• Journal of the Korean association of regional geographers
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• v.11 no.1
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• pp.114-122
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• 2005

To find out the buried age of the relict dune sediments, a luminescence dating bas conducted for a relict dune from the Sindu dunefield on the Taean Peninsula. It shows that the deposition of the dune sands at 3m depth began about 690$\sim$730 years ago. From 3m to l.5m depth, the lower part of the dune bas remained stable, but a relict dune deposit appear at 1.3m depth. This part yields an age of about 68 years. The two samples that were collected from the lower part of the dune at depths of the 1.5 m and 3.0 m below the surface show a net accumulation rate of around 0.75 cm/y which is relatively slow for a coastal dune. The chronology obtained in this study demonstrates that a significant amount of sediments has been replaced or remobilized in the area over the past 1000 years, and there was at least a soil formation process during the same time period. These suggest that a new approach is necessary to identify the formation age of the so-called paleo-dune at the Sind dunefield.

• Economic and Environmental Geology
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• v.4 no.1
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• pp.1-9
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• 1971

The "Younger Granites" in Korea were being believed to be late Cretaceous in age and named "Bulkuksa granites" by all previous works until the writer had discovered Jurassic granite in 1963. The present paper is to prove its validity by age dating on these granites which was carried out by Professor Y. Ueda, Tohoku University, Japan. The age of 37 granites samples from various localities ranges from 68 my to 181 my. Of these 10 samples belonged to early Jurassic, 6 samples to mid-Jurassic, 4 samples to late Jurassic, 5 samples to early Cretaceous, and 12 samples to late Cretaceous in age. It is of the writer's opinion that the granites intruded in from early Jurassic to early Cretaceous age belong to Daebo granites and are syntectonic plutons associated with Daebo orogeny, and only those of late Cretaceous age belong to Bulkuksa granites that were associated with Bulkuksa disturbance. Daebo granites are aligned along NE-SW Sinian direction in the middle parts of Korea and crop out in the cores of folded mountains which were formed by Daebo Orogeny, such as Charyong, Noryong, Sobaek, and Dukyu Ranges. On the contrary Bulkuksa granites are restricted in Kyongsang basin and adjacent few localities in distribution and show no alignment. Granites supposedly associated with other disturbances of post-precambrian Have not been found so far in S. Korea. Age dating of granites has revealed that Daebo orogeny might be continuous from Songrim distur bance of late Triassic age. From this viewpoint, it could be assumed that Daedong system of Jurassic age were deposited in separate intermontain basins while Daebo orogeny was active, so that Daedong system in separate localities in Korea could not been correlated in their lithology as well as stratig raphy.

• 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.

• 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.

• Journal of The Geomorphological Association of Korea
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• v.27 no.2
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• pp.47-64
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• 2020

The Baengnyeongdo-island, located at the northernmost point of the west coast, has developed several coastal landforms. Although the coastal landforms of Baengnyeongdo-island are widely used as a tourism resource, a lot of academic research has not been conducted. In this study, particle size analysis, XRF, and OSL age dating were performed on the BR sandy deposits to find out the formation of coastal sand dunes on Baengnyeongdo-island. Based on the physicochemical properties, the BR section was divided into three parts; BR-A, BR-B and BR-C. First, about 56ka, which corresponds to the MIS 3, fine sand was deposited and forms the BR-C section. Second, the BR-B which located middle part of BR section, showed reversed age stratigraphy. The BR-B was interpreted as reworked sediments based on sedimentary facies and chemical weathering intensity. And, the BR-A composed of fine and medium sands was formed in middle Holocene. This research has significance in that it finds out the paleo sand dunes formed in Pleistocene. This study can contribute to understanding coastal sand dune development on the west coast.

