Geologic ages of the Chinen Formation and the "Reddish Limestone" in Komesu and Giza areas in southern Okinawa-jima based on calcareous nannofossil biostratigraphy

DOI Web Site Web Site 7 Citations 38 References
  • Odawara Kei
    Institute of Geology and Paleontology, Graduate School of Science, Tohoku University Present address: Hot Springs Research Institute of Kanagawa Prefecture
  • Iryu Yasufumi
    Institute of Geology and Paleontology, Graduate School of Science, Tohoku University
  • Matsuda Hiroki
    Department of Science, Faculty of Science, Kumamoto University
  • Sato Tokiyuki
    Institute of Applied Earth Sciences, Faculty of Engineering and Resource Science, Akita University
  • Chiyonobu Shun
    Institute of Geology and Paleontology, Graduate School of Science, Tohoku University
  • Sakuma Daiki
    Institute of Applied Earth Sciences, Faculty of Engineering and Resource Science, Akita University

Bibliographic Information

Other Title
  • 沖縄本島南部米須・慶座地域の知念層および“赤色石灰岩”の石灰質ナンノ化石年代
  • オキナワ ホントウ ナンブ コメス ギザ チイキ ノ チ ネンソウ オヨビ セキショク セッカイガン ノ セッカイシツ ナンノ カセキ ネンダイ
  • Geologic ages of the Chinen Formation and the “Reddish Limestone” in Komesu and Giza areas in southern Okinawa-jima based on calcaerous nannofossil biostratography (in Japanese)

Search this article

Description

The Chinen Formation in southern Okinawa-jima, southwestern Japan, is composed of calcareous sandstone and sandy limestone correlative with the transitional lithofacies between massive siltstone of the Upper Miocene to Pliocene Shimajiri Group and detrital to reefal limestone of the Pleistocene Ryukyu Group. The "Reddish Limestone" is the lowest lithostratigraphic unit in the Ryukyu Group in southern Okinawa-jima and consists mainly of highly altered detrital and rhodolith limestones. The calcareous nannofossil biostratigraphy of the Chinen Formation and the "Reddish Limestone" in two boring cores from Komesu and Giza areas were studied. Abundant specimens of the calcareous nannofossil, Gephyrocapsa spp. (small), whose base occurred at 2.09 Ma, were recognized in the uppermost Shimajiri Group to large part of the Chinen Formations in the two cores. Although the latest Pliocene datum plane, the last occurrence of Discoaster brouweri. (1.97 Ma), was recovered from the lower Chinen Formation in Komesu core, it was not detected in Giza core due to relatively rare and sporadic occurrence of this genus. It was likely that two early Pleistocene datum planes, the first occurrence of Gephyrocapsa caribbeanica (1.73 Ma) and the first occurrence of G. oceanica (1.65 Ma), were concentrated at the base the "Reddish Limestone". The early Pleistocene datum plane, the first occurrence of Gephyrocapsa spp. (large) (1.45 Ma), is situated in the "Reddish Limestone" in Giza core and possibly at the top of the Limestone in Komesu core. These indicate that the Chinen Formation is correlated with the latest Pliocene (>1.73 Ma) and that the "Reddish Limestone" formed in Early Pleistocene time between 1.65 Ma and 1.21 Ma. <br>

Journal

Citations (7)*help

See more

References(38)*help

See more

Keywords

Details 詳細情報について

Report a problem

Back to top