[B-PT05] 地球史解読：冥王代から現代まで

[BPT05-22] 北西太平洋の遠洋性堆積物中の白亜紀／古第三紀境界層付近における deep-water agglutinated foraminifers

*大田 隼一郎^1,2、中村 謙太郎²、安川 和孝^2,3、藤永 公一郎^3,2、飯島 耕一¹、岩森 光^1,4、加藤 泰浩^2,1,3 (1.海洋研究開発機構、2.東京大学大学院工学系研究科、3.千葉工業大学、4.東京工業大学大学院理工学研究科)

キーワード：deep-water agglutinated foraminifers、白亜紀／古第三紀境界、遠洋性堆積物、北西太平洋

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.