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.