南海北部晚第四纪高分辨率浮游氧同位素地层学及其古气候信息

对南海北部MD05-2904孔45 m的连续沉积物中提取的浮游有孔虫Globigerinoides ruber(白色)进行稳定同位素分析, 得到晚MIS 8以来(时间跨度257 ka, 平均时间分辨率228 a)的高分辨率沉积记录, δ18O和δ13C的频谱分析显示了强烈的岁差(23.4 ka、19.8 ka)、半岁差(11.7 ka、9.9 ka)周期.MD05-2904孔MIS 24时间段的氧同位素记录了格陵兰冰心中发现的Dansgaard/Oeschger和Heinrich事件.与葫芦洞石笋记录及南海邻区浮游有孔虫氧同位素记录的对比显示了受季风控制的区域因素, 如降雨、河流输入导致的盐度变化等对表层海水组成的影响.氧同位素在MIS 3、MIS 6的早期以及MIS 7.4偏轻; 而在MIS 5.5偏重, 这种现象解释为降雨量和蒸发量共同作用的结果.而末次冰盛期高达6570 cm/ka的沉积速率反映了低海平面时孔位离岸距离缩短带来丰富的沉积物源. 

Late Quaternary High Resolution Monsoon Records in Planktonic Stable Isotopes from Northern South China Sea

Oxygen and carbon stable isotope records (with an average time resolution of 228 a) were obtained from Core MD05-2904 (19°27.32', 116°15.15', water depth 2 066 m), using the mixed-layer dwelling planktonic foraminifer Globigerinoides ruber (white). The 45 m core spans from end of MIS 8 to the Holocene, representing the sediment record of the last 257 a. Strong precession periods (23.4 ka and 19.8 ka) were found from spectral analysis of both δ18O and δ13C records, following with semi-precession cycles (11.7 ka and 9.9 ka). The high resolution δ18O record of MD05-2904 reveals nearly all the Dansgaard/Oeschger and Heinrich events during MIS 2-4, as defined in the Greenland ice core record. A better correlation between MD05-2904 planktonic δ18O, the Hulu stalagmite δ18O record and previously published planktonic δ18O records from the SCS suggests that the planktonic δ18O record is influenced by monsoon-dominated regional factors, such as rainfall and river discharge related salinity changes. Lighter δ18O values in early MIS 3, early MIS 6 and MIS 7.4, and heavier values in MIS 5.5 are due to changes in precipitation and evaporation affected by monsoon. Sedimentation rates increased to 65-70 cm/ka in LGM, indicating more sediments when the site location was closer to the river mouth during glacial at lower sea level.