有孔虫稳定氧碳同位素实验处理、测试与应用

EXPERIMENTAL TREATMENT,MEASUREMENT AND APPLICATION OF FORAMINIFERAL STABLE OXYGEN AND CARBON ISOTOPES

本研究对位于葡萄牙岸外的IODP U1385站位一沉积物样品中的浮游有孔虫Globigerina bulloides进行不同前处理,其稳定氧碳同位素测试结果表明,在上机测试前无论是否打开壳体房室进行清洗以及是否对样品进行碾磨均一化处理,壳体的稳定氧碳同位素均未发生明显差异。在此基础上,研究对另两个浮游有孔虫属种Globorotalia truncatulinoides和Globorotalia inflata在不同样品量条件下进行打开房室和碾磨处理并测试,均发现当样品量适中时,稳定氧碳同位素值十分接近;而当样品过量时,稳定氧碳同位素值发生不同程度的正向偏移。50–80μg的样品量最佳,其对应的信号强度在仪器的最佳线性区间内。通过上述对有孔虫壳体不同前处理的比较研究,本实验平台确立了一套有孔虫壳体前处理和高质量稳定氧碳同位素测定的操作流程,为其他钙质微体化石如介形虫化石和轮藻化石的稳定氧碳同位素前处理和测试分析提供了重要参考。

Planktonic foraminifera Globigerina bulloides in a sediment sample retrieved from IODP Site U1385 drilled off the Portuguese margin was treated in different ways and measured before the isotopic analyses.The results suggested that whether the foraminiferal shells were poked with a needle and whether they were ground into powder prior to measurement had no obvious effect on the stable oxygen and carbon isotopes.Based on the results,another two planktonic foraminifera species Globorotalia truncatulinoides and Globorotalia inflata were poked,ground and measured but with different weights(specimens).The study found that when the sample weight was moderate,no significant difference was observed in stable isotopes.However,stable oxygen and carbon isotopes experienced positive excursions of varying degrees when the samples were excessive.50–80μg is a optimal weight which can ensure that the signal intensity is in a fine linear range of the Finnigan MAT 253 mass spectrometer.According to the comparative studies,an operation procedure for the high-quality stable oxygen and carbon isotopic measurement was established,thus expected to provide important reference for other calcareous fossil stable isotopic measurements.