华北克拉通南缘古元古代晚期汝阳群微体化石及其古环境意义:来自微细构造和生物标志化合物的证据  

Microfossils and Paleoenvironmental Significance of Late Paleoproterozoic Ruyang Group in South Margin of North China Craton:Evidence from Microstructure and Biomarker

作　　者：李猛[1,2] 王钊飞 姚志亮 Li Meng;Wang Zhaofei;Yao Zhiliang(Xi’an Center of Geological Survey,Orogen Research Center,China Geological Survey,Xi’an 710054,China;Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits,Ministry of Natural Resources,Xi’an 710054,China;No.711 General Party,Northwest Nonferrous Geological Exploration Co.Ltd.,Hanzhong 723000,China;Xi’an Northwest Nonferrous Chemical Exploration Team Co.Ltd.,Xi’an 710068,China)

机构地区：[1]中国地质调查局西安地质调查中心,中国地质调查局造山带地质研究中心,陕西西安710054 [2]自然资源部岩浆作用成矿与找矿重点实验室,陕西西安710054 [3]汉中西北有色七一一总队有限公司,陕西汉中723000 [4]西安西北有色物化探总队有限公司,陕西西安710068

出　　处：《地球科学》2021年第11期4072-4083,共12页Earth Science

基　　金：国家自然科学基金项目(No.41602005);陕西省自然科学基金项目(No.S2019-JC-QN-2490);中国地质调查局项目(Nos.DD20190065,DD2016002)。

摘　　要：华北克拉通南缘古元古代晚期汝阳群白草坪组页岩中产出大量的具刺和细网状纹饰的球形疑源类,其中以Shuiyousphaeridium macroreticulatum与Dictyosphaera macroreticulata化石标本最具代表性.利用扫描电子显微镜结合光学生物显微镜对其膜壳微细构造进行观察,结果显示:膜壳表面的刺饰形态具有多样性分叉;其膜壳壁可能是由多边形网脊及膜层构成,而不是由多角形板片及膜层构成.同时通过对比研究,认为两种最具代表性的特征分子可能是同一生物不同阶段的产物.此外,通过对赋存微体化石页岩进行生物标志化合物分析,检测到的姥鲛烷/植烷比(Pr/Ph)大于1、伽马蜡烷丰度中等及生物标志化合物(C_(30)藿烷、C_(27)甾烷和三环萜烷),结合前人关于汝阳群沉积环境的研究,不仅指示了汝阳群微体化石群沉积古环境应为正常的海洋环境——滨海-浅海相,也指示了元古代真核生物已经存在,为重建微体化石群和探讨早期生命演化提供了重要的理论依据.There are a large number of acritarchs with spines and fine reticular patterns,well exposed in the shale of Baicaoping Formation of Ruyang Group in western Henan,such as Shuiyousphaeridium macroreticulatum and Dictyosphaera macroreticulata which are the most representative fossil specimens.In this paper,the microscopic structure of the membrane shell was observed by scanning electron microscope combined with optical biological microscope.Moreover,the two representative fossil specimens(Shuiyousphaeridium macroreticulatum and Dictyosphaera macroreticulata) may be produced at different stages of the same organism.These features not only reveal more information about the original characteristics of the microbe,but also enrich the morphological classification of the microfossils in Ruyang Group.In addition,based on the analyses of biomarker from shale with microfossils,it shows that pristane/phytane ratio(Pr/Ph) is greater than 1,the abundance of gammacerane is medium and there is biomarker(C_(30) hopane,C_(27) sterane and tricyclic terpane),which not only indicates that the paleoenvironment of microfossils in Ruyang Group should be normal marine environment-coastal-shallow sea facies,but also indicates the existence of Proterozoic eukaryotes,which provides an important theoretical basis for the reconstruction of microfauna and the discussion of the evolution of early life.

关 键 词：汝阳群 白草坪组 微体化石 生物标志化合物 古元古代 古生物学 

分 类 号：P52[天文地球—古生物学与地层学]