| 研究課題/領域番号 |
16K05571
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| 研究機関 | 秋田大学 |
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研究代表者 |
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| 研究分担者 |
横山 祐典 東京大学, 大気海洋研究所, 教授 (10359648)
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| 研究期間 (年度) |
2016-04-01 – 2019-03-31
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| キーワード | stratigraphy / age modeling / tephra identification |
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| 研究実績の概要 |
Cores were split, imaged with the high-resolution scanner developed for this project, scanned by XRF scanner at the Kochi Core Center, and sub sampled for radiocarbon analysis and oxygen isotopes of diatoms. Stratigraphic correlation was performed using the core images and XRF data. A composite splice was created for each site at Lakes Motosu, Sai, and Kawaguchi. Following the splice for each site, color reflectance was calculated for each image. Offsets between bulk organic matter radiocarbon dates and terrestrial macrofossil radiocarbon dates was determined, and age modeling was performed for Lake Motosu sites using methods developed for this project. Differential expansion between adjacent sections of different cores collected from the same depth below the sea floor at the same site was assessed to estimate the uncertainty imparted onto the calculated sedimentation rates. Tephra layers were identified to verify the fidelity of the age models. Based on XRF elemental data and color reflectance data, a number of eruptions of Mount Fuji were identified. Initial work to assess the amount and type of diatoms needed for oxygen isotopes was started.
The age modeling method developed for the Fuji Five Lakes has been widely applied to other locations, including the Baltic Sea and the northwestern Australian continental shelf.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
The annual layers expected at Lakes Sai and Motosu were unfortunately not present, so no varve counting is being performed. However, the radiocarbon age model from Lake Motosu in particular is confirmed to be of unexpectedly high fidelity with the age of known tephras well within the uncertainty of the age model. Co-PI and research collaborator are proceeding with microfossil analysis and radiocarbon, as planned for the fiscal year.
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| 今後の研究の推進方策 |
Age modeling will be performed for Lake Sai that takes into account any possible debris flows. Preliminary analysis of diatom assemblages and oxygen isotopes will also be performed for monsoon reconstruction. Correlation of observed scoria layers will be compared to known ages of Mt. Fuji eruptions. XRF data will be evaluated to determine a proxy for the delivery of material from mainland Asia for Westerly wind reconstruction.
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| 次年度使用額が生じた理由 |
There was no need to purchase a microscope because no varves were present.
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| 次年度使用額の使用計画 |
The remaining amount will be put towards additional analyses.
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