516 



GEOLOGY OF CENTRAL WISCONSIN. 



-•^ 





quartzite is indistinct. 



At the southern end of the section — the "Jaws of the 



Narrows " — horizontal sandstone layers, altematingly hard 



S and quartzitic, and soft and friable, are seen abutting 



■S against and overlying heavy beds of northward- sloping, 



g pinkish-gray, dark-gray, and purple, vitreons quartzite 



o (121S, 1274). The exact contact of the two formations is 



§ _ finely exposed, the sandstone filling the cracks between the 



^ a layers of quartzite and including large detached masses of 



mS the latter rook. A short distance northward, along the wall 



H § of the gorge, this quartzite is terminated by a steep ravine, 



is on the north side of which comes in the veined quartzite 



g..2 that forms the body of the ridge. This curiously veined 



"-a rock (1267, 1275) may be described as a hght to dark-red- 



S ^ dish, sometimes purple, usually somewhat vitreous, quartz- 



oS ite, which has 

 6 P ^ 

 g =1 been shattered Fig. 33. 



S § o- throughout into 



B ^a small, sharply 



H ^-p angular frag- 



fe SS ments, and 



« "gv,- these cemented 



g " g together again 



< ll by milky- white 

 ■§ a vein quartz, the 



S .S " numerous cavi- 



P |s tics in which 



I,' S'g are lined with 



a ^-o' small, brilliant, 



« a" and very per- 



B ^-^ feet quartz cry s- 



g 5^1 tals. The ex- 

 f«.H tensive Assuring 



5 33 to wliich this 



gag rock has been 



subjected is indicated not only in the interlacing veins of 



white quartz, which often make up half the mass, but al- 



= 2' so in the fi-equent juxtaposition of different looking frag- 



po ments of the quartzite. Certain portions of the rock are 



3|^ more fissured than other neighboring portions, and then 



1 g appear like wide vems mto which numerous fi-agments 



2 Z of the wall rock have fallen. Fig. 33 represents a smkU 

 i a area, two feet by one and a half feet, of the veined 

 S.^.. quartzite, the white representing the vein-quartz, tlie 

 S* black the fragments of red quartzite. In sOme of the crys- 

 i tal-hned cavities a soft white coating is noticed on the crys- 

 ^ tals. The same material is seen sometimes lying loose in 

 ^.- the cavities and again filling minute cracks in a more coni- 

 ,- paoted condition. According to Prof. DanieUs' analysis it 



contains sQica, 53.15 per cent , and alunima, 45.09 per cent., 



the balance being water. The bedding of the veined 



It appears to stand at a liigh angle to the northwai-d. 



Veined Quartzite. 



Iz; •c 



North of and overlying the veined rock is another belt of quartzite (1277) witiiomt 



