• Journal of The Geomorphological Association of Korea
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• v.17 no.3
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• pp.31-47
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• 2010

The history of mass movement has been reconstructed from the Angol basin in Guryongcheon drainage basin. Sedimentary facies study, radiocarbon dating, particle size analysis, magnetic susceptibility and geomorphological analysis have been performed to reconstruct the paleo-environmental history of Angol basin. From 40,480 to 9,850yrBP there were five periods of slope instability and from 9,850yrBP to present there were at least four periods of slope instability. Magnetic susceptibility curves match well with the sedimentary facies data. This study may help reconstruct the denudational history of the small basins in Cheonan area and could be the cornerstone of the paleo-climatological study of the Korean Peninsula.

• Journal of The Geomorphological Association of Korea
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• v.18 no.1
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• pp.101-112
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• 2011

Coastal terrace was developed at 7.2m height near Shinchon village in Geoje Island. It is located on the east side of southern coast in Korean Peninsula, where sea-level changes caused by ebb and flow of the tide, embayment are relatively low. Due to the breccia layer by mass-movement, dark grayish clayey formation, marine origin's rounded gravel are deposited sequentially in a cross-section of coastal terrace, so it provides a good example which understand Holocene sea level changes to determine the effect on the various sedimentary environments. For the purpose of identifying the morphogenetic process, Grain size, Roundness, XRD, AMS dating analysis was attempted. As a result, after last glacial age, Holocene sea level rise to +5.6m(4,740±100yrs BP). At that time, various geomorphological features are considered to be formed.

• Economic and Environmental Geology
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• v.48 no.4
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• pp.287-299
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• 2015

The metapsammite distributed in the Yeongam-Gangjin area had been classified into age-unknown Yongamsan Formation, Seologri Formation and age-unknown Seogisan Formation, and these formations are reported as each other different formations. These formations have been renamed Precambrian Galdu or Permian Songjong Formations. In this study, we present detrital zircon SHRIMP U-Pb age data from the metapsammite to examine deposition time and stratigraphy. The analyzed U-Pb zircon ages dominantly reveal Paleoproterozoic ages of ca. 1.87Ga and the youngest detrital grains are constrained by the age of 246-265 Ma. The youngest age indicates late Permian or early Triassic for the deposition time. Therefore, the metapsammite in the Yeongam-Gangjin area is considered to be the upper formation of the late Paleozoic Pyeongan Group which is correlated with the Gohan-Donggo Formations or Nokam Formation of the Samcheock coal field and the Cheonunsan Formation of the Hwasun coal field. The metapsammite of the study area is the late Paleozoic Pyeongan Group by the zircon age rather than Precambrian Galdu and Permian Songjeong Formations are no longer meaningful. Therefore, we propose the upper Paleozoic 'metapelite' and 'metaspammite', or original formation name defined by 1:50,000 geological maps, instead of Galdu and Songjeong Formations.

• Journal of the Korean association of regional geographers
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• v.17 no.6
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• pp.649-665
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• 2011

Estuary of River Nakdong(in south-eastern coast of Korean Peninsula) is the most representative site of delta in Korea. This study is to elucidate morpho-structural background associated with the embayment area and sedimentation processes, having allowed development of the delta. In this area, Great morphological trait of the embayment area had been formulated by differential erosion exploiting regional fracture system(NNE-SSW, NNW-SSE, E-W,...) of tectonic origin. For this reason, outline of the embayment basin shows quadrangular plan, and ridges and dissected valleys of neighbouring mountains draw frequently morphological lineament pattern. At the last glacial age when delta deposit had not yet filled the actual embayment basin of the Nakdong, mechanical weathering(frost shattering) and mass-movement processes had provided detritus materials composed of blocks, boulders on bottom the basin. With the postglacial transgression in the Holocene, the basin had been submerged, then began to be filled with fluvio-marine deposits from Kimhae-Yangsan area toward actual estuarine zone, so that Nakdong delta have been formed. Analysis and synthesis of from hundreds of boring data of the delta area reveal that progression of delta formation have been accompanied with the development of barrier islands. If the barrier islands had grown as forming a plural row, then their intervals have posteriorly filled with another fluvio-marine deposits. Besides, it shows that delta deposits are essentially alluvial. However, at the periphery of the delta, intervention of fine marine deposits is frequently found.

