The volcanic rocks are distributed in Duofutun faulted basin, in a north-south ribbon, with an exposed area of about 126 square kilometers and a thickness of more than 1,200 meters.  They are a set of continental facies volcanic ejecta. The main lithologies include massive, stratified amygdaloidal basalt, basalt andesite, etc. And the volcanic clastic rock includes tuff, volcanic breccia, etc. Yanshanian volcanoes manifest basic volcanic eruption with continental rift type.  And the formed volcanic rocks are one of the few records of intracontinental volcanic activities in the northeastern Tibetan Plateau, which indicates an important geological event that the West Qinling Orogenic Belt experienced a strike slip pull apart to fissure volcanic eruption in the late Early Cretaceous 100 million years ago.