南海表层沉积钙质超微化石氧碳同位素研究

PRELIMINARY STUDY ON THE OXYGEN AND CARBON ISOTOPE OF CALCAREOUS NANNOFOSSILS IN SURFACE SEDIMENTS OF THE SOUTH CHINA SEA

对南海34个站位表层沉积中的钙质超微化石进行了氧碳稳定同位素分析.结果表明,钙质超微化石δ18O变化范围为-2.656‰～0.006‰,平均为-1.517‰;δ13C值变化范围为-1.510‰～0.778‰,平均为0.140‰.通过与有孔虫同位素分析结果相比较,发现钙质超微化石δ18O值高于浮游有孔虫而低于底栖有孔虫,δ13C值低于浮游有孔虫而高于底栖有孔虫.从平面分布来看,南海表层沉积钙质超微化石氧同位素在东北和西南各存在一个小于-1.5‰的低值区,碳同位素在东北存在一个小于0的低值区.钙质超微化石与有孔虫同位素值的差异性可能与其生命效应及生活环境有关.而钙质超微化石与有孔虫同位素平面分布规律上的不同也揭示了海水温度、盐度、营养水平等海洋参数可能对超微化石和有孔虫同位素的分馏起不同控制作用.

Oxygen and carbon isotopic analyses have been carried out on calcareous nannofossils in 34 surface sediment samples from the South China Sea. The results demonstrated that the δ^18O values of calcareous nannofossils is from -2. 656%o to 0. 006‰ and the average 3180 value -1. 517‰. The 313C value of nannofossils is from -1. 510‰ to 0. 778%o and the average δ^18O value 0. 140‰. By comparison with the isotopic data of planktonic and benthic foraminifera, it is found that the δ^18O value of nannofossils is higher than that of planktonic foraminifera but lower than that of benthic foraminifera. It is also found that the δ^18O value of nannofossils is higher than that of benthic foraminifera but lower than that of planktonic foraminifera. There is a depleted δ^18O value tongue at the northeastern and southwestern ends of the South China Sea respectively. And there is also a depleted δ^18O value tongue at the northeastern end. The isotopic difference between nannofossils and foraminifera may be caused by the vital effect of them and by the different water depth they lived. Temperature, salinity and nutrient level control the different pattern of isotope of both nannofossils and foraminifera in surface sediment.