70 THE PRNOKEE IKON-BEARING SERIES. 



the immediate sucoessidii of tlie micascliist formation above tlie oic formation is a 

 further indication of tlie yonnger age of this group. . . . 



Starting from tlie landing on the west shore of Gogebic lake, situated in the 

 center of Sec. 17, T. 47, R. 42, on an old Indian trail, we meet for the first two miles 

 no rock exposures; thence repeatedly in the hillsides to the lett of the path blulfs of 

 rock are seen to- project, which on examination are either granite or the brecciated 

 diorite rock mentioned in the previous chapter ; farther on quartzite beds iwe seen to 

 underlie the surface, on tlic right hand side of the trail, as we ai)i)r()acli the mining 

 canq) of Mr. Gillis, situated in the SW. \ of Sec. 14, T. 47, R. 43, where, by natural 

 and artiticial denudation, wears enabled to see a cross section of about 8(M» or 9(M) feet 

 of strata, which dip at a liigh angle to the north. The aforesaid brecciated dioritic 

 schists are seen in tlie hillside south of the camp as the lowest rocks ; on them sncceedsa 

 belt of dark conglomerate, composed of (luartz jiebbles of various cohir, and of granite 

 pebbles cemented by an arenaceous groitndmass, in which is a considerable amount 

 of feldspar grains besides the quartz sand. Then follow thick-bedded gray quartzite 

 layers; on them rest a tlesh-red colored comiiact granular quartz belt, which by 

 exposure weathers and becomes porous and absorbent, like an ordinary sandstone. 



Higher still, are brecciated quartzite layers, composed partly of chalcedonic 

 quartz masses, and intersected by irregular fissure seams filled with galena. 



On this brecciated quartzite belt follow thinly Liminatcd quartz layers of very 

 uneven surface, with interjiosed narrow wedge like seams of blacli shaly material, 

 which causes rapid disintegration of this belt into shelly fragments. Within this 

 series occur streaky, interrupted concretionary seams parallel with the stratification, 

 which are filled with galena. 



Higher beds, likewise mainly of qnartzose nature, are even-bedded, delicately 

 striped or lineated in the direction of the bedding by the alternating intermixture of 

 linear graphitic seams, with the granular qnartzose feldspathic groundmass, which 

 besides holds a good proportion of the carbonates of lime and of iron. Weathered 

 surfaces of the white and black striped rock are therefore rusty brown. In some of 

 these layers the shaly graphitic material predominates over the qnartzose, which 

 cau.ses them to be softer and more pliable ; tlu^ upheaving pressure therefore foldefl them 

 throughout their substance into innumerable small wrinkles, as we often observt* this 

 same iihenomenon of corrugation in still softer sericitic or micaceous scliists in otiier 

 geological horizons. North of these beds follow uniformly black fine grained slate- 

 rock layers, which are from time to time interlaniinated with seams of harder siliceous 

 ledges, likewise black colored by carbon. The aggregate thickness of this uiiperinost 

 grai»hitic slate rock belt aniouuts to about .'iOO or G0(» feet. It comes, on the north 

 side, in direct cont.act with the diabases of the copper-bearing rock gionit, which 

 apjiears to be conformably sui>erimposed on it. . . . 



The galena-bearing (iiiaitz formation and tlie gra])liitic slate series above it are 

 traceatile by extensive exposures in the hillsides along tlie trail until they cross the 



