攀西宁南地区上震旦统灯影组麦地坪段C、O同位素特征和震旦系/寒武系界线的划分  

Carbon and oxygen isotopic compositions of the Dengying Formation Maidiping Member of Upper Sinian and Sinian-Cambrian boundary division in Ningnan area,western Panzhihua,Sichuan,China

作　　者：余光模[1] 梁斌[1] 钟长洪[2] 胡立[1] 唐帧俊[1] 任志栋[1] 

机构地区：[1]西南科技大学环境与资源学院,四川绵阳621000 [2]四川省地质矿产勘查开发局攀西地质队,四川西昌615000

出　　处：《地质通报》2010年第6期901-906,共6页Geological Bulletin of China

基　　金：中国地质调查局项目<西南地区基础地质调查及数据更新>(编号:1212010610206)资助

摘　　要：对上震旦统灯影组麦地坪段的C、O同位素组成进行了分析,并根据δ13C值在剖面上的变化特征,讨论了该地区震旦系/寒武系的界线。结果表明,麦地坪段白云岩δ13C值在-3.19‰～2.86‰之间,平均值为0.10‰;δ18O值在-10.75‰～-5.17‰之间,平均值为-7.82‰。在剖面上δ13C值出现了有规律的变化,剖面下部2～21层,δ13C值均为正值,在0.04‰～1.68‰之间,平均值为0.92‰;上部23～32层,δ13C值均为负值,在-3.19‰～-1.42‰之间,平均值为-2.13‰,δ13C值存在一个显著的负漂移,变化高达4‰。麦地坪段白云岩δ13C值的变化特征与国内外同期地层非常相似,具有全球可对比性,可作为震旦系/寒武系划分的地球化学标志。This paper has discussed composition characteristics of carbon and oxygen isotopes, and discussed Sinian-Cambrian boundary of the area according to the δ^13C content variation in the profile. The results showed that the δ^13C values of the Maidiping bed dolostone are between -3.19‰～2.86‰～ with an average value of 0.10%o; the δ^13O values are between -10.75‰～-5.17‰ with an average value of-7.82‰. Within the profile, the δ^13C values follow a certain law. At the bottom of the profile, from 2 to 21 bed, all δ^13C values are positive, between 0.04‰～-1.68‰, with a calculated average value of 0.92%0. At the bottom of the profile, form 23 to 32 bed,all δ^13C values are negative, between -3.19‰～-1.42‰ with a calculated average of-2.13‰. There is a significant negative drift, and the variation can be as much as ＋4‰.The δ^13C variation tendency of the Maidiping Member dolostone is similar to those of the strata during the same period worldwide. Therefore it can be used as geochemistry symbol for defining the Sinian-Cambrian boundary.

关 键 词：灯影组麦地坪段 震旦系/寒武系界线 C、O同位素 四川 

分 类 号：P534.31[天文地球—古生物学与地层学] P534.41[天文地球—地质学]