Late Quaternary polycystine radiolarian datum events in the Sea of Okhotsk

Abstract.

Five radiolarian datum events have been recorded in the Late Quaternary sediment section from the Sea of Okhotsk, using age assignments based on oxygen-isotope stratigraphy: the last occurrence datum (LOD) of Stylacontarium acquilonium (at about 329 ka), the LOD of Spongodiscus sp. (at about 287 ka), the LOD of Amphimelissa setosa (at about 72 ka), the LOD of Lychnocanoma nipponica sakaii (at about 28 ka), and the L. nipponica sakaii acme event (at about 72 ka). The LODs of S. acquilonium, Spongodiscus sp. and A. setosa appear to be synchronous in comparison with those in the Subarctic North Pacific, but the LOD and the acme event of L. nipponica sakaii show an apparent diachroneity with the corresponding North Pacific events.