广西西北部二叠系—三叠系界线碳、氧同位素组成异常及其意义  

The Anomaly of Carbon and Oxygen Isotopic Compositions Across the Permian--Triassic Boundary in Northwest Guangxi, South China, and Its Significance

作　　者：王大锐[1] 王新平[2] 孙晓婷[2] 

机构地区：[1]中国石油天然气集团公司油气地球化学重点实验室,北京100083 [2]北京大学地质学系,100871

出　　处：《地质论评》2001年第3期225-228,共4页Geological Review

基　　金：国家自然科学基金(编号49572084)

摘　　要：我国广西西北部平果太平剖面二叠系—三叠系界线处为保存良好的海相碳酸盐岩沉积,根据牙形石化石带推断,该剖面在二叠系—三叠系界线处的连续沉积性良好。在该界线附近处,碳同位素组成发生了突然的负向波动,δ^(13)C值从1.3‰～2.2‰。(PDB)降至-0.9‰～-0.2‰,波动范围达 2.8‰,进入下三叠统后一直呈负向发展;氧同位素组成波动虽不与碳同位素组成同步,但趋势相同,在二叠系—三叠系界线处达到了最小值-8.2‰,下降幅度达2‰。这种同位素组成的波动已在我国西藏、浙江等的同时代的沉积中发现,此外,还在中东、北美洲、欧洲等地的二叠系—三叠系界线处发现,因此,它可以成为大区域乃至洲际之间的二叠系—三叠系界线对比标志,这同时表明,二叠纪末期的重大地质事件发生的时间短、影响范围大,几乎是全球性的。Marine carbonate deposits are well developed and preserved on the Permian - Triassic boundary of the Taiping section, Pingguo County, northwest Guangxi, South China. A very good sedimentary continuity can be identified on this section depending on the evolution of conodont zones. Carbon isotopic compositions within the carbonates exhibit a sudden negative shift around the boundary, that the δ13C values drop from 1. 3‰~2. 2‰ (PDB) down to -0. 9‰--0. 2‰,varying in a range of about 2. 8‰; the trend of the shift of oxygenisotopic compositions is similar to that of carbon isotopes, though they are not synchronous, which drop down to a minimum of -8. 2‰, with a varying range of about 2‰. Such isotopic shifts have been found on geological sections in Tibet and Zhejiang, southwest China, and Middle East, North America and Europe, so these sudden shifts of carbon and oxygen isotopic compositions could become a precise detector of the Permian-Triassic boundary for wide and even intercontinental stratigraphic correlation. Meanwhile, it suggests that the significant event involving mass extinction was active in a short episode and widely affected the biosphere and litho-sphere and almost the whole globe.

关 键 词：广西 二叠系 三叠系 地层界线 碳同位素 氧同位素 

分 类 号：P59[天文地球—地球化学]