Abstract: The foraminifera Mesorbitolina sp.occurs in the unfossiliferous strata in the Gase region,northern Xizang.The stratigraphic ages are traced back to the Late Jurassic-Early Cretaceous.The strata should be assigned to the upper part of the Shamuluo Formation.The timing of the strata is significant to the sedimentary facies analysis and palaeogeographic reconstruction of the Shamuluo Formation.