HIGH-RESOLUTION PALEOCEANOGRAPHIC RECORDS DURING THE LAST 40 000 YEARS FROM THE NORTHERN SLOPE OF THE SOUTH CHINA SEA
南海北部陆坡近四万年的高分辨率古海洋学记录

A high sedimentation rate record of hemipelagic deposits was found in Core 17940 taken from the northern slope of the South China Sea (20°07' N, 1 17°23' E, w.d. 1 727m), about 400 kin southeast of Hong Kong, during the R/V SONNE cruise 95 in 1994. Based on magnetic susceptibility and stable isotope data, a composite-depth (c. d.) section was spliced. A total of 40 samples of Planktonic foraminifers Globigerinoides ruber or G. sacculifer have been measured for AMS 14C dating, and a high-resolution downcore sequence of oxygen and carbon isotopes of G. ruber s.s. (white) was obtained from samples in 1-2 cm interval.Judging from the results of isotopic analyses, the Holocene of the section reaches 6.5m in thickness, displaying the highest hemipelagic sedimentation rate in the South China Sea (40- 85cm/ 103a). Accordingly, a 1cm-sampling provides a bine resolution of less than 20 years for the Holocene. The glacial section displays a lower sedimentation of about 19 cm/ 103a in average. The Younger Dryas is clearly recorded as a major δ 18O increase by 0.7‰ and the total core length 13.30m has recorded a history of ca. 41 000 years.The range of frequent fluctuations in δ 18O reaches 0.7‰ or even 1.0‰ in the Holocene, reflecting the changes in precipitation driven by summer-monsoon implying subndllennial Periods of 775 years and 102 / 84 years in the East Asian monsoon regime. The δ 18O minima recorded in the glacial section obviously correspond to the bosgaard/Oeschger warm events recorded in the GISP2 ice core.Although the present paper is a brief report of the high-resolution stratigraphy and oxygen isotope records of core 17940, without detailed discussions on monsoon variations based on its siliciclastic grain-size, foraminiferal and pollen analyses, it is already clear that the hemipelagic depositS from the northern South China Sea are extremely promising in providing high-resolution records of East Asian Monsoons and environmental changes in the Western Pacific region.