94 REPORT OF THE SPECIAL COMMITTEE 



the Pokegama quartzite. This series dips at a gentle angle to the 

 south. At the base of this series at Biwabik is a conglomerate which 

 rests upon a series of slates and graywacke, the latter in nearly verti- 

 cal attitude. The unconformity between the two is most pronounced. 

 The slate and graywacke where crossed has a considerable breadth. 

 It flanks a green-schist series. The slate and graywacke formation 

 adjacent to the green-schist is conglomeratic. Many of the frag- 

 ments of the conglomerate are from the underlying green schists. 

 At the locality visited it could not be asserted that the break between 

 the slate-gray wacke formation and the green- schist series is great, 

 although nothing was seen which is contrary to this view. The 

 granite constituting the Mesabi range is reported by the United States 

 geologists as intruding both the green-schist and the slate-graywacke 

 series, but not the Mesabi series. At the east end of the district a 

 newer granite is reported as intruding both the Mesabi and the 

 Keweenawan series, and in the central portion of the district small 

 areas of granite porphyry are reported as antedating the slate-gray- 

 wacke series. 



In the Vermilion district the Upper series, where seen, consists of 

 (i) Knife slates and (2) Ogishke conglomerate. The Ogishke con- 

 glomerate contains very numerous fragments of all the underlying 

 formations noted — porphyries, green schists, iron formation, granite 

 — and we have no doubt that there is a great structural break at the 

 base of the Ogishke. The series below this unconformity, the Ver- 

 milion series, consists of (1) the Ely greenstone and (2) the Soudan 

 formation. The Ely greenstone is the dominant formation. It is 

 mainly composed of green schists and greenstones, many of which 

 show the ellipsoidal structure described by Clements. The other 

 important formation of the Vermilion series is the Soudan iron forma- 

 tion. The structural relations of the Ely greenstone and the Soudan 

 formation are most intricate. No opinion is here expressed as to 

 their order. The Ely greenstone and the Soudan iron formation 

 are cut by porphyries, and, according to the reports of the United 

 States Geological Survey, are cut in a most complex way by the great 

 northern granite, but the localities illustrating this were not visited. 

 It is worthy of mention that the United States geologists report 

 granite as intruding the Knife slates and Ogishke conglomerates in 



