Dating pelagic sediments from the northwestern Pacific Ocean by integration of Multi-geochronologic approaches

As the largest promising rare earth elements and yttrium (termed as REY) resource in the world, pelagic sedi-ments enriched in REY (REY-rich sediments) have gained extensive attention. However, the mechanism responsible for the enrichment of REY in pelagic sediments remains unknown, primarily due to the challenge of obtaining robust geochronology. Despite previous attempts, integration of multi-geochronologic approaches seems better suited to determine robust geochronology for pelagic sediments. Here, we present a continuous chronostratigraphic framework for a pelagic sediment core collected from the northwestern Pacific Ocean, integrating authigenic 10Be/9Be dating, 230Thex dating, and magnetostratigraphy. Our results indicate that the REY-rich sediments deposited prior to -2.5 Ma, and a highly REY-rich sediment layer deposited at -11.5-9.5 Ma in the study area. We suggest that a low sedimentation accumulation rate (SAR) was necessary for REY enrichment in pelagic sediment, while the deposition of highly REY-rich sediments should be attributed to the additional contribution from active bottom currents. Our study proposes that the enrichment of bioapatite fossils and micronodules related to enhanced bottom currents under a low SAR sedimentary environment could pro-mote the widespread highly REY-rich sediments in the study region.