冲绳海槽表层沉积物中浮游有孔虫壳体的氧同位素分布特征及其影响因素

选择冲绳海槽的3个剖面A、B、C上的现代表层沉积物样品，对浮游有孔虫Globigerinoides ruber、Glo-bigerinoides sacculifer和Neogloboquadrina dutertrei进行了氧同位素分析，结果表明，几乎所有样品从G.ruber到G.sacculifer到N.dutertrei其氧同位素值均由轻变重，表明3种有孔虫其生活水层依次由浅到深，进一步证实了这3个种的生态生活习性在冲绳海槽区域与开放大洋同样一致，在槽穿海槽的A、C两个剖面上，G.ruber和N.dutertrei的氧同位素有相似的变化，从西向东氧内闰素值依次由轻变重，然后又变轻，表明剖面西侧站位有孔虫壳体氧同位素因受冲淡水影响较强而变轻，而在东侧站位受高温黑潮的影响氧同位素同样有变轻的趋势，沿海槽轴向展布的剖面B上的氧同位素变化主要受冲淡水的影响，表层水体在剖面中部和南端冲淡水影响相对较大，而次表层水只在剖面南端受冲淡水影响相对较强，剖面A、C上的N.dutertrei和G.ruber的氧同位素差值有着相反的变化趋势，在剖面A上，氧同位素差值从近陆端向近岛弧端逐渐由小变大，而在剖面C上，则逐渐由大变小，上述变化可能表明了磁部区域黑潮支流对表层水体的影响要大于次表层水体，而在南部海槽区域，黑潮暖流对次表层水体有相对较强的影响。

OXYGEN ISOTOPE DISTRIBUTION CHAR ACTERISTICS AND INFLUENCING FACTORS OF PLANKTONIC FORAMINIFERAL TESTS IN SURFA CE DEPOSITS OF THE OKINAWA TROUGH

Oxygen isotope analysis of planktonic foraminifera( Globigerinoides ruber,Globigerinoides sacculifer and Neogloboquadrina dutertrei )is made for modern surface deposits from 3 sections(A,B and C) in the Okinawa Trough.The analysis results show that oxygen isotopic values of Globigerinoides ruber,Globigerinoides sacculifer and Neogloboquadrina dutertrei in the samples all turn from light to heavy,indicating that these 3 foraminifer species lived in successively deeper water environments in the same ecologic manner as in open oceans.On the sections A and C that go across the trough, G.ruber and N.dutertrei have similar changes in oxygen isotope values,which show the tendency of light-heavy-light from west to east,implying that foraminiferal tests give a light oxygen isotopic value due to the influences of freshening water in the west of the sections,and also oxygen isotopic values tend to be lighter because of high temperature kuroshio in the east of the sections.Oxygen isotopic changes from section B extending along the trough axis are mainly controlled by freshening water.Surface water is greatly influenced by freshening water both at the central and south parts of the section,while secondary surface water is given the influence only at the south part of the section.Differences in oxygen isotopic values of N.dutertrei and G.ruber show an opposite change tendency on sections A and C. On section A,oxygen isotopic value difference becomes larger gradually from near land part to near island arc part,but on section C,the difference becomes smaller gradually.The above mentioned changes have indicated that,in the north of the trough,kuroshio tributary has a larger influence on the surface water than on the secondary surface water,while in the south of the trough,kuroshio current has a very strong influence on the secondary surface water.