) during the Mid-to-late Miocene (IODP Exp 318 Site U1359) (동남극 윌크스랜드 대륙대의 마이오세 중-후기 동안 생물기원 오팔 생산과 고기후 변화(IODP Exp 318 Site U1359))

  • Song, Buhan;Khim, Boo-Keun
    • Ocean and Polar Research
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    • v.37 no.1
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    • pp.23-35
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    • 2015
  • A 450 m-long sediment section was recovered from Hole U1359D located at the eastern levee of the Jussieau submarine channel on the Wilkes Land continental rise (East Antarctica) during IODP Expedition 318. The age model for Hole U1359D was established by paleomagnetic stratigraphy and biostratigraphy, and the ages of core-top and core-bottom were estimated to be about 5 Ma and 13 Ma, respectively. Biogenic opal content during this period varied between 3% and 60%. In the Southern Ocean, high biogenic opal content generally represents warm climate characterized by the increased light availability due to the decrease of sea-ice distribution. The surface water productivity change in terms of biogenic opal content at about 10.2 Ma in the Wilkes Land continental rise was related to the development of Northern Component Water. After about 10.2 Ma, more production of Northern Component Water in the North Atlantic caused to increase heat transport to the Southern Ocean, resulting in the enhanced diatom production. Miocene isotope events (Mi4~Mi7), which are intermittent cooling intervals during the Miocene, appeared to be correlated to the low biogenic opal contents, but further refinement was required for precise correlation. Biogenic opal content decreased abruptly during 6 Ma to 5.5 Ma, which most likely corresponds to the Messinian salinity crisis. Short-term variation of biogenic opal content was related to the extent of sea-ice distribution associated with the location of Antarctic Polar Front that was controlled by glacial-interglacial paleoclimate change, although more precise dating and correlation will be necessary. Diatom production in the Wilkes Land continental rise increased during the interglacial periods because of the reduced sea-ice distribution and the southward movement of Antarctic Polar Front.

China's Pursuit for Seapower and New U.S.-China Relationship (중국의 해양강국 추구와 새로운 미중관계)

  • KIM, Heung-Kyu
    • Strategy21
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    • s.36
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    • pp.59-93
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    • 2015
  • A Paradigm shift is in process in China's foreign policies during Xi Jinping's era. Such changes occur with changing national identities from developing country to great power, and from continental power to continental-maritime power. China's pursuit for sea power embraces its global strategy. Accommodating the new identity of maritime power, China is developing its maritime strategy. New silk-road strategy actively utilizes China's advantage in economy, while avoiding direct military challenges against the U.S. China seeks an associated balance of power with the U.S. On the other hand, China make its determination clear to protect its core national interests, particularly Taiwan straits issue, deploying Anti-Access and Area-Denial strategy. 'Pax-Americana 3.0' and 'China's rise 2.0' have convoluted and evolved in complexity. South Korea faces much tougher challenges ahead in its foreign and security environments.

Modeling of Near Fault Ground Motion due to Moderate Magnitude Earthquakes in Stable Continental Regions (안정대륙권역의 중규모지진에 의한 근단층지반운동의 모델링)

  • Kim, Jung-Han;Kim, Jae-Kwan
    • Journal of the Earthquake Engineering Society of Korea
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    • v.10 no.3 s.49
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    • pp.101-111
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    • 2006
  • This paper proposes a method for modeling new fault ground motion due to moderate size earthquakes in Stable Continental Regions (SCRs) for the first time. The near fault ground motion is characterized by a single long period velocity pulse of large amplitude. In order to model the velocity pulse, its period and peak amplitude need be determined in terms of earthquake magnitude and distance from the causative fault. Because there have been observed very few new fault ground motions, it is difficult to derive the model directly from the recorded data in SCRs. Instead an indirect approach is adopted in this work. The two parameters, the period and peak amplitude of the velocity pulse, are known to be functions of the rise time and the slip velocity. For Western United States (WUS) that belongs active tectonic regions, there art empirical formulas for these functions. The relations of rise time and slip velocity on the magnitude in SCRs are derived by comparing related data between Western United States and Central-Eastern United States that belongs to SCRs. From these relations, the functions of these pulse parameters for NFGM in SCRs can be expressed in terms of earthquake magnitude and distance. A time history of near fault ground motion of moderate magnitude earthquake in stable continental regions is synthesized by superposing the velocity pulse on the for field ground motion that is generated by stochastic method. As an demonstrative application, the response of a single degree of freedom elasto-plastic system is studied.

A Combined Effect of Differential Cooling and Topography on the Formation of Ulleung Warm Eddy

  • SEUNG Young Ho;NAM Soo Yong;LEE Sang Yong
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.22 no.6
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    • pp.375-384
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    • 1990
  • A numerical experiment is made to study the combined effect of differential cooling and bottom topography on the formation of Ulleung Warm Eddy. The Ulleung Warm Eddy appears after the passage around the Ulleung Basin of coastal trapped baroclinic waves generated in the north initial density front to the north, the continental slopes both to the west and south, and the Yamato Rise to the east. It resides therefore always inside the Ulleung Basin, as confirmed by observations.