• The Journal of the Petrological Society of Korea
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• v.10 no.3
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• pp.172-178
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• 2001

K-Ar dating system of Korea Basic Science Institute (KBSI) was installed in 1997 and has been used since then. The system consists of high temperature graphite furnace, gas purification system, and mass spectrometer with data acquisition system. K-Ar age is determined by the measurement of the concentrations of Ar and K through isotope dilution method using $^{38}Ar$ as spike and flame spectroscopy, respectively. The accuracy and reliability for the K-Ar age are checked using the several K-Ar standard materials. Although the exact age determination for young samples of less than 1 Ma is hampered by small fluctuations of sensitivity and mass discrimination, the present system yields the reliable K-Ar age compared to the standard materials of Tertiary and Mesozoic age. The measurements for the SORI93 biotite with the recommended K-Ar age of $92.6\pm$0.6 Ma and Bern4M muscovite of $18.5\pm$0.6 Ma yield the reliable age of $92.1\pm$1.1 Ma and $17.8\pm$0.2 Ma, respectively.

• 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.

• Economic and Environmental Geology
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• v.45 no.2
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• pp.181-188
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• 2012

The 1M and $2M_1$ stacking sequences are the most frequently encountered in the illite species among the possible 6 polytypes. The $1M_d$, derived from the 1M polytype which exhibits a variable degree of disorder in the stacking sequence, is also observed in illite samples. In this paper, the author introduces and reviews the theoretical background of the quantitative analysis method of illite polytypes, and considers the possibility to determine the fault age and its reactivation age using K/Ar age-dating based on the quantification of illite polytypes in the fault system. For the increase of the accuracy and precision of the illite age analysis method, the occurrence, identification, and mineralogical characterization of illite polytypes should be defined in detail. The broadening effect of (hkl) reflections, due to disordering of 1M polytype and the presence of I/S minerals with expandability, are also considered as the main parameters controlling the quantification of illite polytypes using the WILDFIRE(C)simulation.

• Journal of Radiation Protection and Research
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• v.36 no.2
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• pp.52-58
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• 2011

OSL dating for three hearths having the sequence of use and discard in No. 29 and 29-1 dwelling sites at Sogol cultural site was carried out. Resulting from the deconvolution of natural CW-OSL decay curve and thermal zeroing test, it was turned out that OSL signal was entirely composed of the heat- and light-sensitive fast component with high photoionization cross-section and all quartz OSL signals were thermally bleached under $300^{\circ}C$ which is the minimum temperature related to heating and cooking in Bronze age. After dose recovery test and plateau test, paleodose of each hearth sample was evaluated by using SAR method, and OSL age was determined from the ratio of paleodose to annual dose rate. For the purpose of the precision improvement of OSL age, Bayesian statistics was applied to each hearth's age and the archaeological sequence information. Finally, it could be concluded to the accurate use period of each hearth from the resultant OSL ages.

• Fisheries and Aquatic Sciences
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• v.24 no.1
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• pp.53-62
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• 2021

Gindai (Pristipomoides zonatus) is one of six snappers in a management complex called the Deep 7 of the Hawaiian Islands. Little is known about its life history and a preliminary analysis of otolith thin sections indicated the species may exhibit moderate growth with a lifespan approaching 40 years. Preliminary age estimates from the previous study were reinvestigated using the same otolith sections in an attempt to validate those ages with bomb radiocarbon (¹⁴C) dating. From the misalignment of birth years for the otolith ¹⁴C measurements with regional references - the post-peak bomb ¹⁴C decline period - it was concluded that previous ages were inflated from overcounting of the earliest growth zone structure in otolith sections. The oldest gindai was re-aged to 26 years once the age reading was adjusted for early overcounting, 13 years younger than the original estimate of 39 years for this fish. In general, the earliest otolith growth of gindai was massive and complicated by numerous subannual checks. The approach of lumping the early growth structures was supported by the alignment of ¹⁴C measurements from otolith core material (first year of growth). The result was greater consistency of calculated birthdates with the ¹⁴C decline reference, along with minor offsets that may indicate age estimation was imprecise by a few years for some individuals. The revised von Bertalanffy growth function applied to the validated age-at-length estimates revealed more rapid growth (k = 0.378 cf. 0.113) and a lifespan of approximately 30 years. The findings presented here are a case study of how the bomb ¹⁴C decline period can be used as a tool in the refinement of age reading protocols.