著者

駿河湾団体研究グループ

出版者

地学団体研究会

雑誌

地球科学 (ISSN:03666611)

巻号頁・発行日

vol.35, no.3, pp.145-158, 1981

被引用文献数

3

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In the present paper, authors describe stratigraphy, biostratigraphy and geologic structure of the Neogene Formations in the Hamaishidake area, in the southwestern margin of socalled "Fossa Magna". The formations consist of flysch-like alternations, coarse-grained sediments and pyroclastics ranging from Late Miocene to Pliocene in age. They are complicated with faulting and folding. Results of the studies are surmmarized as follows: 1) The investigated area is formed of two formations, the Kogouchi Formation and the Hamaishidake Formation in ascending order. 2) The Kogouchi Formation consists of alternation of mudstone and sandstone, and the Hamaishidake Formation consists mainly of conglomerate, sandstone and tuff breccia. 3) The Hamaishidake Formation unconformably overlaps the Kogouchi Formation. 4) The geological age of the Formations is inferred from planktonic foraminiferal assemblages and molluscan index species. The Kogouchi Formation is Late Miocene and the Hamaishidake Formation is Pliocene in age. 5) The Hamaishidake Formation is subdivided into four sub-formations which are named the Murono, the Sattatoge, the Utugino and the Shishihara in ascending order. 6) Each stratigraphical relationships in the four sub-formations are discontinuity. 7) The Formations consist of a series of N-S trending structure, and all axes of anticlines and synclines plunge north. 8) Many trace fossils are observed in the Kogouchi Formation. This trace fossil facies are suspected to be corresponded with Cruziana facies (SEILACHER, 1967).