Late Quaternay Paleoceanography as Recorded by Planktonic Foraminifera in the Ulleung Basin, East Sea

Kim, Gil-Young,Kim, Dae-Choul,Shin, Im-Chul,Yi, Hi-Il,Kim, Jeong-Chang The Korean Society of Oceanography 1998 Journal of the Korean Society of Oceanography Vol.33 No.1

Paleoceanographic history of the East Sea is reconstructed based on several environmental parameters (coarse fraction content, planktonic foraminifera/benthic foraminifera ratio, fragmentation and assemblages of planktonic foraminifera, and coiling ratio of Neogloboquadrina pa-chyderma, etc,) of the late Quaternary sediments obtained from the Ulleung Basin. N. pa-chydeyma and Globigerina bulloides are dominant species (greater than 90% in abundance)among the total planktonic foraminifera assemblages in the late Quaternary sediments. The benthic foraminifera rarely occurred throughout the cores. Sinistrally-coiled specimens of N. pa-chyderma representing cold water temperature are observed more abundantly than dextrally-coil-ed ones. In addition, the sinistrally-coiled N, pachydeyma showed more the amount at the lower part of the cores than at the upper part suggesting the restriction of the Tsushima Warm Current into the East Sea during glacial period. G. bulloides, a species representative of upwelling condition, shows more abundant occurrence in the sediments of Core 941013 than those of Core 941006. This implies that Core 941013 is more influenced by upwelling than Core 941006. The upper part of the two cores contain more fragmentation of planktonic foraminifera suggesting significant dissolution by corrosive bottom wafer. Ascending CCD also played an important role for the absence of planktonic foraminifera at the upper part of the cores.

Suspended Sediment Budget in Gwangyang Bay through the Yeosu Sound

Kim,Dae-Choul,Kang,Hyo-Jin 韓國海洋大學校 附設 海洋科學技術硏究所 1992 硏究論文集 Vol.1 No.1

여수해만 광양만 입구의 조류 및 부유 퇴적물 함량 분석을 통하여 광양만 내의 부유 퇴적물 수지 균형을 조사하였다. 만 입구의 부유 퇴적물 함량은 바닥이 평균 약 17.80㎎/ℓ로 표층의 평균 약 4.75㎎/ℓ에 비해 상당히 높으며, 조류도 표층 부근에서는 썰물이 강하나 저층에서는 오히려 밀물이 강하여 유속의 비대칭 현상을 보이고 있다. 이러한 저층의 높은 부유 퇴적물 함량과 밀물우세 조류로 인하여 이 지역의 부유 퇴적물 이동은 저층을 통한 이동이 큰 중요성을 갖으며, 따라서 광양만의 내부 특히 서쪽 부분은 전체적으로 세립 퇴적물의 순수 퇴적이 이루어지고 있다. 이러한 조류에 의한 세립 퇴적물의 순수 유입량은 약 5.66×10??g/day로 계산되며, 이 순수 유입량이 만의 서부에 퇴적된다면 그 퇴적율은 약 1.15m/1,000years 정도가 될 것이다 Suspended sediment budget in Gwangyang Bay was investigated using the data of suspended sediment concentration and vertical distribution of tidal currents at the mouth of the bay in the Yeosu Sound (Yeosu Haeman). At the mouth of the bay suspended sediment concentration shows much higher value of approximately 17.80㎎/ℓ on the average near the bottom than the concentration near the surface where the average is 4.75㎎/ℓ. Tidal currents also show an asymmetry in magnitude between flood and ebb. Near the surface ebb is stronger than flood, while flood is stronger than ebb near the bottom. Due to the higher concentration and stronger flood current near the bottom, transport of suspended sediment near the bottom plays a major role to the sediment budget in the bay, and the bay is in net-depositional environment. The western part of the bay seems to gain the suspended sediment of approximately 5.66×10?g/day, which corresponds to a sedimentation rate of about 1.15m/1,000 years.

Laboratory/In situ Sound Velocities of Shelf Sediments in the South Sea of Korea

Kim, Dae-Choul,Kim, Gil-Young,Jung, Ja-Hun,Seo, Young-Kyo,Wilkens, Roy H.,Yoo, Dong-Geun,Lee, Gwang-Hoon,Kim, Jeong-Chang,Yi, Hi-Il,Cifci, Gunay The Korean Society of Fisheries and Aquatic Scienc 2008 Fisheries and Aquatic Sciences Vol.11 No.2

Compressional sound velocities of shelf sediments in the South Sea of Korea, were measured in situ and in the laboratory for six cores. In situ sound velocity was measured using the Acoustic Lance (frequency of 7.5-15 kHz), while laboratory velocity was measured by the pulse transmission technique (frequency of 1MHz). Physical properties were relatively uniform with sediment depth, suggesting little effect of sediment compaction and/or consolidation. Average in situ velocity at each core site ranged from 1,457 to 1,488 m/s, which was less than the laboratory velocity of 1,503 and 1,604m/s. In muddy sediments the laboratory velocity was 39-47 m/s higher than in situ velocity. In sandy sediments, the difference was greater by an average of 116 m/s. Although the velocity data were corrected by the velocity ratio method based on bottom water temperature, the laboratory velocity was still higher than the in situ velocity (11-21 m/s in muddy sediments and 91 m/s in sandy sediments). This discrepancy may be caused by sediment disturbance during core collection and/or by the pressure of Acoustic Lance insertion, but it was most likely due to the frequency difference between in situ and laboratory measurement systems. Thus, when correcting laboratory velocity to in situ velocity, it is important to consider both temperature and frequency.

