• Journal of the Korean Geophysical Society
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• v.2 no.3
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• pp.191-200
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• 1999

Analysis of chirp high-resolution seismic profiles from the central Yellow Sea reveals that depositional environments in this area can be divided into three distinctive zones from west to east: (1) subaqueous delta system near the Shandong Peninsula, (2) erosional zone in the central Yellow Sea, and (3) tidal sand ridges and sand waves near the Korean Peninsula. The Shandong subaqueous delta, extending southward from the Shandong Peninsula, changes gradually into prodelta southeastward. The sediments originated from the Yellow River are transported southward along the Chinese coastal area. The erosional zone in the central Yellow Sea contains numerous paleochannels and shows linear erosional features trending northwest-southeast. The erosional zone would be dominated by non-depositional or erosional processes during the Holocene. Tidal sand ridges and sand waves are well developed along the western coast of Korea. The residual sands, which were originally fluvial sediments at the sea-level lowstand, are interpreted as the result of winnowing process during the sea-level rise. Modern sand ridges generally migrates in a northeast-southwestern direction, which coincide with dominant tidal current direction.

• Journal of The Geomorphological Association of Korea
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• v.21 no.4
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• pp.109-120
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• 2014

This study is an analysis on gravel and sand of sand-gravel bar that stretches variously in the Duchon stream basin, which is one of Hong-Cheon River(a well-developed sand-gravel bar in upstream river)'s upper stream basin. The purpose of this study was to understand the characteristic of the stream's topographic development that variously occur in the small basin by comparing the differences between the aspects of development and the sediment of sand-gravel bar in each section and by examining the transition of sediments moving from upstream to downstream. Through the analysis on the roundness and flatness of gravel, we observed an irregular trend following the increase in supply of granite gravel and gneiss gravel as we traveled downstream. As for the aspect of change in sand's grain size, the overall ratio of medium-coarse sand was very high, but the results showed no big difference in the change following the inflow of stream from the main stream section to the gneiss and granite zone.

• Journal of The Geomorphological Association of Korea
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• v.18 no.2
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• pp.1-14
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• 2011

Remarkable development of sand bars is an important characteristic of fluviatile landform of Korea. Their development owes, in one part, to the supply of abundant sandy materials to river valley floor, originated from the weathering of essentially granitic rocks, distributed almost all over the country. It owes, in other part, to river valley disposition presenting many angular sinuosity guided by fracture grid, impeding regular migration of sandy materials along valley floor. Besides, high amplitude of river discharge fluctuation of the country plays is proved to be favorable hydrological factor for the development of the sand bars. The sand bars play important roles in favor of river hydro-ecological environment. They mitigate the amplitude of discharge fluctuation regime. In flood spell, sand grains in the main channel migrate so as to broden wet section. At the spell of low water level, they newly accumulate as to impede rapid stream discharge. Especially high quantity of reserved water in porous space of sand bar is preciously available both for human livelihood and for ecological environment.

• Economic and Environmental Geology
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• v.47 no.5
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• pp.533-540
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• 2014

The Wangdol-cho area, in the Hupo Bank, plays a very important role in main fishing grounds, leisure tourism and marine environmental researches of the East Sea. We analyzed the detailed bathymetry and classified the seabed characteristics of the Wangdol-cho area, based on seafloor backscattering images and sediment grain size. The Hupo Bank is developed in parallel with the eastern coastal line of Korean peninsula, and the shallowest area (Wangdol-cho) of the Hupo Bank is located along the eastern part of Hupo Port. The Wangdol-cho comprises three summits; north summit, middle summit, and south summit. The middle summit area among the three summits has the most shallow water depth with minimum about 6 m. The north summit shows about 8 m minimum depth and the south summit about 9 m. The bathymetry data around three summits represent undulating seabeds with many scattered underwater reefs and shallow water depth. The area between the underwater reefs, the flat seafloor in the northeastern part of the survey site, and the western steep slope area have relatively coarse sediments such as sandy gravel and gravelly sand. The bathymetry in the western side of the Wangdol-cho shows steep slope seabed, extending to the Hupo Basin. Fine sediments including mud and silty sand occur in the Hupo Basin area of the survey site. The submarine detailed topography and the analysis of the seafloor characteristics of the survey area are expected to contribute to management for marine environmental researches and sustainable use of ecosystems in the Wangdol-cho.

