扬子西北缘二叠纪瓜德鲁普统—乐平统界线识别及意义  

Identification and Significance of the Permian Guadelup-Lopingian Series Boundary in the Northwestern Margin of the Yangtze Craton

作　　者：刘宣威 田亚铭[3] 姜福杰[1,2] 王鹏威 张慧[3] 柳昊 李飞[5] LIU XuanWei;TIAN YaMing;JIANG FuJie;WANG PengWei;ZHANG Hui;LIU Hao;LI Fei(State Key Laboratory of Oil and Gas Resources and Exploration,Beijing 102249,China;School of Earth Sciences,China University of Petroleum(Beijing),Beijing 102249,China;Key Laboratory of Tectonic Metallogenesis and Reservoir Formation,Ministry of Natural Resources,Chengdu University of Technology,Chengdu 610059,China;SINOPEC Petroleum Exploration and Development Research Institute,Beijing 102206,China;SINOPEC Exploration Branch,Chengdu 610041,China)

机构地区：[1]油气资源与探测国家重点实验室,北京102249 [2]中国石油大学(北京)地球科学学院,北京102249 [3]自然资源部构造成矿成藏重点实验室,成都理工大学,成都610059 [4]中国石化石油勘探开发研究院,北京102206 [5]中国石化勘探分公司,成都610041

出　　处：《沉积学报》2025年第2期387-407,共21页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41872128)。

摘　　要：【目的】中—晚二叠世的瓜德鲁普统—乐平统界线(PLB界线)是地学界长期以来研究的难点。一方面,中—晚二叠之交的抬升运动造成了沉积间断和差异剥蚀,给界线的厘定和与全球剖面的对比带来了困难。另一方面,多个剖面记录有PLB界线相关的碳同位素负漂移事件,但发生时间具有差异,其成因尚不清楚。【方法】选取扬子板块西北缘三堆镇、王家沟、大两乡等7个剖面Guadalupian统晚期地层为研究对象,通过岩性特征和牙形石刺确定地层时限,结合主微量及稀土元素分析手段,补充了区域碳同位素漂移事件的环境证据,同时对其与地质事件的联系进行了梳理。【结果】(1)自Jinogondolella.postserrata到Clarkina.dukouensis带,可识别出生屑灰岩(含云灰岩)、硅质岩(泥质灰岩)、煤层和含泥灰岩4个岩性段,代表了海平面平稳—下降—上升三个阶段;(2)以古暴露面、岩性突变面和其上C.dukouensis牙形石的首现面为依据,识别出PLB界线所处的位置;(3)三堆镇剖面J.postserra-J.shannoni带和J.altudaensis-J.xuanhanensis带记录了两次海退事件,造成Sr/Ba及Y/Ho比值同步负偏,轻稀土相对富集。【结论】峨眉山大火成岩省在J.altudaensis带开始活动,热液的输入造成区域稀土元素总量骤增。生物种群在J.postserrata带开始受到灭绝事件波及,事件持续直至PLB界线处。该研究为扬子西北缘剖面与全球记录到的碳同位素负偏事件在时间和期次上的差异补充了剖面证据并进行了解释。[Objective]The Guadelup-Leping boundary(PLB boundary)of the Middle-Late Permian has long been considered a difficult academic issue for geoscientists.On the one hand,the uplift movement at the turn of the Middle and Late Permian caused a sedimentary discontinuity and differential denudation,which made determining the boundary and comparing it with the global profile difficult.On the other hand,the reason several profiles recorded negative carbon isotope drift events related to the PLB boundary with different occurrence is still unclear.[Methods]This study selected seven sections of the late Guadalupian strata(including Sandui Town,Wangjiagou,Daliang Township)along the northwest margin of the Yangtze Plate as research object and identified the formation time limit through lithological characteristics and conodonts.Major trace and rare earth element analyses also complement the environmental evidence of regional carbon isotope drift events[.Results]The results show that:(1)From the Jinogondolla.postserrata to Clarkina.dukouensis zone,the field sections can be divided into four lithologic sections,bioclastic limestone(containing dolomite),siliceous limestone(argillaceous limestone),coal seam,and marl-bearing limestone,representing three stages of sea level:stabilization-decline-rise.(2)The characteristic key bed of the PLB boundary identified based on the paleoexposure,lithologic mutation,and first appearance surfaces of the C.dukouensis is marked as the lowest Leping boundary.(3)Two regression events were recorded in the J.postserra-J.shannini zone and J.altudaensis-J.xuanhanensis zone of the Sandui Town profile,resulting in synchronous negative deviation of Sr/Ba and Y/Ho values and relative enrichment of light rare earth elements.[Conclusions]The Emeishan Large Igneous Province began to move in the J.altudaensis belt,and the input of hydrothermal fluid caused a sharp increase in the total rare earth elements in the region.The biological population was affected by the extinction event in the J.postserrata belt tha

关 键 词：扬子板块 生物地层 牙形石 PLB界线 生物灭绝 

分 类 号：P534.46[天文地球—古生物学与地层学]