File:Report of a geological survey of Wisconsin, Iowa, and Minnesota - and incidentally of a portion of Nebraska Territory - made under instructions from the United States Treasury Department (1852) (14728584016).jpg

Identifier: reportofgeologic00owen (find matches)
Title: Report of a geological survey of Wisconsin, Iowa, and Minnesota : and incidentally of a portion of Nebraska Territory : made under instructions from the United States Treasury Department
Year: 1852 (1850s)
Authors: Owen, David Dale, 1807-1860 Leidy, Joseph, 1823-1891 Norwood, Joseph Granville. 1807-1895 Parry, Charles Christopher. 1823-1890 Pratten, Henry Shumard, B. F. (Benjamin Franklin), 1820-1869 Whittlesey, Charles, 1808-1886 Dwight, Jonathan, 1858-1929, former owner. DSI Tucker, Marcia Brady, former owner. DSI Dawson, H. B., former owner. DSI Dall, William Healey, 1845-1927, former owner. DSI United States. General Land Office United States. Department of the Treasury
Subjects: Geology Paleontology Botany Botany Plants Plants Birds Birds
Publisher: Philadelphia : Lippincott, Grambo & Co.
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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owerside of the dike, the slate through which it cuts is altered for some distance.About thirty-six feet from the trap, it is but slightly changed, except whereit is intercalated with a bed of basaltic rock, when it assumes something of a trap-pous character (No. 2). Twenty-five feet from the dike, it is still more altered(No. 4), and in still nearer proximity, some of the beds are converted into aschistose quartz-rock. The width of the dike is two hundred and twelve feet ,:and its height above the fall, in the direction of Grand Portage Bay, is one hun-dred and ninety-four feet. It bears north 45° east. The slates, which, with 406 DESCRIPTION OF THE COUNTRY BORDERING the intercalated and overlying trap-beds, ascend nearly to the summit of theridge, dip southeast, at an angle of 4°. Overlying the slates, on the flank of theridge, is a bed of crystalline greenstone (No. 5), the same that is found cappingthem over a large district of country. The junction of the slates with the green-
Text Appearing After Image:
GORGE AND FALLS OF PIGEON RIVER. stone is exhibited, by the first section on page 407, by Major Owen, of an escarp-ment, a short distance above the fall. In the drift on the summits of the ridges,many fragments of red sandstone (No. 6) occur. About one mile further up the river, is a small fall, where the exposure of theslaty beds is sixty feet thick, and capped by a bed of greenstone. Below this fall, ON THE NORTHWEST SHORE OF LAKE SUPERIOR. 407 the slates have no perceptible dip. Between the two falls, the argillaceous beds areextremely fissile (No. 12), for the height of fifteen or twenty feet above the river-level, and then become gradually more and more altered, until they assume acolumnar structure as the greenstone-bed is approached, as shown in the secondsection on this page.

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