Geomagnetic paleointensity variations in the northern South China Sea since the Late Pleistocene

Abstract

The geomagnetic field plays multiple roles in the investigation of the geodynamic processes of Earth's internal fluids and dating of deposition sequences. However, discrepancies in geomagnetic field intensity on suborbital and millennial time scales across different regions have hindered discussions on these topics. In this study, we constructed a master relative intensity curve (SPIS-150) covering the past ∼150 kyr by stacking the data from a new core (PC27) with published intensity curves for the northern South China Sea based on the chronology established through the oxygen isotope stratigraphy and relative paleointensity (RPI) correlation. Rock magnetic experiment results reveal that the sediments effectively record geomagnetic field information, although the magnetic minerals are primarily composed of terrestrial and biogenic magnetite. The stacked relative paleointensity (SPIS-150) exhibits a consistent pattern with the global stacked master curve on the orbital time scale, reflecting dipole-dominated changes in the geomagnetic field. However, specific features, such as the profound intensity lows between 75 and 85 kyr and a relatively low peak during 110–120 kyr, display potential differences with the global stacked virtual axial dipole moment (VADM) curves. Additionally, the disagreement in RPI across different regions have emerged significantly since about 25 kyr. Our record appears to align with the western tropical Pacific Ocean and the southern hemisphere but, to some extent, contradicts the stacked VADM from the northern hemisphere. This pattern may indicate the possible influence of reverse flux patches along the magnetic equator and normal flux patches in the north hemisphere.