Detailed sea-level variation was investigated for Marine Isotope Stage (MIS) 19, based on diatom and grain size analyses of a marine sequence in a core of the Osaka Group. Diatom sea-level proxies represent precession-related signals correlated with highstands MIS 19.3 and 19.1, and lowstand MIS 19.2. Astronomical tuning shows the marine sequence has a uniform accumulation rate of about 60 cm ka−1. A rapid sea-level fall event was found in the earliest MIS 19, demonstrated by several independent sea-level proxies of diatom and grain size. This event began with a rapid sea-level drop, followed by a gradual recovery, at about 783–782 ka. A maximum abundance of pelagic diatom taxa at a core depth of 402.20 m evidently shows the highest sea-level peak in MIS 19, supported by many other proxies. Based on the diatom data, sea-level change across MIS 19.1 is characterized by centennial to millennial fluctuations. The sea-level fall event began just after the onset of a cooling event previously reported from the same core. Observations of a comparable sea-level fall signal in many deep-sea core records suggest the event is global.
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