RANDVILLE DOLOMITE m PELOH MOUNTAIN" EANGE. 407 



Archean mica-schists into contact with the dolomite and quartzite in the 

 northern part of the same section, the Randville formation runs east in a 

 single belt, which probably continuously widens as the throw of the fault 

 diminishes. It has been found in several places in the north half of sec. 

 31, T. 42 N., R. 28 W., and near the east line of this section the appearance 

 of the overlying mica-schists again divides it into two belts, which pass to 

 the north and south of the Felch Mountain syncline. The northern belt 

 has been proved by test pits only, but the southern is well exposed naturally 

 in the neighborhood of the Northwestern mine. Other exposures also 

 occur south of the unconformable mica-schists and quartzite of the upper 

 series, in the central portion of sec. 33, T. 42 N., R. 29 W. 



The dolomite is relatively a Aveak rock, and generally occupies lower 

 ground than either the quartzite below or the iron formation above it. The 

 belt in contact with the southern belt of quartzite especially is valley 

 making throughout most of its extent. The outcrops usually form low, 

 steep-sided knolls elongated with the strike and of slight relief above the 

 basement; these occasionally unite into linear ridges, as in sec. 35, T. 42 N., 

 R. 30 W. The northern belt is one of low general relief, from which, how- 

 ever, similar isolated knobs often protrude. The largest and most prominent 

 of these is the peak in the northeast quarter of NW. ^ sec. 36, T. 42 N., 

 R. 30 W., which rises 80 feet above its base, covering 8 or 10 acres. 



No actual contacts between the Sturgeon and Randville formations 

 have been found, but from their close association and continuity, as well as 

 from the structural characters, when these are determinable, they seem 

 everywhere to be strictly conformable. Near the quartzite the dolomite 

 becomes distinctly more impure and contains a larger proportion of silicates 

 and quartz. It is altogether probable that between them come transition 

 beds, as indeed is shown by some of the drill records. In one of these 

 "talcky mica-schists, micaceous limestone, altered actinolite-schist, and 

 quartzite" are described as being interbedded near the junction. 



The determination of the thickness of the Randville formation is beset 

 with the same difficulties as are encountered in the case of the quartzite, 

 namely, the uncertainty as to the exact position of the contacts and the 

 possibility of faults and subordinate folds within the formation itself The 

 best sections give a wide range of values from a minimum of about 500 



