BULLETIN OF THE GEOLOGICAL SURVEY OF JAPAN
Online ISSN : 2186-490X
Print ISSN : 1346-4272
ISSN-L : 1346-4272
Article
Molluscan associations and paleoenvironment of the Pliocene formations around Umikawa River in Itoigawa City, Niigata Prefecture, central Japan.
Mitsuhisa EndoKazutaka AmanoYukio Yanagisawa
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2006 Volume 56 Issue 11-12 Pages 411-424

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Abstract

Marine Pliocene deposits around the Umikawa River in Itoigawa City, Niigata Prefecture consists of the Kawazume and Nadachi Formations in ascending order. Diatom biostrati-graphy indicates that the lower part of the Nadachi Formation is assigned to the subzone NPD 7Bb (early Pliocene),while the upper part of this formation can be correlative with the zones NPD 8 and NPD 9 (late Piocene). In the molluscan faunas of the Kawazume and Nadachi Formations, the following seven associations were recognized; the upper bathyal to lower sublittoral Conchocele-Solemya, AcilaLucinoma, Conchocele, Portlandia, Macoma-Axinopsida associations, and the lower sublittoral Acila,Ophiodermella-Turritella associations. Based on the characteristics of these molluscan associations,the Umikawa area was placed in the upper bathyal to lower sublittoral zones during the Pliocene age.

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© 2006 National Institute of Advanced Industrial Science and Technology, Geological Survey of Japan
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