Basal Huronian Conglomerates of Menominee and Calumet Districts, Michigan

The contacts of the Huronian and the granitic masses northeast of the Menominee and north of the Calumet districts, respectively, proved to be unconformities as earlier postulated by W. S. Bayley and his co-workers. Basal conglomerates truncating the foliation of the basement gneiss were found below the Lower Huronian Sturgeon quartzite in five key areas mapped in detail. No intrusive granite was found. In the Fern Creek area (Sec. 34, T. 41 N., R. 29 W.) the basal conglomerate is overlain by an argillite containing numerous ice-rafted granite blocks, which in turn is overlain by a tillite. The tillite, though limited in extent, is unique in the Southern Subprovince.