| 概要 |
A shell-bearing sandy silt bed is developed widely in the subsurface younger Qu taernary of the coastal plain of Fukuoka. Block samples, 25cm × 25cm x 15cm each, were collected from five horizons (I-V...) ranging from -5.0m to -6. 5m in the shell bearing bed at Arato, two kilometers west of the city center. Autochthonous elements of the molluscan asesmblages of those samples indicate successive changes of water-depth from the I to the V horizon at the time of deposition. After calibration of the crustal element of the relative change of the sea-level, three meters higher sea-level between 5800-6000 y. B. P. and abrupt fall after 5500 y. B. P. are suggested. The suggested sealevel changes are, however, remarkably different in their phase from both FAIRBRIDGE's (1976) and MAEDA's (1976), which show the closest similarity to the present one among ever proposed sea -level changes in the Medial Holocene time. What is the reality of the Holocene eustatic chages is left to be solved in future. Selected four species, Macoma incongrua v. MARTENS, Umbonium (Suchium) moniliferum (LAMARCK), Batillaria zonalis (BRUGUIERE), and B. multi formis (LISCHKE), are discriminated through comparison of their size-frequency distribution and size-specific survival curves with those of living and thanatocoenose populations. Result of the analysis revealed the fossil populations of M. incongrua, a deep burrower in the muddy bottom of the tidal zone, is quite autochthonous and the others are critically reworked before the final burial. Transportation and sorting of the dead snails are ascribed to hermit crabs.続きを見る
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Mendeley出力
