| Project/Area Number |
05640510
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Stratigraphy/Paleontology
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| Research Institution | Tohoku University |
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Principal Investigator |
MORI Kei Department of Geoenvironmental Science, Faculty of Science, Tohoku University, Professor, 理学部, 教授 (00004466)
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| Co-Investigator(Kenkyū-buntansha) |
NAMAMORI Toru Department of Geoenvironmental Science, Faculty of Science, Tohoku University, A, 理学部, 助教授 (00192229)
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| Project Period (FY) |
1993 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1994: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1993: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | growth bands / geochronometry / rugose corals / scleractinian corals / 成長率 / 酸素安定同位体比 / 年輪 |
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| Research Abstract |
Although it has been widely accepted that the number of days per year have decreased through geological time based on daily and annual growth increments of corals, our study indicates that ancient coral growth bands should be reconsidered for daily and monthly geochronometric calibrations. Minute growth bands in two fossil scleractinian coral species from the Pleistocene of Japan were counted by SEM and the oxygen stable isotope ratio was measured to obtain their annual growth rates.
There are really two different types of bands and they have different origins. In Truncatoflabellum formosum, each band is demonstrated to have formed per half-month interval.
The band widths (0.05-0.20 mm) are nearly equivalent with those of rugose corals. In Tachyphyllia geoffroi, each band was formed daily and the band widths are much finer than the former species. This study suggests that "daily" bands derived from the rugose corals were not previously thought formed daily. Furthermore, lunar monthly periodicities postulated in the Paleozoic corals were probably really annual.
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