Centennial- to millennial-scale change of Holocene shallow marine environments recorded in ostracode fauna, northeast Japan

Using the record of shallow-marine ostracode fauna and sediment grain size data from an 865-cm-long piston core obtained from Mutsu Bay, northeast Japan, paleoceanographic changes of the bay were determined at high resolution for the early to middle Holocene. Changes in the relative frequencies of several species showed periodicities of 1300–1800 years similar to Bond cycles. At around 10,300 cal yr BP and again, at 9500–9300 cal yr BP, cold water strongly influenced the bay owing to cooling events. Since at least 10,200 cal yr BP the Tsugaru Warm Current influenced the surface waters, and, since ca. 7400 cal yr BP, also the bottom waters of the bay. Since ca. 8400 cal yr BP the water depth rapidly increased and peaked at 7000–5900 cal yr BP due to global sea-level rise. Subsequently, a drop of water temperature and sea level in the bay at 5900 and around 4000 cal yr BP influenced the composition of the ostracode assemblages. These millennial-scale oscillations in relative sea level and bay temperature during the Holocene can be correlated to paleoclimate records elsewhere.