• Journal of The Geomorphological Association of Korea
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• v.19 no.4
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• pp.157-168
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• 2012

The Eonyang section is located at the confluent area of Samdong River to Taehwa River in Sinhwa-ri, Samnam-myeon, Ulju-gun, Ulsan-si, Korea. Physical analyses such as the OSL age dating, magnetic susceptibility and grain size analysis were performed. Coarse grains in the upper section were deposited by the aeolian processes from the local sources and the grains in the lower section by the fluvial processes. The Eonyang section shows the large differences such as the irregularity in the variations of magnetic susceptibility, large deviations in the Y values and very poor sorting values from the loess sediments in Bongdong, Geochang and Daecheon in Korea. These characteristics in the Eonyang section suggest the multi-source areas such as the Chinese Loess Plateau and nearby floodplain or the influences by the other processes. The loess sediments of Eonyang section were formed during the period from the late MIS 3 to MIS 2.

• Journal of the Korean earth science society
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• v.44 no.1
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• pp.36-46
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• 2023

In this study, small bird tracks from the Cretaceous Sanbukdong Formation in Gunsan City, South Korea, were briefly described. Detrital zircon SHRIMP U-Pb dating was conducted of the tuffaceous sandstone from the formation to determine the depositional age of the vertebrate track-bearing strata. Small bird tracks are not well-preserved but divided into two types: two consecutive tracks and three isolated tracks. They are small, asymmetric, slender, functionally-tridactyl tracks, which lack a web between digits. The consecutive and isolated tracks were identified as Koreanaornis dodsoni? and Koreanaornis ichnosp., respectively. This study adds avian tracks to the Sanbukdong tetrapod track assemblage composed of theropods, ornithopods, and pterosaur tracks. According to the U-Pb dating, the estimated age of the Sanbukdong Formation is 112.5±5.8 Ma, regard as the Aptian Stage, representing the maximum depositional age for the Sanbukdong Formation. The Sanbukdong Formation can be correlated with the lower part of the Jinju Formation in the Gyeongsang Basin. Thus, small avian tracks may represent the oldest Korean occurrence of Koreanaornis.

• Journal of the Korean earth science society
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• v.24 no.8
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• pp.657-667
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• 2003

Deep-drilled core sampling and high-resolution seismic survey were carried out to identify a Holocene-late Pleistocene boundary in Gyeonggi Bay, western coast of Korea. Analysis of core sections revealed the existence of an oxidized and semi-consolidated sediment layer, Iying immediately below a Holocene horizon (Unit I) and being developed at the top of a late Pleistocene deposit (Unit II). The oxidized sedimentary layer (uppermost part of Unit II) is characterized by semi-consolidated, yellowish sediments showing signs of desiccation and alteration such as high N value, low water content, periglacial cryogenic structure, depletion of smectite, and high geochemical weathering index (Ba/Sr ratio). This feature, together with radiocarbon ages, suggests that the layer has formed as a result of prolonged subaerial exposure of Unit II sediments during the late Wisconsin sea-level lowstand, producing a regional unconformity. Such unconformitic-bounding surface corresponds to a prominent near-surface reflector (R), which is observed in seismic profiles obtained across the drilled-core sections in the study area. Consequently, the buried oxidized-sedimentary layer associated with the seismic reflector possibly plays a key horizon for the understanding of late Quaternary environmental changes as well as evidence of the emergence of the Yellow Sea shelf during the late Wisconsin sea-level lowstand.

• The Journal of the Petrological Society of Korea
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• v.26 no.4
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• pp.341-352
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• 2017

The Jipum Volcanics, occurred in western Yeongdeok, are a stratigraphic unit that is composed of rhyolitic pyroclastic rocks, tuffites, andesitic hyaloclastites, rhyolite lavas, tuffaceous conglomerates and andesite lavas. The SHRIMP U-Pb zircon dating yielded eruption ages of $68.5{\pm}1.6Ma$ from the rhyolitic pyroclastic rocks. Around the time, the unit was generated by dominant rhyolitic volcanisms and locally added by concomitant andesitc volcanisms from another vents. The rhyolitic volcanisms first produced the pyroclastic rocks by phreatomagmatic explosions from rhyolitic magma, later made of the rhyolite lava dome by lava effusions from reopening of the rhyolitc magma at the existing vent. At the time between first and second rhyolitic volcanisms, the tuffites were deposited at a shallow depression in the distal volcanic edifice, and andesitic volcanisms first made of the hyaloclastites by quench fragmentation when hot andesite lavas flew into the depression to contact with cold water. and the Jipum volcano was finally covered with the thin andesitic lavas by lava effusions from another vent.

• 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.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.3
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• pp.189-201
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• 2012

Radiocarbon is a powerful tool for studies of carbon cycling in the ocean. Development of measurement technology of accelerator mass spectrometry has enabled researchers to measure radiocarbon even in specific compounds. In this paper, a brief introduction on radiocarbon measurement and reporting of radiocarbon data is provided. Researches that used radiocarbon measurements on bulk organic matter, organic compound classes, and specific organic compounds are reviewed. Examples include works to understand the cycling of particulate and dissolved organic matter, biochemical composition of particulate organic matter, post-depositional transport of sedimentary organic matter, selective incorporation of fresh organic matter by benthic organisms, chemoautotrophy by archaea, and sources of halogenated chemical compounds found in marine mammals.

• The Korean Journal of Quaternary Research
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• v.4 no.1
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• pp.27-40
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• 1990

$^{14}C$ age dating by AMS (accelerator mass spectrometry) technique was performed on twenty five small sized fossil shells and one peat taken from the sixteen piston cores in the southern and southeastern Korean Sea. AMS technique is available to date only a few milligram of amorphous carbons compare than conventional dating technique. It is described in detail of sample pre-treatment and experimental, and applied to the reconstruction of the sea level changes since the late Pleistocene in the Korean Sea. Dated age ranges from 520$\pm$100 to older than 33,500 years. Sedimentary facies in the study area represents a different environmental set which is affected by sea level fluctuation since the late Pleistocene.

