• Economic and Environmental Geology
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• v.50 no.6
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• pp.467-476
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• 2017

Volcanic rocks related to the Guamsan cadera, which find in the southeastern Cheongsong, are divided into Volcanic breccia, Guamsan Tuff and Post-collapse intrusions. We determined their eruption, intrusion and caldera-forming timings based on SHRIMP U-Pb zircon dating. The dating results yield earlier eruption age of $63.77{\pm}0.94Ma$ from the lower ash-flow tuff and an later eruption age of $60.1{\pm}1.8Ma$ from the upper ash-flow tuff of the Guamsam Tuff, and intrusion age of $60.65{\pm}0.95Ma$ from the rhyolite ring dyke of the Post-collapse intrusions. The age data suggest that the Guamsan caldera is formed in 60.65~60.1 Ma between eruption of the upper ash-flow tuff and intrusion of the rhyolite ring dyke. The Guamsan cadera exhibits the volcanic processes of a perfect igneous cycle passing from ash-flow eruptions through caldera collapse to ring intrusions during 63.77~60.1 Ma.

• Proceedings of the KSEEG Conference
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• 2003.04a
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• pp.191-193
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• 2003

무등산 지역은 광주광역시 동부와 전남 화순군 서부 및 담양군 남부지역이 만나는 곳에 위치한 무등산(1187m)과 그 주위 지역을 포함하는 곳으로, 기존 연구는 광주지질도폭(김규봉 외, 1990)과 동복지질도폭(김봉균과 박병권, 1966)조사에서 비교적 자세히 수행되었으며, 화성암체에 대한 연구는 김용준 교수팀(김용준 외, 2003)에 의해 수행되었다. 본 연구는 이 지역의 화산암류를 중심으로 암석-광물의 화학적 특징, 분출시기 및 광물조성을 밝힘으로서 광주 동부지역에서의 백악기 화성활동과 이들 화산암류의 암석화학적 특징을 밝히는데 있다. (중략)

• The Journal of the Petrological Society of Korea
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• v.25 no.1
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• pp.69-83
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• 2016

Radiocarbon and OSL ages of three monogenetic volcanoes inferred to be the last volcanoes on Jeju Island, Korea were determined to identify a volcano described in historical records. The results show that the ages of those volcanoes are roughly <3.8 ka (Songaksan), >4.5 ka (Biyangdo), and <6~7 ka (Ilchulbong). Though our efforts to make a positive match between historical records and volcano-chronological dating were not successful, we make a new suggestion in this paper that two historical records of volcanic activity in 1002 and 1007 A.D. could be interpreted to be the sequential volcanic events from a single monogenetic volcano. In addition, based on a volcanological reinterpretation of historical records, we infer that the volcano described therein is most likely Mt. Songaksan, in Daejeongeup, which had early phreatomagmatic and late magmatic activities after 3.8 ka ago. Furthermore, considering the geopolitical relationship between the Goryeo Dynasty and the Tamna Kingdom, in addition with the culture of the era, this study sheds new light on the possibility that there is a time gap between the actual eruptions and the historical recording of them by ancient people.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.33-36
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• 2008

For the past 300 Ma, massive extinctions are associated with major flood basalt eruptions. The geomagnetic Superchrons (Cretaceous Normal Superchron, Kiaman Long Reversed Superchron, Moyero Long Reversed Superchron) precede the major flood basalt eruptions and massive extinctions. It is likely that upswing of mantle plumes is responsible for the generation of continental flood basalt. Eruption of flood basalts results in a catastrophic climate change as well as a massive genus depletion.

• The Journal of the Petrological Society of Korea
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• v.27 no.1
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• pp.25-36
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• 2018

The volcanic rocks around Mieukdo Island, Tongyeong, are classified as lower andesitic rocks (Jusasan Subgroup) and rhyolitic rocks (Unmunsa Subgroup), and upper andesitic rocks (Yokji Subgroup) and rhyolitic rocks (Saryang Subgroup). We confirmed their eruption timings and stratigraphic relationships, based on SHRIMP U-Pb zircon dating for zircons from major stratigraphic units of the subgroups. By the SHRIMP U-Pb dating, the samples yield the concordia ages of $88.95{\pm}0.44Ma$(n=11) in Punghwari Tuff and $82.56{\pm}0.95Ma$(n=10) in Chudo Tuff of the lower andesitic rocks, and $73.01{\pm}0.75Ma$(n=11) in Dara Andesite of the upper andesitic rocks. And then samples show a concordia age of $71.74{\pm}0.47Ma$(n=14) in Namsan rhyolite dyke of the upper rhyolitic rocks and an apparent age of $70.7{\pm}3.5Ma$ in granodiorite dyke, These data confirm the eruption or injection timings of the units and allow them to distinguish chronostratigraphy of Jusasan, Unmunsa, Yokji and Saryang Subgroups around the Mireukdo Island. In addition, the subgroups give a clue that can make a chronostratigraphical correlation with different volcanic units of the Late Cretaceous Yucheon Group in the Gyeongsang basin.

