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

Kenji M Matsuzaki,Noritoshi Suzuki

doi:10.5194/jm-37-1-2018

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.

Highlights

In order to clarify the relationship between tectonic and climate changes during the Neogene, Expedition 341 of the Integrated Ocean Drilling Program (IODP) retrieved sediment cores at five sites off the southern Gulf of Alaska between 29 May and 29 July 2013 (Jaeger et al, 2014; Gulick et al, 2015)
Important datums: We identified the first occurrences (FOs) of L. sakaii in this zone as being between samples 341-U1417A, 13H-2, 50–52 cm and U1417C, 14H-1, 50–52 cm at a median depth of 113.18 m Composite Core Depth Scale F-B (CCSF-B) (Fig. 3 and Table 4)
Among the bioevents recognized in the northwestern Pacific, eight last occurrence (LO) were recognized at Site U1417: Lychnocanoma sakaii, Amphimelissa setosa, Schizodiscus japonicus, Axoprunum acquilonium, S. universus, E. matuyamai and Actinomma robustum

Summary

Introduction

In order to clarify the relationship between tectonic and climate changes during the Neogene, Expedition 341 of the Integrated Ocean Drilling Program (IODP) retrieved sediment cores at five sites off the southern Gulf of Alaska (northeastern Pacific) between 29 May and 29 July 2013 (sites U1417 to U1421) (Jaeger et al, 2014; Gulick et al, 2015). Of particular interest in the retrieved cores are polycystine radiolarians, which are siliceous microorganisms that inhabit shallow, intermediate and deep waters (e.g., Renz, 1976; Anderson, 1983; Kling, 1979; Kling and Boltovskoy, 1995; Nimmergut and Abelmann, 2002; Okazaki et al, 2004; Suzuki and Not, 2015; Matsuzaki et al, 2016) Their skeletons composed of amorphous silica are generally well-preserved and abundant in the seafloor of the North Pacific, and the high levels of radiolarian preservation and abundance in deep-sea sediments of this region have facilitated numerous paleoceanographic and biostratigraphic studies (e.g., Hays, 1970; Kling, 1973; Foreman, 1975; Morley et al, 1982; Motoyama, 1996; Pisias et al, 1997; Matul et al, 2002; Kamikuri et al, 2004, 2007; Matul and Abelmann, 2005; Itaki et al, 2012; Matsuzaki et al, 2014a–c, 2015a; Kamikuri, 2017).

Methods

Findings

Discussion

Conclusion