南华系莲沱组与南沱组的古气候与氧化还原环境演化新证据  

New evidence for the evolution of paleoclimate and redox environment of the Liantuo and Nantuo Formations in the Nanhua Period

作　　者：隋佩珊 肖媛媛[1,2,4] 孙卫东 SUI Peishan;XIAO Yuanyuan;SUN Weidong(CAS Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,Shandong,China;Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266061,Shandong,China;University of Chinese Academy of Sciences,Beijing 100049,China;Center for Ocean Mega-Science,Chinese Academy of Sciences,Qingdao 266071,Shandong,China;Center of Deep-Sea Research,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,Shandong,China)

机构地区：[1]中国科学院海洋研究所海洋地质与环境重点实验室,山东青岛266071 [2]青岛海洋科学与技术国家实验室,山东青岛266061 [3]中国科学院大学,北京100049 [4]中国科学院海洋大科学研究中心,山东青岛266071 [5]中国科学院海洋研究所深海研究中心,山东青岛266071

出　　处：《地球化学》2023年第2期199-211,共13页Geochimica

基　　金：国家自然科学基金项目(41776069)资助。

摘　　要：新元古代是冰川作用发育的重要时期,其中有2个重要的全球性冰期,即Sturtian和Marinoan冰期,对全球古环境、古气候、古海洋演化具有重要意义。中国宜昌地区分布的莲沱组和南沱组分别代表了在扬子板块发育的与Sturtian冰期前和Marinoan冰期相对应的沉积地层。随着地球化学分析方法的进步,新的地球化学手段,包括新的地球化学指标和Fe同位素等,可以为进一步探讨莲沱组与南沱组的沉积环境提供新的思路和证据。本研究对宜昌九龙湾剖面南沱组冰碛岩进行系统采样,并和莲沱组以砂岩为主的碎屑沉积岩进行对比分析,利用化学蚀变指数(CIA)、氧化还原敏感元素Mo、V、U和Fe同位素对比探讨二者古气候与氧化还原环境的演化。CIA的变化(53~78)表明,莲沱组沉积主体处于温暖的古气候下(CIA平均值约为78),直到Sturtian冰期前,莲沱组顶部出现气候转冷特征(CIA平均值为53);随着Marinoan冰期到来,南沱组沉积持续处于寒冷的古气候环境(CIA平均值为58)。莲沱组与南沱组样品均具有较低的Mo/Al、V/Al和U/Al值,表明二者沉积均处于氧化环境,但莲沱组主体比南沱组和莲沱组顶部样品具有更低的Mo/Mo*、V/V*以及更高的Fe同位素值,反映了莲沱组主体的沉积环境更为氧化。The Neoproterozoic is an important glaciation period in Earth’s history.Sturtian and Marinoan are two important global glaciations that occurred during the Neoproterozoic period and were important in the evolution of the global palaeoenvironment,palaeoclimate and palaeoocean.The Liantuo and Nantuo Formations widely developed in Yichang area;the former corresponds to pre-Sturtian glaciation and the latter corresponds to Marinoan glaciation.With the development of geochemical analytical methods,updated geochemical methods,including new geochemical indices and Fe isotopes,can provide new ideas and evidence for further studies of the sedimentary environment of the Liantuo and Nantuo Formations.We evaluated samples from the Liantuo and Nantuo Formation from Jiulongwan section of Yichang area.We focused on the chemical index alteration(CIA),redox-sensitive elements(Mo,V,U),and Fe isotope to examine the evolution of paleoclimate and redox conditions of the Liantuo and Nantuo Formations.The variation in the CIA(from 53 to 78)showed that the Liantuo Formation was deposited under warm conditions(with the average CIA value of 78),and the climate became obviously colder at the top of the Liantuo Formation until the pre-Sturtian glaciation(with an average CIA value of 53).With the arrival of the Marinoan glaciation,the Nantuo Formation was deposited under cold conditions with an average CIA value of 58.Both the Liantuo and Nantuo Formations showed low Mo/Al,V/Al and U/Al ratios,indicating an oxidized depositional environment.The Liantuo Formation has lower Mo/Mo*and V/V*values and a heavier Fe isotope composition compared to those of the Nantuo Formation,reflecting a more oxidized condition than that for the Nantuo Formation.

关 键 词：南沱组 莲沱组 FE同位素 古气候 氧化还原条件 

分 类 号：P532[天文地球—古生物学与地层学] P595[天文地球—地质学]