SOUDAN FOEMATION. 195 



anything else than a case of infolding-. As the result of the accompanying- 

 movement, the greenstone was rendered schistose immediately adjacent to 

 the jasper and nearest to the plane between the rocks of diverse character 

 along- which the greatest movement naturally took place, this schistosity 

 diminishing in degree away from the plane of greatest movement. 



In several places in the district careful search made expressly therefor 

 has disclosed the greenstone with a conglomerate lying on , it and con- 

 sisting- of material derived from the greenstone. The conglomerate is 

 followed by finer-grained clastic sediments of essentially the same cliaracter 

 as the conglomerate itself, and these sediments are in turn succeeded by 

 the iron formation proper, consisting of the normal cherts, jasper, and iron 

 oxide in alternate liands. Occasionally a clastic band occurs with the iron 

 formation proper. Such definite relationships were observed at several 

 places, as in sec. 10, north of Armstrong Lake. Here the greenstone is 

 overlain by a conglomerate derived from it, which is succeeded to the north 

 by the iron formation, which contains a large quantity of iron pyi-ites. The 

 greenstone also contains large quantities of the iron pyrites scattered 

 through it in crystals which liave to a great extent been changed to 

 limonite. Another locality is north of Robinsons Lake, just south of the 

 north quarter post of sec 7, T. 62 N., R. 13 W. A number of other places 

 were found in which, however, the relations were not quite so clear, the 

 complete sequence being interrupted by lack of exposures ; they are there- 

 fore not referred to specifically. The above-mentioned relations show 

 clearly that the main part of the iron formation rests upon the greenstone 

 as a basement, and consequently is younger than the greenstone. 



But is all of the iron formation younger than all of the greenstones of 

 the Vermilion area? Apparentl}^ not, but there is occasionally an inter- 

 bedding of the iron formation with some of the greenstone. The evidence 

 for this is found in the distribution of the iron formation in long belts 

 separated from one another by areas of varying widtli underlain by the 

 greenstones.- These belts have been, traced for various distances, in one 

 case for a distance of 16 miles. In no case is the iron-bearing f()rmation 

 continuously exposed over such extent, but the exposures are, nevertheless, 

 so numerous as to show conclusively that the intervening areas without 

 exposures are underlain by the iron-bearing rocks. Associated with the 

 iron-formation rocks of these belts there is more or less greenstone. This 



