570 GEOLOGY OF CENTRAL WISCONSIN. 



but has been readied by a small shaft sunk on tiie summit of the bluff. The shaft pen- 

 etrates: ^1) sandrock, lower layers thin, white and shaly, 25 feet; (2) green and red shale 

 2)^ feet, and ends in (3) sandrock again, the same as that seen on the cliffs. The green 

 shale appeal's to be of the same kind as that known at several horizons in the Lower 

 Sandstone in other parts of the state, but is soft and clayey, unusually free from sili- 

 cious sand, and of a deep green color. 1 The red shale (1342) is soft, slightly sandy, non- 

 calcareous and of a brick-red color. This shaly layer has influenced the denudation of 

 other bluffs seen to the southeast, which have their summits at the same elevation as 

 this bench. It appears probable that the Camp Douglas bluffs may owe their con- 

 stancy of elevation to the same cause. All the sandstone on the cliffs of the Mauston 

 bluff is non-calcareous, generally moderately coarse, brownish, pinkish and light-colored 

 in different layers, anJ much of it firm enough to use in ouilding. It is quarried near 

 the south end of the bluff, at the base of the cliff, where firm, heavy layers are ob- 

 tained of a light-colored, medium-grained rock (1347); and also at the summit of the 

 cliff, near the north end of the bluff. At the latter place, immediately above the quarry 

 beds, and just beneath the green shale, are a few layers of a porous, very friable brown- 

 ish sandstone, with numerous iron -stained points and cavities and indistinct fossil im- 

 pressions, which consists of subangular grains of glassy quartz. On the cliff below the 

 quarry the sandstone is penetrated by numerous brownish veins, one-sixteenth to one- 

 half an inch in width, which, on close examination, are seen to be made up of the 

 grains of the sandrock, more glassy than usual, and closely cemented by a small amount 

 of hydrous iron oxide. 



In the southern part o the town of Lyndon, on Sec. 28, T. 14, R. 5 E., a narrow, 

 ridgy crest rises 200 feet above the general level of the watershed, reaching an altitude 

 of nearly 700 feet above Lake Michigan. At the summit a white, cherty material (1330) 

 resembling that described as occurring on Sec. 12, town of Wonewoc, remains in place. 

 It is peculiar in showing numerous little rounded holes, that give to the mass some ap- 

 pearance of an organic structure. Ten feet below the chert, fine-grained, non-calcareous, 

 whitish sandstone (1332) is exposed, made up of grains of very fine, sharply angular, 

 glassy, quartz, and resembling that seen below the chert on Sees. 12 and 1, town of 

 "Wonewoc. The horizon is evidently the same, and is just beneath the base of the Lower 

 Magnesian limestone. 



The gorge known as the Dalles of the Wisconsin has been briefly described on a 

 previous page. Along the walls of the gorge, which are from 50 to 100 feet in height, 

 the rock is quite uniform in character, being coarse, very friable, light to dark brown in 

 color, non calcareous, and consisting of very much rolled grains of quartz (1443). The 

 most remarkable feature of these exposures, which are nearly continuous for as much as 

 seven miles, is the cross lamination which affects layers as much as 12 feet thick, and is 

 abruptly terminated above and below by horizontally bedded layers. The transverse 

 laminae themselves are quite thin, and easily separable from one another. They are not 

 plane, but constitute much warped surfaces. The structure is quite well shown in the 

 view represented on Plate 1A, which is taken from one of Mr. H. H. Bennet's excellent 

 photographs. Plate I, also from one of Mr. Bennet's photographs, shows a peculiar 

 erosion form, known as Stand Rock, which occurs well up on the north face of the high 

 ground through which the Palles are cut, and far above the gorge itself. It illustrates 

 well the way in which much of the lower part of the Potsdam series is worn thin layers, 

 somewhat more ferruginous and firm than the rest, though still quite friable, protecting 

 the softer, scarcely coherent rock below. Half a mile east of the upper end of the 

 Dalles, on the east side of the S. E. qr. of Sec. 21, T. 14. R. 6 E., the " Elephant's 



'This green shale has been the object of exploitation as a copper ore, a considerable amount of 

 money having been expended in sinking shafts, etc. It is hardly necessary to say that the money 

 is thrown away. 



