南海NS90－103沉积物柱样沉积年代研究

A STUDY ON THE DATING OF DEPOSIT CORE NS90-103FROM THE SOUTH CHINASEA

本文结合浮游有孔虫氧同位素地层学和不平衡铀系测定沉积速率的方法来确立取自南沙海域的沉积物柱样（ＮＳ９０－１０３）的时间坐标、根据连续取样获得的δ（１８）Ｏ曲线可以将该柱划分为７个主要气候期次，底部（５５０ｃｍ）相当于氧同位素第７．４阶到第７．５阶之间，年龄约２３８ｋａ；而根据不平衡铀系的过量（２３０）Ｔｈ方法获得２．３ｃｍ／ｋａ的沉积速率，计算出底部年龄为２３９ｋａ；两个结果在误差范围内完全一致。

The sediments from the core NS90-103 from the South China Sea were dated by the oxygen isotopic stratigraphy established by planktonic foramilifera Globigerinoides Sacculifer and deposit accumulating rate established by uranium series disequilibrium method. The curve of δ￣(18)O value vs. depth of samples collected continuously from the core NS90-103, shows that the core had spanned 7 main climatic periods and the lowest end of the core (550cm in depth) was equal to the period between oxygen stage 7.4 and stage 7.5, which was about 238ka in age. A deposit accumulating rate of about 2.3cm/ka was obtained by measuring excess￣(230)Th of the deposits. According to this rate, the age of the lowest end of core NS90-103 was about 239ka, which was concordant with that of the oxygen isotopic stratigraphy.