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通过对辽西及邻区白垩纪不同剖面的磁性地层资料的综合分析,对比国际中生代地磁极性年表,指出义县组含鸟化石层的地质时代至少应老于M13正极性时(129.6Ma)所对应的地质年代,介于131.71～142.27Ma之间。综合研究表明,Swisher等通过沉凝灰岩中透长石Ar-Ar法测定的义县组含鸟化石层的同位素年龄(124.6±0.2)Ma值得商榷。
Based on the comprehensive analysis of the Cretaceous strata in the western Liaoning Province and the adjacent areas, comparing the international Mesozoic polar history chronology, it is pointed out that the geologic age of the fossil birds in the Yixian Formation should be at least older than M13 (129.6Ma) The corresponding geological age, between 131.71 ~ 142.27Ma. The comprehensive study shows that the isotopic age (124.6 ± 0.2) Ma of the Yixian Formation-containing fossil layer measured by the Swisher et al. Through the Ar-Ar method of the sedimentary limestone is questionable.