STUEGBON QUARTZITE IN FELCH MOUNTAIN RANGE. 399 



tain, in sec. 32, T. 42 N., R. 28 W., it outcrops immediately south of the 

 abandoned Northwestern mine, and has also been found in drilling on the 

 west and in test pits on the east of the natural exposures through a distance 

 of half a mile. In sec. 33, T. 42 W., R. 28 W., a small ledge, a few feet 

 square, occurs between the overlying dolomite and the Arcliean, 200 feet 

 east of the road to the Calumet and Hecla (iron) mines. East of this the 

 contact between the Archean and the Algonkian is a faulted one, and the 

 quartzite is buried beneath the overlying formations. 



The northern zone of the Sturgeon formation is not nearly so well 

 exposed, nor for the most part does it fall within the artificial line that 

 bounds our detailed work on the north. Sees. 34 and 35, T. 42 N., R. 30 W., 

 on the west contain a few scattered outcrops, one of which is of exceptional 

 petrographical interest and to be noticed later. The next exposures are 

 5 miles east, along and just north of the north line of sec. 35, T. 42 N., 

 R. 29 W, The main northern zone of the Sturgeon formation coming from 

 the west lies south of these exposures and is entirely covered. Between 

 the two the tongue of Archean schists already described is faulted up. Two 

 miles farther east quartzite again appears in test pits, low-lying outcrops 

 and drill holes along the northern border of sec. 31, T. 42 N., R. 28 E., 

 and in section 29, immediately north of section 32, is well exposed in a broad 

 belt that reaches north almost to the east-and-west quarter line. 



The quartzite often forms distinct linear ridges, which in spite of the 

 chemical stability and apparent homogeneity of the rock seldom rise to the 

 mean altitude of the neig'hboring Archean areas. An exception to this rule 

 is the succession of ridg-es formed by the southern zone in the 3-mile stretch 

 west of sec. 31, T. 42 N., R. 29 W.; these frequently overtop the adjacent 

 Ai'chean plateau. Very frequently, also, the quartzite zones occupy lower 

 ground not only than the Archean but even than the immediately overly- 

 ing dolomite. The southern zone, for some unknown reason, is a distinctly 

 weak belt east of sec. 32; T. 42 N., R. 29 W., and for several miles forms 

 the bed rock of the Sturg-eon and the connecting ^-alleys. 



FOLDING AND THICKNESS. 



It is extremely difficult in most cases to determine directly the attitude 

 of the Sturgeon formation, owing to its generally massive and homogeneous 

 character. This is due, as will be shown hereafter, to the completeness of 



