1. College of Earth Sciences��Jilin University��Changchun 130061��China; 2. Shenyang Institute of Geology and Mineral ��esources��Shenyang 110034��China; 3. Geological Party No. 243��CNNC��Chifeng 024006��Inner Mongolia��China

In this paper�� two groups of sandstone samples from the Jurihe area in Jarud Banner�� Inner Mongo- lia��have been collected and examined by the zircon LA- -ICP- -MS U- -Pb dating which were originally regarded as the Upper Permina Linxi Formation�� Both of the two groups of samples showed significant Triassic age peak��i. e. ��244 Ma for sample ZL010 and ��250 Ma for sample ZL011��which indicates that the studied area once existed Early- Middle Triassic sedimentation and the original scheduled Permian strata was Triassic actually�� Moreover��the youngest ages of 242 ±4 Ma (sample ZL010) and 241 ± 4 Ma (sample ZL011) have been obtained��suggesting that the lower limit age of the deposit was Middle Triassic�� Combining with the previously discovered Early and Middle Triassic continental fossil evidences in the middle part of the Great Khingan Mountains��we concluded that the Early-Middle Triassic sedimentation were probably widespread in the Great Khingan Mountains��northeastern Inner Mongolia�� Subsequently�� the large- scaled tectonic uplift movement took place in the Great Khingan Mountains in Late Triassic��leading to the intensity denudation of the Triassic strata in Jurihe area��