A lot of meta-basalts and mafic dykes occurred in the northern Liaohe Group in Haicheng-Caohekou area, among which, the meta-basalts of Dashiqiao Formation in  south Helan, Liaoyang, Liaoning Province preserved a good pillow structure. Based on their occurrence, zircon dating and previous research data, it is suggested that the meta-pillow lava is formed at ~1 880 Ma which could represent the forming age of Dashiqiao Formation, and the granite pegmatite is at ~1 860 Ma which can be considered as a marker of the end of orogeny, and the meta-diabase dyke at ~1 830 Ma which may indicates the beginning of post-orogeny extension.