5D6 GEOLOGY OF CENTRAL WISCONSIN. 



Minnesotensis. The top of this sandstone ledge is on a level with the base of the lime- 

 stone in Wood's quarry, directly beneath which a small exposure of smilar sandstone is 

 seen. South of the sandstone ledge, on the south line of Sec. 10, as shown on the map 

 and section of Fig. 49, is the valley of Skillet's creek, and south of this, again, rises the 

 southern quartzite range. About % mile north from Wood's quarry, and 40 feet be- 

 low its base, in the high bank of Skillet's creek, is an exposure of yellowish, rough-sur- 

 faced limestone (1263), which closely resembles the typical Mendota rock, leaving on 

 solution 23.68 per cent of a very fine aluminous residue. The exposure is somewhat 

 broken, but a thickness of about 15 feet is seen. At the foot of the bank, sandstone is 

 in place. This yellowish limestone would appear to he the rock alluded to by Dr. B. F. 

 Shumard in Owen's Geological Survey of Wisconsin, Iowa and Minnesota, p. 522, as 

 occurring " in the bank of a small stream %ths of a mile south of the Baraboo." He 

 refers it to the " cncrinital bed of F. I," the same as the Mendota horizon of the writer's 

 reports. It will be noticed that the quarry limestone, the sandstone carrying Scolitlms 

 and Dicelloceplialus, and the yellowish limestone on Skillet's creek, have the proper re- 

 lations and characters for the Lower Magnesian, Madison and Mendota beds. The up- 

 per limestone has just about the same altitude as that at Eiky's quarry, and appears 

 beyond question to belong to the same horizon. Below the Mendota normally there is 

 always found loose, fine-grained sandstone, with some calcareous matter, and narrow, 

 brownish, calcareous bands, this character holding for a thickness of 40 to 60 feet. Be- 

 low the lower limestone on Skillet's creek, however, we find no such layers, but at the 

 falls, a few rods down stream, are seen fifteen feet of very regular beds of much in- 

 durated, entirely non-calcareous, sandstone having a slight slant southward, and bear- 

 ing no resemblance whatever to the ordinary infra-Mendota layers. Do the two lime- 

 stone layers, with the intervening sandstone, form a patch" lying upon an eroded surface 

 of much older sandstone, represented by the indurated rock at the falls, as suggested 

 already in the case of the limestone of Eiky's quarry? 



A short distance northeast of Devil's Lake, on the east line of the N. E. qr. of Sec. 

 13, T. 11, R. 6 E., on the south flank of a projecting point of the south quartzite range, 

 are numerous large masses of fossiliferous sandstone, evidently near home. The rock 

 is medium-grained, friable and brownish, containing many Scolithus markings, and 

 other fossil fragments, chiefly of trilobites, among which casts of large cephalic shields 

 of Dicelloceplmlus Minnesotensis are most readily made out. Prof. A. Winchell iden- 

 tified and described also the following, 'in specimens from this place, sent him a number 

 of years ago: Orihis Barabuensis; Stramrollus (Ophileta) primordialis ; Phurotoma- 

 ria? advena; Dicellocephalus Pepinensis; Ptycliaspis Barabuensis. The altitude at 

 which these sandstone masses occur is 5'ZO to 560 feet, or 70 to 110 feet above the lime- 

 stone at Wood's and Eiky's quarries, and 110 to 155 feet above the Mendota-like rock 

 in the banks of Skillet's creek, Sec. 10, T. 11, R. 6 E. Across the ravine on the north 

 side of which these fossils are found, are bowlder-conglomerate and sandstone beds seen 

 lying directly upon the quartzite, as previously described and figured. These occur at 

 the north point of the east cliff of Devil's Lake, a north and south section through 

 which is given on Plate XIX of this volume. The summit of the cliff, which for some 

 distance is a mere crest, rises rapidly southward, horizontal sandstone layers flanking it 

 on the side away from the lake, and rising with it to an altitude of over 600 feet. The 

 sandstone cliff immediately opposite the Devil's Nose, shown also in one of the sections 

 of Plate XIX, has already been described as extending between the altitudes of 391 

 and 622 feet, or from 50 feet below Wood's quar y, to 175 feet above it, and as ex- 

 tending far above any apparently possible horizon of the Lower Magnesian. The same 

 appears to be true of the sandstone in all of the region about Devil's .Lake. At the 

 south end of the west bluff, for instance, are horizontal sandstone ledges at an altitude of 

 over 700 feet. 



