32 THE PENOKEE IROI^-BEAEING SERIES. 



The iron range imder fiuisideratiou may be regarded as the eastern prolongation 

 of the Peuokie i;inge of Wisconsin, as well as the western extension of the Marqnette 

 series, the whole being Huronian. The position of the range is tolerably well defined 

 by magnetic observations and notes on the U. S. Land Ortice plats. On these we find 

 mention of iron and magnetic attractions on Sees. 7 and 8, T. 47 N., E. 45 W., as 

 also in Sees. 13 and 14 of the town west. The belt of Huronian rocks, as made 

 out by us, extends nearly east and west through the north part of T. 47, ranges 44, 

 45, 4(), and 47, crossing the Montreal river in Sees. l(i and 21 of the last named 

 township, (ioiiig east, the range was lost before it reached lake Gogebic. 



The geological boundaries of this range are fortnnately of the most unmistak- 

 able natnre and render a detailed description of its position nnne<-essary. 



On the north is tlie high, broad, irregular ridge, or series of ridges, constituting 

 the South Copper range, the rocks of which are greenisli and brownish, massive and 

 amygdaloidal copper-bearing traps, tlieir bedding being exceedingly obscyre, with 

 occasional beds of sandstone and an imperfect conglomerate. The stiike of these 

 rocks, so far as it could be made out, was east and west, with a dip to the north at a 

 high angle, thus conformhuj with the Huronian rocks nnderneath.' 



Against and over the copper series on tlie north abut the h(n-izontiilly bedded 

 lowei' Silurian sandstones, which are beautifully exposed on tlie west branch of the 

 Ontonagon river, in See. i.'.3, T. 40, R. 41. These sandstones foi-m the surface rock, 

 and occupy the broad belt between the two copper ranges from the region we are 

 describing to Keweenaw bay, but taper to a point before reaching the Montreal river 

 in going west. 



On the south of tiie Iron-bearing rocks are a series of granites, chloritic gneisses, 

 and obscure schists, whieli, except the latter, are numistakably Laurentian in their 

 lithological character, and are ii on conformably overlaid by the Huronian rocks. The 

 general structural relations of the four great systems here enumerated are shown in 

 the accompanying diagram. (Pp. 183, 184.) 



The best h)cality in which to study the character of the iron series in the West 

 region, is on Black river and its tributaries, especially on the outlet of Sunday lake, 

 T. 47, ranges 45 and 46. Hei-e will be found banded ferruginous jnspery s"hists, 

 chloritic greenstones, brown ferruginous slates, black and gray banded siliceous slates, 

 siliceous flag ores, several varieties of quartzites, and clay slate. The whole series 

 strike east and west, and dij) north away from flie granites and gneisses and under 

 the coi)])er rocks at an angle of from 40° to '.W^. (P. 185.) 



Ill Part II of the saiiie volume (being Prof. Pumpelly's report on the 

 Copper-Bearing Rocks), Chapter i contains the same statements, reproduced 

 ahuost verbatim, ^vitli regard to tlie Montreal-Gogebic iron belt, as are 

 above quoted from a paper published jointly by Brooks and Puinpelly. 



