华南扬子地区早志留世布拖期碳-氮循环模式与古海洋氧化还原状态转变  

Carbon and nitrogen cycling patterns and paleo-oceanic redox conditions during the Early Silurian Butuo Period in the Yangtze area of South China

作　　者：杨向荣 严德天[2] 李双建[3] 张宝 张利伟 YANG Xiang-rong;YAN De-tian;LI Shuang-jian;ZHANG Bao;ZHANG Li-wei(School of Geosciences,Yangtze University,Wuhan 430199,China;Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education,China University of Geosciences(Wuhan),Wuhan 430070,China;Sinopec Petroleum Exploration&Production Research Institute,Beijing 100083,China)

机构地区：[1]长江大学地球科学学院,武汉430199 [2]中国地质大学(武汉)构造与油气重点实验室,武汉430070 [3]中国石化石油勘探开发研究院,北京100083

出　　处：《矿物岩石地球化学通报》2023年第6期1288-1299,共12页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金资助项目(41690131)。

摘　　要：本次研究对华南扬子地区下志留统布拖组沉积物进行了地球化学与同位素分析。结果显示,布拖组的δ^(15) N和δ^(13) Corg值由布拖组下部至上部逐渐升高,其中布拖组下部沉积物的低δ^(13) Corg值与全球范围内强烈的火山活动有关,低δ^(15) N值与缺氧海洋条件下的生物固氮作用有关,而布拖组上部沉积物的高δ^(15) N值则与扬子海逐渐富氧化有关。研究结果表明,早志留世布拖期强烈的火山活动引发的生产力升高和海洋底层水体缺氧,导致了深水地区龙马溪组页岩和浅水地区灰岩、泥灰岩中有机质的富集,而布拖早期持续的海洋缺氧则可能抑制晚奥陶世生物大灭绝后生物的复苏。The Early Silurian was an important period of significant changes in climate and biota types.In order to reveal biotic recovery patterns and deposition mechanisms of organic-rich shales in the Longmaxi Fomation of South China,and to reconstruct the evolution of carbon and nitrogen cycling and the geochemistry of ancient seawater,the geochemistry,carbon(δ^(13) Corg)and nitrogen(δ^(15) N)isotopes sediments from a shallow marine section(Wuke)of the Lower Silurian Butuo Formation were investigated in this study.The results showed that the lower Butuo Formation had lowerδ^(13) Corg andδ^(15) N values,while the upper Butuo Formation had higherδ^(13) Corg andδ^(15) N values.This study suggested that the lowδ^(13) Corg values in sediments of the lower Butuo Formation might be due to the release of 12 CO2 from volcanic activities,while the variation ofδ^(15) N were controlled by the redox condition of ancient seawater,with anaerobic nitrogen fixation leading to lowerδ^(15) N values in the lower Butuo Formation and assimilation of NO-3 leading to higherδ^(15) N values in the upper Butuo Formation.In summary,high primary productivity under the influence of intense volcanic activity stimulated the enrichment of organic matter in the sediments,while seawater anoxia delayed the biotic recovery in the Rhuddanian.

关 键 词：扬子地区 布拖组 龙马溪组 黑色页岩 碳同位素 氮同位素 

分 类 号：P593[天文地球—地球化学]