Neogene planktonic foraminiferal biostratigraphy of the northern coast of Suruga Bay and Izu Peninsula

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In this study, planktonic foraminiferal biostratigraphy of Neogene sequences on the northern coast of Suruga Bay and Izu Peninsula is examined.As the strata on the northern coast of Suruga Bay have strongly been affected by neotectnics of the Fossa Magna, various methods for hard rock samples utilizing Kalibor, Sodium chloride and vacuum oven were tried to examination of planktonic foraminifera.As a result, following new data on planktonic foraminiferal age-assignments of sequences of the area could be obtained. From occurrences of age-diagnostic species, the Shizuoka, Wadajima and the Kawaino Groups are assigned to N.17 of late Miocene age. These three groups are included in a same interval. The Kogochi Group corresponds to N.17b-18 of late Miocene to early Pliocene age, the Seikenji Group to N.19 of Pliocene age, and the Hamaishidake Group to N.21 of Pliocene age.In Izu Peninsula, some new data on planktonic foraminiferal biostratigraphy could be obtained. Based upon occurrences of age-diagnostic species in an outcrop near the Yugashima Spa, a part of the Yugashima Group is assigned to N.8 of the latest Early Miocene age. Some Pliocene sequences of the Shirahama Group are found exposed on hill tops of about 400-500m above sea level in the central part of Izu Peninsula, which suggest an upwarping of the peninsula sinc Pliocene time.