二叠纪-三叠纪之交的古海洋水化学条件变化证据--以贵州织金剖面为例

基于贵州织金剖面的二叠系-三叠系界线附近的岩石薄片鉴定及古生物化石识别，划分出了2种碳酸盐岩沉积相、2种亚相和5种微相；有机质碳同位素组成测试结果表明晚二叠世时期有机质的δ13C_org值（-27.7‰）向早三叠世时期的δ13C_org值（-28.3‰）逐渐偏负，反映了有机质类型由高等植物向低等微生物变化的过程；全岩的δ13C_rock值由晚二叠世（-24.2‰）向早三叠世（-20.9‰）变大，反映了二叠纪末期生物大灭绝事件造成了海洋生物的消失，进而引起12C在海洋中强烈富集；Fe-_HR/Fe-_T、Fe_py/Fe-_HR以及微量元素V/（V+Ni）与V/（V+Cr）比值大小，反映了二叠纪末期该区域的海水为氧化环境或弱还原环境，而三叠纪初期海水处于还原与铁化环境，在盆地内部没有发生硫化作用；V/Ni的值从晚二叠世的0.97~1.97向早三叠世的1.67~7.33明显变大，表明水体逐渐加深的过程，该结论与沉积微相变化相符；在生物演化上，从二叠纪末期的有孔虫-藻屑-三叶虫生物组合演变到三叠纪初期小型介壳-微生物组合，反映了该时期中国南方统一的两幕式生物灭绝与演化样式。

Characteristics of Deep-marine Sedimentation and Evidence on Evolution of the Paleo-oceanographic Chemistry Conditions across the Permian-Triassic Boundary: A case study on the Zhijin profile in the Guizhou province

Two types of carbonate sedimentary facies,two types of subfacies,and five types of carbonate microfacies are identified based on rock thin section identification and fossil identification from the Permian-Triassic boundary at Zhijin profile of Guizhou province.The values of δ13Corg turn negative from-27.7‰ to-28.3‰ from the later Permian to the early Triassic period,reflecting the change of organic matter types from higher plant to lower microbes.The values of δ13Crock present increasing from-24.2‰ to-20.9‰ in the late Permian period and into the early Triassic period,reflecting a mass extinction event in the late Permian.This resulted in the disappearance of marine organisms and the intensive enrichment of 12C in the ocean.Mixed organic matter is not neglected in the testing process.The values of Fe-HR/Fe-T,Fepy/Fe-HR,V/(V+Ni) and V/(V+Cr) distributed at the boundary of the Permian and Triassic indicate that the paleooceanographic chemistry condition at the end of the Permian was oxidation and weak reduction environment.These values also reveal that the paleooceanographic chemistry condition at the early of Triassic was reduction and iron environment,and there was no sulfide environment within the basin.The ratio of V/Ni increases from 0.97～1.97 (in the upper of Permian) to 1.67 ～ 7.33 (in the lower of Triassic),which shows a deeper process of seawater.This conclusion coincides with the result of carbonate microfacies evolution.From the view of biogenic evolution,biotic assemblages change from the type of foraminifera-algal-trilobite in the Late Permian to the type of small scale of shelly and microbial assemblage zones in the Early Triassic,which indicate two ceremonies of extinction and organic evolution model in the late of Permian and early of Triassic in the southern China.