Geo-environmental changes since the Late Pleistocene recorded by Borehole DC01, the southwest plain of Bohai Bay

Geo-environmental history since the Late Pleistocene was reconstructed by the study of litho-, bio- and chronostratigraphy and geochemistry of Borehole DC01 drilled in the southwest plain of Bohai Bay. Before the Holocene, the study area had experienced environmental transformation of river- salt marsh- upper intertidal/lower salt marsh-estuary-lagoon-desalinated lagoon environments. During the Holocene, the area changed from lacustrine to fluvial environment. The less marine- influenced sediments, nearly 10m thick, were found at the depth of 22.4~12.7m. AMS ¹⁴C ages show that such sediments were formed earlier than 4.35ka cal BP, thus probably during the earlier stage of MIS 3 (6.0~5.5ka cal BP) or even MIS 5 (12~8ka cal BP). Relative sea level for this period was also reconstructed with a highest elevation at -13.31m. Borehole DC01 lacks the sediments deposited in the period of MIS 4~2 or MIS 2.