古江累層の微小古生物学的研究 : 島根半島第三系の地質学的研究(その3)

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Field evidence shows that the lower Fujina member distributed along the southern side of Shinji Lake and the Furue mudstone member bordering the northern side are obviously contemporaneous and equivalent in their stratigraphic positions., Although both lithologic units consist of very fine-grained sediments, their areas of deposition within the same sedimentary basin are not the same as proved by their contained foraminiferal faunas., The lower Fujina member is characterized by such calcareous foraminiferal genera as, Uvigerina, Cibicides, Cassidulina, and Epistominella., On the other hand, the Furue mudstone member is represented by such arenaceous foraminiferal genera as, Cyclammina, Haplophragmoides, Martinottiella, Goesella, and Plectina., This dissimilar microfauna is quite contrary to what would be expected from a lithologically similar facies., The contrasting microfauna can be explained by referring to the depositional and ecological environments of the two similar lithological units by their contained elements., The lower Fujina member may be regarded to have been deposited in the outer neritic zone and the Furue member in the outer bathyal zone., Structurally the Fujina and Furue members occupy the southern and northern wings of the same syncline., By reconstructing the two members to their original positions and referring them to one sedimentary basin, it becomes evident that the basin configuration must have had a characteristic contour, such as a "graben-trough"., Further data upholding the view of a special environment are now progressively accumulating.,
日本地質学会の論文
1955-09-25

古江累層の微小古生物学的研究 : 島根半島第三系の地質学的研究(その3)

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