摘要
中国西南地区中下三叠统广泛发育多层凝灰岩,贵州望谟甘河桥剖面安尼阶底界,即中/下三叠统界线位于火山凝灰岩之下0.5m处为国际上奥伦尼克阶/安尼阶(Olenekian-Anisian)界线层型牙形石划分标志Chiosella timorensis首现的位置。从火山凝灰岩分离出20颗岩浆成因锆石的SHRIMP年龄测定,获得206Pb/238U加权平均年龄为247.6±1.7Ma(95% conf.)或±1.4(2σ)Ma,此结果与贵州关刀剖面Olenekian-Anisian界线附近凝灰岩用TIMS方法得出的247.2±0.1 Ma年龄有很好的一致性。望谟甘河桥剖面中下三叠统界线凝灰岩在华南地区大面积分布,本文的结果为区域地层对比和划分提供了新的年龄数据,同时为研究三叠纪初期生物复苏时限提供了新的年龄参考。
New zircon U-Pb age is obtained for late Early and Middle Triassic tuff layer from the Ganheqiao section, Wangmo country, Guizhou province. The first appearance of conodont Chiosella timorensis was discovered just 0.5 m below the tuff, which is used to define the Olenekian-Anisian boundary of the Lower/Middle Triassic. Twenty zircons defined a weighted mean ^206Pb/^238U age of 247.6± 1.4 Ma （2σ）. The new dates is in better agreement with a 247.2 Ma age obtained from the Guandao section of Guizhou Province, which was identified using TIMS method and was proposed for the boundary age of Olenekian-Anisian. The tuff layer found in the Ganheqiao section is wide distributed in southwest China. Our result defines a new dating for the regional stratigraphic correlation, and also provides a reliable dating for the duration of biological recovery in the Early Triassic after the extinction of Permo-Triassic.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2010年第8期1112-1117,共6页
Acta Geologica Sinica
基金
国家基础研究专项(编号2006FY120300-12)
中国地质科学院古地磁重点实验室项目(编号2009-SYS-20)资助成果
