The rare earth elements and yttrium (REY) in bioapatite from deep-sea sediments are potential proxies for reconstructing paleoenvironmental conditions. However, the REY enrichment mechanism and the reliability of this tracer remain elusive because of the lack of key information from ambient pore water. Here, we report high-resolution geochemical data for pore water, bottom water, and bioapatite from deep-sea sites in the western Pacific. Our results reveal that the benthic flux of REY from the deep sea is less substantial than from the shallow marine realm, resulting in REY-rich sediment. The depth distribution of REY in pore water is opposite to that of bioapatite, and REY patterns and neodymium isotopic compositions are not uniformly distributed within bioapatite. These results indicate alteration of REY and neodymium isotopic compositions during early diagenesis. Therefore, we infer that REY from bioapatite are not robust recorders of the deep marine environment through Earth’s history.

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The Philippine Sea is a well-preserved, extinct, marginal basin, and due to generally deeper than the carbonate compensation depth, the geochronology and its geological significance of the abyssal sediments are less studied in previous researches. In this work, we studied the magnetostratigraphy of four gravity cores from the centre of the West Philippian Basin and establish a reliable chronology for sedimentary sequences in the Pleistocene. The main results include: (a) several magnetozones are recognized in the studied four cores, which can be correlated to the geomagnetic polarity timescale from chrons C1n to C2An (0-3.0 Ma); (b) since~1.2 Ma, the depositional rates across the West Pacific are relatively consistent, about 160-250 cm/ Myr; (c) a transition in depositional rates around~1.2 Ma was identified in the studied area, from a spatial variety in the Early Pleistocene to a persistent pattern since the Middle Pleistocene. Based on these findings, we report that this sedimentary shift in the Philippian Sea can be correlated to global climate changes during the Mid-Pleistocene transition, representing a major change in the studied area. Therefore, we suggest that the sedimentary processes in the studied area can be linked to a common shift in palaeoclimatology across the inner Asian continent, the Philippian Sea, and the tropical Pacific during the late Early Pleistocene.