| Project/Area Number |
08304031
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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 | Tohoku University |
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Principal Investigator |
NAKAMORI Toru Tohoku University, Division of Science, Associated Professor, 大学院・理学研究科, 助教授 (00192229)
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| Co-Investigator(Kenkyū-buntansha) |
IRYU Yasufumi Tohoku University, Division of Science, Research Associate, 大学院・理学研究科, 助手 (00250671)
MATSUDA Shinya Ryukyu University, College of Education, Associated Professor, 教育学部, 助教授 (30157317)
OMURA Akio Kanazawa University, Department of Earth Science, Professor, 理学部, 教授 (70019488)
OTA Yoko Senshu University, Department of Geography, Professor, 文学部, 教授 (80017714)
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥5,000,000 (Direct Cost: ¥5,000,000)
Fiscal Year 1997: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1996: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Keywords | Kikai-jima / Holocene / Raised Coral Reef / hermatypic corals / giant clam / oxygen isotope ratio / sea surface temperature / salinity / 成長線 / vital effect / 炭素同位体比 |
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| Research Abstract |
Field surveys on the Holocene Raised Coral Reef and present coral reefs around Shido-oke in the northern coast of Kikai-jima Island, Ryukyus, southwest Japan were carried out in 1996 and 1997. Six core samples (T-1-T-6) ranging from 2.44 to 3.99 min length and 5 cm in diameter were obtained by using hand corer which was equipped by this Grant. on the Terraces II to IV.Tabular and encrusting Acropora, such as A.hyacinthus, A.digitifera, A.gemmifera, and A.monticulosa predominate in the hermatypic coral assemblages. Species combination indicates that the all cores were deposited in the shallow marine environments from 0 to 10 min depth. Skeletons of the living Porites spp., Tridacna spp. and sea water samples were collected from every 5 m from 0 to 30 min depth on the reef slope off Shido-oke.
SoftX-ray photos of the living and Holocene coral slabs were taken in the laboratory and the annual growth bands were studied to date the samples. The living (KS01-09) sample was taken from 9 min depth. Useries age of the fossil sample (1805) is 9.2 ka after Ota et al.(1998). Carbon and oxygen stable isotope ratios of the coral skeleton were measured by the mass spectrometry. Present sea surface temperature (SST) and monthly mean salinity around Kikai-jima Island are reconstructed from IGOSS SST data and 1ﾟ mesh salinity data of JODC,respectively.
Paleo- and present SSTs around Kikai-jima were estimated according to the oxygen isotope anomaly model including the vital effects and the ice sheet size. It predicts that-the present mean SST is 21.9ﾟC,2.6ﾟC lower than the actually measured data. Early Holocene mean SST was also estimated to be 22.0ﾟC,which is discordant with the results calculated on the transfer function..
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