[M-IS03] Evolution and variability of the Asian Monsoon and Indo-Pacific climate during the Cenozoic Era

[MIS03-P05] Precession control on coarse fraction in the western Pacific warm pool sediment during Plio-Pleistocene periods

*佐川 拓也¹、久保田 好美²、Saeidi Ortakand Mahsa² (1.金沢大学理工研究域、2.国立科学博物館)

キーワード：西赤道太平洋暖水塊、粗粒画分、国際深海科学掘削計画

Orbital-scale paleoenvironment change provides keys to understanding the Earth’s climate system. Coarse fraction of carbonate ooze sediments has been used as a proxy for bottom water carbonate chemistry as it closely relates to fragmentation of foraminiferal shell. Previous studies showed that the variability of coarse fraction in the tropical Pacific sediment cores had eccentricity cycle, suggesting the orbital control on the global carbon cycle. However, little is known about its relationship to orbital parameters with higher frequencies, i.e., precession and obliquity. Here, we investigate coarse fraction of IODP Site U1488 with 2-kyr spacing and benthic oxygen isotope stratigraphy. The result shows clear periodicities related to Milankovitch cycles, but their relative strength and phase relationship changed across the mid-Pleistocene transition (MPT). Obliquity signal is more dominant before MPT, whereas precession and eccentricity are more dominant after MPT. The relationship between coarse fraction and precession parameter changed from negative to positive correlation across the MPT. These results imply that the mechanism of orbital control over the global carbon cycle varies with the Earth’s climatic condition.