THE LOWER SILURIAN ROCKS. 569 



the valley rises rapidly from it, 200 to 300 feet, but shows sandstone only, except in one or 

 two places where exceptional elevations are reached. One such place is on the county line 

 in the southwest corner of the town of Wonewoc, just south of which, on the S. E. qr. of 

 the N. E. qr. of Sec. 6, T. 13, R. 2 E., Sauk county, the Lower Magnesian limestone is 

 quarried, at an elevation of 300 feet above the railroad track at the village of Wone- 

 woc, or at a total altitude of 630 feet. Only a small thickness (3 to 4 feet) of limestone 

 is exposed, and immediately below are seen ledges of coarse, brownish, non-calcareous 1 

 sandstone, intermingled with which, and in the uppermost layers predominating, is a 

 whitish, chert-like material, having somewhat the appearance of a grayish, granular 

 quartzite (1350). Limestone appears also to cap the high ground in Sec. 1 of Wonewoc, 

 and in portions of the corner sections of the three adjoining towns. The limestone was 

 not seen here in place, but on the north side of the ridge large, fallen m-asses were noticed, 

 showing the ordinary characters of the Lower Magnesian; and the sandstone exposures 

 do not extend to the summit. On the west side of the ridge, where the Mauston and 

 Wonewoc road descends into the valley of a small stream on the north side of Sec. 12, 

 50 feet of red and pink, friable, finely laminated, non-calcareous sandstone, with firm, 

 white bands (1340) are exposed. The white bands are exceedingly fine-grained, and 

 made up of sharply angular grains of glassy quartz, being in this respect quite different 

 from most of the sandstone of the Potsdam series. Scolithus occurs quite abundantly 

 in this rock. On tho south side of the stream, sandstone is again exposed of similar 

 character, and rising higher, the uppermost layers containing the peculiar quartzitic or 

 cherty material (1353) mentioned above as occurring just beneath the limestone on Sec. 

 6, T. 13, R. 2 E. The highest point of this sandstone is about 15 to 20 feet below the 

 summit of the ridge in Sec. 1. 



From the lowest exposures along the Baraboo river to the limestone on the tops of tho 

 ridges, the whole thickness of sandstone is not less than 300 feet. The peculiar red- 

 and- white-banded and cherty sandstone occurring just beneath the limestone appeal's 

 to be without doubt in the Madison horizon, but with an unusual thickness. The Men- 

 dota limestone was not noticed anywhere in the region, though benches occur on tho 

 hills, at the proper elevation, which might be due to its presence. The dolomitic bands 

 that characterize the Upper Potsdam further southward, were also not seen. 



Along the northern face of the watershed between the Earaboo and Leinonweir rivera, 

 from Camp Douglas to the Dalles, numerous isolated bluffs and towers of sandstone oc- 

 cur. At Camp Douglas Junction, Sec. 28, T. 17, R. 2 E., is a group of -these bluffs, 

 and a number more occur within a radius of two or three miles. Target Bluff, a few 

 rods west of the depot, is a flat-topped mass of sandstone about % of a mile long, and 

 120 feet high, with nearly vertical sides. The lowest layers are thick, cross-laminated, 

 coarse, non-calcareous, brownish, and exceedingly friable, having almost no coherence. 

 The same characters, except the cross lamination, are persistent nearly to the top, where 

 thin, lighter- colored, medium-grained layers (1353)^) are seen, made up of much rolled 

 grains of dull, translucent quartz. It is noteworthy that many of the bluffs in tin's vicin- 

 ity have the same elevation, a f act evidently to be attributed to the existence at that ele- 

 vation of some peculiar layer in the sandstone series. 



Immediately south of the village of Mauston, on Sec. 13, T. 15, R. 3 E., is a large 

 and very prominent sandstone bluff, about 200 feet high, half a mile long in a north 

 and south direction, and surrounded on all sides by vertical cliffs flanked below with a 

 long talus of loose sand and sandstone fragments. The cliffs are boldest on the eastern 

 face, where they run from 50 to 100 feet in height. One hundred and eighty feet above 

 the base is a flat bench, above which a narrow ridge rises some 20 to 30 feet, carrying 

 the summit of the bluff to a total altitude of about 500 feet. The bench is due, un- 

 doubtedly, to the presence of a layer of green and red shale, which is not exposed, 

 1. 'Whenever this adjective is used without qualification, the rock has been directly tested. 



