| Project/Area Number |
21H01169
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Review Section |
Basic Section 17030:Human geosciences-related
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| Research Institution | Nagoya University |
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Principal Investigator |
HUMBLET Marc 名古屋大学, 環境学研究科, 准教授 (40623616)
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| Co-Investigator(Kenkyū-buntansha) |
井龍 康文 東北大学, 理学研究科, 教授 (00250671)
藤田 和彦 琉球大学, 理学部, 教授 (00343377)
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) |
2021-04-01 – 2024-03-31
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| Project Status |
Granted (Fiscal Year 2023)
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| Budget Amount *help |
¥18,200,000 (Direct Cost: ¥14,000,000、Indirect Cost: ¥4,200,000)
Fiscal Year 2023: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2022: ¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000)
Fiscal Year 2021: ¥14,300,000 (Direct Cost: ¥11,000,000、Indirect Cost: ¥3,300,000)
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| Keywords | Coral reef / Sea level change / Climate change / Quaternary / Okinawa / Sea-level change |
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| Outline of Research at the Start |
Information on Earth’s geological history contained in sediments and rocks is key to understand the past, present, and future evolution of our planet. Fossil coral reefs in particular are treasure troves of information concerning climate and sea-level changes because their growth is constrained by sea level and sea surface temperature. In this project, we will study fossil reef deposits in southern Okinawa to constrain the timing and amplitude of sea-level change during the Quaternary and investigate how coral reef ecosystems responded to these perturbations.
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| Outline of Annual Research Achievements |
Five boreholes (10-27 m in length) were drilled into late Middle Pleistocene limestone (Minatogawa Formation) along a transect perpendicular to shore in southern Okinawa Island in December 2022 and January 2022. The total cored length is 90 m. After shipping the cores to the Kochi Core Center for safe storage, each core was X-ray CT-scanned. The cores were then split in half, photographed, and their lithology, sedimentary structures, and major fossil biotic components, particularly corals, coralline algae, and foraminifers, were carefully described in September 2022. Seven additional boreholes (8-23 m in length) were drilled in the same geological formation in August and September 2022. The total cored length is 98 m. Five of these boreholes were drilled along a second transect perpendicular to shore situated 800 m to the south-west of the first transect. One borehole was drilled between the first and second transect, and another borehole was drilled along the first transect. The seven new cores were shipped to the Kochi Core Center for storage in January 2023. Sampling of the cores of the first transect was conducted at the Kochi Core Center in February 2023 for sedimentological analysis, radiometric dating, taxonomic identification of corals, crustose coralline algae, and foraminifers, as well as elemental and stable isotope geochemistry. In addition, the corals observed in the cores of the first transect were identified at the lower taxonomic level possible and their status (in situ vs. not in situ) duly noted. The thickness of coralline algal crust was also recorded.
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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
A total of twelve boreholes were drilled into the Minatogawa Formation with an excellent recovery of close to 100 %. The drilling campaign went according to plan and all the cores we planned to collect were successfully recovered. The cores of the first transects were X-ray CT scanned and split in half as planned. The description and sampling of the cores of the first transect have also been completed.
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| Strategy for Future Research Activity |
During FY2023, cores of the seven new boreholes which are stored at the Kochi Core Center will be X-ray CT scanned. Like for the other cores, the XCT scan images will provide information about their lithology, sedimentary structures, and fossil content. The cores will then be split in half. One half will be photographed and the other half will be sampled at a later date. A visual description of the cores will be conducted at the Kochi Core Center, with particular attention given to describing the different lithologies, sedimentary structures (e.g., discontinuities, paleosols), fossil content, particularly corals, coralline algae, and foraminifers. After the visual description of the cores is completed, a sampling party will be organized. Samples will be collected for sedimentological analysis, radiometric dating, taxonomic identification of corals, crustose coralline algae, and foraminifers, as well as elemental and stable isotope geochemistry. Coralline algae and foraminifers will be identified by Prof. Yasufumi Iryu (Tohoku University) and Prof. Kazuhiko Fujita (University of the Ryukyus), respectively. Data on lithologies, sedimentary structures, and fossil content of all the cores will be integrated to produce a model of facies architecture. In parallel, samples of fossil corals will be screened to identify well-preserved specimens that can be radiometrically dated. The geochemical analyzes of the carbonate samples will be conducted by a graduate student of Nagoya University.
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