• Journal of The Geomorphological Association of Korea
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• v.17 no.2
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• pp.87-98
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• 2010

There have been growing concerns for the sea level rise due to global warming in recent years. Sea level rise is a serious problem to densely populated coastal areas, because it may affect the coastal landforms to be damaged. Especially coastal sand deposits like coastal dunes are more sensitive than the other coastal landforms. In this paper, Ground Penetrating Radar (GPR) and Optically Stimulated Luminescence (OSL) dating method were used to identify the Holocene geomorphic changes of coastal dune field in Shinduri located at the western coast. The main results in this study that are the dunefield in the study area may have begun to form at around 6.8 ka and it has grown seaward thereafter. Then, dunefield appears to have extensively developed since 3.7 ka. This result, together with previous works on the sea level and climatic changes in the western coast of Korea suggest that the dunefield has been affected by the sea level regression since the Holocene high stand in the Holocene at around 6 ka and climatic change from warm and humid to cold and dry conditions occurred at 4.5 ka.

• 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.

• Journal of The Geomorphological Association of Korea
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• v.26 no.2
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• pp.39-54
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• 2019

In this paper, based on evidence of coastal sediment, we show that erosion and sedimentation environments are very sensitive to sea level changes during the Medieval Warm Period (MWP) and the Little Ice Age (LIA). We identified four sedimentary units(4.57-3.07m), which formed in the Dark Age Cool Period (DACP), MWP and LIA were classified based on the lithostratigraphy, grain size distribution, magnetic susceptibility and geochemistry of a drilling core taken from the west coast of Hwaseong City. The unconformity surfaces as boundaries of the units were also identified by the lithostratigraphy shown on the drilling core. We propoese that sedimentation was dominant in the area during the periods of sea level rise, whereas erosion prevailed during the periods of sea level fall. Particularly, extreme events, such as floods and typhoons are believed to have accelerated these processes, and we found the associated evidence in sediments of two units. This study provides an example of estimating the relative sea level variation using coastal sediments and may be useful for studying past sea level changes around the Korean Peninsula.

• The Journal of the Petrological Society of Korea
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• v.23 no.3
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• pp.187-195
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• 2014

In this paper, we report new OSL ages of the marine terrace sediments at Suryum fault site, using single grains of quartz, and briefly discuss their chronological implications on the timing of terrace formation along the southeastern coast of Korea. Of 1200 grains measured, 93 quartz grains were found to have OSL properties suitable for dating, the equivalent dose ($D_e$) values of which varied significantly, ranging from 50 Gy to 610 Gy with the overdispersion of $30{\pm}4%$. Applied to the Central Age Model (CAM) and Minimum Age Model (MAM), these quartz grains showed the OSL ages of $83{\pm}4ka$ and $60^{+3}{_{-7}}ka$, respectively, both of which are stratigraphically inconsistent with the previously reported OSL ages of lower $2^{nd}$ terrace (MIS 5a; ~80 ka). However, Finite Mixture Model (FMM) revealed that a small fraction of the measured quartz grains ($6{\pm}4%$) were of the ages ($194{\pm}24ka$) corresponding to MIS 7. Conclusively, based on single grain OSL ages, it would be prudent not to exclude the possibility that the marine terrace sediments at Suryum fault site have formed during MIS 7. Further, our single grain OSL ages imply that multiple grain(single aliquot) OSL dating methods are not applicable to the marine sediments at Suryum fault site.

