浅谈华南上扬子区中奥陶统铁质鲕粒沉积  

A BRIEF DISCUSSION ON THE MIDDLE ORDOVICIAN FERRUGINOUS OOIDAL DEPOSITS IN THE UPPER YANGTZE REGION,SOUTH CHINA

作　　者：栾晓聪 吴荣昌 王光旭[1,2] 魏鑫[3] 詹仁斌 LUAN Xiao Cong;WU Rong Chang;WANG Guang Xu;WEI Xin;ZHAN Ren Bin(State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008;Center for Excellence in Life and Paleoenvironment,Chinese Academy of Sciences,Nanjing 210008;The Key Laboratory of Orogenic Belts and Crustal Evolution,Ministry of Education,School of Earth and Space Sciences,Peking University,Beijing 100871;University of Chinese Academy of Sciences,Beijing 100049)

机构地区：[1]中国科学院南京地质古生物研究所现代古生物学和地层学国家重点实验室,江苏南京210008 [2]中国科学院生物演化与环境卓越创新中心,江苏南京210008 [3]北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室,北京100871 [4]中国科学院大学,北京100049

出　　处：《地层学杂志》2022年第1期23-39,共17页Journal of Stratigraphy

基　　金：国家自然科学基金(42102130、41972011);中国科学院战略性先导科技专项(XDB26000000);江苏省自然科学基金(BK20191101);现代古生物学和地层学国家重点实验室共同资助。

摘　　要：中奥陶统铁质鲕粒(简称铁鲕)沉积在华南上扬子区广泛分布,但迄今仅有零星报道,缺乏系统的研究。本文在前人工作的基础上,通过开展广泛的野外勘察和分析测试,全面阐述了这套铁鲕沉积的分布规律、发育特点及其控制因素与环境背景。该铁鲕沉积主要见于华南上扬子区中—上奥陶统华弹组、十字铺组和牯牛潭组,在川滇交界至川西南以鲕铁岩、砂页岩、灰岩形式产出,在滇东北—川南—黔北及陕南—川北多为灰岩,含铁矿物主要包括赤铁矿、鲕绿泥石、针铁矿等。铁鲕沉积的时代主要为达瑞威尔中—晚期,在多数地点发育1~2层,个别可见3层,可归属于两期。铁鲕的形成主要受沉积或早期成岩环境的影响或控制,如区域构造运动、古海洋水物理化学条件、微生物活动等。华南的铁质核形石、叠层石和海相红层等独特沉积记录同样发育在大致同期的台地上,共同构成一套含铁质“时征相”。进一步系统研究这套铁鲕沉积,将为全面认识铁质沉积、深入理解华南乃至全球奥陶纪古地理与古环境演变、探索地史时期重大事件等奠定基础。The Middle Ordovician ferruginous ooidal deposits of South China received less attention,despite the widespread distribution in the Upper Yangtze region.In the present paper,their tempo-spatial distribution,developmental characteristics,controlling factors and depositional backgrounds are discussed based on literatures reviewing,field investigations and sample analyses.The Middle-Upper Ordovician Huadan,Shihtzupu and Kuniutan formations are major ferruginous ooids-bearing units in the Upper Yangtze region.The lithology is characterized by ooidal ironstones,and siliciclastic or carbonate rocks in southwestern Sichuan and its border area with Yunnan,and mostly the carbonate rocks in northeastern Yunnan,southern Sichuan,northern Guizhou,southern Shaanxi and northern Sichuan,respectively.The iron minerals of ferruginous ooids are mainly hematite,chamosite and goethite.The ferruginous ooidal deposits,occurring at one to two levels,or rarely three levels in the successions,are of two developing period with their age roughly falling the Middle-Late Darriwilian.Those deposits were mainly controlled by syn-sedimentary and/or early diagenetic processes,such as tectonic movements,paleo-oceanic water conditions and microbial activities.The coeval iron-rich microbialites(oncoids and stromatoids) and marine red beds are recorded in the platform environment of South China,in association with these ferruginous ooidal deposits as a set of “time-specific facies”.A further comprehensive study in future on these ferruginous ooidal deposits may contribute to the understanding of ferruginous deposits and Ordovician paleo-geography and paleo-environments,as well as providing new insights into the major events during geologic time.

关 键 词：铁质鲕粒 环境变化 时征相 华南 奥陶纪 

分 类 号：P534.42[天文地球—古生物学与地层学]