304 THE VERMILION IRON-BEARING DISTRICT. 



rence there was in general agreement with the description given by 

 N. H. Winchell." Furthermore, the contact was found between the con- 

 glomerate and the small ridge of greenstone which lies just along the south 

 shore of Ogishke Muncie Lake, and a number of additional contacts were 

 observed on the south side of the great anticline north and northeast of 

 Gobbemichigamma Lake. The fragmeutal character of some of these 

 deposits was recognized by the Minnesota survey, but it was not seen that 

 they were sedimentary deposits of later age than the g'reenstone. They 

 were, on the contrary, reg'arded as fragmeutal volcanic rocks, and were 

 included, with the greenstone, in tlie Archean.'' 



Relations to the Soudan formation. — The actual contact between the 

 conglomerate and the iron-bearing formation was observed at only one 

 place. Here, however, the evidence is indisputably clear. The jasper of 

 the Soudan formation is overlain by a conglomerate containing fragments 

 of jasper derived from it as well as fragments of greenstone derived from 

 the greenstones, which in their turn underlie the iron-bearing formation. 

 In addition to this direct contact, where the evidence is perfectly clear, 

 there have also been found at a number of places scattered all over the 

 district quantities of jasper pebbles in the conglomerate. Their presence 

 is sufficient, of course, to prove that the Soudan formation is older than 

 these conglomerates. 



The fragments of slate and of the conglomerate or breccia which 

 occur in the Ogishke conglomerate south of Moose Lake are of especial 

 interest, since they indicate the existence of a series of clastic sediments 

 prior to the formation of the Ogishke conglomerate. The field evidence 

 for such a clastic deposit below the normal iron-bearing formation has 

 already been given. In this series there are slaty rocks associated with 

 conglomeratic elastics. The fragments of slate and conglomerate may very 

 well have been derived from these. In the conglomerate there were found 

 a number of slate pebbles. Their source has not been very satisfactoi'ily 

 accounted for. If we accept the presence of certain sediments mentioned 

 as lying in a position between the iron-bearing formation and the green- 

 stone as indicative of the fragmeutal sedimentary horizon underlying the 



«Geol. and Nat. Hist. Survej' of Minnesota, Fifteenth Ann. Kept., 1886, pp. 372-374. Final 

 Eept., Vol. IV, 1899, p. 451. 



''Geol. and Nat. Hist. Survey of Minnesota, Final Kept., Vol. IV, 1899, p. 466, ' 



