The Horizon and Age of the Confuciusornis in Beipiao, Western LiaoningLi Peixian, Cheng Zhengwu (Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037)Pang Qiqiang (Shijiazhuang University of Economics, Shijiazhuang 050031) Over the area between Beipiao City and Yixian County, Hebei Province, there outcrop trachyte-trachyandesite volcanic rocks of the Upper Jurassic Zhangjiakou Formation and sedimentary series of the Dabeigou Formation. The 40Ar-39Ar datings of the volcanic rocks give an age of 143.9 Ma. The most recently defined basalt member in the lower part of the Cretaceous Yixian Formation was dated at 137(129 Ma, while the andesite member in the upper part at 126(120 Ma. It is ascertained that sedimentary rocks with Confuciusornis, i.e. the Jingangshan Formation around Sihetun, are of 123(120 Ma in age. Based on fossil records, isotope ages and horizons of the Yanliao (Beijing-Hebei-Liaoning) area, it is considered that Confuciusornis and the beds containing such fossils should belong to the Early Cretaceous.Key words: western Liaoning, Upper Jurassic, Lower cretaceous, isotope
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