Abstract：The study area is located at the interseltion of Qiangtang plots and Bangong-Nujiang junction. Since there is well-preserved Late Jurassic-Early Cretaceous marine sedimentary record, this area is believed to be an ideal site for the research of Late Jurassic-Early Cretaceous environmental evolution and basin sediment types. In order to discuss the stratigraphic age of Ouli Formation and types of sedimentary basins in this area, careful study was taken on lithology combination, sedimentary environment, paleontological characteristics and so on. A lot of Late Jurassic fossils, such as Actinastraea minor Wu, Allocoenia trochiformis Etallon, Stylina andoensis Liao et Li, Stylosmilia michelini Milne-Edwards et Haime, were found in the Ouli Formation. The presentence of these fossils provides strong evidence to verify that the stratigraphic age of Ouli Formation is the Late Jurassic. The Ouli Formation is mainly made up of the restricted platform-tidal flat siliciclastic deposits intercalated with the carbonate deposits and sandwiched tidal channel gravel limestone. The results show that the sedimentary basin is a back-arc foreland basin in the study area in the Late Jurassic-Early Cretaceous.
2017, Vol. 4 
