Event-like enrichment of beryllium isotopes and rare-earth elements at ~10.2 Ma from IODP Site U1430, Ulleung Basin (East Sea)

Abstract Marine sedimentary archives can preserve transient perturbations to the Earth system, including potential inputs of extraterrestrial material. While evidence for nearby supernova activity during the late Pliocene–Pleistocene has been identified using cosmogenic and interstellar radionuclides (Wallner et al., 2016; Koll et al., 2025), comparable records from older Miocene sediments remain limited. Here we present authigenic beryllium isotope (¹⁰Be and ⁹Be) and rare-earth element (REE) records from Integrated Ocean Drilling Program (IODP) Expedition 346 Site U1430 in the Ulleung Basin (East Sea). A pronounced anomaly centered at ~ 10.2 Ma is characterized by a sudden, high-amplitude increase in decay-corrected cosmogenic ¹⁰Be accompanied by synchronous enrichment of stable ⁹Be and authigenic REE, observed independently in two sediment cores. The magnitude, abrupt onset, and short stratigraphic duration of this coupled signal are inconsistent with gradual sedimentary, climatic, or oceanographic processes alone. Although authigenic ⁹Be can vary under terrestrial conditions (von Blanckenburg and Bouchez, 2014), its coeval enrichment with cosmogenic ¹⁰Be indicates an event-like perturbation consistent with transient extraterrestrial material input. These results provide robust geochemical constraints on an anomalous external contribution to the Earth system during the late Miocene.