conflicting Views of Lake Superior Stratigraphy. 123 



A short distance north of the Ogishki Manissi conglomerate, 

 in Ontario, adjacent to Knife Lake on Hunter's Island, is the 

 extension of the Vermilion Lake iron-bearing series, carrying 

 large bodies of ore and jasper. That the iron-bearing series 

 of Vermilion Lake and Hunter's Island are the source of the 

 fragments found in these conglomerates there can be no doubt, 

 and as the contained fragments are precisely like those found 

 in the original position, there can be no question that the 

 underlying series had reached its present condition before the 

 deposition of the overlying conglomerate. We have here, 

 then, very strong presumptive evidence of the existence of a 

 considerable unconformity. 



Unconformity in the Kaministiquia district. — Our recent 

 work has shown that an exactly similar conglomeiate is found 

 very extensively developed in the neighborhood of Kaministi- 

 quia, Ontario. This is associated with a series of rocks 

 which are the exact duplicate of the Vermilion Iron-Bearing 

 Series. The reproduction in lithological phases is more perfect 

 between these series than between any other detached series of 

 rocks known to us in the Lake Superior region. The Ontario 

 rocks have been subjected to folding so as to repeat the 



» series, in this respect only differing from the Vermilion Lake 

 rocks. The most abundant Kaministiquia rocks are the pecu- 

 liar slates and schists, not easily described, but having charac- 

 teristics easily recognized by any one who has studied the equiv- 

 alent Minnesota series. These rocks, as at Vermilion Lake, con- 

 tain abundantly the various phases of ore, chert and jasper well 

 exposed at Tower and Ely and have an extent for many miles. 

 The slates and schists are locally carbonaceous and graphitic as 

 at Vermilion Lake, as for instance north of Port Arthur. 

 The iron-bearing formation is in many places in its upper parts 

 an iron carbonate which varies into ferruginous cherts and 

 jaspers. These facts point to their derivation from an original 

 cherty carbonate, as shown by Irving* to be probably true of 



* Origin of the Ferruginous Schists and Iron Ores of the Lake Superior Region, 

 R. D. Irving: this Journal, III, xxxii, 267-270, 1886. 



Prof. N. H. Winchell and H. V. Winchell deny the derivation of the Ver- 

 milion ores from an original iron carbonate ou account of the alleged lack in that 

 district of this material. (On a Possible Chemical Origin of the Iron Ores of the 

 Keewatin in Minnesota: Proc. Am. Assoc. Adv. Sci., 38th meeting, 1889, pp. 

 235-242; Am. Geo!., vol iv, pp. 291-300, 1889.) That it is there found has 

 already been shown by Irving, and the objection wholly falls to the ground in the 

 Kaministiquia district. 



Dr. M. E. Wads worth maintains that the Lower Marquette ores and jaspers 

 - are eruptive. (Notes on the Geology of the Iron and Copper Districts: Bull. Mus. 

 Comp. Zool., 1880, vol. vii, pp. 28-52.) Many facts are cited to show the way in 

 which the jasper and ore intrude the associated schist or have irruptive contacts 

 with it. The facts, however, indicate the eruptive character of the ore and jasper 

 only if the schists are of sedimentary origin. Our later investigations have 

 shown that the Lower Vermilion and Lower Marquette iron-bearing members con- 

 tain many schistose dykes, and also that in many cases the massive greenstone 



