• The Korean Journal of Petroleum Geology
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• v.12 no.1
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• pp.9-13
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• 2006

Volcanic glass shard, which shows relatively homogeneous chemical composition in volcanic eruption materials, is used to determine ages of tephra layers and then to correlate tephra layers each other for understanding of evolution of Quaternary geomorphology. For reducing processing errors in age determination and correlation of units, amorphous glass shard should be separated carefully from soil sample through laboratory procedures such as washing, separation, and identification. Introduction of these processes in detail could be reduced errors in tephrochronology by using volcanic glass shard.

• Journal of the Korean earth science society
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• v.43 no.6
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• pp.680-690
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• 2022

Tephrochronology uses regional tephra for age dating and stratigraphic correlations. Regional tephras are important in Quaternary geology and archaeology because they can be used as stratigraphic time-markers. In this review, identification and dating methods of tephra are summarized. In addition, the characteristics of regional tephras in terrestrial deposits of the Korean Peninsula are elaborated, and geological applications and limitations of the regional tephra layers are also discussed. So far, AT, Ata, and Kb-Ks tephra layers from Kyushu, Japan have been found in Pleistocene paleosol, marine terrace deposits, and lacustrine deposits in Korea. Also, although not officially confirmed, Aso-4 tephra is likely to occur in terrestrial deposits. The regional tephra layers are vital for dating, especially with regard to sediments over 50 ka beyond the range of radiocarbon dating, and for dating of active faults. Furthermore, it can provide important information for preparing countermeasures against volcanic disasters. However, in order to use the tephra layer geologically, it must be confirmed whether it is a primary deposit based on sedimentological study.

• Journal of the Korean earth science society
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• v.42 no.1
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• pp.55-64
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• 2021

Tephrochronology is the study of tephra layers to correlate and date geologic events. As tephra layers can be used as time-markers, they are essential for the dating of Quaternary deposits. In this study, two types of tephra layers were found in the upper and lower parts of marine terrace deposits distributed in the Sanha-dong and Jeongja-dong, Ulsan areas. Based on the morphological features of glass shards, refractive indices, major element compositions, and similarity coefficients, the upper and lower tephras were identified as AT (ca. 25 ka) and Ata (ca. 105-110 ka) tephra, respectively. To the best of our knowledge, this is the first official report of Ata tephra on terrestrial deposits in Korea. These results are expected to aidin the research of the Quaternary paleoclimate, paleoenvironment, and active faults in the southeastern part of Korea.

• The Korean Journal of Quaternary Research
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• v.17 no.2
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• pp.15-15
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• 2003

In South Korea, marine terraces have been well developed along the eastern coastal zone, and previous researches on the marine terraces have also been focused on to this coastal zone. The marine terraces of the eastern coast of South Korea had been classified into three terrace groups, that is, the higher, middle, and lower surface ones, according to the heights of marine terraces by previous studies(Oh, 1981 ;Chang, 1987 ;Yoon et. al, 1999, 2003 ; Hwang and Yoon, 1996 etc.). Recently, however, it tends to classify the marine terraces based on the concept of geomorphic surface units(Lee, 1987 ; Kim, 1990 ; Choi, S. 2003; Choi S. et. al 2003a,b, etc). For example, it was proposed that the marine terrace surfaces of Eupcheon coast of the southeastern coastal area of Korea could be classified into 16 geomorphic surfaces, i.e., Eupcheon 1terrace(former shoreline height of 160m), 2(153m), 3(140m), 4(130m), 5(124m), 6(115m), 7(100m), 8(92m), 9(82m), 10(71m), 11(62m), 12(53m), 13(43m), 14(35m), 15(18m) and 16(10m) surfaces, in descending order, according to the former shoreline heights(Choi, S, 2003 ; Choi, S. et. al, 2003a,b). Among these terraces, Eupcheon 1, 2, 4, 5 and 7 surfaces had not been reported in previous works. Among the above mentioned marine terraces, Eupcheon 15 terrace, the most widely and continuously distributed marine terrace have been identified as marine terrace of the Last Interglacial culmination period(oxygen isotope stage 5e) which was based on amino acid dates(124∼125ka BP) and geomorphological features such as red soil, pollen analysis, fossil cryogenic structures and crossing terrace concept. Eupoheon 15 terrace surfaces have also been proposed as the key surface for the identification and correlation of the so-called '5e' marine terrace in the eastern coast of South Korea. This terrace was reconfirmed as the Last Interglacial culmination period, which was based on the identification of Ata tephra, one of the wide-spread marker tephra which indicates the Last Interglacial culmination period in Japan by Sasaki et. al(2002). It was thought that marine terraces of the eastern coast of South Korea had been formed by the steady-state uplifting during the Quaternary glacio-eustatic sea level changes(Choi, 1997). The uprift rate of 10cm/1,000years had been proposed in the eastern coast of South Korea based on the former shoreline altitude(18m) of the above Eupcheon 15 terrace. Therefore, it can be estimated that Eupcheon 1 terrace had been formed in the early Pleistocene from the above uprift rate. The OSL dating for the samples of Eupcheon 7, 9, 13, 15 and 16 terraces and identification of marker tephra in the terrace deposits are in progress. It is expected that more elaborate chronology on themarine terraces of the eastern coast of South Korea could be established by these absolute dates and marker-tephra.

• Economic and Environmental Geology
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• v.48 no.6
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• pp.501-508
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• 2015

The purpose of this study is to provide an inquiry into paleovegetation (paleoenvironment), eruption age and inferred emplacement temperature of pyroclastic deposit using charcoal occurred in the Quaternary Nari Caldera, Ulleung Island. In order to obtain the data, we carried out species identification and tree-ring analysis, radiocarbon dating for the charcoal. This sample was collected from pumiceous deposit in lowermost member(Member N-5) of the Nari Tephra Formation, which corresponds to the wood branch that has well preserved the tree-ring structure. Speciation and outermost tree-ring of wood reveal Picea spp. and $263+{\alpha}$ years. The calibrated ages from the center(pith) to the outermost tree-ring are $20,260{\pm}230$, $19,995{\pm}245$, and $19,975{\pm}265cal\;BP$, respectively, which are accordant with the tree-ring position. The youngest age, <19,710 cal BP would have implications for the eruptive age of Member N-5. Our results indicate that Picea spp. is the paleovegetation representing that Nari Caldera was under cold and wet climate conditions during the late Pleistocene. Based on the silky luster, brittleness, color, and streak of charcoal, etc., the lowest emplacement temperatures of pyroclastic flow are interpreted to have been at least as high as $350{\sim}500^{\circ}C$.