398 THE CRYSTAL FALLS IRON-BBAEING DISTRICT. 



SECTION IV. THE STITEGEOIN^ QUAKTZITE. 



The lowest member of the Algoiikian in the Felch Mountain range 

 is a formation consisting mainl}-^, but not exclusively, of coarse vitreous 

 quartzite. Typical exposures of this formation, as well as one of the rare 

 contacts between it and the underlying Archean, occur along the Sturgeoii 

 Eiver, and it is therefore named the "Sturgeon Quartzite." 



DISTRIBUTION, EXPOSURES, AND TOPOGRAPHY. 



The Sturgeon formation, next to the Randville dolomite, is the most 

 widespread member of the Algonkian series in the Felch Mountain range. 

 Its general distribution throughout the area mapped is in two parallel zones, 

 of varying width, immediately adjoining the northern and southern Archean, 

 except when displaced from this 230sition for relatively short distances by 

 faults. These zones extend east and west for the whole length of the range. 

 Their stirface width varies with the complexity of the structure and the 

 depth of erosion. In part of sec. 35, T. 42 N., R. 29 W., the higher 

 formations have been entirely removed, and the two zones come together, 

 leaving the quartzite as the only Algonkian rock at the present surface. 



On the Avhole the Sturgeon formation is fairly well but very unevenly 

 exposed. Beginning at the west the zone in contact with the southern 

 Archean furnishes frequent outcrops from the south quarter post of see. 34, 

 T. 42 N., R. 30 W., to the south quarter post of sec. 36, T. 42 N., R. 30 W., 

 a distance of 2 miles. Then follows a gap of a mile in which no outcrop:, 

 have been found. Near the north and south quarter line of sec. 31, T. 42 N., 

 R. 29 W., they begin once more, and are supplemented by test pits as far 

 as the west sixteenth line of section 32, next east. 



Then follows another gap without exposures, 2J miles in length. 



Near the north-and-south quarter line of sec. 34, T. 42 N., R. 29 W., 

 outcrops begin again and continue for a mile to the east, with frequent inter- 

 ruption, as far as the north-and-south quarter line of section 35, where in 

 the valley of the Sturgeon tlie southern zone broadens and joins the north- 

 ern, in consequence of the general westward pitch which has carried the 

 higher formations above the present surface of denudation. East of this 

 point the quartzite is known in only a few scattered localities. In the 

 southern part of sec. 36, T. 42 N., R. 29 W., it is in contact with the 

 Archean on the south bank of the Sturgeon River. South of Felch Moun- 



