摘要
在地质历史时期中,海相碳酸盐的锶同位素组成具有全球基本一致的演化规律,并且海水锶同位素组成受锶的来源控制,其比值与海平面的变化有内在的联系。西藏岗巴地区晚白垩世—古近纪早期地层发育良好,笔者对宗山、宗浦两个剖面中未经蚀变的26个海相碳酸盐样品进行锶同位素测试,根据得出的数据绘制演化曲线与全球锶同位素曲线有较好的可对比性。曲线的负偏极值与地层界线较为一致,宗山剖面曲线的负向峰值(0.707612)与上/下白垩统界线相对应,宗浦剖面中,锶同位素曲线的负偏值(0.707761)与古新统/始新统界线相对应,晚白垩世—古近纪锶同位素演化曲线也与海平面变化相一致。另外,还讨论了岗巴地区锶同位素变化的原因。
In the geologic record, the strontium isotopic composition of marine carbonate reflects the evolution of the global strontium balance between reservoirs. This balance is thus inherently related to changes in sea level through time. Late Cretaceous-early Paleogene strata in the Gamba area, Tibet, are well developed. Strontium isotope analysis was performed on 26 unaltered oceanic carbonate samples from sections in Zongshan and Zongpu and the evolutionary curve drawn by the data obtained is well correlated with the global oceanic strontium isotope record. The negative extreme values of the curves are nearly consistent with the negative extremes of the stratigraphic boundaries. The negative peak value （0.707612） of the curve of the Zongshan section corresponds to that of the Upper/Lower Cretaceous boundary, and the negative extreme value （0.707761） of the curve of the Zongpu section corresponds to that of the Paleocene/Eocene boundary. The Late Cretaceous-Paleogene strontium isotope curve also agrees with the known sea level change. In addition, the cause for the change in strontium isotope values in the Gamba area is discussed.
出处
《中国地质》
CAS
CSCD
2008年第4期598-607,共10页
Geology in China
基金
国家"973"项目(G2006CB701403)
国家自然科学基金项目(40672020)资助
关键词
西藏岗巴
锶同位素
晚白垩世
古近纪
Gamba Tibet
strontium isotope
Late Cretaceous
Paleogene
