• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.4
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• pp.297-309
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• 2016

This study was carried out to investigate the differences in sedimentary environments and benthic polychaete communities between farming grounds and natural habitats (non-farming ground) in Gamak Bay. Sampling stations of natural habitats were evenly distributed in the entire bay. And mussel farm, oyster farm and ark-shell farm were selected as farming grounds. Dominant sedimentary facies was mud in most sampling stations of farming grounds and natural habitats. However organic contents were higher in the farming grounds than natural habitats of the bay. The species number and mean density of polychaetous community in the natural habitats were greater than those from the farming grounds. Lumbrineris longifolia, known as potential organic enrichment indicator species, was first dominant species both in farming grounds and natural habitats of the bay. However, the next dominant species consisted of different species between two benthic habitats. As a result of community analysis using cluster analysis and nMDS, the natural habitats were divided into several station groups, but most of stations in farming grounds were clustered into one group. Pearson' correlation analysis and PCA showed high relationships between sedimentary environmental factors and benthic polychaetous community in natural habitats, but low or no relationships in farming grounds. That means benthic polychaetous community established in farming ground was under unusual condition such as high input of organic matter. Thus it is necessary to improve the benthic environmental quality of the farming grounds as well as the north-western inner part in Gamak Bay through long-term monitoring efforts.

• The Korean Journal of Quaternary Research
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• v.17 no.2
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• pp.17-23
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• 2003

In Korea terrestrial fluvial sequences can be used as pedological and sedimentological markers indicating a millenium-scale environmental and climatic changes imprinted in fluvial sub-environments, which in turn are represented by the cyclicity of fluvial sands, backswamp organic muds, and flooding muds intercalations of frostcracked or dessicated brown paleosols. Post LGM and Holocene fluvial and alluvial sedimentary sequences of Korea are formed in such landscapes of coastal, floodplain, backswamp and hillslope areas. Among them, the most outstanding depositional sequences are fluvial gravels, sands and organic mud deposits in coastal, fluvial, or alluvial wetlands. The aim of this study is to explain the sedimentary sequences and palynofloral zones since the last 15,000years, on the basis of organic muds layers intercalated in fluvial sand deposits. Jangheung-ri site of Nam river, Soro-ri site of Miho river, Youngsan rivermouth site in Muan, Oksan-ri site of Hampyeong and Sanggap-ri site of Gochang are illustrated to interpret their sedimentary facies, radiocarbon datings, and palynofloral zonation. Up to the Middle to Late Last Glacial(up to 30-35Ka), old river-bed, flooding, and backswamp sequences contain such arboreal pollens as Pinus, Abies, and Picea, and rich in non-arboreal pollens like Cyperaceae, Gramineae, Ranunculaceae, and Compositae. During the LGM and post-LGM periods until Younger Dryas, vegetation has changes from the sub-alpine conifer forest(up to about 17-11Ka), through the conifer and broad-leaved deciduous forest, or mixed forest (formed during 16,680-13,010yrB.P), to the deciduous and broad-leaved forest (older than 9,500yrB.P). In the Earliest Holocene flooding deposits, fragments of plant roots are abundant and subjected to intensive pedogenic processes. During Holocene, three arboreal pollen zones are identified in the ascending order of strata； Pinus-Colyus zone(mixed conifer and deciduous broad-leaved forest, about up to 10Ka), Alnus-Quercus forest (the cool temperate deciduous broad-leaved forest, about 10Ka-2Ka), and Pinus forest (the conifer forest, about after 2Ka), as examplified in Soro-ri site of Cheonwon county. The palynological zonations of Soro-ri, Oksan-ri, Sanggap-ri, Youngsan estuary, and Gimhae fluvial plain have been recognized as a provisional correlation tool, and zonations based on fluvial backswamp and flooding deposits shows a similar result with those of previous researchers.

• Ocean and Polar Research
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• v.39 no.2
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• pp.85-106
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• 2017

