Quaternary radiolarian biostratigraphy in the subarctic northeastern Pacific (IODP Expedition 341 Site U1417) and synchroneity of bioevents across the North Pacific

Abstract

Abstract. Expedition 341 of the Integrated Ocean Drilling Program (IODP) retrieved sediment cores spanning the time interval between the Pleistocene and Miocene from the southern Gulf of Alaska. Onboard Pleistocene radiolarian biostratigraphy is hereby refined by increasing the sampling resolution. The 178 core samples from the upper 190 m CCSF-B (Composite Core Depth Scale F-B) of Site U1417 contained faunal elements similar to the northwestern Pacific; for example, the three biozones in the northwestern Pacific (i.e., Eucyrtidium matuyamai, Stylatractus universus and Botryostrobus aquilonaris) were also recognized in the Gulf of Alaska, spanning 1.80-1.13 Ma, 1.13-0.45 Ma, and the last 0.45 Myr, respectively. Based on the age model that we used in this study and the shipboard paleomagnetic reversal events, the first occurrences (FOs) of Amphimelissa setosa and Schizodiscus japonicus in the northeastern Pacific were preliminarily determined to be 1.48 and 1.30 Ma, respectively. The last occurrence (LO) of Eucyrtidium matuyamai and the FO of Lychnocanoma sakaii, both well-established bioevents in the northwestern Pacific, were dated at 0.80 and 1.13 Ma, respectively. The LO of E. matuyamai is a synchronous event at 1.05 ± 0.1 Ma in the North Pacific, while the FOs of A. setosa and S. japonicus at 1.48 and 1.30 Ma, respectively, are significantly older than what has been found elsewhere.

Paleoceanographic history of the Japan Sea over the last 9.5 million years inferred from radiolarian assemblages (IODP Expedition 346 Sites U1425 and U1430)

“…The species A. setosa is an extant species inhabiting subsurface water depths (50-300 m) in the Arctic Ocean (Bjørklund et al 2015;Ikenoue et al 2016;Itaki 2003;Matul and Abelmann 2005). However, this species disappeared from the subarctic North Pacific between marine isotope stages (MISs) 4 and 5 (0.07-0.05 Ma) (e.g., Matul and Abelmann 2005;Ikenoue et al 2016;Matul et al 2002;Matsuzaki and Suzuki 2018). In addition, the first occurrence of this species is recorded at 1.48 Ma in the Northeast Pacific (Matsuzaki and Suzuki 2018).…”

“…However, this species disappeared from the subarctic North Pacific between marine isotope stages (MISs) 4 and 5 (0.07-0.05 Ma) (e.g., Matul and Abelmann 2005;Ikenoue et al 2016;Matul et al 2002;Matsuzaki and Suzuki 2018). In addition, the first occurrence of this species is recorded at 1.48 Ma in the Northeast Pacific (Matsuzaki and Suzuki 2018). In the Japan Sea, this species occurred between 1.47 and 0.05 Ma, although our sampling resolution is relatively Plate 1 Photomicrographs of select radiolarian species used in this study: 1.…”

Data report: Pleistocene radiolarian biostratigraphy, IODP Expedition 346 Site U1427

“…Using an astronomically tuned age model, the first common occurrence (FCO) of this species at IODP Site U1341 in the Bering Sea was dated at ~1 Ma (Ikenoue et al, 2016). Most recently, Matsuzaki and Suzuki (2018) report that the FO of this species occurred at 1.48 Ma in the Gulf of Alaska, the eastern subarctic Pacific.…”