480 THE CEYSTAL FALLS IKON-BEAEING DISTRICT. 



and conglomeratic and brecciated beds. As a rule, exposures are small and 

 scattered. Their distribution has already been described. All ledges 

 observed may be seen by reference to the map (PL LI). 



IMPOKTANT EXPOSURES. 



Grood exposures of the dolomites occur in the NW. J sec. 6, T. 42 N., 

 R. 28 W. The ledge nearest the northwest corner of the section is a hard 

 flesh-colored dolomitic marble, containing here and there little quartz 

 grains. This is cut by joints, and is traversed by small chert bands. The 

 bedding is more or less contorted, but its general strike is N. 45° E., and 

 its dip is 45° NW. About one-fourth mile east of this ledge is a small, bare 

 knoll, composed of interlaminated pink marbles, conglomerates, red sand- 

 stones, and red slates, varying in thickness from a few inches to a foot or 

 more. The conglomerate consists of marble pebbles and slate and chert 

 fragments in a calcareous quartzitic matrix. The strikes and dips are uni- 

 form throughout the ledge, the former being nearly east and west and the 

 latter 45° S. The difference in dip of the beds of these two exposures 

 indicates plainly the presence in this place of a little westward-pitching 

 anticline. 



Other prominent exposures of the dolomite series are in the NW. ^ 

 sec. 1, T. 42 N., R. 29 W., and in the SE. ^ sec. 35, T. 43 N., R. 29 W. In 

 the first-named locality is a high, bare knob, and a cluster of small ledges, 

 in which dolomites, conglomerates, and slates are all well exposed. The 

 dolomites, for the greater part, are massive pink marbles crossed by joint 

 planes. In places the rocks take on a greenish-yellow tinge, and become 

 schistose. At 1,500 paces N., 1,930 W., of the southeast corner of sec. 

 1, T. 42 N., R. 29 W., the dolomite forms a well-defined bed, striking 

 N. 45° E. and .dipping 70° SE. Above this, to the southeast, is a bed of 

 coarse-grained granitic sandstone or quartzite, which in turn is over-lain 

 by beds of gray quartzite alternating with thin slates and fine-grained 

 conglomerates. Farther south is a ridge of well-bedded, fine-grained 

 quartzite and bluish-gray slate, the individual layers being usually less 

 than one-half inch in thickness. This rock grades into a gray schistose 

 dolomite, and the whole quartzite-slate series strikes N. 75° E. and dips 

 63° S. The ex]30sures in section 35 are almost pure marbles, in which no 

 traces of bedding have been detected. 



