• The Korean Journal of Quaternary Research
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• v.15 no.1
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• pp.29-35
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• 2001

The coastal deposits along Moonamni, Kangwon Province, Korea have been investigated by using deeply cored sediments(down to the basement rocks : Pre-Cambrian metamorphic rocks and granitic rocks) in order to understand and propose the late Quaternary stratigraphy and related major unconformities. Three major stratigraphic -depositional units are proposed. The neolithic cultural sites in the Moonamni area are considered as middle Holocene coastal dunes, which were developed due to active supply of beach sands from Unit I(Holocene transgressive deposit). Such coastal dune sediments are characteristic in the upper part of Unit I(Holocene in age). So far, Unit II and Unit III are considered as continental deposits, such as fluvial-swamp and alluvial deposit, respectively.

• 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 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.

• Economic and Environmental Geology
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• v.37 no.5
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• pp.533-541
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• 2004

A steadily consolidated conglomerate formation (CCF) is developed thickly around Tabjeong-ri and Janghang-ri to the east of Tohamsan, Gyeongju City. The CCF has been regarded to a basal conglomerate, Cheonbug Conglomerate, of the Yonil Group by Tateiwa (1924). Son et al. (2000) correlated the CCF to the Songjeon Formation, which occupies the southwestern block of Tertiary Waup Basin. However, the Songjeon Formation stratigraphically does not face to the extension of the CCF. OSL (Optically Stimulated Luminescence) data on the reddish brown to bluish gray psammitic layers, which are intercalated in the CCF, yielded to 85∼92 ka. Therefore, the age of CCF constrains to the last interglacial stage (MIS 5c-5e) rather than the Early Miocene Cheonbug Conglomerate. The Late Pleistocene Tohamsan Formation (TF) is newly named to the CCF and is subdivided to megabreccias and boulders. A rectangular basin, in which the TF is accumulated, is bounded by Oedong and Yonil faults (segments of Yonil Tectonic Line) and is given a name of Toham Basin. Neotectonically, Pliocene EW-transpression gave an effect of the top-up-to-the-west reverse faulting and the accompanied normal fault movement during the last interglacial age (ca. 100 ka). The basin is graben type, in which basin fills are composed of collapsed colluvial deposits, TF.

• Geophysics and Geophysical Exploration
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• v.13 no.4
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• pp.349-356
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• 2010

Analysis of high-resolution seismic profiles acquired from the southeastern continental shelf of Korea reveals that the late Quaternary transgressive deposits consist of six seismic units created in response to sea-level rise. These units with different seismic facies and geometry can be grouped into two distinct depositional wedges (paralic and marine) bounded by a ravinement surface. The paralic component underlying the ravinement surface consists of the sediment preserved from shoreface erosion and contains incised-channel fill, ancient beach-shoreface deposit and estuarine deposit. The top of paralic unit is truncated by a ravinement surface and overlain by marine component. The marine component consists of the sediment produced through shoreface erosion during landward transgression and contains mid-shelf sand sheet, mid-shelf sand ridge and inner shelf sand sheet. Such transgressive stratigraphic architecture of six sedimentary units 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.

• The Korean Journal of Quaternary Research
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• v.25 no.1
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• pp.15-30
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• 2011

Three sediment cores from two different locations (UJ-03 and UJ-12 cores of valley sediment in Paju area, and CL-4 core of wetland sediment in Cheollipo area) along the western Korean Peninsula yield crucial information on the timing and spatial pattern of century-scale climate changes and subsequent surficial responses during the Holocene. In Paju area, the sediments included abundant coarse-grained sediment (coarse sands and pebbles) from 7100 to 5000 cal. yrBP, total organic carbon (TOC) values showed a marked increase from 5000 to 2200 cal. yrBP, several intermittent depositional layers were observed from 2200 cal. yrBP. In Cheollipo area, lake environment developed from 7360 to 5000 cal. yrBP, the deposition of organic materials increased from 5000 to 2600 cal. yrBP, peatland formed from 2600 cal. yrBP. The two patterns of surficial responses to the climate changes through the Holocene are different to each other. This might be due to the dissimilarity in geomorphic conditions. However, the approximate simultaneity of environmental changes in two areas shows that they both can be correlated to the major climate changes. Two areas which have undergone significant changes indicated that the hydrological factors including precipitation and strength of water flow were most responsible for the landscape and geomorphic evolutions. Although the upwards trend in relative sea-level also played a primary role for environmental changes in coastal area (Cheollipo area), detailed studies have still to be undertaken.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.4
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• pp.369-379
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• 2003

