THE DISCOVERY OF CALCAREOUS NANNOFOSSILS IN MESOZOIC MARINE STRATA AT GYANGZE, SOUTHERN TIBET AND ITS SIGNIFICANCE

The marine strata around the Jurassic-Cretaceous boundary crop out well in southern Tibet. The samples collected from the Jiabula Formation in the Jiabula-Gokou section of Gyangze area were analyzed by the authors under high-resolution microscope. The calcareous zonal nannofossils of Berriasian-Valanginian stages of early Cretaceous were found for the first time in the section. Some global or intercontinental species with regional significance for correlation were also discovered. In general, the nannofossils discovered have the same features of the Early Cretaceous assemblage. The discovery provides new paleontological evidence for delineation of the Jurassic-Cretaceous boundary in southern Tibet.