THE MESOZOIC STRATA AND THE JURASSIC-CRETACEOUS BOUNDARY IN THE DAXINGANLING REGION

The Jurassic-Cretaceous strata in Daxinganling region are studied regarding the lithostratigraphic units,contact relation,distribution,paleontology and isotopic chronology.The J-K boundary is discussed on the basis of such study.The U-Pb isotopic ages of zircon by SHRIMP are greater than 145 Ma.With the support of fossil assemblages of Peipiaosteus,Nestoria-Keratestheria and Ferganoconcha,the J-K boundary is set between Baiyingaolao formation and Meiletu and Yixian formations.