石灰質微化石からみた紀伊半島・四国沖の底質

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Joint researches with the Research Group of the Tectonic Development of the Shimanto Geosyncline and Shikoku Basin and the Ocean Research Institute, University of Tokyo were held three times from 1970 to 1972 in the southern sea area off the Kii Peninsula and Shikoku Island. In the course of the researches, the authors have surveyed by the R/V Tansei-maru of the Ocean Research Institute (KT-70-3, KT-71-9 and KT-72-2 Cruises) and the R/V Hakuho-maru of the same institute (KH-72-2 Cruise). In these research cruises, the authors have obtained many dredge hauls and three piston core samples at 41 stations. In the present paper, theauthors dealt with 69 samples obtaind from 37 stations. Most samples yield well preserved abundant specimens of planktonic foraminifera and calcareous nannoplankton ranging from Pleistocene to Recent in age. A sample obtained from off the Muroto Cape revealed early Pliocene planktonic foraminifera and nannoplankton assemblages, and the latter was correlated to the lower part of the Yonabaru Formation in Okinawa. Pleistocene to Recent planktonic foraminifera and calcareous nannoplankton assemblages probably occurred in the acoustic "P" formation. Some assemblages which yielded Gephyrocapsa caribbeanica, Reticulofenestra reticulata and Pseudoemiliania lacunosa also occurred in acoustic "K3" formation. The early Pliocene assemblages occurred m the acoustic "K1" formation. Braarudosphaera bigelowi which occurred in D22-1, D35 and D38 samples shows that the sediments of these stations have deposited on the shallow bottom. These stations are, therefore, supposed to subside respectively about 200, 300, 1,000m in "P" stage. The benthonic foraminifera obtained from the same samples, however, do not suggest the subsidence of D35 and D38 stations in that stage. It may be considered that B. bigelowi which is yielded in the samples from these two stations, had been displaced by the the submarine current. The present paper will be one of the basic data in the future geological and paleontological studies of this sea area.
奈良教育大学の論文

石灰質微化石からみた紀伊半島・四国沖の底質

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