Late Jurassic—Early Cretaceous Shamuluo Formation outcropped along the middle—western segment of the Bangongco—Nujiang Belt．Upper Jurassic shore—shallow marine deposits are formed in relatively stable environments，Shamuluo Formation，was named after Shamuluo area of the southern Yanhu district of Geji country．The Structural Belt has been divided into Mugagangri Group and Shamuluo Formation by many geologists based on in different regions，but the stratigraphic sequence division of the two strata has always been characterized by lithologic assemblage difference or granule change．However，they haven’t gotten the solid evidence of angular unconformity．At the bottom of the Shamuluo Formation in the Gengze area，the author discovered for the first time the top clayey weathering crust of the basal conglomerate and the underlying Mugagangri Group，which proved that the unconformitty of the two formations is credible.And then to determine the angle unconformity contact relationship between the Shamuluo Formation and the underlying Mugagangri Group．The discovery of the basal conglomerate is of great geological significance in studying the tectonic evolution of the NeoTethys ocean，the paleogeographic environment，the lower age limit of the Shamuluo Formation stratigraphy and the sedimentary facies．