252 GEOLOGY OF EASTERN WISCONSIN. 



remnant polished spots, and from all these, trains of porphyry bowl- 

 ders stretch away in the direction of the striae. 



THE QUARTZITES OF PORTLAND AND WATERLOO. 



Thirty-five miles south of Pine Bluff, over an area entirely covered 

 by Paleozoic rocks, some as recent as the Galena, we again encounter 

 the Archaean rocks in the form of the quartzites of Portland and 

 "Waterloo. 



The outcrops in the town of Portland * are several in number. The 

 most southwesterly is an oval island, lying mostly in the S. E. qr. of Sec. 

 33, and is entirely surrounded by lowland or marsh. The outcrop at- 

 tains but a slight elevation, and its rounded contour shows abundant 

 evidence of the glacial agencies that have swept over it. ]S r ot only 

 striae, but deep, broad furrows, show the direction of movement to 

 have been S. 15 to 20 W. Bowlders appear in great force upon the 

 protected side of the island, and doubtless thickly underlie the deep 

 morass in that direction, as they appear again upon the hills be- 

 yond. Directly to the east, in sec. 34, there is a slight exposure near 

 the base of a somewhat elevated north and south ridge, of which it 

 doubtless forms the nucleus, if not the chief portion. 



Less than one mile north of these outcrops, the quartzite again dis- 

 covers itself on the brow and west flank of the ridge facing Waterloo 

 Creek. There is no evidence that any later formation overlies the 

 quartzite between this and the two preceding outcrops, and so the 

 three will be found mapped as constituting a single Archaean area. 

 A short distance further to the north (N. W. qr., see. 27), the quartz- 

 ite rises in the midst of a marsh-like lake, constituting Rocky Island. 

 It may be characterized as a low dome covered with unsymmetrical 

 roches moutonees. 



About two miles southeast, at the foot of a hill, and on the edge of 

 a marsh, occurs a low and limited outcrop (sec. 35, S. E. J, and sec. 30, 

 S. W. J). One-half mile to the northeast, across a marsh, there occurs 

 another exposure, similarly situated in the southern extremity of a 

 north and south ridge, and about the same distance to the southwest, 

 still another one may be seen ; the three lying nearly in a straight 

 line, and separated by marshes. They are regarded as being project- 

 ing knobs of a common area, and are so mapped. Between these and 

 the three outcrops first mentioned, as also between both these and 



1 See note on the Age of the Metamorphic Rocks of Portland, Dodge Co., Wis., by 

 R. D. Irving, Am. Jour. Sci., Third Series, Vol. V, p. 282. 



