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doi:10.2204/iodp.proc.346.202.2018

Introduction

Integrated Ocean Drilling Program (IODP) Expedition 346 was conducted on the shelf region of the Yamato Basin off the San’in District of southwest Japan (Fig. F1). At Site U1427 (water depth = 330 m), a hole was cored to 570 m core composite depth below seafloor (CCSF-A) (see the “Expedition 346 summary” chapter [Tada et al., 2015a]). At this site, both calcareous and siliceous microfossils are well preserved in all cores, and a high sedimentation rate (264–630 m/My) over the past 1.4 My was estimated based on biostratigraphy and magnetostratigraphy (see “Biostratigraphy” and “Stratigraphic correlation and sedimentation rates” in the “Site U1427” chapter [Tada et al., 2015b]). Therefore, this drill site was expected to be suitable for paleoceanographic study with high-resolution analysis.

In this report, we provide an updated data set of the available radiolarian datum levels and the abundance of subtropical water species based on 455 samples from Site U1427. Because subtropical radiolarians are closely related to the inflow of the Tsushima Warm Current (TWC) from the East China Sea via the Tsushima Strait (sill depth = 130 m), their abundance can be correlated with marine isotope stages (MIS). In addition, a portion of the initial shipboard results of the planktonic foraminiferal biostratigraphy (Tada et al., 2015a) has been reinterpreted herein to improve the detailed age model, especially for the lower part of the sequence.

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