• 한국해양학회지
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• v.30 no.4
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• pp.302-319
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• 1995

The geochemical properties, sedimentation rates, foraminiferal distributions, and oxygen and carbon isotope records of sediment from Cores S-2 and S-19 were studied to investigate late Holocene paleoceanographic and paleoclimatic changes of the admiralty and Maxwell Bay, King George Island, Antarctica. Total organic carbon contents increased from the lower part to the upper part of Cores S-2 and S-19, whereas calcium carbonate contents decreased from the lower part to the upper part of Cores S-2 and s-19,whereas calcium carbonate contents decreased from the lower part to the upper part of Cores S-2 and S-19. Twenty-seven foraminiferal species were identified, and Globocassidurina biora was mostly a bundant in sediment samples. The sedimentation rates ranged from 24 cm/kyr to 237 cm/kyr based on /SUP 14/C-age dating of G. biora. The sedimentation rates increased rapidly in the upper part of the Cores. б/SUP 18/O values ranged from 0.3% to 6.2% and б/SUP 13/C values ranged from -3.0% to 0.0% with several fluctuations of the values. The lowest part of Core S-2, at 128 cmbsf in depth, had a /SUP 14/C-age of 3,100${\pm}$60 yr B.P. and the lowest part of Core S-19, at 230 cmbsf in depth, of 7,400${\pm}$ yr B.P. The results of geochemical and sedimentological analyses of the core sediments suggested five stages of paleoceanographic and paleoclimatic changes as follows: war,-cold stage of 7,500∼6,500 yr B.P., cold stage of 6,500∼3,600 yr B.P., cold-warm stage of 3,600∼2,770 yr B.P., warm stage of 2,770∼2,380 yr B.P. and cold-warm stage of 2,380∼2,100 yr B.P.

• Journal of the Korean earth science society
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• v.29 no.6
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• pp.454-465
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• 2008

Benthic foraminiferal assemblage and AMS radiocarbon dating of core sediments from the northern shelf of the East China Sea were analyzed in order to understand the paleoenvironment and sedimentary environmental changes around the Korean marginal seas since the last glacial maximum (LGM). The core sediments, containing continuous records of the last 16,000 years, reveal a series of well-defined vertical changes in number of species (S), P/T ratio and species diversity (H) as well as foraminiferal assemblage. Such down-core variations display a sharp change at a core depth of approximately 240 cm, which corresponds to ca. 10,000 year B.P. The sediments of the lower part of the core (240${\sim}$560 cm, Zone I), including the well-developed tide-influenced sedimentary structures, are characterized by high abundances of Ammonia beccarii and Elphidium clavatum (s.l.) and low values in number of species, P/T ratio and diversity. These tide-influenced signatures and foraminiferal assemblage characters suggest that the sediments of Zone I were deposited in a coastal environment (water depths of 20${\sim}$30 m) such as tidal estuary with an influence of the paleo-rivers (e.g., old-Huanghe and Yangtze rivers) during the early phase of the sea-level rise (ca. 16,000 to 10,000 years) since the LGM. In contrast, the upper core sediments (0${\sim}$240 cm, Zone II) are characterized by abundant Eilohedra nipponica and Bolivina robusta with a minor contribution of A. ketienziensis angulata and B. marginata. and high values in number of species, P/T ratio and diversity. Based on relative abundance of these assemblage, Zone II can be divided into two subzones (IIa and IIb). Zone IIa is interpreted to be deposited under the inner-to-middle shelf environment during the marine transgression in the early Holocene (after ca. 9,000 yr B.P.) when sea level rapidly increased. The sediments of zone IIb most likely deposited after 6,000 yr B.P. under the outer shelf environment (80${\sim}$100 m water depth), which is similar to modem depositional environments. The muddy sediments of zone IIb were probably transported from the old-Huanghe and Yangtze Rivers during the late Holocene. We suggest that the present-day oceanographic conditions over the Yellow and the East China Seas have been established after ca. 7,000${\sim}$6,000 yr B.P. when the Kuroshio Current began to influence this area.

