File:Preliminary report on the geology of east central Minnesota including the Cuyuna iron-ore district (1918) (14577590419).jpg

Identifier: preliminaryrepor00hard (find matches)
Title: Preliminary report on the geology of east central Minnesota including the Cuyuna iron-ore district
Year: 1918 (1910s)
Authors: Harder, Edmund Cecil, 1882- Johnston, A. Walfred, author Geological Survey (U.S.)
Subjects: Geology Iron mines and mining
Publisher: Minneapolis, University of Minnesota
Contributing Library: Wellesley College Library
Digitizing Sponsor: Boston Library Consortium Member Libraries

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found both north and south of the Northern Pacifictracks. The ridges trend about east and west and rise from a few feetto 50 feet or more above the surrounding flat region. These ridges havenot as yet been examined in detail. To the northeast they connect withthe extensive exposures of rock along St. Louis River in the vicinity ofCarlton. Thomson, and Cloquet. In the St. Louis River valley slates and graywacke with a few dikesof dark igneous rock are exposed almost continuously along the riverfrom the center of section 1, T. 48N., R. 16W. on the southeast, to theeastern part of section 15, T. 49N., R. 17W. on the northwest, a distanceby river of about 15 miles. These rocks rise as high steep escarpmentson both sides of the river for much of the distance and within this gorgeare numerous falls and rapids. They also rise as long, narrow, east andwest rock ridges, that extend from a few hundred feet to several mileson either side of the river gorge. These ridges are very numerous PLATE X
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B. SMALL DIKE OF DIABASE INTRUDING SLATE AT CARLTON ROCKS OF EAST CENTRAL MINNESOTA 89 locally. In the region around Carlton and Thomson they cover severalsquare miles and continue southwestward from Carlton for some distancein the direction of Otter Creek. In the southeastern part of the region the slate and graywacke areassociated with younger rocks such as the sandstones, conglomerates, andbasic lavas of the Keweenawan. In sections 1 and 2, T. 48N., R. 16W.,a coarse quartzose Keweenawan conglomerate lies unconformably on theupturned edges of the slate and graywacke. In the bed of Mission Creekand its tributaries, in sections 30 and 31, T. 49N., R. 15W., north ofFond du Lac, are several exposures of slate north of the overlyingKeweenawan sandstone. Outcrops of slate and graywacke also occuralong Midway Creek in sections 5 and 6, T. 49N., R. 15W., a short dis-tance west of the border of the lava flows extending northward fromDuluth. The outcrops throughout the St. Louis River valley

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