Paleontological Institute of Shenyang Normal University, Shenyang 110034, China

A set of sediments yielding abundant fossils, sandwiched in volcanic rocks, outcrop in the Linglongta area of  Jianchang County in western Liaoning Province. The fossils consist of conchostracans, ostracods, bi- valves, fish, insects, plants, vertebrates, etc. Based on the regional stratigraphic investigation, measuring geological section and synthetic study of the fossils newly collected in the Daxishan site, the authors have assured the sed- iments belonging to the Tiaojishan Formation aged in Middle Jurassic, and the formation is underlying the Yixian Formation stratigraphically. The fossil assemblage of the Tiaojishan Formation indicates the characters of the Middle Jurassic Yanliao Biota.