<国立科博専報>山形県新庄盆地西部の鮮新統貝類化石群集

概要

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The Nakawatari and Sakekawa formations distributed in Shinjo Basin can be assigned to the Pliocene based on molluscan and calcareous nannoplankton fossils. 49 species of 33 genera of mollusca are reported from the formations, and the fauna can be correlated with that of the Kannonji Formation in the Akumi Oil-field of Yamagata Prefecture. And the molluscan fauna can be considered to represent the Omma-Manganzian fauna which distributes widely in the Pliocene and Pleistocene deposits along the Sea of Japan. However, the mentioned two formations yield some restricted species in the area, these are Clinocardium spp., Vasticardium n.sp.and so on. Yabepecten tokunagai is the most significant species among those which reported from the Cenozoic deposits of Shinjo Basin. The present species has been considered to be an index of the Omma-Manganzian fauna by MASUDA (1962,1973,1980,etc.). According to the specific combination of the Nakawatari and Sakekawa formations, the molluscan fauna can be assigned to correspond to the northern-type of the Omma-Manganzian faunal element in its faunal province (OGASAWARA; 1983). The sedimentary environments of the two formations can be considered to Subneritic to Mesoneritic facies of OYAMA(1952), based on Recent molluscan ecological data.
国立科学博物館の論文
1984-12-01