[B-PT05] Decoding the history of Earth: From Hadean to Modern

[BPT05-22] Cretaceous to Paleogene deep-water agglutinated foraminifers in the western North Pacific pelagic sediments

*Junichiro Ohta^1,2, Kentaro Nakamura², Kazutaka Yasukawa^2,3, Koichiro Fujinaga^3,2, Koichi Iijima¹, Hikaru Iwamori^1,4, Yasuhiro Kato^2,1,3 (1.Japan Agency for Marine-Earth Science and Technology, 2.School of Engineering, the University of Tokyo, 3.Chiba Institute of Technology, 4.Graduate School of Engineering, Tokyo Institute of Technology)

Keywords:deep-water agglutinated foraminifers, K-Pg boundary, pelagic sediments, western North Pacific Ocean

Deep-water agglutinated foraminifers (DWAF) are often composed of the only microfossils well-preserved in pelagic sediments without calcareous and siliceous fossils. DWAF have been studied for a long time for determining a stratigraphic succession and obtaining paleoecological information. While their quantitative distributions in sediments from the Atlantic Ocean were well-documented (e.g., Kuhnt et al., 1992), those from the Pacific Ocean have not been studied sufficiently enough to establish the stratigraphy. Wightman and Kuhnt (1992) investigated DWAF in the sediment cores drilled at Deep Sea Drilling Project Sites 196 and 198, and Ocean Drilling Program Sites 800 and 801 in the western North Pacific Ocean. They reported that the faunal density and diversity of DWAF rapidly declined across the horizon that approximately corresponds to the Cretaceous/Paleogene (K-Pg) boundary.
Recently, we constructed lithological description, including microfossils, for a pelagic sediment core of KR13-02 PC05 collected from the western North Pacific Ocean, and recognized a rapid decline of the density and diversity of DWAF across a spherule-rich layer. The spherules have a very similar appearance to those associated with the Chicxulub impact at the K-Pg boundary. We present a distribution of DWAF across the spherules-rich layer in the core and discuss its paleoceanographic implications.