The Lago Sofia conglomerate in southern Chile is a deep-marine gravelly deposit, which is hundreds of meters thick and kilometers wide and extends laterally for more than 100 km, filling the foredeep trough of the Cretaceous Magallanes Basin. For understanding the depositional processes and environments of this gigantic deep-sea conglomerate, detailed analyses on sedimentary facies, architecture and paleoflow patterns were carried out, highlighting the differences between the northern (Lago Pehoe and Lago Goic areas) and southern (Lago Sofia area) parts of the study area. The conglomerate bodies in the northern part occur as relatively thin (< 100 m thick), multiple units intervened by thick mudstone-dominated sequences. They show paleoflows toward ENE and S to SW, displaying a converging drainage pattern. In the southern part, the conglomerate bodies are vertically interconnected and form a thick (> 400 m thick) conglomerate sequence with rare intervening fine-grained deposits. Paleoflows are toward SW. The north-to-south variations are also distinct in sedimentary facies. The conglomerate bodies in the southern part are mainly composed of clast-supported conglomerate with sandy matrix, which is interpreted to be deposited from highly concentrated bedload layers under turbidity currents. Those in the northern part are dominated by matrix- to clast-supported conglomerate with muddy matrix, which is interpreted as the products of composite mass flows comprising a turbidity current, a gravelly hyperconcentrated flow and a mud-rich debris flow. All these characteristics suggest that the Lago Sofia conglomerate was formed in centripetally converging submarine channels, not in centrifugally diverging channels of submarine fans. The tributaries in the north were dominated by mass flows, probably affected by channel-bank failures or basin-marginal slope instability processes. In contrast, the trunk channel in the south was mostly filled by tractive processes, which resulted in the vertical and lateral accretion of gravel bars, deposition of gravel dunes and filling of scours and channels, similar to deposits of terrestrial gravel-bed rivers. The trunk channel developed along the axis of foredeep trough and its confinement within the trough is probably responsible for the thick, interconnected channel fills. The large-scale architecture of the trunk-channel fills shows an eastward offset stacking pattern, suggesting that the channel migrated eastwards most likely due to the uplift of the Andean Cordillera.

• Economic and Environmental Geology
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• v.40 no.5
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• pp.623-633
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• 2007

Stable isotope and biomarker analyses were carried out for the organic sediments from the exploratory wells in the Jeju Basin in order to understand the characteristics of organic matter. Organic matter in Geobuk-1, Okdom-1, JDZ VII-1 and VII-2 well is predominantly originated from land plants rather than marine algae according to carbon $({\delta}^{13}C_{org})$ and nitrogen $({\delta}^{15}N_{org})$ isotopic compositions. In the Geobuk-1, geochemical characteristics such as carbon $({\delta}^{13}C_{org})$, nitrogen ($({\delta}^{15}N_{org})$ and TOC contents are obviously changed by the depth 2,400 m, which is likely due to the change of origin of organic matter, sedimentary process or sedimentary environments. Analysis of the saturated fraction of the bitumen suggests the contribution of migrated oil to the indigenous bitumen from the samples 2,509, 2,833 and 3,163 m of the JDZ YII-1 and 3,253 m of the Geobuk-1 well. However, this characteristics can be derived from the contribution of the original organic matter. Based on the biomarker analysis, the samples from the Okdom-1 and Geobuk-1 appear to represent sedimentary organic matter of similar composition, that is rotatively immature, and which was probably deposited in the fluvio-deltaic setting with minor offshore marine influence. The samples from JDZ VII-1 appear to have been deposited in a more terrestrially dominated setting.

• Journal of the Korean earth science society
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• v.27 no.6
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• pp.659-669
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• 2006

In Kwangyang Bay, the south coast of Korea, surface sediments and sedimentation rates have been investigated to understand the distribution and variation of tidal flat sediments after the construction of sea dyke. The mean grain size of the surface sediments during autumn is coarser, and decrease from winter to summer except for temporarily coarsening in the early summer. The depositional processes are prevalent in spring, while erosional processes are dominant in summer and autumn. This seasonal variation of sedimentary processes show similar results monitored from 2001 to 2003 before the construction of sea dyke. In the northern area of the bay, net annual sedimentation rates show similar results monitored from 2001 to 2003 before the construction of sea dyke. However, in the western area of the bay, net annual sedimentation rates change from erosion-dominated to deposition-dominated environments. It is considered that the western area of the bay is changed to erosion-dominated environments, as a result of the changes of hydrodynamic conditions, caused by sea dyke construction.

• Journal of The Geomorphological Association of Korea
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• v.23 no.3
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• pp.79-92
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• 2016

Samples from two boreholes of coastal dune field at Jangho-ri coast, Gochang was studied. These were analyzed by grain size analysis geochemical analysis, and the application of OSL dating method to understand the development during the Holocene. The boreholes SB8 and SB9 were classified into three different sedimentary layers by their mean grain size and geochemical characteristics. The results revealed that the upper sand layer is equivalent to the present coastal dune layer, which developed since 1,200 years ago; the silt layer in the middle to the dune slack or lagoon sedimentation layer, which developed between 1,200 and 6,000 years ago; and the sand layer at the bottom to the paleo coastal dune that developed between 6,000 and 7,000 years ago. It was proposed that the forming material of current coastal dune was supplied from the sandy flat in coastal area, while the middle silt layer was supplied from the weathered soil of a bed rock by the comparison with material of surrounding area. In the case of coastal dune, concentrated layer of sands were identified which were buried about 300 and 1,200 years ago, which is identified as the little ice age. This study confirmed the development of Jangho-ri coastal dunes after Holocene Climate Optimum period, and it is likely to assist in the understanding of coastal dunes development.

