Stratigraphic division and correlation of the Yixian Formation in Beipiao area, Liaoning Province

The Yixian Formation in the Beipiao area, Liaoning Province, consists of a series of volcanic-sedimentary rocks, including basic and intermediate-basic volcanic lava, pyroclasts and terrestrial sedimentary rocks. Based on the regularity of volcanic activity, the Yixian Formation was divided into four members from bottom to top. The first member is of basal conglomerate, basic and intermediate-basic volcanic rocks; the second member is of lacustrine sedimentary rocks, or in another word, precious fossil-rich sedimentary beds; the third is of basic volcanic rocks and the fourth is of upper conglomerate. Field mapping and comprehensive study also indicate that there are abundant vertebrate fossils (mainly of Psittacosaurus) in the first member of Yixian Formation. "Jehe Biota" (include Sinosauropterxy,Confuciusorns sanctus, Archaefructus,etc.) was yielded in the second member. From west to east, the volcanic activity of the Yixian Formation took place regularly from early to late and from basic and intermediate-basic to acid(alkali).