Abstract: Basic volcanic extrusive rocks didtributed extensively in Proterozoic strata in the Xunhe area in northern Liaoning were previously called the“Dadianzi andesite”,covering an area of about 2000 sq km.The oreigin and age of the volcanic rocks have long been controversial.According to the data of 1:50000 regional surveys obtained in recent years,the paper deals with the regional distribution,geological occurrence,rock types,mineral composition,textures and structures and petrochemistry of the volcanic rocks.Finally they are confirmed to be marine volcanic rocks—spilite—of Wumishanian age（Proterozoic）and the Erdaogou Subformation has been established.