近2万年来南海北部与西部碳酸盐旋回及其古海洋学意义

CARBONATE CYCLES OF THE LAST 20ka IN THE NORTHERN AND WESTERN SOUTH CHINA SEA AND THEIR PALEOOCEANOGRAPHIC SIGNIFICANCE

通过对南海北部与西部５个活塞取心钻孔的碳酸盐系统分析，并结合部分年代学和有孔虫溶解指数资料研究，认为位于ＣＣＤ界面以上，以稀释作用为主的半深海陆坡区碳酸盐沉积旋回有如下特点：近２万年来区内碳酸盐旋回可以分为６期，并具一定的普遍性和可比性；与同位素和气候旋回相比，碳酸盐旋回在时间上存在“超前”现象，超前时间为１—２ｋａＢ．Ｐ．；早冰后期，约相当于７．０－８．０ｋａＢ．Ｐ．期间，区内存在一次低碳酸盐事件，起因可能主要与区域降温有关。

Systematic carbonate analysis for 5 piston cores drilled in the northern and western South China Sea has been carried out.Sampling intervals were 4—8cm respectively. Following knowledges for the carbonate cycles occurring in the bathyal environment of continental slope(above CCD)of the South China Sea come from carbonate analysis with 14 C dating and foraminiferal indicator of carbonate dissolution. 1.Carbonate cycles of the last 20ka B.P. within the study area could be divided into 6 stages,which locally demonstrate certain universality and compatibility. 2.Compared with oxygen isotope cycles and climatic cycles,the carbonate cycles show the feature of “time lead”,approximately 1—2ka B.P. 3.During the early glacial stage,there was a lower carbonate event,occurring in about 8 0—7 0ka B.P.,which chiefly resulted from the dropping in temperature,and secondly from the increasing of dissolution.