右江盆地富宁地区石炮组化石及顶部凝灰岩年代学特征及意义  

Chronological Characteristics and Significance of Fossils and Tuff at the Top of Shipao Formation in Funing Area,Youjiang Basin

作　　者：李维科 宛胜 刘军平 晏海宝 何世军[5] 赵云江 赵江泰 卢晓萍 LI Weike;WAN Sheng;LIU Junping;YAN Haibao;HE Shijun;ZHAO Yunjiang;ZHAO Jiangtai;LU Xiaoping(Yunnan Institute of Geological Survey,Kunming,Yunnan 650216;Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,Ministry of Natural Resources,Kunming,Yunnan 650051;Institute of Basic Geological Survey,Jiangxi Geological Survey and Exploration Institute,Nanchang,Jiangxi 330030;School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083;The Second Geological Institute of China Metallurgical Geology Bureau,Fuzhou,Fujian 350108)

机构地区：[1]云南省地质调查院,云南昆明650216 [2]自然资源部三江成矿作用及资源勘查利用重点实验室,云南昆明650051 [3]江西省地质调查勘查院基础地质调查所,江西南昌330030 [4]中国地质大学(北京)地球科学与资源学院,北京100083 [5]中国冶金地质总局第二地质勘查院,福建福州350108

出　　处：《地球学报》2024年第4期439-449,共11页Acta Geoscientica Sinica

基　　金：云南省科技计划项目(编号:202305AD160031,202401AT070012);中国地质调查局地质调查项目“云南1:5万那佐幅、里往幅、大普弄幅、花甲幅区域地质调查”(编号:DD20160020);云南省自然资源厅基金项目“云南1:5万大庄幅、法裱幅、底土幅、甸中幅区域地质调查”(编号:D202207)联合资助。

摘　　要：通过野外地质调查,笔者在右江盆地富宁地区中三叠统板纳组与下伏下三叠统石炮组界面之下约100 m采获早三叠世双壳类和菊石等化石,在T_(1)/T_(2)界面之间新发现一套厚约5 m凝灰岩层,对其进行LA-ICP-MS U-Pb同位素定年,自下而上分别获得(249.0±1.9)Ma、(247.9±3.4)Ma、(245.5±1.6)Ma同位素年龄,在误差范围内一致,首次获得石炮组顶界年龄为下三叠统奥伦尼克阶。本次新发现的凝灰岩层及化石可作为早—中三叠世等时地层标志进行区域对比,丰富了右江盆地早三叠世火山岩分布范围,认为右江盆地滇东南地区T_(1)/T_(2)的划分标志以该套凝灰岩作为标志较为合理。结合前人资料,这套凝灰岩、生物化石为华南陆块T_(1)/T_(2)界线的划分提供了重要年代学及古生物证据,认为安尼阶/奥伦尼克阶界线年龄应定为245.5 Ma,可能更为合理。Through field geological investigation,the author collected fossils of Early Triassic bivalves and ammonites about 100 m below the interface between Banna Formation of Middle Triassic and Shipao Formation of Lower Triassic in Funing area of Youjiang Basin,and found a tuff layer with a thickness of about 5 m between T_(1)/T_(2) interface,which was dated by LA-ICP-MS U-Pb isotope.The isotopic ages of(249.0±1.9)Ma,(247.9±3.4)Ma and(245.5±1.6)Ma were obtained from bottom to top,which were consistent within the error range.The upper boundary age of the Shipao Formation was obtained for the first time in the Lower Triassic.The newly discovered tuff beds and fossils can be used as Early-Middle Triassic isochronous stratigraphic markers for regional comparison,which enriches the distribution range of Early Triassic volcanic rocks in Youjiang Basin.It is considered that it is reasonable to use this set of tuff as a marker for the division of T_(1)/T_(2) in southeastern Yunnan of Youjiang Basin.Based on the previous data,this set of tuffs and fossils provides important chronological and paleontological evidence for the demarcation of T_(1)/T_(2) boundary in South China block,and it is considered that the age of the Anniian/Olynikian boundary should be set at 245.5 Ma,which may be more reasonable.

关 键 词：华南陆块 右江盆地 早—中三叠统 凝灰岩 古生物 锆石U-PB年龄 

分 类 号：P597.3[天文地球—地球化学]