Relative Paleointensity Recorded in the Core from Northwestern Philippine Sea over the Last 125 ka and Its Influencing Factors

Abstract

Relative paleointensity (RPI) from sediments provides constraints for geomagnetic field modeling and also the age information of deposits. The relative paleointensity in a core from the northwestern Philippine Sea was reported and its possible influencing factors including rock magnetic and sedimentological property are examined. Except for the rotation of declination in the brown clay at lower part of the core, both directions of anisotropy of magnetic susceptibility and of the geomagnetic field indicate original sedimentary nature. The magnetically uniform sediment conforms to the requirement for relative paleointensity study and the correlation of relative paleointensity proxies NRM/ARM and NRM/κ with PISO1500 and SINT800 produces depth‐age tie points. The sparse oxygen isotopes on paleointensity chronology in this core agree with the global stack LR04, confirming the correlation of paleointensity. NRM/κ is usually lower than NRM/ARM and the latter has no correlation with ARM and ARM/κ and also no astronomical period, but the former is correlated with ARM/κ and κ and a period of 13∼12 ka by spectral and coherence analysis. Therefore NRM/ARM is regarded to shun off imprint of climate. Further investigations of the intensity difference and its influence elements find that differences between NRM/ARM and NRM/κ vary with the super‐paramagnetic content and magnetic size variation, and the latter contributing 90% of the difference. Other elements like carbonate percentage and mineralogy change are not responsible for the difference. How to correct the effect of magnetic size on paleointenstiy estimation is the focus of further work.