第九届青年地学论坛

Quaternary sediment of the South Yellow Sea (SYS) is usually assumed to record both climatic changes, tectonic activities and major river evolutions. However, as an important terrigenous indicator, long sequence of pollen proxy in the SYS was lack for studies of river provenance and climate changes. In this study, we focused on a 150 m pollen record in the SYS that covered most Quaternary period over the past 1.7 Ma. Result shows that high pollen percentages of broadleaved trees such as Castanea/Castanopsis, reflect a dominant provenance of the Yangtze River since ca. 1.8 Ma, and there was a decline trend during the Mid-Pleistocene transition (MPT) mainly between 1.1 and 0.8 Ma. The sharp increase in coniferous pollen, in particular Picea, originated from the Yellow River drainage areas, suggests a major alternation in terrigenous pollen source from the Yangtze River to the Yellow River at ~0.8 Ma, which agrees well with the timing of the final integration of the modern Yellow River. The high pollen amount of Artemisia and Ephedra also shows the enhanced Yellow River provenance where most landscape was covered by semi-arid open vegetation (e.g. steppe). The alternate appearances of marine fossils of foraminifer, dinoflagellate and freshwater wetland (Cyperaceae) through the interglacial intervals from MIS 19/21 demonstrate different estuary sedimentary environments and divers salinity. The pollen concentration suggests the increased terrigenous materials towards the interglacial MIS 11 and the preliminary delta formation of Yellow River. Our data also reveal that the insolation variations caused by obliquity cycles may resulted a spatial change in broadleaved forest distributions. We propose that the terrigenous input from the Yellow River accelerated since the MPT, and combined effect of climate change and tectonic movement drove the evolution of the river delta plains in eastern China.
 

Pollen analysis, Vegetation, Provenance, Middle Pleistocene Transition, South Yellow Sea