Holocene ostracode paleobiogeography in Osaka Bay, southwestern Japan

Osaka Bay, at the east end of the Seto Inland Sea, southwestern Japan, was formed and enlarged by the transgression after the end of the last glacial maximum. The outline, area, and water conditions (e.g., salinity and current strength and direction) of Holocene Osaka Bay mainly depended on sea-level changes. Holocene ostracodes were studied in eight cores from the Bay and adjacent areas, to examine temporal changes in the fauna. Eighty-one ostracode taxa were identified in 81 samples. Changes in ostracode faunas in space and time provide information that enabled us to reconstruct a detailed paleobiogeography of the Bay. Ostracode migrations and faunal changes concomitant with sea-level changes and the opening of straits could be clearly identified on paleogeographical maps. We thus provide a detailed, high-resolution record of the Holocene paleobiogeography of inner bay ostracodes in Osaka Bay.