57J: GEOLOGY OF CENniAL WISCONSIN. 



17. V.ny fine-grained layers, almost loose sand; in alternating red, white, yel- i'l; In,. 

 low, pink and brown bands; the bands usually very thin, and on close 

 inspection often divisible into still tliinner different colored sti-ipes 

 (l;i79)i near the top the following succession was observed: 2 feet white, 

 streaked below with pink; IJi feet pink; 3 feet wliite, stroalced with 

 pink: IJ^feetprnk, cross-lajninated; 5 feel thin pink and white streiiks — 

 the lowest portions weatheilng with a vitrified crust (1380) 20 . . 



Total height of section '-^--1 10 



None of tlie sandstone of this section shows any sign of calcareous or dolomitic mgi'e- 

 dients. 



Half a mile soutli of Roche a Oris, across the valley of tlie north branch of the Little 

 Roche a Oris creek, is the much larger outlier, known as Friendship Mound, winch 

 lies in the east part of Sec. 31, stretoliing southward into the north part of Sec. 6, T. 17, 

 R. 6 E., where its southern end rises abruptly from tlie northern side of the Little Roche 

 tt Oris creek. The bluff is over three-fourths of a mile in length, trending a little west of 

 north, and at base is as much as a third of a mile in widtli. AU around, at an elevation 

 of 150 feet above the base, it presents a marked bench, bounded by sandstone chft's 50 

 to 100 feet in height, which axe flanked below by a long talus of sand. Above the flat 

 bench rises a wooded crest with several rounded summits, the liighest of wliioh is 280 

 feet above tha base of the bluff, 310 feet above the bridge at Friendship, and about 750 

 feet above Lalte Michigan. The whole of the bluff' is wooded with oak and pine, pre- 

 senting in this regard quite a different appearance from the Roche ^ Oris, and aflbrdinfj 

 much poorer opportunity for examination of tlie rock beds. Below the bench the suc- 

 cession of layers appears to be closely like that on the Roche il Oris. At one point on 

 the west side of the mound, just below tlie edge of the bench, the sand rock is quarried. 

 Tlie quarry rock is moderately firm, uniformly brown-tinted and compact, with distinct 

 lamination hues. The base of the quarry is 20 feet below tlie top of the bench, and ia 

 finely ripple-marked. Similar ripple-marks occur again at a lower level, but neither 

 horizon seems to be the same as that at which similar markings were observed on the 

 Rodie a Oris. Above the bench the rock is mostly concealed, but is seen at 40 feet be- 

 low the summit, where it is coarse, friable, and brown-colored, and intersected by Uttle 

 veins of brown iron-oxide. Exposures occur again at 60 feet below tlio swnmit, where 

 the rock is white, friable and Scolith.us-h&a.Ymg. 



On the south bank of the creek, at the Friendship bridge, thin-bedded, crumbling, 

 brown-and-white-banded sandstone is exposed down to the level of the creek, adding 

 about 45 feet to the Roche ^ Oris section. 



Five to ten miles south from Friendship, a. number of outhers of sandstone occur. 

 One of these, Rattlesnake Rock, is about five miles south from Friendship, in the south- 

 ern part of the town of Adams. The bluff is about half a mile in length, is cut into two 

 parts by a central depression nearly to the level of the adjoining low ground, and is 

 mostly grassed and wooded. On each side of the gorge, and on all sides of tlie bluff, 

 are considerable exposures, the cliff' on the west side reaching 50 or even 75 feet in 

 height. A marked bench is 130 feet above the base. Above the bench the bluff rises 

 90 feet, the summit being 255 feet above the bridge at Friendship, and 655 feet above 

 Lake Michigan. Ho far as observed, the rock and the succession of layers are the same 

 as in the Roche a Oris section. At the top of the bluff, the rock (1389) is fine-gruined, 

 very friable, whitish sandstone, made up of glassy quartz gi-ains, and closely resembling 

 the fossil rock on the sumnnt of Roche i1 Oris, to which horizon it evidently belongs, as 

 iiichcatud by its having the same altitude, and numero fossil fragments, as well as by 

 its lithological character. The fossils are cliiefly trilolite fragments, belonging, so far 

 as can be determined, to the genus ConocephaUies, r^nd Scoldhus-hoaags. Ten feet 



