Correlation of the early Pliocene Znp Tephra Bed to the Hjp Tephra Bed around Yoneyama in the Niigata region, central Japan

概要

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The early Pliocene Znp Tephra Bed is one of the prominent submarine tephra deposits in the Niigata region. The Znp Tephra Bed in the Nishiyama Oil Field was correlated to the Hjp Tephra Bed around Yoneyama on the lithology, pertrography and chemical composition of glass shards. The Znp and the Hjp Tephra Beds contain abundant subangular fibrously vesiculated pumice clasts in common. In both Tephras, the shape of glass shards are characterized by bubble-junction type shards accompaning fibrously vesiculated shards. The glass shards show similar chemical composition in both Tephras, especially characterized by CaO contents of 0.52-0.58% in average. The locations of the Hjp Tephra Bed are situated about 40-45km southwestward toward the possible volcanic source area from the type locality of the Znp Tephra Bed at Yamada. In the Niigata region further toward the volcanic source area, the possibility of detection of the correlative tephra beds was also discussed.
新潟大学の論文
2004-02-27