WEIDMAN — QUARTZ KERATOPHYRE OF BARABOO BLUFFS 39 



range horizontal beds of sandstone and conglomerate of the 

 Upper Cambrian epoch. The conglomerate is composed of 

 pebbles and boulders, varying in size from a fraction of an 

 inch to more than a foot in diameter, imbedded in a matrix 

 of quartz grains, stained more or less with ferruginous 

 material. The conglomerate is found in great abundance 

 in the ravines. 



The sandstone which carries the Dikelloceplialus fauna is 

 interbedded with and overlies the conglomerate. It is com- 

 posed of rounded quartz crystals in a matrix of silica, con- 

 taining considerable oxide of iron. The sandstone caps 

 the ridges in thin beds, but along the sides of the range, as 

 in the area of cross-section V of Fig. 1 (see also Plate 1), 

 it reaches a thickness of forty-five or fifty feet. 



QUARTZITE. 



The quartzite is a hard compact rock, and has a reddish 

 purple hue, with a tendency to granular texture. The 

 bedding is not everywhere distinct, but in places it is 

 quite plain. At the contact of the quartz keratophyre 

 along the ridge the bedding dip conforms to the dip of the 

 overlying keratophyre schists, but farther south, at the 

 top of the ridge, the dip is increased to 90°, and some- 

 times apparently dips to the south. On the south side of 

 the range, however, it again dips 75" or 80° to the north. 

 Everywhere the quartzite is jointed, and in many places 

 the rock is seamed with reticulating veins of pure quartz, 

 in which, at times, are to be seen small particles of spec- 

 ular iron ore. 



QUARTZ KERATOPHYRE. 



Areal Extent. — From the map it is seen that quartz kera- 

 tophyre extends along the north face of the range for a dis- 

 tance of over three and one-half miles. Its most eastern 

 limit is in the northeast corner of the southeast i of Sec. 

 23, and its most western is found in the northeast i of 

 the northwest \ of Sec. 20, thus extending along the range 



