辽西义县组的地质时代  

The Geological Age of Yixian Formation in Western Liaoning, China

作　　者：王松山[1] 胡华光[1] 李佩贤[2] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]中国地质科学院地质研究所,北京100037

出　　处：《矿物岩石地球化学通报》2001年第4期289-291,共3页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金资助项目 ( 4 98730 2 3)

摘　　要：长期以来辽西义县组地质时代存在争论。通过对义县组命名地义县上底家沟—砖城子剖面义县组下部玄武岩的定年 ,获得K Ar年龄 131.2± 2 .6Ma ,坪年龄tp130 .4± 1.0Ma ,总气体年龄ttg130 .1± 1.3Ma ,等时年龄tI130 .5± 1.5Ma。这一结果表明 ,辽西义县组的地质时代应属早白垩世 ,其时代可与浙西劳村组、江苏宁芜盆地龙王山组、安徽庐枞盆地砖桥组对比。The Geological age of the Yixian Formation in western Liaoning is appointed to different epoches of Mesozoic Era, Such as the Late Jurassic, the Early Cretaceous or Late Jurassic-Early Cretaceous. Even the dating data are still very different. The paper provides new evidence from Ar-Ar dating. YL23 basalt was collected from the low part of the typical section of the Yixian Fm in western Liaoning. The sample yields a K-Ar age of 131.2±2.6 Ma. Ar-Ar step-heating experiment performed on the YL23 basalt yields a remarkably simple pattern. Apparent ages from step 6-12 comprising over 87% of the 39Ar released, are virtually concordant, and give a plateau age of 130.4±1.0 Ma. The Ar-Ar total gas age (all 15 steps) is 130.1±1.3 Ma. When all data obtained from every step-heating are plotted on correlation or isochron diagram an age 130.5±1.3 Ma is obtained. About the Jurassic-Cretaceous boundary age, there are continuos disputations internationally and both 135 Ma and 144 Ma are proposed for the boundary. Chinese geochronologists prefer the former one. According to above dating results of Yl23 basalt, the geological age of Yixian Fm should be the Early Cretaceous in age.

关 键 词：辽西 义县组 玄武岩 AR-AR定年 早白垩世 

分 类 号：P534[天文地球—古生物学与地层学]