GEOLOGICAL EXPLORATIONS AND LITERATURE. 99 



toward the iioitli, tlic granite ciiQ be seen, on I lie north .side, to lie upon, or at least 

 alongside of, a gray quartzite. There is an abrupt and simple contaet line, with a 

 sudden transition between them. 



About 25 feet farther north is the seeond low north ward-fa<^'ing bluff of granite. 

 It here looks as if the granite had been a molten rock and had flowed unconformably 

 over the (piartzite, the dip of whieh ean not here be ascertained. 



The third low outcroji of the granite is about 10 feet lower tiian the last and 

 about .'SO feet farther north. In the n(n'tli faeeof tliis little bluff, not more than feet 

 hifili, is observable the contaet seen in Fig. - of Fig. S. Here the granite is uncon- 

 formable on and embraces i)ieces and t(»ngues and slabs of the gray quartzite and 

 quartzite slates. This quartzite slate is line grained, banded by sedimentation, and 

 light greenish weathering. It is greenish gray within. At one point in this little 

 bluff is a small area of granite surrouinled by crumjiled and broken portions of the 

 slate. So at least it appears on the face of the bluff, but this isolated granite area is 

 only snperflcial and d(uibtless was, and perhaps is still, united with the main granite 

 mass. 



Tiiese three little bluffs, running, so far as they have apparent extension, in the 

 same direction, do not conform in their trend with the direction of strike of the bedded 

 rocks that intervene between them and the Aurora mine. They vary fi'om it about 

 20°, as illustrated in Fig. 1 of Fig. )S. 



The interpretation of these tiicts and their bearing on the stratigraphic problems 

 that relate to the horizon of the iron ore of the Gogebic range seem to warrani tlic 

 following conclusions : 



(1) The granite acts the role of an eruptive rock, but was origimdly a conglomer- 

 ate. It was so far molten or plastic that it flowed over tiie adjoining sedimentary 

 strata, but not so completely fused as to render the resultant granite entirely homo- 

 geneous. 



(2) Tiie a<conipanyiiig beds of sedimentary rock being a perfect lithologic repre- 

 sentative of the qnartzites and slates of the lower part of the Animike, this con- 

 glomerate can be itarallelized, stratigraphically, with the Ogishke c(Higlomerate of 

 Minnesota, in which have been seen (Fifteenth Annual Report- and later in this 

 report) similai' seniitiued conditions, i)roducing porphyries, syenite, and porphyritic 

 conglomerates. ' 



(3) The horizon of the ore of the Gogebic range is probably that of the Animike 

 rocks. 



(4) The granite is not of Laurentian age, but is younger in its present condition 

 than the Animike slates, though originally ;i conglomerate older than those slates 

 (pp. o0-5!t). 



WiNCHKLL (Alex.). The Gogebic Iron 15elt. In the Geological and Natural 

 History Survey of Minnesota; Sixteenth Annual Rei)ort, for the year 1887; St. Paul, 

 1888, pp. 185-195. 



