沉积学报2024，Vol.42Issue(3)：1073-1091,19.DOI:10.14027/j.issn.1000-0550.2022.091
四川盆地城口地区下寒武统水井沱组有机质富集控制因素
Controlling Factors of Organic Enrichment in the Shuijingtuo Formation in the Lower Cambrian of the Chengkou Area,Sichuan Basin
摘要
Abstract
[Objective]The Lower Cambrian Shuijingtuo Formation black shale is an important source rock and shale gas exploration target in the Sichuan Basin.However,the enrichment mechanism of organic matter in this series of black shale is still unclear.[Methods]Here,we reported total organic carbon(TOC)contents,sedimentary microfacies,major and trace elements,and pyritic framboid size distributions in the lower part of Shuijingtuo Forma-tion in the Chengkou area,northeastern Sichuan Basin on the Upper Yangtze Platform,providing new evidence for reconstructing the paleogeography,paleoenvironment,and main controlling factors of organic matter enrichment.The results show that the black shale succession in the Shuijingtuo Formation developed five sedimentary microfacies which related to the deep-water shelf slope environment.Productivity index(BaXS,P/Ti)and continental input index Ti,Al indicate that the sedimentary environment of black shale in the Shuijingtuo Formation is at a low level of paleo-productivity,and the continental input is relatively stable and has no obvious correlation with TOC.Therefore,paleo-productivity and continental input are not the main controlling factors of organic matter enrichment in the black shale of the Shuijingtuo Formation.The redox-sensitive element index(U/Th,UEF,MoEF)and pyrite framboid size distribu-tions show that the organic matter content is positively correlated with the redox index,indicating that the organic matter enrichment in Shuijingtuo Formation is mainly controlled by the change of redox conditions of the water column.[Conclusions]Based on the above understanding,it can be inferred that the organic matter enrichment of the black shale of the Shuijingtuo Formation was controlled by the fluctuation of redox conditions of the bottom water caused by the large-scale transgression event during the stage 2 to stage 3 Cambrian(529-514 Ma),and the organic matter enrichment model was proposed here.关键词
水井沱组/下寒武统/黑色页岩/氧化还原条件/有机质富集/四川盆地Key words
Shuijingtuo Formation/Lower Cambrian/black shale/redox conditions/organic matter enrichment/Sichuan Basin分类
天文与地球科学引用本文复制引用
古恒,王剑,韦恒叶,付修根..四川盆地城口地区下寒武统水井沱组有机质富集控制因素[J].沉积学报,2024,42(3):1073-1091,19.基金项目
国家自然科学基金项目(41972121,41762003) （41972121,41762003）
中国石油—西南石油大学创新联合体(2020CX010100)[Foundation:National Natural Science Foundation of China,No.41972121,41762003 （2020CX010100）
PetroChina and Southwest Petroleum University Innovation Consortium,No.2020CX 010100] （）