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Sediment Provenance using Clay Mineral in the Continental Shelf and Rise of the Eastern Bellingshausen Sea, Antarctica (벨링스하우젠 해의 동쪽 대륙붕과 대륙대의 코어의 점토광물을 이용한 기원지 연구)

  • Park, Young Kyu;Jung, Jaewoo;Lee, Kee-Hwan;Lee, Minkyung;Kim, Sunghan;Yoo, Kyu-Cheul;Lee, Jaeil;Kim, Jinwook
    • Journal of the Mineralogical Society of Korea
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    • v.32 no.3
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    • pp.173-184
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    • 2019
  • Variations in grain size distribution and clay mineral assemblage are closely related to the sedimentary facies that reflect depositional conditions during the glacial and interglacial periods. Gravity cores BS17-GC15 and BS17-GC04 were collected from the continental shelf and rise in the eastern Bellingshausen Sea during a cruise of the ANA07D Cruise Expedition by the Korea Polar Research Institute in 2017. Core sediments in BS17-GC15 consisted of subglacial diamicton, gravelly muddy sand, and bioturbated diatom-bearing mud from the bottom to the top sediments. Core sediments in BS17-GC04 comprised silty mud with turbidites, brownish structureless mud, laminated mud, and brownish silty bioturbated diatom-bearing mud from the bottom to the top sediments. The clay mineral assemblages in the two core sediments mainly consisted of smectite, chlorite, illite, and kaolinite. The clay mineral contents in core GC15 showed a variation in illite from 28.4 % to 44.5 % in down-core changes. Smectite contents varied from 31.1 % in the glacial period to 20 % in the deglacial period and 25.1 % in the interglacial period. Chlorite and kaolinite contents decreased from 40.5 % in the glacial period to 30.3 % in the interglacial period. The high contents of illite and chlorite indicated a terrigenous detritus supply from the bedrocks of the Antarctic Peninsula. Core GC04 from the continental rise showed a decrease in the average smectite content from 47.2 % in the glacial period to 20.6 % in the interglacial period, while the illite contents increased from the 21.3 % to 43.2 % from the glacial to the interglacial period. The high smectite contents in core GC04 during the glacial period may be supplied from Peter I Island, which has a known smectite-rich sediment contributed by Antarctic Circumpolar Currents. Conversely, the decrease in smectite and increase in chlorite and illite contents during the interglacial period was likely caused by a higher supply of chlorite- and illite-enriched sediment from the eastern Bellingshausen Sea shelf by the southwestward flowing contour current.

Study on Japanese Traditional Aesthetic Sense in Modern Fashion (현대패션에 표현된 일본 전통 미의식에 관한 연구)

  • Lee, Sun-Hee
    • Journal of the Korea Fashion and Costume Design Association
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    • v.10 no.3
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    • pp.15-25
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    • 2008
  • Today, each country's cultural communications are carried briskly and Japan already showed a new trend of world fashion by accepting its own design with aesthetic sense to western Europe in 1970s and built the new area of Japanese fashion. This special traditional aesthetic sense, formed by social, cultural, geographic and religious conditions, is roughly divided into decorated and undecorated beauty; decorated one means splendidness, coquetry, exaggeration and was represented ornamental modification of nature object in dress pattern as ornamental expression means; undecorated one, based on Zen-thought, means simplicity, purity, ugliness and Japan gave rise to the new beauty by receiving and adapting continental culture to its culture openly and creating and developing its own beauty. This study aims to examine the aesthetic sense shown in Japanese traditional dress and understand how traditional beauty is used and applied to modern fashion and analyze the diversity of Japanese traditional aesthetic sense shown in modern fashion. For material analysis, total 220 were collected of photograph related to formative element existence according to aesthetic sense shown in Japanese traditional fashion design using literature research and visual data. The existences of Japanese image among them were confirmed by clothing and fashion department majors so that 7 pieces of which were selected as final analysis object. Likewise, the result suggests that Japanese traditional aesthetic sense creates global design based on folk element-used identity as well as new beauty by adapting continental culture to its culture openly and producing and developing its own creative beauty.

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A Study of Crust Structure at Svalbard Archipelago in Arctic Area by Using Gravity Data (중력자료를 이용한 북극 스발바드 군도의 지각구조연구)

  • Yu, Sang-Hoon;Yi, Song-Suk;Min, Kyung-Duck
    • The Korean Journal of Petroleum Geology
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    • v.13 no.1
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    • pp.17-23
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    • 2007
  • Gravity characteristics are investigated in the vicinity of the DASAN scientific station, located at the Svalbard Archipelago, the Arctic using ArcGP data. Boundary effects of free-air gravity anomalies, which appeared generally at the continental margin, are erased after Bouguer correction was applied. Complete Bouguer anomalies produced after terrain correction by GrOPO30 show that gravity anomalies increase from continent to marine. This phenomena seem to be related to the rise of Moho discontinuity. The cut-off frequency of 0.16 was decided after power spectrum analysis and the gravity anomalies were divided into two parts. Residual anomalies in high frequency part show that characteristics of high values along the faults and of low values related to thick sediments in the continent. Characteristic is low values from basement subsidence of continental slope or thick sediments in the marine. The undulation of Moho discontinuity from 3-D inversion modeling show typical characteristics of continental margin that become higher from Svalbard archipelago to Knipovich ridge bordering Eurasian plate.

