摘要
扬子克拉通西北缘成冰系沉积学研究相对较少,大巴山城口地区更为薄弱,特别是成冰系木座组/明月组和代安河组是否存在冰川沉积缺乏详细的沉积学解释,制约了对扬子克拉通成冰纪沉积演化过程的理解,也不利于该时期地层格架的厘定和区域对比。本文选择城口地区四个典型成冰系剖面开展精细地层学和沉积学解剖,识别出了发育冰川擦痕砾石、坠石和冰下软沉积变形等冰川沉积标志,证明代安河组和木座组/明月组为冰川成因,并划分出陆相冰川、冰缘和海相冰川等沉积相类型。进而依据岩石组合、沉积特征、上下地层结构、地化指标(如化学蚀变指数等)和碎屑锆石U-Pb年龄等特征将代安河组二分,一段对比古城组,二段对比大塘坡组,木座组/明月组对比南沱组。在此基础上开展了区域对比,重新厘定扬子克拉通西北缘成冰系的地层格架,认为其可与相邻神农架以及扬子克拉通东南缘对比。恢复了城口—神农架地区成冰系沉积演化过程:斯图特冰期发育着由冰海至陆地再至冰海的冰川进退旋回,随后间冰期的广泛海侵形成了碳质粉砂质泥岩为代表的潟湖环境;随着全球气温再次下降引发马雷诺冰期,经历了多次从冰海近缘至冰海远缘的冰川沉积动态演化过程,并伴随有冰盖打开最终至成冰纪结束。研究成果厘定了扬子克拉通西北缘成冰系的对比划分,为扬子克拉通成冰系对比提供新的基础资料和重要依据。
There are relatively few sedimentological studies on the Cryogenian in the northwestern Yangtze Craton,especially in the Chengkou area of the Dabashan Mountain.Whether the Cryogenian Muzuo/Mingyue and Dai'anhe formations have glacial sedimentary characteristics is also uncertain due to lack of detailed sedimentological investigation,which limits the understanding of sedimentary evolution process of the Cryogenian in the Yangtze Craton.These lacunae are not conducive to the determination of the sedimentary stratigraphic framework and regional correlation of the Cryogenian.In this paper,four typical Cryogenian sections in the Chengkou area are selected for undertaking a detailed stratigraphic and sedimentological study,and the glacial sedimentary marks such as the gravels with glacial striae,dropstones,and subglacial soft sedimentary deformations are identified to prove the glacial genesis of the Dai'anhe and Muzuo/Mingyue formations.The facies of continental,periglacial and marine glacial are also discerned.On this basis,according to the rock assemblages,sedimentary characteristics,structure of stratigraphic succession,geochemical indices(such as chemical index of alteration)and detrital zircon UPb age,the Dai'anhe Formation is divided into two members.The 1st Member is correlated with the Gucheng Formation,the 2nd Member is correlated with the Datangpo Formation,and the Muzuo/Mingyue Formation is correlated with the Nantuo Formation.Further,through regional correlation,the stratigraphic framework of the Cryogenian in the northwestern Yangtze Craton is re-evaluated,and correlated with that in the adjacent Shennongjia area and southeastern Yangtze Craton.The sedimentary co-evolution process of the Cryogenian in the Chengkou-Shennongjia areas is as follows:during the Stuartian glacial period,the glacial transgressive-regressive cycle from the glaciomarine to the land and then to the glaciomarine developed;subsequently extensive transgression of the interglacial period formed a lagoon environment represented by carbonaceous silty mudstone.With the global temperature falling again,the Marinoan glacial period was triggered,which was reflected in the multiple glacial dynamic evolution from the glaciomarine ice-proximal to the ice-distal environment,and accompanied by the opening of the ice sheet and finally to the end of the Cryogenian.This study has determined the correlation and subdivision of the Cryogenian in the northwestern Yangtze Craton,providing new basic data and important basis for the correlation of the Cryogenian in the Yangtze Craton.
作者
陈骁帅
旷红伟
柳永清
王玉冲
彭楠
祁柯宁
张懿
CHEN Xiaoshuai;KUANG Hongwei;LIU Yongqing;WANG Yuchong;PENG Nan;QI Kening;ZHANG Yi(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;College of Geosciences and Surveying Engineering,China University of Mining and Technology,Beijing 100083,China;School of Resources and Environmental Engineering,Hefei University of Technology,Hefei,Anhui 230009,China;School of Resources and Safety Engineering,Chongqing University,Chongqing 400030,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2023年第12期3943-3966,共24页
Acta Geologica Sinica
基金
国家自然科学基金项目(编号42072135)
国家重点研发计划项目(编号2022YFF0800302,2016YFC0601001)
中国地质调查局项目(编号DD20221649)
北京科委国际创新资源合作项目(编号Z201100008320007)联合资助的成果。
关键词
扬子克拉通西北缘
成冰系
地层格架
冰川沉积
沉积演化
northwestern Yangtze craton
Cryogenian
stratigraphic framework
glacial sedimentology
sedimentary co-evolution
