Box 15, Folder 8: Geological Survey, Draft Report 1874

GEOLOGY

By I. A. Lapham.

The first considerable effort to develop the geological features of the territory now constituting the state of Wisconsin, was made in 1839, by Dr. D. D. Owen, Dr. John Locke, and others, in what is known as the lead region, chiefly in the counties of Grant, Iowa, and La Fayette, in the south=western part of the state. This work was done in pursuance of a resolution of Congress, calling for information relative to the mineral lands of the United States, and the results were reported in an Executive Document (1) with maps, sections and drawings of fossils. The next was also made by Dr. Owen, or under his direction, on behalf of the general government, being a Reconnoissance [Reconnaissance] of the Chippewa Land District, which then included a large portion of the state. The results were reported in 1848 (2) with a large map; and again more fully, in 1852, in a large volume on the Geology of Wisconsin, Iowa, & Minnesota.

(1) House Ex. Doc. No 239, 26th Cong. 1st Session. 1840

(2) Senate Ex Doc No 57,- 30th Cong 1st Session 1848

In Foster + Whitney's Reports upon the Copper and Iron Regions of Lake Superior, (1850 & 1856) are some chapters relating more especially to Eastern and north = Eastern Wisconsin.

The state has made several efforts towards a geological survey of its territory, and a number of "annual reports" in pamphlet form have been published. The Report of Hall + Whitney (1862) forms a volume of 455 pages, with maps, sections and wood cuts of the characteristic fossils, & is the only considerable publication heretofore made by the state. Professors Edward Daniels, Ezra S. Carr, James Hall, J. D. Whitney, James G. Percival + John Murrish, have been employed in this work at various times.

A more complete geological survey of the state is now in progress, under the authority of a law approved in March 1873; but no report of the results has yet been published.

It is proposed to give, briefly, a general idea of the principal facts already known by describing Each rock = formation, in accordance with its relative age, beginning with.

I. The Laurentian.

The oldest and lowest of these formations found in Wisconsin are granytic rocks, which may be regarded as the foundation, or floor upon which all the others have been laid. down. There can be no doubt of the great age of this granytic series of rocks, as was first indicated by Foster + Whitney, being, so far as was then known, older than any organic life, and hence called Azoic : but as they are supposed to contain traces of organic remains elsewhere the name Archaean has been adopted by recent writers. They usually exist in the form of rounded or dome = =shaped knolls of considerable extent and of but little Elevation. Essentially, granyte consists of an aggregation of crystalline grains of quartz, feldspar, and mica; but the name is usually applied to rocks in which hornblende takes the place of mica (Syenyte) and to other crystalline aggregations. When slaty in structure it is Gneiss, or Mica= Slate. All these forms occur in Wisconsin. Some

varieties, especially from the Oconto and Wolf rivers, have a great much resemblance to the Scotch Granyte of which so much is now imported for ornamental purposes; but no attempt has yet been made to quarry any of our granytes, owing to their remoteness from the means of transportation, being mostly in parts of the state but little settled and improved. Other varieties, caused by the varying constituent minerals, and their relative proportions, are found, and might be rendered useful in masonry ; including fine grained & coarse, red, white, gray, light = colored, mottled, porplyritic, graphic &c.

Granyte and granytic rocks are found at Black River Falls, on the Wisconsin river, and Chippewa rivers, and at numerous other localities within the district represented on the accompanying map as "Granytic + Huronian." It will be seen that they underlie portions of the counties of Burnett, Polk, Barron, Ashland, Chippewa, Clark, Wood, Marathon, Lincoln, Portage, Waupaca, Shawano, and Oconto. They are so uniformly covered with "drift" that it is difficult to ascertain their presence or trace their boundaries.

4

II. Huronian Rocks

Resting upon these granytic prominences, and sloping away from their sides in all directions are often found strata of chloritic, talcose, or argillaceous slates, and quartzytes which are supposed to have the same age as the rocks which in Canada are called Huronian. These rocks are of great practical interest on account of the masses of iron ore associated with them; most abundantly at the Penokie Iron Range in Ashland County, and at Black River Falls (Jackson Co.) The famous iron deposits of the Marquette & Menomonee regions in Michigan are in the same series of rock. It is supposed that the iron range near the Menomonee extends across that river into Wisconsin, and measures are in progress for ascertaining the truth of this supposition.

The Penokie Iron = bearing rocks have been traced for a distance of sixty miles; always accompanied by magnetic and specular iron ores varying from a few feet to one hundred in thickness. The ore is mixed with the rock in proportions varying from one or two to Eighty per cent. They have been carefully "sampled" and

5