Compressional Wave Velocity and Electrical Resistivity in Hemipelagic Clay-rich Sediment, Northwestern Pacific

KIM, DAE CHOUL,KIM, KEE HYUN 충남대학교 기초과학연구소 1989 연구논문집 Vol.9 No.-

북서 태평양에 분포하는 반 원양성 점토의 심해저 시추 코어를 이용한 공극율, 음파전달속도, 속도 비등방성, 전기비저항, 비저항 비등방성에 대한 성질이 측정되었다. 음파속도와 비저항은 퇴적물 깊이에 따라 증가하고 반대로 공극율은 감소한다. 깊이에 따른 속도와 비저항의 비등방성의 변화양상은 거의 비슷하다. 수평방향으로 발달된 얇고 긴 공극과 일정한 방향성을 가지고 배열하는 점토광물이 속도의 비등방성의 원인이 될 수 있음이 제시되었다. Properties of porosity, compressional wave velocity, velocity anisotropy, electrical resistivity, and resistivity anisotropy are measured and calculated for two DSDP clay-rich hemipelagic sequences in the northwestern Pacific. Velocity and resistivity increase with burial depth at the expense of decreasing porosity. Profiles of velocity anisotropy and resistivity anisotropy show almost the same trend. Horizontally developed low aspect ratio pores may generate velocity and resistivity anisotropy. The preferred orientation of clay minerals is also believed to be responsible for the observed anisotropy.

Physical properties and geoacoustic provinces of surficial sediments in the southwestern part of the Ulleung Basin in the East Sea

Kim, So Ra,Lee, Gwang-Soo,Kim, Dae Choul,Bae, Sung Ho,Kim, Seong-Pil Elsevier 2017 QUATERNARY INTERNATIONAL Vol.459 No.-

<P><B>Abstract</B></P> <P>A total of 157 piston and box core samples were collected and analyzed to characterize physical properties and geoacoustic provinces of surficial sediments in the southwestern part of the Ulleung Basin in the East Sea. The results and distribution patterns of surficial sediment texture, physical and acoustic properties reflect well the sedimentary environment like distribution and composition of sediment in the study area. The inner shelf and basin slope in this study are dominated by fine-grained sediments and show high porosity and water content, with low bulk density and velocity as well. The trough of the Korea Strait and outer shelf, which is composed of coarse-grained sediments, shows low porosity and water content and high bulk density and velocity. Based on <I>in-situ</I> velocity and sediment properties, the study area is divided into five provinces: (1) Province IA is hemi-pelagic mud partially mixed with intermittent sandy sediments which are derived from the outer shelf due to slide/slump or mass flows (<I>in-situ</I> velocity: 1445 m/s, mean grain size: 8.4Φ, porosity: 84%, and bulk density: 1.24 g/cm<SUP>3</SUP>), (2) Province IB is covered with muddy sediments that were deposited during the Holocene (<I>in-situ</I> velocity: 1445 m/s, mean grain size: 7.9Φ, porosity: 78%, and bulk density: 1.35 g/cm<SUP>3</SUP>), (3) Province II is marked by mixed recent and relict sediments (<I>in-situ</I> velocity: 1477 m/s, mean grain size: 6.1Φ, porosity: 68%, and bulk density: 1.53 g/cm<SUP>3</SUP>), (4) Province III is dominated by coarse-grained relict sediments formed during the Pleistocene (<I>in-situ</I> velocity: 1564 m/s, mean grain size: 3.8Φ, porosity: 54%, and bulk density: 1.77 g/cm<SUP>3</SUP>), and (5) Province IV consists of coarser sediments than Province III (<I>in-situ</I> velocity: 1671 m/s, mean grain size: 3.0Φ, porosity: 46%, and bulk density: 1.91 g/cm<SUP>3</SUP>). The compressional wave velocity, mean grain size, and bulk density increase from Province IA to Province IV, whereas the porosity and water content decrease from Province IA to Province IV. Variability of the physical and acoustic properties tends to follow the general trend of the mean grain size. The classification of each province using the <I>in-situ</I> velocity corrected with the temperature and pressure provides a better reflection of the sediment properties and sedimentary environment.</P>

Sediment echo types and acoustic characteristics of gas-related acoustic anomalies in Jinhae Bay, southern Korea

Dae-Choul Kim,이광수,Gwang-Hoon Lee,Soo-Choul Park 한국지질과학협의회 2008 Geosciences Journal Vol.12 No.1

