Barbados岛珊瑚礁高精度铀系年龄及讨论  

HIGH PRECISION DATING AND DISCUSSION OF CORAL REEFS FROM BARBADOS WITH U SERIES METHOD

作　　者：马志邦[1] 夏明[1] 张承蕙 王兆荣[2] 彭子成[2] 孙卫东[2] 

机构地区：[1]中国科学院地质研究所 [2]中国科学技术大学地球和空间科学系

出　　处：《地质科学》1999年第1期116-122,共7页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金

摘　　要：应用同位素稀释法热电离质谱（ＴＩＭＳ）技术测定珊瑚礁的高精度铀系年龄。通过对ＢａｒｂａｄｏｓⅢ、Ⅳ阶地等样品分析，ＲｅｎｄｅｚｖｏｕｓＨｉｌ和Ｃｕｒａｃａｏ＋６ｍ的ＴＩＭＳ年龄分别为１２９．２±１．２ｋａＢ．Ｐ．和１２５．４±１．１ｋａＢ．Ｐ．，对应深海沉积物氧同位素第５期５ｅ段的高海面；Ｋｅｎｄａｌ山阶地为２０８．１±１．９ｋａＢ．Ｐ．，可能代表７ｃ间冰期高海平面的时代。该结果与Ｅｄｗａｒｄｓ等测定同一阶地的年龄一致，与α谱法数据在误差范围内吻合。另外，探讨了初始铀同位素比值的变化。We have developed newly technique to measure 230 Th abundance in corals by isotope dilution thermal ionization mass spectrometry (TIMS).This has alowed us to reduce significantly the counting statistics for U and Th isotopes and greatly reduce the sample size.So it is suggested that with high precision TIMS technique,the ages of coral from Barbados might be given.Five samples of coral have been analyzed with TIMS. The results of TIMS dating show that the ages of B 1,B 2 and B 3 are 129.2±1.2ka(Rendezvous Hill),125.4±1.1ka(Curacao+6m)and 208.1±1.9ka B.P.(Kendal Hill),respectively,which corresponding to a high sea level of substage 5e and 7c of the oxygen isotope records from deep sea cores.The Rendezvous Hill and Curacao ages are the same as those reported by Edwards et al.For five samples,the agreement between the ages determined by TIMS and the previously ages determined by α counting is generally good within the error limits.The error in age,based on analytical errors,for the TIMS measurement is about ten times smaller than the error in age for the α spectrometric measurement. The results of this study suggest that the change in isotopic compositions for the high precise analysis is probably from post depositional alteration.It would not be detected by thin section or x ray diffraction examination,because higher initial uranium isotope ratios were obtained from samples that met criteria for reliable ages as discussed previously.However,improvement the identify and tests level of the minerals are adequate for obtained reliable ages of TIMS.

关 键 词：Barbados岛 珊瑚礁 铀系 年龄 古气候 

分 类 号：P588.248[天文地球—岩石学] P532[天文地球—地质学]