• The Journal of the Petrological Society of Korea
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• v.26 no.3
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• pp.221-234
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• 2017

The Baengnokdam, the summit crater of Mt. Halla, is one of the representative geosites of World Natural Heritage and Global Geopark in Jeju Island. The crater is marked by two distinctive volcanic lithofacies that comprise: 1) a trachytic lava dome to the west of the crater and 2) trachybasaltic lava flow units covering the gentle eastern slope of the mountain. This study focuses on understanding the formative process of this peculiar volcanic lithofacies association at the summit of Mt. Halla through field observation and optically stimulated luminescence (OSL) dating of the sediments underlying the craterforming volcanics. The trachyte dome to the west of the crater is subdivided into 3 facies units that include: 1) the trachyte breccias originating from initial dome collapse, 2) the trachyte lava-flow unit and 3) the domal main body. On the other side, the trachybasalt is subdivided into 2 facies units that include: 1) the spatter and scoria deposit from the early explosive eruption and 2) lava-flow unit from the later effusion eruption. Quartz OSL dating on the sediments underlying the trachyte breccias and the trachybasaltic lava-flow unit reveals ages of ca. 37 ka and ca. 21 ka, respectively. The results point toward that the Baengnokdam summit crater was formed by eruption of trachybasaltic magma at about 19~21 ka after the trachyte dome formed later than 37 ka.

• Journal of the Korean Geographical Society
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• v.41 no.3 s.114
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• pp.346-360
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• 2006

In order to analyze synthetically geomorphological processes of marine terrace in Korea, this study deals with the distribution of marine terraces, stratification of sedimentary layers, physicochemical properties of deposits, and formative ages of marine terraces based on OSL(Optically Stimulated Luminescence) absolute age at coastal area of Gwangyang Bay in central part of the South Coast. As a result of comparison with physicochemical properties on diverse geomorphic materials, there is not enough distinction in them, because of recycling and mixing of materials at Gwangyang Bay having a geomorphic closure. In Gwangyang bay coast, marine terraces are discovered at least 3 levels and have a small area. Formative age of 1st Terrace, as the lowest level ranging in $10{\sim}13m$ above the sea level, is estimated at MIS(Marine Isotope Oxygen Stage) 5a, based on OSL age dating and properties of deposits. Uplifting rate is calculated at 0.141m/ka in Gwangyang bay coast. For application to this rate, 2nd terrace($18{\sim}22m$) is estimated at MIS 5e, 3rd terrace($27{\sim}32m$) is latter part of MIS 7. Consequently, we might conclude that uplifting and geomorphic process of marine terrace in South Coast is similar to East Coast during the Late Pleistocene in Korea.

• Economic and Environmental Geology
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• v.57 no.2
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• pp.243-251
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• 2024

In this study, a surface geological survey was first conducted to investigate aggregate resources in the Yeongam area of Jeollanam-do, and a drilling survey was conducted in the lower part of the surface, which was difficult to identify through a surface geological survey, to determine the spatial distribution of aggregates. Drilling sites were selected considering the topographical development and Quaternary alluvium characteristics of the study area, and river aggregate drilling surveys were conducted at a total of 5 points and land aggregate drilling surveys were conducted at a total of 28 points. Borehole core sediments were classified into seven sedimentary units to determine whether they could be used as aggregates, and optically stimulated luminescence dating was performed on representative boreholes to measure the depositional period for each sedimentary unit. As a result of the study, most of the Yeongam area had a very wide river basin, so it was estimated that there would be a large amount of aggregate, but the amount of aggregate was evaluated to be very small compared to other cities and counties. Most of the unconsolidated sedimentary layers in the Yeongam area are composed of blue-grey marine clay with a vertical thickness of more than 10 m. The sand-gravel layer corresponding to the aggregate section is distributed in the lower part of the marine clay, thinly covering the bedrock weathering zone. This is because the amount of aggregates themselves is small and most of the aggregates are distributed at a depth of 10 m below the surface, which is currently difficult to develop, so the possibility of developing aggregates is evaluated to be very low. As a result of dating, it can be seen that the blue-grey marine clay layer is an intertidal sedimentary layer formed as the sea level rose rapidly about 10,000 years ago. The deposition process continued from 10,000 years ago to the present, and as a result, a very thick clay layer was deposited. This clay layer was formed very dominantly for about 6,000 to 8,000 years, and the sand-gravel layer in the section where aggregates deposited in the Pleistocene period can exist was measured to have been deposited at about 13.0 to 19.0 ka, and about 50 ka, showing that it was deposited as paleo-fluvial deposits before the marine transgression process.