• Journal of the Korean Geographical Society
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• v.44 no.1
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• pp.17-30
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• 2009

Paleostudies using lake sediment are essential to reconstruct environmental history of cental Mexico, where few documents on ancient civilizations and the colonial period exist. This study aims to reveal changes in the soil erosion rates through the calculation of sediment influx into the lake. The calculation is based on different kinds of chronologies and LOI. Sediment influx and dates for important events could be obtained in great detail through various chronological methods. Results show that corn agriculture was the most important reason to degrade the environmental status of the lake basin and European cattle raising was not much influential within the lake basin at least. It was possible to reveal a lot of recent environmental changes in detail, because the lake sediment used for this study has a very high sedimentation rate. Also, due to an accurate chronological framework, fundamental problems with the sediment were solved and reliable results could be produced.

• The Korean Journal of Petroleum Geology
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• v.7 no.1_2 s.8
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• pp.28-34
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• 1999

The Cretaceous Poongam sedimentary Basin in Kangwon-do, Korea consists alluvial deposits of conglomerates, sandstones, mudstones or siltstones, and volcaniclastics. The Poongam Basin was formed as a fault margin sag or a transpressional basin developed along a strike-slip fault zone, and received huge amount of clastic sediments from the adjacent fault-scaip. It formed an aggrading alluvial fan system and a volcaniclast-supplied marginal lake environment, while tectonic activity and volcanism attenuated toward the end of basin formation. Following the Folk's classification, the sandstones of the Poongam Basin are identified as lithic wackes or feldspathic wackes. The areal and sequential variation of the mineral composition in the sandstones is not distinct. The results of K-Ar age dating from the intruding andesites, volcaniclastics and volcanic fragments in sedimentary rocks show a range of 70 Ma to 84 Ma. It suggests that volcarism occurred sequentially within a relatively short period as the pre-, syn-, and post-depositional events. It was the short period in the late Cretaceous that the basin had evolved i.e., the basin formation, the sediment input and fill, and the , intrusion and extrusion of volcanic rocks occurred. The Poongam sedimentary sequence is a typical tectonic-controlled coarse sedimentary facies which is texturally immature.

• Economic and Environmental Geology
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• v.43 no.4
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• pp.333-341
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• 2010

Fluvial sediments are widely distributed in present and old river-beds of the mid-Keum River, the tributaries of which are the Yugu and Jeongan Rivers. The basement of the mid-Keum River area consists of Mesozoic granites which are easily eroded compared to Precambrian gneisses, which are exposed in the upper-Keum River area. The provenance of the fluvial sediments includes both the Precambrian gneisses and Mesozoic granites, which occur in the catchment of the mid-Keum River. The coarse-grained sediments were probably transported from the river-beds and the overbank floodings of the main Keum River and its tributaries when the climate was warm and wet. The oldest mud deposits were dated at ca. 9,400 yr BP by the radiocarbon method. It has been estimated that the sand deposits below the dated muds were formed in a period from the Late Pleistocene to the Early Holocene. However we have revealed that the major part of the present river-bed sediments was formed at ca. 3,000-6,000 yr BP, i.e., in the mid- to late Holocene, when summer monsoon was very strong due to climatic changes. We have calculated fluvial sedimentation rates of 0.12-0.16 cm/yr and 0.02-0.09 cm/yr for borehole KJ-29 river-bed sediments and borehole KJ-28 floodplain deposits, respectively. We conclude that the sedimentation rate is higher near the present stream channel than near the floodplain.

• Economic and Environmental Geology
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• v.36 no.1
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• pp.9-15
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• 2003

Two piston cores, obtained from the southwestern Ulleung Basin in East Sea, were analyzed to study the geochemical characteristics of the late Quaternary sediments and to detect any changes in sedimentary environment. The results show that the capacity of Total Organic Carbon is remarkably higher (average 1.8%) than that known from general open-sea. According to tephrochronology from known eruption ages, the sedimentation rates are high, ranging from 12.1 to 14.9 cm/kyr. The ratios of nitrogen and TOC (average 6.18-7.42) imply that the organic matter in the study area would be of oceanic origin. The correlation between sedimentation rates and sulfur contents suggests that the study area may be on the whole anoxic and somewhat high in primary productivity. During the Termination 1, inflows of organic matters were high. The sedimentary environments are characterized by rapid rates of sedimentation, and high anoxic values were compatible with accumulation of organic matters.