• The Journal of Engineering Geology
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• v.18 no.3
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• pp.321-330
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• 2008

This study, geological survey was carried out in order to study on the geology, geological structure and volcanic activity of the Ulleung-do volcano body. Ulleung-do is the volcano body of about 3,000m heights from the East Sea seabed. The geology of Ulleung-do is divided into basaltic agglomerate, trachytic agglomerate, trachyte, trachytic pumice and trachyandesite in ascending orders. The faults in caldera of Nari Basin came to make the reverse triangle style in compliance with sinking. The faults in circumference of Nari Basin are ranging with northeast-southwest direction and northwest-southeast direction. The Quaternary volcanic activities in the Ulleung-do are divided into 5 activity period. The engineering geologists and the applied geologists were not easy to apply because complicated geology of Ulleung-do. Therefore, this study supplied simple geology of Ulleung-do for them.

• The Journal of the Petrological Society of Korea
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• v.22 no.3
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• pp.235-249
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• 2013

The Gusandong Tuff (Kusandong Tuff), known as a very significant key bed in the Cretaceous Gyeongsang Basin, is divided into (1) Northern Gusandong Tuff (NKT), (2) Southern Gusandong Tuff (SKT), and (3) Sinsudo Tuff, which were derived from different vents. In order to suggest their more accurate eruption times and to contribute to establishing stratigraphy of the basin, SHRIMP U-Pb zircon ages were determined from the three tuffs. As a result, the virtually same ages of $103.0{\pm}1.2$ Ma and $104.1{\pm}1.3$ Ma were obtained from NKT and SKT, respectively, which mean that they simultaneously erupted during 103~104 Ma. The zircon ages obtained from the Sinsudo Tuff are however divided into two groups i.e. $103.4{\pm}2.1$ and $95.79{\pm}0.98$ Ma. Based on distinctive morphology and cathodoluminescence image of the younger zircons, the younger age, $95.79{\pm}0.98$ Ma, is much more reasonable as the eruption time of the Sinsudo Tuff.

• The Journal of the Petrological Society of Korea
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• v.3 no.2
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• pp.128-137
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• 1994

The northeastern shore of the Anmyondo consists mainly of tuff, basalt, andesite and dacite. The K-Ar ages of the two mugearites are $89.4{\pm}2.4$ Ma and $91.9{\pm}2.3$ Ma which correspond to the middle Cretaceous age. Petrochemical reviews on the volanic rocks of the Cretaceous, Tertiary and Quaternary ages in the Korean Peninsula show that marked differences exist in chemical compositions according to the age of eruption.

• The Journal of the Petrological Society of Korea
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• v.20 no.4
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• pp.231-241
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• 2011

Cheolwon Group in the Cheolwon Basin, which lies northwest of the Gyeonggi massif, has been correlated to the Yucheon Group in the Gyeongsang Basin, but its ages and volcanic times are defined to be considerately earlier than the other one. In this study, SHRIMP zircon U-Pb ages were determined from the igneous rocks in the Cheolwon Basin. The mean ages from zircons are $115.0{\pm}1.1Ma$ in rhyolite, and $111.24{\pm}0.85Ma$ and $109.1{\pm}1.1Ma$ in granite porphyry. The minimum age is 113 Ma in the Jijangbong Tuff. Such age in the rhyolite define the intrusion time of ring dykes, suggesting a caldera collapse following eruption of the Dongmakgol Tuff. Such age in the Jijangbong Tuff represent latest volcanism as postcaldera in the basin. The volcanic rocks in the basin were erupted during late Aptian, and are correlated to the Sindong Group in the Gyeongsang Basin. The plutonism in the basin occurred during $111.24{\pm}0.85Ma{\sim}109.1{\pm}1.1Ma$, following the volcanism. The age distribution of the analyzed zircons in the Jijangbong Tuff indicates the presence of foreign zircons derived from protoliths, regarding a wide span of zircon ages from Cretaceous to Jurassic, Triassic, early and late Protozoic, and Archean. The Archean age suggests the possible presence of the Archean protoliths with such age, which have not been exposed on the surface. The age distribution with wide span suggests that its vent is located in an area that several strata with different ages piled up and intercepted with some intrusives.

• The Journal of the Petrological Society of Korea
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• v.14 no.3 s.41
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• pp.149-156
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• 2005

Ar-Ar, carbon AMS and OSL dating was carried out to clarify the age of the human footmarks on the Hamori Formation, Jeju Island, Korea. $^{40}Ar/^{39}Ar$ ages of trachybasalt from the Songaksan Tuff, which is underlain by the Hamori Formation, range between $10.6{\pm}19.9\;Ka$ and $11.7{\pm}26.3\;Ka$. Radiocarbon AMS ages of humin fractions extracted from sediment samples yielded the maximum limit age of the Hamori Formation as $15,161{\pm}70\;yr$ B.P. The OSL dating of the top and bottom layers of the Hamori Formation gave $6.8{\pm}0.3\;ka$ and $7.6{\pm}0.5\;ka$, respectively, suggesting that timing of the human footmarks formation can be constrained as between ca 6,800 yr B.P. and 7,600 yr B.P.