江南上斜坡早奥陶世海洋-气候特征及初级生产力变化机制  

Early Ordovician ocean-climate characteristics and primary productivity change mechanism in the upper slope of Jiangnan

作　　者：杨丽君 刘欣春[1,2] 王嵩[3] 严雪 武丽婷[1,2] 雷佳洁 YANG Lijun;LIU Xinchun;WANG Song;YAN Xue;WU Liting;LEI Jiajie(Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Keylaboratory of Deep-time Geography and Environment reconstruction and applications of ministry of natural resources,Chengdu University of Technology,Chengdu,Sichuan 610059,China;College of Energy,Chengdu University of Technology,Chengdu,Sichuan 610059,China)

机构地区：[1]成都理工大学沉积地质研究院,四川成都610059 [2]成都理工大学自然资源部深时地理环境重建与应用重点实验室,四川成都610059 [3]成都理工大学能源学院,四川成都610059

出　　处：《矿物岩石》2024年第4期151-165,共15页Mineralogy and Petrology

基　　金：国家自然科学基金青年科学基金项目(批准号:41702113)。

摘　　要：奥陶纪生物辐射是显生宙以来,最重要的两次生物辐射事件之一,海洋环境变化对该事件的研究具有重要意义。全球早奥陶世古海洋环境演化已进行过许多研究,但主要集中于浅水剖面,如扬子台地的古海洋氧化及生物辐射研究。然而对于同时期更深水的古海洋环境研究较少,对于深水环境下的生物环境演化模式认识不清晰。而对深水剖面的研究有利于我们更好的理解奥陶纪生物辐射事件的启动与发展,因此本次研究选择江南上斜坡将军岭剖面作为研究对象,以50cm间距对剖面特马豆克阶顶部-弗洛阶底部暗色页岩样品进行了采集,并对其主微量元素进行了测试分析。获得以下3个主要认识:(1)Mo_(EF)(平均0.13),U_(EF)(平均0.57),Mo_(EF)/U_(EF)(平均0.21),V/Cr(平均1.17),U/Th(平均0.14)等氧化还原指标都指示该地区晚特豆马克期-早弗洛期水体为氧化环境,显示了晚特马豆克期华南海洋水体环境已经完成了由浅水向深水的氧化扩张;(2)Cd/Mo(平均0.49)和Co_(EF)×Mn_(EF)(平均0.31)等指标显示为上升流环境,化学蚀变指数(CIA)(平均81.1)反映本剖面晚特马豆克期-早弗洛期主要为湿热气候,剖面上CIA值与上升流强度之间存在正相关性变化;(3)江南上斜坡地区,Ba富集指数(Ba_(XS))所反映的初级生产力存在与上升流的强弱变化的协同响应,指示上升洋流增强有利于初级生产力的繁盛。The Great Ordovician Biodiversification Event is one of the two most significant biological radi-ation events since the Phanerozoic,and studying this event is crucial for understanding changes in the ma-rine environment.Numerous studies have focused on the evolution of the global early Ordovician paleoma-rine environment,they primarily concentrate on shallow-water profiles(such as the research on paleomar-ine oxidation and biological radiation of the Yangtze Platform).However,there are few studies on the deep-water paleomarine environment of the same period,leading to an incomplete understanding of the e-volution model of biological environments in the deep-water settings.It is essential to examine the deep-water deposition profile to better grasp the initiation and development of biological radiation events during the Ordovician.This study selected the upper slope section of Jiangnan and collected dark shale samples from the top of the Tremadocian stage to the bottom of the Floian stage at 5o cm intervals.We tested and analyzed the major and trace elements of these samples,yielding three key insights:(1)The Redox indices Mo_(EF)(mean 0.13),U_(EF)(mean 0.57),Mo_(EF)/U_(EF)(mean 0.21),V/Cr(mean 1.17),and U/Th(mean O.14)all suggest that water in this region were in an oxidizing environment during the late Tremadocian-early Floian stages.This finding indicates that the marine environment of South China underwent a com-plete oxidation expansion from shallow to deep waters by late Tremadocian.(2)The Cd/Mo(mean O.49)and Cor_(EF)×Mn_(EF)(mean O.31)indices indicate an upwelling environment,while the chemical alteration in-dex(mean 81.1)reflects a predominantly hot and humid climate during late Tremadocian-early Floian,suggested by a positive correlation between the CIA value and upwelling intensity.(3)In the upper slope area of Jiangnan,the Ba enrichment index(Baxs)demonstrates a combined response to the presence of pri-mary productivity and variations in upwelling intensity,suggesting that increased upwelling currents

关 键 词：早奥陶世 江南上斜坡 奥陶纪生物辐射 上升流 初级生产力 

分 类 号：P595[天文地球—地球化学]