Bulletin No. 33. The Geology of the Duluth Metropolitan Area

Abstract

The Duluth area is one of the most interesting parts of Minnesota. It is also a critical area in determining the relationship between various rocks of Keweenawan age in the Lake Superior district. The area, therefore, has received more or less detailed study from time to time. Most of these studies, however, referred only to special phases of the geology of the region and no general description has appeared since Winchell published volume four of his final report, which contains a special chapter on the Duluth area. The object of this project was to map the metropolitan area in as much detail as practicable, accompanied by such laboratory studies as seemed desirable. This work was followed by a compilation of all available geological knowledge on the Duluth area into a readable summary for interested residents, as well as for engineers and others who need geological knowledge of the area in their work. The field work was begun in 1937, and the major portion of the field seasons through 1940 was spent in the Duluth area and adjacent portions of the region. Other projects, mostly a result of the war, interfered with the completion of the field work and compilation of the results. The writer is indebted to many persons for innumerable courtesies during the work. The engineering staffs of St. Louis County and the city of Duluth furnished maps and information that aided greatly in the work. Dr. A. E. Sandberg and Mr. Ray Knutsen each served as field assistant for two years and much of the credit for the field work is due to them. Dr. Sandberg had previously spent a great deal of time on field work in connection with a thesis presented to the University of Cincinnati. Professor Thomas W. Chamberlin of the University of Minnesota, Duluth Branch, kindly prepared the chapter on economic geography which is published under his name. The writer is especially indebted to his colleague, Professor Frank F. Grout, for continued suggestions and advice.