古環境の変遷と対比 : 瀬戸内区中新統の場合

概要

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In this paper, an attempt is made to correlate the Miocene Setouchi series based on vertical change of sedimentary environments in the respective groups inferred from molluscan assemblages. First, molluscan fossils from various exposures in each group are analyzed and grouped into some typical assemblages. Secondly vertical changes in depth of deposition are assumed on each stratigraphic unit from the significance of the molluscan assemblages. Thirdly correlation is made mainly on the basis of mode of bathymetric change referring lithofacies, distribution of pyroclastic sediments, occurrence of pelagic molluscs and others. The results are given in the following lines. 1. Vertical change of sedimentary environment in the Setouchi series represents a transgressive-regressive phase. 2. In the east region (east of the Osaka Bay), the phase consists of the three minor fluctuations, the Haze, Oi and Katada in ascending order. 3. They have a similar transgressive-regressive phase and their amplitudes increase in upward direction. 4. The transgressive-regressive phase in the west region is single and corresponds to the uppermost Katada fluctuation in the east. 5. Correlation is shown in Fig. 3. 6. A remarkable change in molluscan assemblage is recognized between the upper two.
日本地質学会の論文
1973-03-31