| Project/Area Number |
63540629
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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 | Kyushu University |
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Principal Investigator |
SHIMAYAMA Shoichi Kyushu Univ. Science, Assistant, 理学部, 助手 (90136424)
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| Project Period (FY) |
1988 – 1989
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| Project Status |
Completed (Fiscal Year 1989)
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| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1989: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1988: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | Taphonomy / Cv-Fr analysis / Coexistence index of left and right valves (Cv) / Shell size-frequency distribution / Fragmentation rate of shells (Fr) / Oxygen-deficient water in summer / Degree of the autochthonous / 夏季貧酸素水塊 / Cv-Fr分析 / 軟体動物 / 分布帯 / 原地性 / 異地性 / 左右両殻共存率Cv / 殻破壞率Fr |
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| Research Abstract |
Two case studies and a method on formation of distributional zone and information loss in taphonomy process of the molluscan thanatocoenoses at Hakata Bay and Ariake Sea in Kyushu, West Japan were presented as a results of this project. In the case of Hakata Bay, the appearance of oxygen-deficient water in summer has a significant influence of seasonal fluctuation in spatial distribution and population size especially for species living in the innermost bay area. This causes the difference of rank abundance of species between the living community and death assemblage at the same location. Mass mortality under the oxygen-deficient water condition modify the structure of initial death assemblage into a time-averaged assemblage. In the case of Ariake Sea, Cv-Fr analysis of thanatocoenosis has revealed that two series of taphonomic process before the final burial. Decrease of initial information of death assemblages on the first series makes slow progress, but one on the second series makes rapid progress. Special mechanisms of shell transportation on the second series, e.g. "sail effect" of empty shells, and effect of gravity current sometimes form mixed death assemblages at the transitional zone of coast and shelf.
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