PLATE LXXI. 



GRAND RAPIDS PLATE OF THE MESABI IRON RANGE, 1899. U. S. GRANT. 



The geology of this plate is similar to that of Plate LXX, and has been presented 

 in the last chapter. The facts as to the quartzyte are there given, going to show 

 that this quartzyte, so far as it appears at Prairie River falls, is not a part of the 

 Animikie. There may be another quartzyte or sandstone belonging below the taco- 

 nyte, which extends eastward, as represented on this and other plates of the Mesabi 

 range, and this may be that which is mentioned by Mr. Grant in a boulder-strewn 

 belt lying between the outcropping quartzyte and the granite (figure 61, p. 352, 

 vol. iv), evidences of which are not wanting on the Mesabi range further east. If 

 so, these two quartzytes could not be considered parts of the same formation. They 

 may be accidentally brought together at Prairie River falls, but between them must 

 be an interval in which belongs the Animikie and the Cabotian epoch of the Kewee- 

 nawan. From this it would also follow that the Pokegama quartzyte at Pokegama 

 falls is no guide as to the direction of strike of the Animikie and the iron ore, 

 but that the ore might run much further south, and might exist under considerable 

 thickness of that quartzyte. 



The iron ore from the Arcturus mine, in nineteen analyses, gave an average of 

 61.26 of metallic iron, with phosphorus at .037. This mine is situated near the eastern 

 limit of this area, sees. 13 and 24, T. 56-24. 



The Cretaceous is found in the test pits of the Arcturus Iron company. It is 

 highly fossiliferous. N. H. w. 