• Journal of Soil and Groundwater Environment
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• v.25 no.2_spc
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• pp.28-54
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• 2020

Even though a systematic sampling approach is very crucial in both the general and detailed investigation phases to produce the best conceptual site model for contaminated sites, the concept is not yet established in South Korea. The U.S. Environmental Protection Agency (EPA) issued the 'Strategic Sampling Approaches Technical guide' in 2018 to help environmental professionals choose which sampling approaches may be needed and most effective for given site conditions. The EPA guide broadly defines strategic sampling as the application of focused data collection across targeted areas of the conceptual site model (CSM) to provide the appropriate amount and type of information needed for decision-making. These strategic sampling approaches can prevent the essential data from missing, minimize the uncertainty of projects and secure the data which are necessary for the important site-decisions. Furthermore, these provide collaborative data sets through the life cycle phases of projects, which can generate more positive proofs on the site-decisions. The strategic sampling approaches can be divided by site conditions. This technical guide categorized it into eight conditions; High-resolution site characterization in unconsolidated environments, High-resolution site characterization in fractured sedimentary rock environments, Incremental sampling, Contaminant source definition, Passive groundwater sampling, Passive sampling for surface water and sediment, Groundwater to surface water interaction, and Vapor intrusion. This commentary paper introduces specific sampling methods based on site conditions when the strategic sampling approaches are applied.

• Journal of The Geomorphological Association of Korea
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• v.27 no.1
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• pp.33-45
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• 2020

A number of unconsolidated deposits, consisting of a layer of gravels and silt, are found in Dangjeong-ri, Seocheon-gun in the western coast. From below in the stratigraphic sequence, the gravel layer ranging up to a maximum thickness of about 2 meters is interpreted as being formed by fluvial processes of an old channel (Dangjeong S.), and the overlying silt or sandy silt layer of 2 to 3 thickness meters is assumed to be emerged paleo-tidal sediments which was deposited in low tidal-energy environments. As the results of rock surface IRSL datings, the depositional ages of gravels are confirmed as ca. 78,000 ~ 83,000 years BP, indicating that the layer was formed in response to a high-stand sea level of MIS 5a along the Dangjeongcheon estuary. It is presumed that the relative height of 4.5 meter between the altitude of the stream bed (9.5 m) and the altitude of the bedrock boundary in the gravel layer (14 m) indicates the uplift amount since deposition. Paleo-sedimentary environments and an altitude of paleo-shoreline in the study area will be discussed with additional age dating focused on the silt layer.

• The Korean Journal of Quaternary Research
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• v.17 no.1
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• pp.7-16
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• 2003

A 31m-long sediment core (SSDP-102) was taken from the inner shelf (about 40m water-depth) off the northwestern coast of the Korea Strait. Detailed lithofacies and organic-geochemical analyses were performed to establish a high-resolution stratigraphy in the Korea Strait shelf and to reconstruct the paleoenvironmental changes associated with the Holocene marine transgression. The stratigraphic framework of the core was primarily established using 6 AMS $^{14}C$ ages. The sedimentary record of the core SSDP-102 allows for the reconstruction of the paleoenvironmental changes during the last 12.1 ka BP. According to the high-resolution seismic reflection profiles, lithofacies and organic-geochemical data, the core SSDP-102 can be divided into three units (III to I in ascending order) above the acoustic basement. The three units reflect distinct changes of depositional environments resulted from the post-glacial marine transgression. Therefore, it is suggested that three phases of sea-level change have occurred within the inner shelf of the Korea Strait following the Holocene marine transgression. (1) estuarine environments from ca. 12.1 to 6.2 ka BP; (2) near-shore environments with a period of decreased rising of sea level between 6.2 and 5.1 ka BP; (3) near-shore to modem marine environments after 5.1 ka BP. In particular, the present marine conditions influenced by the warm Tsushima Current have been gradually established after ca. 5.1 ka BP.

• Journal of Environmental Science International
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• v.12 no.7
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• pp.753-762
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• 2003

Butyltin compounds (BTs), namely tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT), were measured in surface sediments collected in 2001 inside Hallim Harbor where a lot of shipping occurs as one of major harbors of Jeju Island, in order to evaluate their distribution. BTs were detected in surface sediments of all stations and their concentrations were comparable to those in surface sediments of other sites of domestic and foreign countries. The main species among BTs was MBT, although there was a little difference with a survey site. No correlations were obtained between organic matter or particles size of surface sediments and total BTs, indicating that these factors did not affect on the distribution of BTs. It was estimated that more complex factors including BTs loads and surrounding sedimentary environments, affected on the distribution of BTs. The high correlations between BTs indicated that DBT and MBT were mainly degraded from TBT based on antifouling paints of vessel etc. and other sources, such as DBT and MBT, could be ignored. The butyltin degradation indexes ([DBT] + [MBT]/[TBT]) Ivere in the range of 1.5∼3.3 (mean 2.5), indicating that the parent compound, TBT, were inflowed into the surface sediments a long years ago and degraded.