1. Beijing Research Institute of Uranium Geology，Beijing 100029，China；2. Geological Party No.243，CNNC，Chifeng，Inner Mongolia 024000，China；3. Research Institute No.270，CNNC，Nanchang，Jiangxi 330200，China
In order to accurately determine the prospecting target layer and its age of the sandstone-type uranium metallizotion in the Beierhu depression of Hailaer Basin，Inner Mongolia，the gray mudstone samples in the borehole were collected systematically and analyzed for the sporopollen fossils. The results showed that the sporopollen assemblages of the target layer in the study area were characterized by the development of cyathidites and dissacciatrileti，with 55.5% of the nude sub-pollen and 44.5% of the fern spores，which are similar to the sporopollen assemblages of Cyathidites in the second section of the Lower Cretaceous Yimin Formation，belonging to the Early Cretaceous Barremian period. Based on the comprehensive study of geological conditions of uranium mineralization in the region，it was considered that the main ore-prospecting target layers are Yimin Formation deposited in the warm and humid tropical paleo-climate. The Yimin Formation is with good permeability，stable structure of the mud-sand-mud beds，and great reduction capacity，which are favorablefor the formation of sandstone-hosted deposit.