Response of Magnetic Minerals to the Mid-Brunhes Climate Event Recorded in Deep-Sea Sediments of the West Philippine Sea

The Mid-Brunhes Event (MBE) was one of the most important global climate events since 800 ka. The deep-sea palaeoceanographic changes in the Western Pacific might have been more sensitive to the MBE and they have not been well documented yet. In this study, we investigated a deep-sea core collected from the Western Philippine Sea and then obtained the magnetism record since around 900 ka. The MBE signal in the deposition process was derived from the concentration-dependent (χ, χARM and SIRM) and the grain-size-dependent magnetic parameters (χARM/χ and χARM/SIRM). Across the MBE, the content of magnetic minerals and the fluctuation of the grain size decreased. Both the content and grain-size indices calculated from magnetic parameters are well correlated with the glacial–interglacial alternations and display a major shift at the MBE. The decreased grain size of magnetic minerals may be associated with the flourishing biota in the tropical Pacific during interglacial intervals. The accumulation of magnetic minerals in the Western Philippine Sea was mainly regulated by the sediment accumulation rate, which may be related to the shoaling of the carbonate compensation depth. Overall, this study expanded the environmental magnetism record for the MBE, suggested a new possible influence of this critical climatic event on the deep-sea deposition process in Western Philippine Sea and inferred the interactions between various environmental systems on glacial–interglacial timescales.