Analysis of high-resolution seismic profiles and sediment data from the southeastern continental shelf of Korea reveals that the late Quaternary deposits consist of a set of lowstand (LST), transgressive (TST), and highstand systems tracts (HST) that corresponds to the sea-level change after the Last Glacial Maximum. LST (Unit I) above the sequence boundary consists of sandy mud or muddy sand deposited during the last glacial period and is confined to the shelf margin and trough region. TST (Unit II) between transgressive surface and maximum flooding surface consists of sandy sediments deposited during the postglacial transgression (15,000-6,000 yr BP). Although TST is widely distributed on the shelf, it is much thinner than LST and HST. On the basis of distribution pattern, TST can be divided into three sub-units: early TST (Unit IIa) on the shelf margin, middle TST (Unit IIb) on the mid-shelf, and late TST (Unit IIc) on the inner shelf, respectively. These are characterized by a backstepping depositional arrangement. HST(Unit III) above the maximum flooding surface is composed of the fine-grained sediments deposited during the last 6000 yrs when sea level was close to the present level and its distribution is restricted to the inner shelf along the coast.

• The Korean Journal of Quaternary Research
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• v.23 no.2
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• pp.48-55
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• 2009

To investigate the paleoceanographic environmental changes around the Okinawa Trough, Japan, a piston core (RN88-PC5) was conducted on benthic foraminiferal species composition, assemblage, sedimentological and geochemical analyses. Trubidite sediment intercalated in studied core contains different benthic foraminiferal species, dwelling in shallow coral reef species, from normal hemipelagic sediment. These different benthic foraminiferal species and its assemblage are interpreted as reworked sediment when turbidite current occurred, synchronically. Grain size analysis clearly showed that mean grain size difference occurred between trubidite and hemipelagic sediments. Geochemical analysis also showed the difference of chemical composition between two sedimentary facies. Results of the foraminiferal oxygen isotope analysis showing global surface water warming records since the last 10 ka. The geochemcial analysis and previous works showed that turbidite sediment of studied core indicating sporadic occurrence of regional paleoceanographic events. Assemblage of shallow coral reef benthic foraminifera especially occurred with turbidite layer clearly support the sporadic occurrence of paleoceanographic events such as regional earthquake.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.9 no.1
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• pp.1-12
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• 2004

Sedimentary facies and high-resolution echo facies were analyzed to elucidate sedimentation pattern of the late Quaternary glacial-marine deposits in the northern continental margin of the South Shetland Islands. Six sedimentary facies are classified, based on grain texture and sedimentary structures in gravity cores. The high-resolution (3.5 ㎑) echo characters are classified into 6 echo facies on the basis of clarity, continuity, and shape of bottom and subbottom echoes together with seafloor topography. Distribution of the echo and sedimentary facies suggest that there was a significant change in sedimentation pattern between the Last Glacial Maximum (LGM) and subsequent glacier-retreating period. When the grounded glaciers extended to the present shelfbreak during LGM, coarse-grained subglacial tills were widespread in the shelf area, and deep troughs in the shelf were carved beneath the fast-flowing ice steam. As the glacial margin retreated landward after LGM, dense meltwater plumes released from the retreating ice-front were funneled along the glacier-carved troughs, and accumulated channel- or cannyon-fill deposits in the shelf and the upper to mid slope. At that time, slope sediments seem to have been reworked by slope failures and unsteady contour currents, and further transported by fine-grained turbidity currents along the South Shetland Trench. After the glacial retreat, sediments in the shelf and slope areas have been mainly introduced by persistent (hemi) pelagic settling, and fine-grained turbidity currents frequently occur along the axis of the South Shetland Trench.

• Proceedings of the KSEEG Conference
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• 2005.04a
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• pp.164-164
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• 2005