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Please use this identifier to cite or link to this item: http://hdl.handle.net/11299/56835

Title: Bulletin No. 28. The Geology of the Anorthosites of the Minnesota Coast of Lake Superior
Authors: Grout, Frank F.
Schwartz, George M.
Keywords: geology
anorthosite
Minnesota Geological Survey
northeastern Minnesota
north shore Lake Superior
Keweenawan
Issue Date: 1939
Publisher: Minnesota Geological Survey
Series/Report no.: Bulletin
28
Abstract: The northeast corner of Minnesota, lying north of Lake Superior and comprising Cook and Lake counties and part of St. Louis County, is underlain by Keweenawan rocks except for a narrow strip along the Canadian border. Early studies of these rocks were made principally by Winchell and by Irving, as shown by the list of publications given below. Because of the size and inaccessibility of much of the region, these early studies were confined to a narrow strip along the shore of Lake Superior. Later Grout and other members of the Minnesota Geological Survey made detailed studies of the Duluth gabbro. Between the areas covered by these workers lies a region in which only reconnaissance work had been done previous to the mapping presented in this report. It is planned eventually to map in detail this entire area, but as it embraces approximately 4,000 square miles of forested or brushy country, much of it not easily accessible for detailed work, it will take many field seasons to complete the task. The particular region mapped in this survey was selected because of unusual plagioclase feldspar masses of very high purity, for which it is hoped uses may be found, but the results are also significant as an example of the geology of a great Keweenawan area. The Keweenawan of this region consists almost entirely of igneous rocks. and even the few sedimentary rocks known are closely connected with extrusive igneous activity. It is about centrally located in the Keweenawan area of the north shore of Lake Superior and lies above the thickest part of the Duluth gabbro, but probably is not connected with it by continuous intrusive masses below the drift.
Description: Six map inserts as pdfs, scales from 1:31,500 to 1:250,000.
URI: http://purl.umn.edu/56835
Appears in Collections:Bulletin of the Minnesota Geological and Natural History Survey (1887-2000)

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File Description SizeFormat
MGS_B_28.pdfBulletin 287.91 MBPDFView/Open
bull28_pl6[1].pdfPlate 6844.43 kBPDFView/Open
bull28_pl5[1].pdfPlate 5836.66 kBPDFView/Open
bull28_pl4[1].pdfPlate 41.62 MBPDFView/Open
bull28_pl3[1].pdfPlate 31.56 MBPDFView/Open
bull28_pl2[1].pdfPlate 21.46 MBPDFView/Open
bull28_pl1[1].pdfPlate 11.27 MBPDFView/Open

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