PLATE LX.V. 



ITASCA COUNTY, 1899. II. S. GRANT. 



Granites, schists and greenstones, the last probably sometimes carrying ore like 

 that of the Vermilion Iron range, belonging to the Archean, underlie the most of 

 this county. Across the southeastern corner of the county the iron-bearing rocks of 

 the Mesabi Iron range have occasional outcrops, lying on the granite. They have an 

 outcropping belt about two miles wide, anil so far as known consist of quartzyte and 

 taconyte. Overlying these are supposed to be the black slates found in that position 

 further east, belonging to the Animikie, but they have not been proven to occur 

 in this county. 



Unconformably upon the foregoing the Cretaceous is known to lie, having been 

 found at various places on the Bowstring and Little Fork rivers, and also on the 

 Mesabi Iron range. 



The southern one-third part of this county is quite broken by morainic deposits, 

 and sprinkled thickly with lakes. It is probable that when it is carefully examined 

 certain continuous moraines can be traced entirely across the county, but at present 

 it can only be said, from the observed directions of glacial strias, and from what is 

 known of Beltrami county, that the Lake Superior ice-lobe had a maximum northern 

 limit along a line running from the centre of town 149 on the western boundary east- 

 northeast to the south side of town 64 at the eastern side of the county. It is prob- 

 able that in some of its earlier history this lobe was confluent about along this line 

 with the more north-south ice-flow, which was a part of the great Laurentide glacier; 

 but it appears to have maintained independent existence and movement in this county 

 after the withdrawal of the main glacier entirely from this county. Yet, at a date 

 not much later than the uncovering of northern Itasca county, the northern ice-lobe 

 must have covered Lake of the Woods, in its northern part, Rainy lake and the region 

 both east and west, thus* obstructing the drainage to Hudson bay and forming that 

 extension of lake Agassiz which included northern Beltrami and Itasca counties. 



It is because of the prevalence of lake Agassiz that the northern portion of the 

 county is smooth and nearly free from lakes, and that a thin-bedded, horizontal, fine 

 clay, the result of its sedimentation, is found along the main streams. 



The extreme northeastern part of Itasca county, bordering on Rainy lake, is 

 quite different from all the foregoing, in that the drift deposits are quite scant, thus 

 belonging, in glacial history, with the northern part of the Lake of the Woods, and 

 with much of Minnesota further east. Here the schists and granite are abundantly 

 exposed, indicating that the glacier margin retired rapidly toward the northeast. No 



