湖成層の珪藻化石群集を用いた水域古環境解析 : その3 大分県安心院-院内地域津房川層(上部鮮新統)

概要

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The Tsubusagawa Formation is a lacustrine deposit of the Late Pliocene in the Ajimu-Innai area of Oita Prefecture, Kyushu. Some animal fossils were reported from the lower part of the formation (Takahashi and Kitabayashi, 2001). Iwauchi and Hase (1986) showed the environmental changes during sedimentation of the formation through the analysis of pollen and macrofossil plants. In this study, aquatic environmental changes of the formation were made evident by changes of fossil diatom assemblages. As a result of diatom analysis, the assemblages were observed from each columnar section of 24, 18, 19, 14, 27 and 9. Columnar section 24 was divided at I-2〜I-10 : Navicula spp., Stauroneis spp., I-46〜I-49 : Fragilaria spp., and I-50〜I-60 : Fragilaria spp., Navicula spp. Columnar section of 18 : Fragilaria spp., Navicula spp., of 19 : Fraglaria spp., Cocconeis spp., Navicula spp., of 14 was O-1〜G-63 : Fragilaria spp., and G-64〜G-100 : Aulacoseira spp., Stephanodiscus spp., Fragilaria spp., of 13 : M-1〜M-24 : Fragilaria spp., Navicula spp. and M-25〜M-89 : Stephanodiscus opp., Aulacoseria spp., of 27 : Cyclotella sp.1, Aulacoseira spp.,of 9 : Aulacoseira spp., Stephanodiscus spp., Cyclotella spp. As the results, it is determined that an aquatic environment of the Tsubusagawa Formation evolved through three stages from swamp to swampy lake to lake.
熊本大学の論文
2007-03-30