• KOMUNHWA
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• no.64
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• pp.75-107
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• 2004

The Noeun-dong Paleolithic site located at the construction area of Daejeon World Cup Stadium, has been excavated two times between 1998 and 1999. The site is situated at 60-75m above sea level on a gentle slope. According to the absolute dating results a

• Proceedings of the Korean Quaternary Association Conference
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• 2004.06a
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• pp.46-46
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• 2004

Van Mijenfjorden은 스발바드 군도의 Spitsbergen 서부에 위치하는 두 번째로 큰 피오르드로 온난하고 염분도가 높은 북대서양의 표층수가 북극해로 유입되는 Gateway에 위치하기 때문에 전지구적이며 지역적인 기후변화의 영향을 받는 지역이다. 1999년 IMAGES 프로그램의 일환으로 프랑스 탐사선인 'R/V Marion Dufresne'을 이용하여 북극해의 스발바드 군도에 위치하는 Van Mijenfjorden (77$^{\circ}$ 46.87'N and 15$^{\circ}$ 17.81'E)에서 약 18m의 빙ㆍ해양 퇴적물 코아(MD99-2305)를 시추하여 마지막 최대 빙하기 이후의 고환경변화를 연구하였다. AMS 14C 연대 측정에 의하면 diamicton 층인 하부 2m를 제외한 16m의 퇴적층은 지난 12cal. ka BP경에 피오르드에 존재하던 조수빙하(tidewater glacier)가 해빙되기 시작한 이후에 퇴적되었다. 특히 유기지화학 자료와 부유성과 저서성 유공충의 산출양상 그리고 저서성 유공충인 C. reniforme의 산소ㆍ탄소 안정동위원소 비에 의하면 코아 MD99-2305에는 Van Mijenfjorden에서 홀로세 동안에 일어난 퇴적환경변화를 잘 기록하고 있다. 특히 홀로세 동안에 피오르드내의 퇴적환경 변화는 조수빙하의 확장과 후퇴와 밀접한 관계가 있으며, 유기물의 탄소동위원소(13Corg) 비는 -24에서 -22$\textperthousand$ 값의 변화를 보인다. 이는 Van Mijenfjorden 퇴적물에 공급된 유기물은 육상과 해양기원이 혼합되어 퇴적되었음을 지시한다. 지난 12 cal. ka BP 이후 13Corg 값이 뚜렷하게 변하는 것은 Van Mijenfiorden에서 조수빙하의 변동과 표층수에서의 생산력의 변화를 강하게 반영한다. 강하게 반영한다.53%가 이공계 출신, 100대 기업 CEO의 38.4%가 이공계 출신, 대입수능시험에서 자연계 지원비율이 감소 -40.1%('99)\$\longrightarrow$34.7%('00)\$\longrightarrow$29.4%('01)\$\longrightarrow$26.9%('02)\$\longrightarrow$30.3%('03)\$\longrightarrow$31.5%\$\longrightarrow$'04)필요성, 효과적인 운전자 교육 정책 등이 그것이다. 자동차 긴급 피난 차선은 유용한 시설로 여러곳에서 그 기능이 발휘되고 있으므로 많은 고속도로 관계자들은 설계, 시공 및 유지 관리 측면에서 유의해야 할 것이다.미세조직을 광학현미경으로 압출방향에 평행한 방향과 수직방향으로 관찰하였고, 열간 압출재 이방성을 검토하기 위하여 X선 회절분석을 실실하여 결정방위를 확인하였다. 전기 비저항 및 Seebeck 계수 측정을 위하여 각각 2$\times$2$\times$10$mm^3$ 그리고 5$\times$5$\times$10TEX>$mm^3$ 크기의 시편을 준비하였다.준비하였다.전류를 구성하는 주요 입자의 에너지 영역(75~l13keV)에서 가장 높은(0.80) 상관계수를 기록했다. 넷째, 회복기 중에 일어나는 입자들의 유입은 자기폭풍의 지속시간을 연장시키는 경향을 보이며 큰 자기폭풍일수록 현저했다. 주상에서 관측된 이러한 특성은 서브스톰 확장기 활동이 자기폭풍의 발달과 밀접한 관계가 있음을 시사한다.se that were all low in two aspects, named "the Nonsignificant group". And the issues were

• Journal of the Korean earth science society
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• v.33 no.4
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• pp.320-328
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• 2012

To investigate geomorphic development of alluvial plains and climatic environment change during the late Holocene carbon dating, soil organic carbon analysis and humus analysis of sediments from alluvial plain of Hampyeongcheon basin were performed. The lowest peat layer was formed under warm and humid climates, which is considered to correspond to the Atlantic period in the Holocene. Yellowish brown sandy clay layer was deposited in the natural levee, which we think were deposited in the generally warm and dry climates. The carbon dating age is 1,879-1,532 BC, and this period correspond to the Sub-boreal period in the Holocene. Light brown clay layer is assumed to have been deposited in transitional environment from the natural levee to the back marsh. The climatic environment was warm and humid, which is considered as transitional period from the Sub-boreal to the Sub-Atlantic in the Holocene. Light yellowish brown and light brown clay layer of the upper part are regarded as sediments of the back marsh. Light yellowish brown clay layer was deposited in the cold and dry climates, which is considered to correspond to the Sub-Atlantic period in the Holocene. Light brown clay layer was deposited in the warm and dry climates. The carbon dating age is 211-427 AD, this period corresponds to the Post Roman Warm Period in the Holocene.