华南泥盆-石炭系界线剖面旋回地层学研究  

Cyclostratigraphy of the Devonian/Carboniferous boundary sections in South China

作　　者：李山 吴怀春[1,2] 房强[1,2] 许俊杰 时美楠[1,2] LI Shan;WU Huaichun;FANG Qiang;XU Junjie;SHI Meinan(School of Ocean Sciences,China University of Geosciences(Beijing),Beijing 100083,China;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Beijing 100083,China)

机构地区：[1]中国地质大学(北京)海洋学院,北京100083 [2]中国地质大学生物地质与环境地质国家重点实验室,北京100083

出　　处：《地学前缘》2022年第3期329-339,共11页Earth Science Frontiers

基　　金：国家自然科学基金项目(41925010,41790451);教育部、科学技术部高等学校学科创新引智计划(“111计划”)项目(B20011);中国石油勘探开发研究院学科发展项目(YJKT2019-3)。

摘　　要：泥盆-石炭纪过渡期是地球演化过程中的一个重要阶段,发生了地球气候系统从温室向冰室转型和生物灭绝等重大事件。准确且高分辨率的年代格架是理解这些事件的基础。本文利用高分辨率磁化率作为古气候替代指标,对贵州省长顺县睦化Ⅱ剖面和大坡上剖面以及广西壮族自治区南丹县度里剖面的泥盆-石炭系界线附近深水沉积序列进行旋回地层学研究。识别出受到短偏心率、斜率和岁差控制的沉积旋回厚度分别为1.09~2.39、0.29~0.73、0.18~0.51 m。利用轨道短偏心率进行天文校准,结果证实泥盆纪晚期短偏心率、斜率、岁差周期分别为约100、32.2~27.2和20.9~15 ka。利用大坡上剖面已知的U-Pb放射性同位素年龄和天文校准结果建立高精度浮动天文年代标尺并进行旋回地层对比。确定了泥盆-石炭系界线附近牙形类生物带和Hangenberg生物灭绝事件的持续时间,并计算出泥盆-石炭系界线年龄为(359.58±1.9) Ma。The Devonian/Carboniferous transition is one of the most important intervals in Earth’s history characterized by the greenhouse-icehouse transition and mass extinction.To understand this event,an accurate and high-resolution geochronological framework is needed.In this paper,high-resolution magnetic susceptibility is used as the paleoclimate proxy to study the cyclostratigraphy of the deep-water sequences across the Devonian/Carboniferous boundary(DCB)in the Muhua II and Daposhang sections,Changshun County,Guizhou Province,and the Duli section,Nandan County,Guangxi Zhuang Autonomous Region.The sedimentary cycles with thicknesses of 1.09-2.39 m,0.29-0.73 m,and 0.18-0.51 m were interpreted as short eccentricity,obliquity,and precession cycles,respectively.After astronomical calibration of short eccentricity to~100 ka,the obliquity and precession periods of late Devonian were estimated to be 27.2-32.2 ka and 15-20.9 ka,respectively.The conodont zones and Hangenberg Crisis near the DCB were constrained by the newly constructed astronomical time scale in combination with the published U-Pb radioactive isotope age.The new DCB age,constrained by high-precision cyclostratigraphic correlation among different sections,was estimated to be 359.58±1.9 Ma.

关 键 词：轨道旋回 天文年代格架 泥盆-石炭系界线 Hangenberg生物灭绝事件 

分 类 号：P534.44[天文地球—古生物学与地层学] P534.45[天文地球—地质学]