6 Unique Geology and Geoheritage of the Lake Superior Region

Monday, 18 May 2020
8:00 AM - 12:00 PM
Saint Louis River Room

THE FIRST GEOLOGICAL SURVEY OF MINNESOTA'S NORTH SHORE: THE OWEN/NORWOOD REPORT OF 1852, ITS HISTORICAL CONTEXT, AND ITS PLACE IN THE EVOLUTION OF GEOLOGICAL SCIENCE

Paper number: 6-11
Program: Theme Sessions
Time: 11:00 AM – 11:20 AM

Authors

  • John C. Green Presenting Author
    Professor Emeritus, University of Minnesota Duluth, Duluth, MN

Abstract

The Owen/Norwood geological survey of Minnesota's North Shore of Lake Superior was carried out in a dynamic period of both American socioeconomic history and the growth of the science of geology. Begun in 1847, it charged David Dale Owen with surveying most of WI, MN, IA and part of NB. Owen was assisted in much of this huge area by other notable geologists; Joseph G. Norwood examined the North Shore and adjacent areas.

This was part of the "manifest destiny" of Euroamerican occupation of North America. Access to the interior of the Old Northwest was facilitated by successive treaties with Native Americans (mostly Chippewa here), in which lands in MI and WI were ceded in 1836, 1837, and 1842 to the U. S. Douglass Houghton had recently (1840-1841) surveyed the Upper Peninsula for the State of MI and had described its abundant native copper deposits, and the U. S. wanted to determine what the mineral potential might be for an anticipated land cession in the wilderness of northeastern MI Territory.

Norwood was a medical doctor, but he had also studied geology and mineralogy in Europe. However, although geology had developed greatly between the 1790s and 1840s with James Hutton's uniformitarianism and Charles Lyell's "Principles of Geology" (1830), most of this progress had involved sedimentary geology, and the origins of "crystalline" (basically igneous and metamorphic) rocks were still poorly understood. Norwood's hand-sample mineralogy was remarkable, and although he correctly recognized that many, if not most, of the bedrock types were igneous ("trap" and "amygdaloid"), he attributed most of the rest of this 10-km thick volcanic pile to the metamorphism of sediments and slates.

Other geologists who followed Norwood, such as Henry Eames and N. H. Winchell also struggled with North Shore rock origins, but by the time of R. D. Irving (1883) their basic igneous, and especially volcanic, nature was well established.

Meanwhile, Louis Agassiz had developed the concept of recent continental glaciation, and had moved to America in 1846 and was giving popular lectures in Eastern cities. Norwood must have read Agassiz's "Etudes sur les glaciers" (1840) or attended his lectures, as in many places in his report he calls attention to surficial deposits, erratics, and bedrock scratches that are clear evidence for glaciation.

Geological Society of America Abstracts with Programs. Vol. 52, No. 5

doi: 10.1130/abs/2020NC-346718

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