南海北部17924站位氧同位素3期古海洋学变化

PALEOCEANGRAPHIC VARIATIONS OF THE NORTHERN SOUTH CHINA SEA FROM SITE 17924 DURING MARINE ISOTOPE STAGE 3

文章选用采自南海东北部冬季风上升流区的17924-2沉积柱状样(19°24.7′N,118°50.8′E;水深3440m),对浮游有孔虫绝对丰度和碎壳率进行分析,并与南海西部越南岸外夏季风上升流区的17954站位(14°47.8′N,111°31.5′E;水深1515m)进行对比。由于这两个站位具有不同的碳酸盐旋回类型,它们对东亚冬、夏季风也有着不同的反馈。东亚冬季风主要由高纬过程驱动,位于溶跃面之下的17924站位的浮游有孔虫绝对丰度和碎壳率呈反相变化,其碳酸盐旋回主要受溶解作用的影响,且浮游有孔虫绝对丰度对北半球的高纬信号Heinrich事件有着很好的响应;而位于溶跃面之上的17954站位碳酸盐旋回主要受表层生产力和稀释作用的影响,其浮游有孔虫绝对丰度对夏季风带来的降水和陆源输入的影响有明显的反馈。

Site 17924 is located in the northeastern .South China Sea （19°24.7＇N, 118°50.8＇E）, in the modern winter monsoon upwelling area, with a water depth of 3440m. Planktonic foraminiferal abundance, the fragmentation and coarse fraction of the sediment records of Core 17924 -2, are analyzed and compared data from its counterparts of Core 17954 in the southwestern South China Sea（ 14°47.8＇N, 111°31.5＇E） ,with a water depth of 1515m,which shows an intensified summer upwelling. Two different types of carbonate cycles were identified in these two sites. The Planktonic foraminiferal abundance and coarse fraction of Core 17924-2 shows distinct Heinrich events（H3 H6,30 -29ka B. P.,40 -38ka B. P.,46 -45ka B. P.,54 -52ka B. P. and 60 -59ka B. P. ） ,which suggested the northern high latitude processes had a strong influence over East Asian winter monsoon. Meanwhile,the variations of fragmentation showed good correlation to Dansgaard-Oeschger interstadial events（ IS 3 -17） , but were in anti-face to the planktonic foraminiferal abundance records. The carbonate content of Core 17924-2 below the lysocline, which was mainly affected by dissolution. And the ＂ Pacific type＂ carbonate cycle was observed. The planktonic foraminiferal abundance of Core 17954 above the lysocline was affected by surface productivity and terrigenous dilution. The carbonate cycle was ＂Atlantic type＂. Both of the sediment records of the two sites were related to the changes of East Asian monsoon.