Palynoflora and climatic dynamics of the Laizhou Bay of Bohai Sea, North China Plain, since the late middle Pleistocene

The coastal plain of Laizhou Bay in Bohai Sea is a transitional area of land–sea interaction. Sediments in this area can bear significant information of sea-level fluctuation, climate change, as well as regional geological setting. Here, in this study, new sporopollen data from three boreholes (GK138, GK111 and GK95) in the coastal plain of Laizhou Bay, Bohai Sea were investigated, and the pollen spectrum since the late middle Pleistocene was established as six sporopollen assemblage zones (I–VI), i.e., Pinus–Quercus–Artemisia, Gramineae–Artemisia–Chenopodiaceae, Picea–Pinus–Quercus–Artemisia, Picea–Pinus–Betula–Gramineae–Artemisia, Picea–Pinus–Cupressaceae–Chenopodiaceae and Pinus–Quercus–Gramineae–Artemisia–Chenopodiaceae. Combining with existing sedimentary successions and detailed radiocarbon dating results of the sediments from the three boreholes, paleovegetation and climatic evolution since the late middle Pleistocene were reconstructed. The findings revealed that climatic changes in this area since the late middle Pleistocene were characterized by alternating cold-arid and warm-humid conditions, which were well correlated with marine isotopic stages (MIS). The present study offers specific insight into the climatic dynamics in the North China Plain since the late middle Pleistocene and provides evidence of a clear link among the palynoflora in the area, the glacial–interglacial period climate-driven sea-level changes, and the marine δ¹⁸O records.