Analysis of Chirp profiles from Jinhae Bay, south-ern Korea, revealed three sediment echo types (echo type I III)and acoustic anomalies associated with shallow gas such as acous-tic blanking and turbidity. Echo type I, characterized by low-to-high amplitude internal reflectors, almost parallel to the seafloorand seen away from the Gadeog Channel, probably represent mudtransport. Echo type II, characterized by truncation at the seaf-loor and seen only in the Gadeog Channel, is interpreted to betidal-channel deposits. Echo type III is acoustically transparentand interpreted as distal prodelta deposits. The acoustic blankingand turbidity were further divided into AB-I I and AT-I I,respectively. AB-I has a very strong, shallow top reflection that isparallel to the seafloor, crosscutting the stratigraphy. Depths of AB-I may correspond to the sulphate-methane transition that remainsshallow probably due to large supply of methane. The top reflec-tion of AB-II is of high amplitude and follows the bedding planes,probably controlled or limited by lithology. AB-III is character-ized by a very iregular or highly diffractive and strong top reflec-tion, which may be due to very closely-spaced patches of high-concentration gas. AT-I exhibits a weak and highly iregular topreflection, sugesting low gas concentration. AT-II, comprised ofisolated weak diffractions, is likely due to isolated accumulationsof low concentration gas. C/N ratios (6.88.6) of the organic matterin the cored sediments in the study area suggest mixed marine andterrestrial sources

Ultrasonic Characterization of Fluid Mud: Effect of Temperature

Kim, Gil-Young,Kim, Dae-Choul,Kim, Jeong-Chang The Acoustical Society of Korea 2004 韓國音響學會誌 Vol.23 No.e4

A laboratory study was carried out to investigate the change of ultrasonic velocity as a function of temperature for fluid mud (i.e., suspension). Pulse transmission technique with ultrasonic wave was used for ultrasonic velocity measurement. The five samples for fluid mud were prepared for concentration range of $30.6{\%}\;(1.24\;g/cm^{3}\;in\;density),\;23.3{\%}\;(1.19\;g/cm^{3}),\;11.5{\%}(1.10\;g/cm^{3}),\;7.8{\%}\;(1.08\;g/cm^{3}),\;and\;3.8{\%}\;(1.05\;g/cm^{3})$ by weight. The ultrasonic velocity in fluid mud was investigated to increase $(approximately\;2.83\;to\;4.95\;m/s/^{\circ}C)$ with increasing temperature, due to the effect of viscosity and compressibility of water with changing temperature. But the increasing rate tends to decrease at temperature higher than $30^{\circ}C,$ caused by the effect of viscosity. The concentration of fluid mud more affect to the ultrasonic velocity at higher temperature range than that at lower temperature. Overall the temperature effect on the ultrasonic velocity in fluid mud was a similar rate as for distilled water and seawater, suggesting fluid mud significantly depends on the behavior of water.

Sedimentation and Physical Properties of Inner Shelf Sediment, South Sea of Korea

Dae-Choul Kim(김대철),Yong-Ahn Park(박용안),Chang-Bok Lee(이창복),Hyo-Jin Kang(강효진),Jin-Hyuk Choi(최진혁) 대한지질학회 1992 지질학회지 Vol.28 No.6

Laboratory/In situ Sound Velocities of Shelf Sediments in the South Sea of Korea

Dae Choul Kim,Gil Young Kim,Ja Hun Jung,Young Kyo Seo,Roy H. Wilkens,Dong Geun Yoo,Gwang Hoon Lee,Jeong Chang Kim,Hi Il Yi,Gunay Cifci 한국수산학회 2008 Fisheries and Aquatic Sciences Vol.11 No.2

Application of Sediment Physical Properties to Paleoclimatic Interpretation: Preliminary Results in the Ulleung Basin, the East Sea

Kim, Gil-Young,Kim, Dae-Choul,Keene, Jock,Kim, Jeong-Chang The Korean Society of Oceanography 1999 Journal of the Korean Society of Oceanography Vol.34 No.4

Sediment physical properties (compressional wave velocity, grain density, dry bulk density, and wet bulk density) are correlated to the paleoenvironmental parameters (coarse fraction, oxygen isotope, and planktonic foraminifera fragmentation) to reveal the possible interrelationship in the latest Quaternary sediments of the Ulleung Basin, the East Sea of Korea. Laboratory determinations of physical properties and paleoenvironmental parameters have been conducted on four piston core sediments. There are slight differences in the physical properties between glacial and interglacial period sediment sections. This is due to the large fraction of coarse grains of volcanic and terrigenous sediments relative to carbonate sediments. However, dry bulk density as an indicator of carbonate abundance in pelagic environment shows higher values at the lower part of cores, reflecting deeper CCD in the glacial period. Changes in velocity also relatively parallel to those in sediment coarse fraction, number of planktonic foraminifera, and wet bulk density. Therefore, we suggest that high-resolution physical properties may be used as a valuable tool for paleoenvironmental interpretation in the Ulleung Basin.