FORAMINIFERAL Mg/Ca AND δ¹⁸O RECORDS IN THE MUD AERA OF THE EAST CHINA SEA DURING THE LAST 8 000 YEARS AND THEIR PALAEOENVIRONMENTAL IMPLICATIONS

The geochemistry of foraminiferal tests from the core MD06-3040,that was taken from the shelf mud area of the East China Sea (27°43.3663'N, 121°46.8822'E, water depth 47 m,core length 19.36 m), provides a high-resolution Mg/Ca and δ¹⁸O records of benthic foraminifera (Rotalinoides gaimardii) and planktonic foraminifera (Globigerina bulloides). By comparing with micropaleontological and sediment grain-size data, it is suggested that the changes in Mg/Ca and δ¹⁸O are controlled principally by the coastal current,warm current and the monsoon related. The paleoenvironmental history of the last 8 000 years has been proposed as following:between 8.0 and 4.1 cal.kaBP, the summer monsoon and the corresponding Taiwan Warm Current and Kuroshio Current were markedly enhanced, particularly during the 5.7~5.2 and 4.6~4.1 cal.kaBP periods, providing both the bottom and surface water with higher temperature, salinity and δ¹⁸O; during 4.1~0.7cal.kaBP period, the winter monsoon and the Zhe-Min Coastal Current prevailed, resulting in a marked decrease in temperature, salinity and δ¹⁸O of both the bottom and surface water, due to a great increase in the supply of the diluted water originated from the Changjiang and Qiantang rivers; after 0.4 cal.kaBP the summer monsoon and the warm currents prevailed again, causing a paleoceanographical condition similar to the early period.