Kenji M. Matsuzaki

A new radiolarian data set for transfer function estimates of past sea surface temperature (SST) and intermediate water temperature was developed in this study for the northwestern Pacific Ocean covering a region from 1° to 50°N and 120° to 167°E. We analyzed 87 sediments surface samples, selected 30 species and/or species group found in shallow water for estimating past summer SST and 17 species and/or species group found in the intermediate water for estimating past intermediate water temperat

Abstract Previous studies showed that the evolution of the Japan Sea paleoceanography since the Miocene has been influenced by the regional tectonism (e.g., opening/closing of the connecting seaways) and regional/global climate. In the Japan Sea, Expedition 346 of the Integrated Ocean Drilling Program (IODP) retrieved core sediments dating back to the Miocene at two sites (U1425 and U1430). In this study, we reconstruct shallow-to-deep-water hydrography of the Japan Sea during the Mio-Pliocene b

A continuous 740-kyr Quaternary sedimentary sequence containing abundant siliceous microfossils was recovered from Hole C9001C during the D/V Chikyu 2006 Mission off the Shimokita Peninsula, Japan. This region is characterized by mixed water reflecting the influences of one warm current (Tsugaru Current), one cold current (the Oyashio Current), and several intermediate and deep water masses. Polycystine radiolarians (a siliceous microfossil group) are useful for reconstructing paleoceanographic

The East China Sea (ECS) is a shallow marginal sea that is sensitive to glacio-eustatic sea-level changes and is influenced by warm oligotrophic water of the Kuroshio Current (KC), the nutrient-rich Taiwan Warm Current, and freshwater discharges from rivers in southern China during the East Asian summer monsoon season. In this area, local paleoceanographic changes for times prior to 40 ka remain poorly studied because of high sediment accumulation rates on the seafloor. During Integrated Ocean D

Polycystine radiolarian remains were collected during Expedition KS15-4 in a plankton tow sample from 0 to 3000 m water depth at station (Sta.) 1 (30°28.8537′N, 132°24.9532′E). Obtained data from this site provide precious information about radiolarian assemblages living at deep-water depths. Based on R-mode cluster analysis, the surface water is characterized by well known subtropical species such as the Tetrapyle circularis/ fruticosa group and Didymocyrtis tetrathalamus. The subsurface water

Abstract The Japan Sea was a semi-closed marginal sea mainly connected to the subarctic northwestern Pacific via shallow seaways during the late Miocene. We use a multiple regression analysis with common extant radiolarian species groups to estimate the sea-surface temperature (SST) for the period between 9.1 and 5.3 Ma. Our results show a cooling of 8 °C between 7.9 and 6.6 Ma, when the SST dropped from 24 °C to 16 °C. We infer that this cooling dominantly reflects wintertime cooling related to

Abstract. A continuous Quaternary sediment sequence was recovered from Hole 902-C9001C during the D/V Chikyu 2006 mission along the northeastern margin of Japan. The age and rate of deposition of this core were estimated using calcareous nannofossil biostratigraphy and oxygen isotope curves measured from benthic foraminifera (Uvigerina akitaensis) and dated from 740 ka to the present, a period that spanned the Brunhes normal polarity epoch. Sediment consisted of diatomaceous siltstone and contai

High-resolution studies of sedimentary sequences have reconstructed paleoceanographic changes in the Atlantic and southern and equatorial Pacific Oceans during the Late Miocene and Pliocene, but comparable analyses are lacking for the North Pacific Ocean. However, continuous samples of hemipelagic sequences covering this time interval were obtained at Integrated Ocean Drilling Program sites U1425 and U1430 in the Japan Sea during expedition 346. Because the paleoceanography of the Japan Sea was