著者

桑原 徹

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.7, no.4, pp.235-247, 1968-12-20 (Released:2009-08-21)

参考文献数

61

被引用文献数

33 26

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The tectonic development of the Noobi sedimentary basin is discussed in relation to crustal movements of southwest Japan in the period of the Quaternary.The basin is an eastern part of the Second Setouchi sedimentary province formed in the inland area of southwest Japan during the Plio-Pleistocene. In the Setouchi province, two types of tectonic movements originated in crustal undulation are recognized: Type-1 is of long-wave undulation which has formed the main depressional zone with parallel axis to the trend of the Setouchi province. Type-2 is of short wave undulation crossing, in almost cases, the trend of the axis of the province, which has formed the alternating arrangement of basin and ridge in the depressional zone.From the tectonic point of view, the province is divided into three crustal blocks from east to west:-(1) Chubu, (2) Kinki and (3) Chugoku.The eastside of the Chubu block is marked off by the Fossa Magna, and westside by the Tsuruga-Ise bay line. The Noobi basin is situated in the western end of this block. A subsidence of the basin has been largely caused by tilting movements of the block active since the Pliocene, and less by the crustal undulation. This tilting block movement in large scale is a tectonic movement characteristic in the Setouchi province. And also in the Chubu block, the trend of axis of type-2 undulation changes into parallel direction to that of the Setouchi province.The rate of the tilting movement in the Noobi basin seems to increase in the latest periods. The mean rate of the tilting movement is estimated to be 7×10-8 per year during the latest 35, 000 years according to geological evidences. This figure is almost the same to the one of the recent crustal movements measured geodetically in Japan.