2016 Fiscal Year Research-status Report
Monsoon variability and Holocene sea level in the Nankai Region
| Project/Area Number |
16K05571
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| Research Institution | Akita University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
横山 祐典 東京大学, 大気海洋研究所, 教授 (10359648)
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Keywords | stratigraphy / age modeling / tephra identification |
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| Outline of Annual Research Achievements |
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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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
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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| Strategy for Future Research Activity |
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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| Causes of Carryover |
There was no need to purchase a microscope because no varves were present.
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| Expenditure Plan for Carryover Budget |
The remaining amount will be put towards additional analyses.
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[Journal Article] The undatables: Quantifying uncertainty in a highly expanded Late Glacial - Holocene sediment sequence recovered from the deepest Baltic Sea basin - IODP Site M00632017
Author(s)
Obrochta, S.P., Andren, T., Fazeka, S.Z., Lougheed, B. C., Snowball, I., yokoyama, Y., Miyairi, Y., Kondo, R., Kotilainen, A.T., Hyttinen, O., Fehr, A.
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Journal Title
Geochemistry, Geophysics, Geosystems
Volume: 18
Pages: n/a
DOI
Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
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