A statistical study of the orientation of current structures in the sediments of the Portage Lake lava series and Copper Harbor conglomerate was made to determine the sources of the Keweenawan conglomerates of northern Michigan. These data clearly indicate that the major paleogeographic features in the Lake Superior region during Keweenawan time were an elongate basin, trending northeast between Isle Royale and the Keweenaw Peninsula, with bordering highlands to the west and southeast. The principal source area for the conglomerates on the Keweenaw Peninsula was probably not more than 10 miles southeast of the present outcrop belt, with the genera] area of the Huron Mountains being an important center of dispersal. The conglomerates on Isle Royale were derived from nearby highlands in Minnesota and Canada.