THE EASTERN AREA. 423 



the Eastern area l)ears frai^inents of I'ed jasper iit one place, and the upper 

 formation contains nincli chert (h'tritns, wliicli in all probabilit}' was derived 

 from the Cherty limestone formation itself Consequently the rocks of the 

 Eastern area bear tlic same relation to the Cherty limestone as do the 

 Penokee series proper. Finally, the outcrops of the iron formation of the 

 Penokee series proper and those of this formation placed w ith the Eastern 

 area have such relations as to leave little doubt that the two are continuous. 

 It is therefore concluded that the rocks of the Eastern area are the continu- 

 ation of the Penokee series proper. 



Relations of the belts of the Eastern area to one another. — It is evident that 

 the rocks of the Eastern area have formed under different conditions from 

 those of the western extension. This is indicated, as has been seen, l)v the 

 presence, hrst, of a great thickness of rocks, whlcli arc mingled clastic and 

 nonclastic sediments ; second, by the presence ))etween the northern and 

 southern boundary of the normal rocks of the area of a great thickness of 

 greenstone-conglomerates; and, third, 1)}' numerous southeini dips found in 

 the slate.s and conglomerates. These differences do not seem to be so great, 

 however, as necessarily to preclude a belief in a simple conformal)le 

 succession like that to the west. At any rate, tlu- expectation of such 

 a successiou here is a natural one, and, if this explanation fairly represents 

 the known facts, should be preferred to any which implies either folding or 

 a reference of a part of the rocks contained within the outer limits of the 

 area to other than the Penokee series. 



The two evident obstacles to considering the Ea.stern area as a simple 

 succession are, first, the great width of the series in the eastern part of T. 

 47 N., R. 44 W., Michigan, as compared with its width a ii:'\\ miles east or 

 west; and, second, the southern dips. 



Great width of ixirts of the Eastern area. — The uiuisual width of the 

 Eastern area in T. 47 N., R. 44 W., and T. 47 N., R. 43 W., Michigan, is 

 almost wholly due to the greenstone-conglomerates and greenstones. It 

 has been seen that the greater part of this area is composed of volcanic 

 products. A considerable thickness is composed of direct surface flows. 

 Another large part is volcanic products, which in places have been mingled 

 to some extent with water deposited sediments. Now, the accumulation of 



