The volcanic rocks are distributed in Indosinian Volcanic Basin in the Mt.Maixiu area, in an east-west ribbon, with an exposed area of about 250 square kilometers and a thickness of more than 3,200 meters.  They are a set of continental facies volcanic rocks, formed in the Late Triassic about 200 million years ago. The Indosinian volcanoes have the strong eruption and complete lithology and lithofacies, which is a natural laboratory for the study of plate movement and volcanic geology of Qinghai-Tibet Plateau.