Abstract:
The history of the environment of the northern continental shelf of the South China Sea during the last 280 ka BP, e.g. Marine Isotope Stages 1-8 (MIS 1-8), was reconstructed based on the pollen record from the top 225 m of ODP Site 1144. During the interglacial periods, pollen assemblages are dominated by pine, similar to those of the present day, indicating that the environment during the interglacial periods was more or less close to that of today. Nevertheless, those from glacial periods are characterized by a large amount of herbaceous pollen, e.g. Artemisia, Gramineae, Cyperaceae, etc., inferring that grasslands covered the merged continental shelf when the sea level lowered and the continental shelf was exposed. The exposed areas of the shelf were insignificant before MIS 5, but enlarged since MIS 4 and reached their maximum during MIS 2 according to ratios of pollen percentages between pine and herbs. The history of different exposures of the shelf can be compared with transgression records of the coastal areas of China, and might result from neotectonic movement of the Chinese continent. Some changes also took place in the components of grasslands growing on the shelf during glaciations. Gramineae is the main element during MIS 8. Then Artemisia increased upwards through the profile and at last became the main component at the Last Glacial Maximum (MIS 2). Such changes in vegetation might have occurred in response to a cooler and drier climate.