High-resolution and high-precision correlation of dark and light layers in the Quaternary hemipelagic sediments of the Japan Sea recovered during IODP Expedition 346

Abstract

The Quaternary hemipelagic sediments of the Japan Sea are characterized by centimeter-to decimeter-scale alternation of dark and light clay to silty clay, which are bio-siliceous and/or bio-calcareous to a various degree. Each of the dark and light layers are considered as deposited synchronously throughout the deeper (> 500 m) part of the sea. However, attempts for correlation and age estimation of individual layers are limited to the upper few tens of meters. In addition, the exact timing of the depositional onset of these dark and light layers and its synchronicity throughout the deeper part of the sea have not been explored previously, although the onset timing was roughly estimated as~1.5 Ma based on the result of Ocean Drilling Program legs 127/128. Consequently, it is not certain exactly when their deposition started, whether deposition of dark and light layers was synchronous and whether they are correlatable also in the earlier part of their depositional history. The Quaternary hemipelagic sediments of the Japan Sea were drilled at seven sites during Integrated Ocean Drilling Program Expedition 346 in 2013. Alternation of dark and light layers was recovered at six sites whose water depths are >~900 m, and continuous composite columns were constructed at each site. Here, we report our effort to correlate individual dark layers and estimate their ages based on a newly constructed age model at Site U1424 using the best available paleomagnetic datum and marker tephras. The age model is further tuned to LR04 δ 18 O curve using gamma ray attenuation density (GRA) since it reflects diatom contents that are higher during interglacial high-stands. The constructed age model for Site U1424 is projected to other sites using correlation of dark layers to form a high-resolution and high-precision paleo-observatory network that allows to reconstruct changes in material fluxes with high spatio-temporal resolutions.

Pliocene integrated chronostratigraphy from the Anno Formation, Awa Group, Boso Peninsula, central Japan, and its paleoceanographic implications

“…Some tephra marker beds (An51, An53, An77, An85, An112, An129, and An130) are widely recognized throughout the Japanese Islands and are known as Trb1-Ya4, Sk-Ya5, Ksg-An77, Znp-Ohta, Ymp-SF8.3, Hgs-An129, and Sr-Ity, respectively (Kurokawa and Higuchi 2004;Satoguchi et al 2005;Tamura et al 2005Tamura et al , 2008Tamura and Yamazaki 2010;Satoguchi and Nagahashi 2012). In particular, the Znp-Ohta and Sr-Ity tephra beds, which facilitate the comparison of Pliocene stratigraphies and paleoenvironmental records between the Japan Sea and the northwestern Pacific Ocean, have also been observed at the deep-sea sediment cores in the Japan Sea (Tada et al 2018).…”

“…The upper Awa Group is a middle Miocene-upper Pliocene marine deposit that is distributed throughout the Boso Peninsula and faces the North Pacific subarctic front between the Kuroshio and Oyashio Currents, which are wind-driven western boundary currents (Suzuki et al 1995;Qiu 2001;Fig. 1a, b).…”

Construction of perfectly continuous records of physical properties for dark-light sediment sequences collected from the Japan Sea during Integrated Ocean Drilling Program Expedition 346 and their potential utilities as paleoceanographic studies

“…2). After correction, each core-section is nearly continuous such that correlation among these sites using their color banding patterns allows reasonably isochronous horizons to be studied across wide regions of the Japan Sea over millennial time scales (Tada 1994;Tada et al 1999;Tada et al 2018). Combination of the reliably continuous stratigraphy at each site and its correlation to the reference site such as U1424 ) enabled more precise tuning age construction at other drilled sites in the Japan Sea.…”

High-resolution Quaternary record of marine organic carbon content in the hemipelagic sediments of the Japan Sea from bromine counts measured by XRF core scanner

“…During IODP Expedition 346, these dark and light layers were recovered at six sites in the Japan Sea at water depths deeper than 900 m (Tada et al 2015a). The deposition of dark and light layers started at approximately 2.6 Ma (million years ago) and became increasingly distinct at approximately 1.45 Ma (Tada et al 2015a;Tada et al 2018). Distinct dark layers have been correlated among the six sites , and their deposition was synchronous basinwide, suggesting that the Japan Sea has been acting as a single system responding to climatic-oceanographic change in climatic-tectonic coupling in Asia throughout the Quaternary (e.g., : Clift 2017.…”

“…Another reason to choose Site U1424 is that a high-precision and high-resolution age model has been constructed at this site ( Fig. 2; Tada et al 2018).…”