• 한국해양학회지
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• v.30 no.1
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• pp.1-12
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• 1995

The modal analysis was carried out for the total of 216 subface sediments of southern continental shelf of Korean peninsula. Sandy mud or muddy sand distributed in the range of 70∼100 m water depth revealed the bimodal type (sand and mud components). The relations of textural parameters obtained from every modal were consistent with those of shallow marine sediments. The characteristics of sand component between bimodal were as follows: (1) the distributions of mean grain size, sorting, shell content were repeatedly distributed like the directions of depth contour lines. (2) Sand component was composed of medium to fine sand (Mz, 1-3$\psi$) containing many shell fragments, a few pebbles, and iron-stained quartz. (3) The surface of quartz revealed the concordial breakage and V-shaped features formed at high energy environment. (4) In CM-pattern, sand component was plotted in rolling and bottom suspension area. These characteristics imply that sand component probably derives from shoreface sediments deposited at the beach environment.

• Journal of the Mineralogical Society of Korea
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• v.31 no.1
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• pp.1-12
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• 2018

A gravity core (RS14-C2) was collected at site RS14-C2 in the continental slope to the east of Pennell-Isellin Bank of the Ross Sea (Antarctica) during PNRA XXIX (Rosslope II Project) Expedition. In order to trace the sediment source, magnetic susceptibility (MS), sand fraction, and clay mineral compositions were analyzed, and AMS $^{14}C$ ages were dated. Core sediments consist mostly of hemipelagic sandy clay or silty clay including ice-rafted debris (IRD). AMS $^{14}C$ age of core-top indicates the modern and Holocene sediments. Based on AMS $^{14}C$ dating, sediment color, MS and sand fraction, core sediments are divided into interglacial and glacial intervals. The interglacial brown sediments are characterized by low MS and sand fraction, whereas the glacial gray sediments are characterized by high MS and sand fraction. Among clay mineral compositions of core sediments, illite is highest (61.8~76.7%), and chlorite (15.7~21.3%), kaolinite (3.6~15.4%), and smectite (0.9~5.1%) are in decreasing order, and these compositions are also divided into the interglacial and glacial/deglacial intervals. During the glacial period, the high content of illite and chlorite indicate sediment supply from the bedrocks of Transantarctic Mountains under the Ross Ice Sheet. In contrast, because of decreasing supply of illite and chlorite by the glacial retreat, smectite and kaolinite contents increased relatively during the interglacial period. During the interglacial period, smectite may be transported additionally by the northeastward flowing surface current from the coast of Victoria Land in the western Ross Sea. Kaolinite may be also supplied to the continental slope by the Antarctic Slope Current from the kaolin-rich metasedimentary rock outcropped on the Edward VII Peninsula.

• 한국해양학회지
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• v.29 no.3
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• pp.217-227
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• 1994

From northeast to southwest, discontinuous sand ridges distribute on the western continental shelf of Korean Peninsular. The dimension of sand ridges is 3 to 21 m high, 3.1 to 6.8 km wavelength and 9-64 km long with 0.5 steep slope. they are probably originated and reformed by the intensity of tidal current according to the sea level rise. The characteristics of sand ridges revealed in study area are summarized as follows: (1) The sand ridges line up with the long axes of the tidal current ellipses, indicating a tidal control. (2) these are composed of two sedimentary sequences on the 3.5 kHz seismic profiles and core sediments. The upper sequence characterized by prolonged type is covered with thin veneer of massive fine sand(Mz, 2-3$\phi$) with Olive Gray(5Y 5/2). The lower sequence is characterized by internal reflector type with parallel and discontinuous. It consists of sandy mud or muddy sand(Mz, 5-7$\phi$) with laminar structures. the parallel internal reflectors are truncated on the slope of sand ridges. (3) Asymmetrical sand waves are superimposed on the sand ridges, and facing to the crest. However, symmetrical sand waves lie on the crest. Sand ridges having characteristics above is originated by scouring of tidal current, covered with coarase relict sediments, and modified by sadware.

