华南二叠系卡匹敦阶高分辨率浮点年代标尺  

High-resolution floating point time scale(FPTS)of Permian Capitanian Stage in South China

作　　者：薛武强[1] 李波[2] 颜佳新[1] Brooks B.Ellwood Jonathan H.Tomkin 王艳 朱宗敏[1] 

机构地区：[1]中国地质大学(武汉),地球科学学院,生物地质与环境地质国家重点实验室,武汉430074 [2]国土资源部海底矿产资源重点实验室,广州海洋地质调查局,广州510075 [3]Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803, USA [4]School of Earth, Society, and Environment, University of Illinois, Urbana, IL 61801, USA [5]广东省有色地质勘查院,广州510080

出　　处：《地球物理学报》2015年第10期3719-3734,共16页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41472087;41072078);科技部973项目(2011CB808804);国土资源部海底矿产资源重点实验室开放基金课题(KLMMR-2014-A-12);美国国家科学基金会(EAR-0745393003)联合资助

摘　　要：基于详细的生物地层学研究,以磁化率为古气候替代指标,对广西来宾铁桥剖面卡匹敦阶地层开展时间序列分析,建立高分辨率浮点年代标尺（FPTS）.结果表明,磁化率记录了铁桥剖面中二叠世晚期沉积序列中的米兰科维奇旋回,卡匹敦阶上部磁化率突然增加与峨眉山玄武岩喷发和卡匹敦晚期全球性海退有关,这些事件导致同期沉积物中碎屑物质增加.铁桥剖面瓜德鲁普—乐平统界线附近磁化率和蓬莱滩剖面（乐平统底界GSSP）表现出一致的变化趋势,具可对比性.利用多窗谱法（MTM）和傅里叶变换（FT）从磁化率序列中识别出五个米兰科维奇周期：长偏心率周期（E2,405ka）、短偏心率周期（E1,100ka）、长地轴斜率周期（O2,44.1ka）、长岁差周期（P2,20.95ka）和短岁差周期（P1,17.7ka）.对比基于E2周期建立的磁性地层磁化率（MSS）带和标准参考带（SRZ）,建立整个沉积序列的高分辨率（200ka）FPTS,提出卡匹敦阶的时限为3.85 Ma（存在＋0～0.28 Ma误差）,整段沉积序列的平均沉积速率为2.91cm·ka^-1.同时计算出卡匹敦阶内部七个牙形石带的时限,从最短26.6ka到最长2.3 Ma.另外,估算出峨眉山大火成岩省喷发启动时间为262.67 Ma,位于瓜德鲁普—乐平统界线之下1.42 Ma.The Capitanian stage is a critical time interval when fierce eruption of the Emeishanlarge igneous province（LIP）occurred with onset of a double-episodic Paleozoic-Mesozoic biocrisis.However,the time duration of the Capitanian stage is geochronologically poorlyconstrained due to a lack of absolute age data with radioactive dating method constraining both the basal and the top boundary of the Capitanian stage.Cyclostratigraphy can provide a highresolution astronomical time scale by tuning the cyclic stratigraphic records to astronomical solutions.In this study,a floating point time scale（FPTS）for the Capitanian stage was developed based on the result of time-series analysis of magnetic susceptibility（MS）and additional biostratigraphic data sets.In addition,we estimate the age and time duration of the Emeishan LIP eruption.1456 unoriented samples（sampling interval～0.1m）for MS measurement and 45 samples for biostratigraphic study were collected from outcrops with stratigraphic interval of～147.5m.The bottom horizon of sampling range is located at～31.2 m below the Wordian-Capitanian（W-C）boundary. We conducted continuous sampling with the top horizon at 2.6m above the Capitanian-Wuchiapingian（C-W）boundary at Tieqiao section,Laibin in South China,as a supplementary reference section for the Guadalupian-Lopingian（Middle-Upper Permian）Global Boundary Stratotype Section and Point（GSSP）.The stratigraphic succession consists of alternations between thin-bedded chert and micritic limestone recognized as typical slope-basin facies with carbonate cap on shallow-water platform.Representative samples were selected to be carried out thermomagnetic susceptibility measurements after analysis of low-field bulk susceptibility for all samples.Then spectral（time-series）analysis of the MS data was performed by means of Multi Taper Method（MTM）and Fourier Transform（FT）analysis.Samples for biostratigraphic study were processed using acetic acid digestion in order to obtain conodont fossils.Se

关 键 词：磁化率 牙形石 时间序列分析 卡匹敦阶 峨眉山大火成岩省 浮点年代标尺 

分 类 号：P318[天文地球—固体地球物理学]