辽西地区白垩纪张老公屯组火山岩的层位及时代

辽西地区白垩系义县组之上存在一期火山喷发活动已得到大多数学者的认可，但其所属层位仍有争议，主要有4种意见：位于孙家湾组之上；位于孙家湾组与阜新组之间；位于九佛堂组与阜新组之间，与沙海组层位相当；位于沙海组与九佛堂组之间.根据野外出露情况、区域分布特征及同位素年代资料等，认为该期火山岩位于孙家湾组之下，覆盖于义县组、九佛堂组、沙海组、阜新组等不同层位上，同位素年龄为97~106 Ma，属早白垩世晚期.

THE HORIZON AND AGE OF THE CRETACEOUS ZHANGLAOGONGTUN FORMATION IN WESTERN LIAONING PROVINCE

It has become a common understanding that the Cretaceous volcanic rocks(Zhanglaogongtun Formation) overlap the Yixian Formation and other older strata in Western Liaoning Province.However,the horizon and age of the volcanic rocks are in dispute.There are four major viewpoints: 1) above the Sunjiawan Formation: 2) between the Sunjiawan and Fuxin formations;3) between the Fuxin and Jiufotang formations;and 4) between the Shahai and Jiufotang formations.According to the sequence of strata,regional stratigraphic correlation and isotopic age data,the Zhanglaogongtun Formation should occur between the Sunjiawan and Fuxin formations,overlapping the Yixian,Jiufotang,Shahai and Fuxin formation and other older strata.The isotopic age ranges 97-106 Ma,indicating a late Early Cretaceous age.