518 GEOLOGY OY CENTIIAL WISCOIsSm. 



insensibly on to the Lower Magnesian limestone. Eastward, in sections 24 and 25, the 

 descent of 200 feet to the headquarters of Seeley creek is very rapidly made, and sand- 

 stone is exposed through nearly the whole vertical distance. 



On Sec. 35, a large exposure of reddish glassy quartzite occurs in a ravine, at an ele- 

 vation much below that of the country occupied by sandstone to the northward. A few 

 rods up the ravine, sandstone ledges occur at a higher level. Taken together with the 

 construction of the high country all through the east side of the town of Wcstfleld, this 

 outcrop is believed to indicate the existence throughout of a quartzite core only slightly 

 covered with sandstone layers. 



The outcrop just referred to is on the slope downward towards the valley of the Wis- 

 consin, and is really the western end of the southern quartzite range. From here east- 

 ward to Devil's Lake, we find this range as bold and wide as it is east of the lake, and 

 characterized by the same heavy timber and clay soil. In T. 10, R. 5 E., Honey 

 Creek, the southern slope of the range is in the northern row of sections. In the south 

 side of T. 11, R. 5 E., Freedom, are very high rounded swells, some of which are 

 amongst the highest points on the range. On the northern slope, in this town, the 

 streams flowing north into the Baraboo set back into the ridge in deep ravines, about 

 which sandstone sometimes occurs at high levels. On the N. W. qr. of Sec. 22, the 

 quartzite shows in two bluffs, 150 feet high, on either side of the creek, with a distance 

 between of about one-eighth of a mile. The rock here is for the most part closely like 

 that at Devil's Lake, ))ut portions are unusually Kght-oolored (1,271), showing a hght- 

 brown weathered surface, and a nearly white, shghtly granular, fresh fracture. Regu- 

 larly intcrbedded is a soft, hghi-gray, greasy, finely laminated, clay-plate (1,272), con- 

 taining according to analysis by Mr. A. C. Presoott: silica, 59.84; alumina and iron 

 oxide, 35..39; magnesia, 0.10; water, 4.67^100; the iron oxide being in very small 

 amount only. Both quartzite and slate are plainly bedded, the strike being N. 23° W., 

 the dip 16° N. 



On the road extending southward from Bloom's Station across the range, into Honey 

 creek, horizontal sandstone ledges axe seen, as far as the N. W. qr. of Sec. 23, at an ele- 

 vation of 530 feet. In the southern part of the same section, quartzite is exposed at an 

 elevation of 700 feet, and along the east side of Sec. 26, an elevation of 830 feet is 

 reached. 



In the southern row of sections of T. 11, R. 6 E., Sumpter, the south slope of the 

 range is very bold and prominent, owing to the low ground of Sauk Prairie, which 

 stretches from the foot of the bluffs for eight or nine miles to the southward. AU along 

 the slope towards the prairie are large rough exposures, — as, for instance, on the west 

 Sauk road on Sec. 34; in the ravine on Sec. 27; on the east Sauk road, in Sec. 35, and 

 all along the range eastward from here to the Devil's Nose. On the north slope of the 

 range in the N. E. qr. of Sec. 15, T. 11, R. 6 E., dark-grayish, somewhat granular 

 quartzite shows in a large exposure, with a dip of 26° N. 



Within the circuit of the quartzite ranges, arc a few isolated pomts of quartzite 

 and schistose rocks, which rise through the sandstone that forms the basement of the 

 valley. One of these, on the south line of Sec. 29, T. 12, R. 7 E., on Peck's Prairie, is 

 a low rounded ridge 75 feet high. The rook here (1,247) is a hght pinkish-grey meta- 

 Morphic conglomerate, composed of small rounded pebbles of quartzite l-16th to l-8th 

 inch in diameter, embedded in a finer-grained matrix of similar character. An obscure 

 N. 70° dip is to be seen at a few points, and veins of miUcy quartz occur, cairying nests 

 of large-surfaced brilliant specular iron (1,248). One of these veins is 75 feet long and 

 2 feet wide, with nests and seams of specular iron, 1 to 3 inches wide. A few rods west 

 of the quartzite, at the center of the north line of the N. W. qr. of Sec. 82, horizontal 

 sandstone ledges are seen. 



Other areas showing quartzite and slato occur on Sec. 5, T. 11, R. 6 E.; Sec. 4, T. 11 



