A discussion on Tuchenzi fossils and paleoclimate sedimentary environment in Qianjiadian basin of Yanqing County:Suspected dinosaur bones discovered for the first time in Yanqing, Beijing

The Tuchengzi Formation in Qianjiadian Basin of Yanqing County is composed of three lithologic members:the first member mainly consists of polymictic gravel and glutenite, the second member mainly consists of purplish red shale and argillaceous sandstone, and the third member mainly consists of compound gravel and gravel-bearing grit sandstone. A lot of fossils found in the second member have been reported, such as bivalves, conchostracans, Palaeontologists, plant fossils and dinosaur footprint. Neverthe-less, no relevant reports on the fossils of ostracods, sporopollen and dinosaur bones are found. In this study, the suspected dinosaur bone fossils were discovered for the first time in the second member of the Tuchengzi Formation in Qianjiadian Basin of Yanqing County, and LA-ICP-MS zircon U-Pb dating of the argillaceous sandstone was carried out. According to the age values of the low-er part of the first member (15.762±0.69Ma, ) and the upper part of the second member (157.13±0.96Ma), the formation age of the Tuchengzi should be early Late Jurassic. On the basis of previous studies, the ancient climate and sedimentary environment of the Qianjiadian basin are discussed.