6:15 PM - 7:30 PM
[MIS32-P01] Quaternary radiolarians biostratigraphy in the Alaska margin (IODP Exp.341 Site U1417)
Keywords:Quaternary, Radiolarians, Biostratigraphy
Therefore, in this study, samples from the upper 200 m CCSF-B of Site U1417 were analyzed in order to establish the depth-age model based on shipboard diatom/radiolarian biostratigraphy and paleomagnetic polarity stratigraphy for enables further paleoceanographic studies. Indeed, several radiolarian datum events such as the last occurrences (LOs) of Stylatractus universus, Lychnocanoma sakaii and Amphimelissa setosa appear to be important for chronostratigraphic use. Particularly, temporal distribution of Amphimelissa setosa is highly interesting because the LO records at the MIS 4/ 5 boundary (77 ka) in the North Pacific, while this species is still extant in the Arctic Ocean, Norwegian Sea, or in the Labrador Sea. In this study, we could establish the LOs of Sphaeropyle robusta (1,500 ka, 161.9 m CCSFB at the median depth), Eucyrtidium matuyamaii (1,250 ka, 143.3 m), Stylatractus universus (450 ka, 74.9 m), Axoprunum acquilonium (350 ka, 61.5 m) and Amphimelissa setosa (77 ka, 25.0 m), and acme of Lychnocanoma sakaii (61 ka, 18.81 m). On the other hand, the FO of Amphimelissa setosa could be established for the first time in the northeastern Pacific between the LO of Eucyrtidium matuyamaii and the base of Jaramillo magnetic normal polarity epoch (1,072 ka).