Evidence is presented to show that a granite conglomerate of the Archaean Yilgarn succession rests uncomformably on granite in the Jones Creek area of Western Australia, 400 km north of Kalgoorlie. South of Jones Creek the conglomerate evidently overlies with angular discordance the lower section of Archaean greenstone (mainly metabasalt and layered metagabbro). The relationship between this lower greenstone and granite is obscured by recent cover, hence the granite is either 'middle' Yilgarn in age or represents the basement on which the Yilgarn succession was deposited. The conglomerate is fairly well stratified, characteristically with rounded granite clasts and an arkosic or marie matrix. Other types of igneous clast are locally present but sediment clasts are absent. Its proposed formation name is Jones Creek Conglomerate. Copyright.