HOLOCENE SEDIMENTARY SEQUENCE, FORAMINIFERA AND OSTRACODA IN WEST COASTAL LOWLAND OF BOHAI SEA, CHINA

The Holocene sedimentary sequences in the west coastal lowland of the Bohai Sea consists in ascending order of: pre-transgression river and lake sediments, transgressive tidal flat and estuarine sediments, shel f sediments, and prograding delta and river deposits. The delta deposi ts are the thickest and are typically composed of two imbricating Yell ow River delta super-lobes that acted at different periods. There are three marker horizons in the sequence at: (1) the bottom of marine sed iments; (2) the bottom of shelf deposits; and (3) the boundary between two imbricating delta superlobes. Environmental changes were mainly c ontrolled by a rising sea level prior to 6000 BP and by delta prograda tion after 6000 BP. Stratigraphic distribution of foraminifera and ost racoda vary according to variations in salinity and sedimentation rate . There is no evidence that the Yellow River delta developed during th e Holocene transgression but rather during a later prograding phase. A n understanding of the shelly ridges in the coastal lowland indicates that the ridges were formed at a similar level to the present and ther e is no evidence for Holocene sea levels 1-2 m higher than the present sea level.