K. Hagino , Expedition 370 Scientists
18 April 2018
International Ocean Discovery Program Expedition 370 recovered marine subsurface sediments from 189 to 1126 meters below seafloor (mbsf) at Site C0023, which was established on the Nankai Trough, off Muroto Peninsula, Japan. Biostratigraphic studies based on calcareous nannofossil assemblages revealed the ages of sediments are from the middle Miocene to Pleistocene. Samples from 1126.885 to 796.530 mbsf yielded Miocene taxa such as Coccolithus miopelagicus, Cyclicargolithus floridanus, Catinaster calyculus, and Discoaster quinqueramus. The interval 790.285–774.984 mbsf spans the late Miocene to the early Pliocene, as it corresponds to bioevents spanning from the last occurrence (LO) of D. quinqueramus to the first occurrence of Ceratolithus cristatus. Samples from 769.440 to 639.982 mbsf are referred to the Pliocene based on occurrences of C. cristatus, Reticulofenestra pseudoumbilicus (≥7 µm), and/or Discoaster surculus. Sediments from 630.440 to 190.483 mbsf are dated to the Pleistocene, as an interval above the LO of Discoaster pentaradiatus. Preservation of calcareous nannofossils is poor or moderate in the middle Miocene samples and moderate to good in the samples from the upper Miocene to Pleistocene.