Ostracods reveal the palaeoenvironmental changes in Laizhou Bay, Bohai Sea (eastern China) since the Late Pleistocene

Abstract

Laizhou Bay is located in the Bohai Sea, eastern China. Since the Late Pleistocene, Laizhou Bay has gone through frequent transgressive and regressive activities and both marine and non-marine sediments have been deposited. In order to further understand the palaeoenvironmental changes since the Late Pleistocene, a core (DK06) was drilled on the coastal plain of Laizhou Bay. From this core, we obtained abundant well-preserved ostracod specimens. After environmental analysis and cluster analysis of these ostracods, four biofacies have been recognised: Biofacies I (shallow marine facies), Biofacies II (estuarine facies), Biofacies III (brackish water facies), Biofacies IV (freshwater facies). The studied ostracod assemblages suggest that the palaeoenvironment of Laizhou Bay went through four transgressions including three well-known marine transgressions during MIS 1, MIS 3 and probably MIS 5 and three regressions since the late Pleistocene, indicating substantial impact of glacial-interglacial sea level changes on the Bohai Sea coastal areas and their biota.