• Economic and Environmental Geology
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• v.52 no.5
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• pp.471-484
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• 2019

Liquefaction occurs by a temporal loss of sediment strength as a consequence of increased pore water pressure during the re-arrangement of unconsolidated, granular sediments. Liquefaction is dependent on the physical properties of the sediments and cause surface cracks, landslide, and the formation of soft-sediment deformation structures(SSDS). SSDS is formed by the combined action of the driving force and deformation mechanism(liquefaction, thixotropy, and fluidization) that is triggered by endogenic or exogenic triggers. So research on the SSDS can unravel syndepositional geological events. If detailed sedimentologic analysis together with surrounding geological context suggest SSDS formed by earthquakes, the SSDS provide a clue to unravel syndepositional tectonic activities and detailed paleoseismological information(> Mw 5) including earthquakes that leave no surface expression.

• Journal of Korean Society of Forest Science
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• v.76 no.1
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• pp.17-26
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• 1987

To develop the rehabilitation measures for rockily denuded forest lands which are widely distributed in Seoul metropolitan area, erosional characteristics of denudation should, first of all, be evaluated and analysed. As a fundamental study for developing such technical measures, the rockily denuded lands were classified into 6 types according to denudation features of the mountain land, and also movements of stone debris-and-sand on rock-exposed hillslopes were measured and analysed. The 6 basic types of denudation features include a) natural rock-outcrop-exposed land, b) stone debris-and-sand scattered land, c) stone debris-and-sand deposited land, d) coarse sand producing bare land susceptible to weathering and erosion, e) dwarfed pine growing land, and f) torrential valley susceptible to the debris slides. In the stone debris-and-sand scattered hillslopes (type b), average amount of moved-down debris reached to about 3.9 ton/ha/yr due to surface washing and slidings. In the particle size distribution of the moved-down debris, it amounts to about 25% of 10-25mm, about 15% of 5-10mm, about 24% of 2-5mm, and about 36% of less than 2mm in diameter class, respectively. The detailed experimental studies should be accomplished further more about the denudation processes including weathering, erosion and debris slides on rock-exposed hillslopes.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.2
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• pp.59-70
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• 1998

Two-dimensional trend-vector model of sediment transport is first tested in the tidal flat of Garolim Bay, mid-western coast of the Korean Peninsula. Three major parameters of surface sediment, i.e., mean grain size, sorting and skewness, are used for defining the best-fitting transport trend-vector on the sand ridge and muddy sand flat. These trend vectors are compared with the real transport directions determined from morphology, field observation and bedforms. The 15 possible cases of trend vectors are calculated from total sediments. In order to find the role of coarse sediments, trend vectors from sediments coarser than < 4.5 ${\phi}$, (sand size) are separately calculated from those of total sediments. As compared with the real directions, the best-fitting transport-vector model is the "case M" of coarse sediments which is the combined trend vectors of two cases: (1) finer, better sorted and more negatively skewed and (2) coarser, better sorted and more positively skewed. This indicates sand-size grains are formed by simpler hydrodynamic processes than total sediments. Transported sediment grains are better sorted than the source sediment grains. This indicates that consistent hydrodynamic energy can make sediment grains better sorted, regardless of complicated mechanisms of sediment transport. Consequently, both transported vector model and real transported direction show that the source of sediments are located outside of bay (offshore Yellow Sea) and in the baymouth. These source sediments are transported through the East Main Tidal Channel adjacent the baymouth. Some are transported from the subtidal zone to the upper tidal flat, but others are transported farther to the south, reaching the south tidal channel in the study area. Also, coarse sediment grains on the sand ridge are originally from the baymouth, and transported through the subtidal zone to the south tidal channel. These coarse sediments are moved to the northeast, but could not pass the small north tidal channel. It is interpreted that the great amount of coarse sediments is returned back to the outside of the bay (Yellow Sea) again through the baymouth during the ebb tide. The distribution of muddy sand in the northeastern part of study area may result from the mixing of two sediment transport mechanisms, i.e., suspension and bedload processes. The landward movement of sand ridge and the formation of the north tidal channel are formed either by the supply of coarse sediments originating from the baymouth and outside of the bay (subaqueous sand ridges including Jang-An-Tae) or by the recent relative sea-level rise.