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Comparison of Sulfate Reduction Rates Associated with Geochemical Characteristics at the Continental Slope and Basin Sediments in the Ulleung Basin, East Sea (동해 울릉분지에서 대륙사면과 분지 퇴적물의 지화학적 특성에 따른 황산염 환원 비교)

  • You, Ok-Rye;Mok, Jin-Sook;Kim, Sung-Han;Choi, Dong-Lim;Hyun, Jung-Ho
    • Ocean and Polar Research
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    • v.32 no.3
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    • pp.299-307
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    • 2010
  • In conjunction with geochemical characteristics, rate of sulfate reduction was investigated at two sediment sites in the continental slope and rise (basin) of the Ulleung Basin in the East Sea. Geochemical sediment analysis revealed that the surface sediments of the basin site (D2) were enriched with manganese oxides (348 ${\mu}mol$ $cm^{-3}$) and iron oxides (133 ${\mu}mol$ $cm^{-3}$), whereas total reduced sulfur (TRS) in the solid phase was nearly depleted. Sulfate reduction rates (SRRs) ranged from 20.96 to 92.87 nmol $cm^{-3}$ $d^{-1}$ at the slope site (M1) and from 0.65 to 22.32 nmol $cm^{-3}$ $d^{-1}$ at the basin site (D2). Depth integrated SRR within the top 10 cm depth of the slope site (M1; 5.25 mmol $m^{-2}$ $d^{-1}$) was approximately 6 times higher than that at the basin site (D2; 0.94 mmol $m^{-2}$ $d^{-1}$) despite high organic content (>2.0% dry wt.) in the sediment of both sites. The results indicate that the spatial variations of sulfate reduction are affected by the distribution of manganese oxide and iron oxide-enriched surface sediment of the Ulleung Basin.

Sediment Distributions and Depositional Processes on the Inner Continental Shelf Off the West Coast (Middle Part) of Korea (한국 서해 중부해역 대륙붕 퇴적물의 분포와 퇴적작용)

  • 박용안;최진용
    • 한국해양학회지
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    • v.29 no.4
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    • pp.357-365
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    • 1994
  • The sediments on the continental shelf off the west coast (middle part) of Korea are divided into northern sandy deposits and southern muddy sediments, respectively. The sandy sediments consist dominantly of quartz and feldspar grains, representing mature-stage sediment in composition. Further-more, the presence of iron-stained quartz grain and glauconite does indicate that the sediments are similar to the relict sediments on the outer shelf of Yellow Sea and East China Sea. These sandy sediments are interpreted as a basal sands that were deposited during the transgression period due to sea-level rise after to last glacial maximum (LGM). The tidal deposits in the Namyang Bay, the west coast of Korea are divided vertically into the upper layer of muddy sediments and the lower layer of sandy sediments. the upper layer sediments contain abundant rock fragments, and are interpreted as the modern tetragenous sediments. The lower layer sediments, on the other hand, are rich in quartz and feldspar grains, representing high index of sediment maturity ratio. the lower layer sandy deposits show the presence of iron-stained.

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Seismic Stratigraphy and Depositional History of Holocene Transgressive Deposits in the Southeastern Continental Shelf, Korea (한국 남동해역 홀로세 해침퇴적층의 탄성파층서 및 퇴적역사)

  • Yoo, Dong-Geun;Kim, Seong-Pil;Lee, Chi-Won;Park, Soo-Chul
    • Economic and Environmental Geology
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    • v.44 no.4
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    • pp.303-312
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    • 2011
  • Analysis of high-resolution seismic profiles from the southeastern continental shelf of Korea reveals that the Holocene transgressive deposits consist of five sedimentary units characterized by retrograding or backstepping depositional arrangements. Unit I, forming a linear sediment body along the shelf margin, is an ancient beach/shoreface deposit formed during the early stage of transgression. During the transgression, the paleo-channels were backfilled with fluvial or coastal-plain sediments, forming Unit II as an incised-channel fill deposit. The near-surface sediment was reworked and eroded by shoreface erosion, forming a thin lag of sands (Unit III) on the midshelf. During the middle stage of the transgression, the shoreline may have stabilized at around 70 - 80 m below the present sea level for some period of time to allow the formation of sand ridge systems (Unit IV). Unit V in the inner shelf was deposited in an estuarine environment during the middle to late stage of transgression. Such transgressive stratigraphic architecture is controlled by a function of lateral changes in the balance among rates of relative sea-level rise, sediment input and marine processes at any given time.