华南四川凉山娃文拉土剖面上奥陶统凯迪阶旋回地层学综合研究  

COMPREHENSIVE CYCLOSTRATIGRAPHY OF THE KATIAN STAGE(UPPER ORDOVICIAN)AT THE WAWENLATU SECTION IN SICHUAN,SW CHINA

作　　者：王凯[1] 李明松 郑澳男 吴荣昌 魏鑫 刘建波[1,2] WANG Kai;LI Ming Song;ZHENG Ao Nan;WU Rong Chang;WEI Xin;LIU Jian Bo(School of Earth and Space Sciences,Peking University,Beijing 100871;The Key Laboratory of Orogenic Belts and Crustal Evolution,Ministry of Education,School of Earth and Space Sciences,Peking University,Beijing 100871;State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008)

机构地区：[1]北京大学地球与空间科学学院,北京100871 [2]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 [3]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

出　　处：《地层学杂志》2024年第3期253-278,共26页Journal of Stratigraphy

基　　金：国家重点研发项目(2022YFF0800200);国家自然科学基金(41972027)共同资助。

摘　　要：晚奥陶世凯迪期和赫南特期,全球发生了一系列重要生物和地质事件。由于该时期华南高精度古环境研究工作相对缺乏、地层缺少高精度同位素测年数据等因素,阻碍了人们对这些生物和地质事件的时间进程的认识。旋回地层学研究是实现高精度地层划分与对比和推进年代地层学研究的有效手段。扬子台地西缘四川凉山布拖娃文拉土剖面的上奥陶统出露连续,发育了一套相对较浅水且具有良好沉积旋回性和互层性的碳酸盐岩地层,非常适合进行旋回地层学研究。本研究在该剖面的“大箐组”和铁足菲克组(含观音桥层)中共识别出12类沉积微相,利用岩石地层发育趋势和无机碳同位素记录实现了区域内和跨区域的地层对比,识别出凯迪期至赫南特期的多次碳同位素漂移事件。对基于沉积微相获得的相对古水深波动赋值参数和X射线荧光光谱(XRF)测试所得的Al相对含量数据组进行旋回地层学分析,识别出可靠的长偏心率、短偏心率、斜率和岁差天文周期和沉积速率演化趋势,证实了基于沉积学特征恢复的古水深波动参数是在旋回性和互层性良好的古生代海相碳酸盐岩地层开展旋回地层学研究的有力指标。利用405 kyr长偏心率周期进行天文调谐后得出凯迪阶Hamarodus brevirameus带至赫南特阶底界延续时长约为8.28 Myr,其中牙形类Hamarodus brevirameus带延续时长约为3.37 Myr,牙形类Protopanderodus insculptus带延续时长为2.45 Myr,笔石Dicellograptus complexus带和Paraorthograptus pacificus带延续时长为2.46 Myr。碳同位素正漂移事件GICE后期峰值点位及Kope、Fairview、Waynesville、Whitewater等漂移事件的峰值点位距凯迪阶Hamarodus brevirameus带底界分别约0.85 Myr、2.85 Myr、4.72 Myr、5.51 Myr、6.79 Myr,HICE事件的3个峰值间隔时长分别约0.23Myr、0.35Myr。这些新的年代地层学结果为晚奥陶世凯迪期地质-生物事件的The Upper Ordovician Katian and Hirnantian stages witnessed a series of significant global biotic and geological events.However,the lack of high-resolution paleoenvironmental studies in South China and precise radiometric dating hindered further understanding of these events.Cyclostratigraphy provides as an effective tool to achieve precise stratigraphic correlation and advance chronostratigraphic studies.Continuous Late Ordovician strata crop out at the Wawenlatu section of the western Yangtze Platform,South China paleoplate.Relatively shallow-marine carbonates were developed at the section with well-developed shallow-upward cycles,which are suitable for cyclostratigraphic research.Twelve sedimentary microfacies were recognized in the Taching and Tiezufeike formations(including the Kuanyinchiao Bed).By utilizing the developmental trends in lithostratigraphy and carbon isotope records,local and regional stratigraphic correlations were achieved,and the multiple carbon isotope excursion events from the Katian to Hirnantian were reconized.Cyclostratigraphic analysis was conducted using parameters obtained from fluctuation in the relative paleowater depth based on sedimentary microfacies and X-ray fluorescence(XRF)measurements using relative Al content,from which reliable long and short eccentricity,obliquity,and precession astronomical cycles,as well as trends in sedimentation rate evolution were identified,confirming that paleowater depth fluctuation parameters based on sedimentological fabrics are a robust indicator for cyclostratigraphic studies on Paleozoic marine carbonate strata with good cyclicity and interbedding.The floating astronomical time scale of the Katian Stage was established based on astronomical tuning using the 405 kyr long eccentricity cycle.The duration from the base of the Hamarodus brevirameus zone to the base of the Hirnantian is approximately 8.28 Myr.The durations of the Hamarodus brevirameus zone,the Protopanderodus insculptus,the Dicellograptus complexus,and the Paraorthograptus pacificu

关 键 词：旋回地层学 浮动天文年代标尺 古水深指标 碳同位素漂移 沉积微相 

分 类 号：P534.42[天文地球—古生物学与地层学]