Depositional ages of sedimentary rocks obtained from the sea floor around the northern Tokara Islands during GB21-3 cruise, based on calcareous microfossil assemblages, and their geological significance

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  • ARIMOTO Jun
    AIST, Geological Survey of Japan, Research Institute of Geology and Geoinformation
  • UTSUNOMIYA Masayuki
    AIST, Geological Survey of Japan, Research Institute of Geology and Geoinformation

Bibliographic Information

Other Title
  • GB21-3 航海においてトカラ列島北部周辺海域で採取された堆積岩の石灰質微化石に基づく堆積年代と地質学的意義

Abstract

<p>Calcareous nannofossil and planktic foraminiferal assemblages were examined to determine the depositional ages of sedimentary rocks obtained during GB21-3 cruise at around the Tokara Islands, northern Ryukyu arc. Depositional ages of examined microfossil-bearing samples are shown to be the Early Pleistocene (Calabrian) or younger. Several samples from the western margin of the Tane–Yaku Spur in the forearc side and from between the Higashi–Shin Sone and Sango Sone in the back-arc side, are correlated with calcareous nannofossil biozone CN14a and/or planktic foraminiferal biozone PT1a, and their depositional ages fall between 1.59 and 0.43 Ma during the Early–Middle Pleistocene (Calabrian–Chibanian). The other younger samples are correlated with calcareous nannofossil biozone CN15, which constrains the depositional ages younger than 0.29 Ma (Middle Pleistocene to Recent). Our observation on lithology and microfossil assemblages imply that the sedimentary rock units which derived the examined samples likely have geological records of volcanogenic sedimentation and tectonic influence on uppermost crustal recycling at the northern Ryukyu arc during the Pleistocene.</p>

Journal

  • BULLETIN OF THE GEOLOGICAL SURVEY OF JAPAN

    BULLETIN OF THE GEOLOGICAL SURVEY OF JAPAN 74 (5-6), 245-257, 2023-12-28

    National Institute of Advanced Industrial Science and Technology, Geological Survey of Japan

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