2006 Fiscal Year Final Research Report Summary
Late Holocene paleoenvironmental analysis from submarine cave deposits
| Project/Area Number |
16340159
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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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| Research Field |
Stratigraphy/Paleontology
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| Research Institution | Shizuoka University |
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Principal Investigator |
KITAMURA Akihisa Shizuoka University, Institute of Geosciences Faculty of Science, Associate Professor, 理学部, 助教授 (20260581)
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| Co-Investigator(Kenkyū-buntansha) |
KASE Tomoki National Science Museum, Division of Invertebrate Paleontolog, Chief, 地学研究部, 室長 (20124183)
SAKAI Hideo Toyama University, Institute of Geosciences Faculty of Science, Professor, 理学部, 教授 (30134993)
FUJITA Kazuhiko Ryukyu University, Institute of Geosciences Faculty of Science, Associate Professor, 理学部, 助手 (00343377)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Holocene / climate changes / marine environments / coral reef / submarine cave / Paleontology |
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| Research Abstract |
We examined a sediment layer and surface sediments in a submarine limestone cave (31 m depth) on the fore-reef slope of Ie Island, off Okinawa mainland, Japan. In addition, oxygen isotope analysis was performed on the cavernicolous micro-bivalve Carditella iejimensis from both cored sediments and surface sediments, and the water temperature within the cave was recorded for nearly one year. These data lead to the following conclusions : 1) although the biotic and non-biotic environments within the cave have persisted for the past 5,000 years, the environmental conditions of the innermost cave area gradually spread to the entrance of the cave ; 2) the alternation of water masses within the cave is caused by the tidal cycle ; 3) the δ^<18>O-derived temperature of C. iejimensis indicates spring temperature at 30 m deep outside the cave ; 4) the δ^<18>O-derived temperature of C. iejimensis from cored sediments implies that there were two warmer intervals, at about AD 280 and AD 1050 ; 5) a sediment layer containing pumice grains (BC 440 ± 40 to AD 640 ± 80) was identified and named as Daidokutsu pumice. These suggest that submarine-cave sediments and oxygen isotope records of cavernicolous shells are a useful tool to reconstruct century-scale paleoenvironmental and climatic variability for the subtropical Okinawa Islands during the Holocene.
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