Advances in the study of non-marine Jurassic-Cretaceous biostratigraphi cal boundary and candidate stratotype in Luanping basin,northern Hebei

The Jurassic-Cretaceous Dabeigou and Dadianzi Fms ,in Luanping basin,is typical and no hia-tus non-marine depositional succession,within it Jehol fauna is founded,around the northern Hebei and western Liaoning.Dabeigou and Dadianzi Fms at Zhangjiagou of Luanping basin is characterized by contin-uning terrestrial lake deposition from beach to deep lake subfacies,which is considered as an ideal candidate section for stratotype and ostracoda and conchostracans are prevailing biota within it.On the basis of sedi-mentary facies and successions ,ostracoda and conchostracans biota,herein is given a conclusion to the Jurassic-Cretaceous biostratigraphical boundary and stratotype.The boundary is marked by the disappear of Luanpingella,Nestoria?Pseudograpta and Keratestheria,and first occurrence of Cypridea and Eosestheria,and the top part of fan-delta front subfacies is also another marker for the boundary.