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Tokuyasu, Kayoko; Yasue, Kenichi; Komatsu, Tetsuya; Tamura, Itoko; Horiuchi, Yasuharu
QST-M-2; QST Takasaki Annual Report 2015, P. 189, 2017/03
Understanding the stage of mountain building is crucial to the stability assessment of geological environments in geological disposal system. In this context, we have carried out the research and development of provenance analysis techniques to elucidate the mountain-building stage. Here we present the results focusing on the R&D using the Electron Spin Resonance (ESR) signals from quartz in sediments and their basement rocks.
Yasue, Kenichi; Komatsu, Tetsuya; Tokuyasu, Kayoko; Tamura, Itoko; Horiuchi, Yasuharu
no journal, ,
no abstracts in English
Hoshi, Hiroyuki*; Tamura, Itoko; Komatsu, Tetsuya
no journal, ,
no abstracts in English
Tokuyasu, Kayoko; Yasue, Kenichi; Komatsu, Tetsuya; Tamura, Itoko; Horiuchi, Yasuharu
no journal, ,
We have carried out the research and development of provenance analysis techniques to elucidate the mountain-building stage using quartz ESR signals in sediments. The R&D was conducted using the Tokai Formation including Toki Sand and Gravel Formation distributed over the Tono area. In the northern part of the area, bedrocks consist of sedimentary rocks, Nohi Rhyolite and Sanyo Granite, whereas consist of Ryoke Granites in the southern part. Samples of sediments were taken from the quarry located between the Tsukechi River and Atera fault. Basement rock samples were also taken in and around the quarry. Outcrop observation indicates that the provenance of sediments changed between the lower and upper parts. Quartz grains for ESR measurements were extracted from all samples. As a result, granitic rocks of Sanyo belt were not exposed to the drainage basin during the deposition of the lower part between 3.9 and 2.0 Ma, then the granitic rocks were exposed during the deposition of upper part after about 2.0 Ma. We conclude that it is possible to estimate the sediment provenance using ESR properties.
Tokuyasu, Kayoko; Tamura, Itoko; Komatsu, Tetsuya; Yasue, Kenichi
no journal, ,
The uplift rate during the past hundred thousand years is estimated from the elevation and emergence ages of terrace surfaces which are used as geomorphologic standard. OSL dating is effective method to determine the emergence ages. Here we report a case study of quartz OSL dating of fluvial terrace sediments, and its adequacy is considered in the correlation with intercalated marker tephra. All samples were collected from fluvial terrace sediments along Kiso River and Tsukechi River which is a tributary of the Kiso. The investigated fluvial terrace sediments are composed of laminated sand layer and pumice layer which is likely to be reworked. The pumice was identified as On-Pm1 tephra by mineral composition, refractive indices of volcanic glass and phenocryst minerals, and the major element composition of volcanic glass. This indicated that the fluvial terrace sediments were deposited after 100ka. The extracted quartz grains from terrace sediments were measured by conventional SAR protocol. The obtained OSL ages are about 40-50 ka, being underestimated because the OSL decay curves from all samples were dominant by medium component which is unsuitable for OSL dating. We thus attempt to determine the equivalent dose using the isolated fast component OSL signal which is suitable for OSL dating.
Tokuyasu, Kayoko; Yasue, Kenichi; Komatsu, Tetsuya; Tamura, Itoko; Horiuchi, Yasuharu
no journal, ,
We have carried out the research and development of provenance analysis techniques to elucidate the mountain-building stage using quartz ESR signals in sediments. The R&D was conducted using the Tokai Formation including Toki Sand and Gravel Formation distributed over the Tono area. In the northern part of the area, bedrocks consist of sedimentary rocks, Nohi Rhyolite and Sanyo Granite, whereas consist of Ryoke Granites in the southern part. Samples of sediments were taken from the quarry located between the Tsukechi River and Atera fault. Basement rock samples were also taken in and around the quarry. Outcrop observation indicates that the provenance of sediments changed between the lower and upper parts. Quartz grains for ESR measurements were extracted from all samples. As a result, granitic rocks of Sanyo belt were not exposed to the drainage basin during the deposition of the lower part between 3.9 and 2.0 Ma, then the granitic rocks were exposed during the deposition of upper part after about 2.0 Ma. We conclude that it is possible to estimate the sediment provenance using ESR properties.
Kagami, Saya; Yokoyama, Tatsunori; Umeda, Koji*; Yasue, Kenichi*; Niwa, Masakazu; Furusawa, Akira*; Tamura, Itoko*
no journal, ,
Tephrochronology is important to understand geotectonic events for the last few Myr. Tephra is usually characterized by petrographic characteristics and chemical compositions (mainly major elements) of volcanic glass shards. When tephras similar in the characteristics are discriminated, trace element compositions are valid for identification of tephra. We focus on the enrichment of the database of trace elements compositions in widespread tephras, which is not reported enough. We used EPMA and LA-ICP-MS for major and trace element concentration of volcanic glass shards in Znp-Ohta tephra and Tng tephra, of which major elements similar to Znp-Ohta tephra. In this study, it was clear that Znp-Ohta tephra had zirconium concentration [Zr] = 44-58 ppm and Zr/Pb = 2.5-3.4, while Tng tephra had [Zr] = 70-81 ppm and Zr/Pb = 3.8-4.6. Znp-Ohta and Tng tephras were discriminated not only by characteristic type, Ba/La, and La/Y of glass shards (Tamura and Yamazaki, 2004) but also by Zr-Pb correlation. In the future, we compare the trace element concentrations of Znp-Ohta tephra in multiple sites for evaluation of secondary effect during the deposition.
