High Quality Content by WIKIPEDIA articles! The Duluth Complex, the related Beaver Bay Complex (often treated as part of the Duluth Complex), and the associated North Shore Volcanic Group are rock formations which comprise much of the basement bedrock of the northeastern part of the U.S. state of Minnesota. The Duluth and Beaver Bay complexes are intrusive rocks formed during the formation of the Midcontinental Rift system; these adjoin and are interspersed with the extrusive rocks of the North Shore Volcanic Group produced during the same geologic event. These formations are part of the Superior Upland physiographic region of the United States, which is associated with the Laurentian Upland of the Canadian Shield, the core of the North American Craton.