| 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 |
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| 引用本文：李维科,宛胜,刘军平,晏海宝,何世军,赵云江,赵江泰,卢晓萍.2024.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[J].地球学报,45(4):439-449. |
| DOI：10.3975/cagsb.2024.042802 |
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| 基金项目: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) |
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| 中文摘要: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T1/T2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T1/T2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T1/T2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。 |
| 中文关键词: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 |
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| Chronological Characteristics and Significance of Fossils and Tuff at the Top of Shipao Formation in Funing Area, Youjiang Basin |
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| Abstract: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 T1/T2 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 T1/T2 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 T1/T2 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. |
| keywords:South China block Youjiang Basin Early–Middle Triassic tuff paleontology zircon U-Pb age |
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