OUTLINE OF MONOGRAPH, 



Chapter I. The Vermilion iron-bearing district of Minnesota resembles the 

 other iron-bearing districts of the Lake Superior region in that the rocks are of 

 very great geologic age. Its economic importance has been known for a rela- 

 tively short time, the first published statement of the occurrence of iron ore in this 

 district having been made in 1850. A brief statement is made of the geologic work 

 previously done in this district, including the names of the geologists by whom it 

 was done, and the scope of the paper is then outlined. The territory included in 

 the Vermilion iron-bearing district lies in the extreme northeastern portion of 

 Minnesota, including portions of St. Louis, Lake, and Cook counties. The district 

 has an area of approximately 1,000 square miles. It is a narrow belt trending east- 

 northeast, which ranges from 2 to 18 miles in width, and has a length of somewhat 

 over 100 miles, extending from the west end of Vermilion Lake to Gunflint Lake, 

 on the international boundary. From a topographic standpoint the Vermilion 

 district is divisible into four areas, each of which is characterized b}- a fairly 

 distinct type of topographic development. The first of these areas described is 

 the one including the Giants range, the most prominent topographic feature of the 

 Vermilion district. The range reaches an extreme height of 2,120 feet above sea 

 level, but in general is not a very prominent feature throughout its extent. It 

 forms the backbone of the district, extending across it in a northeast direction and 

 dividing it into unequal areas. The second area described lies north of the Giants 

 range and includes all of the areas underlain by the most important iron-bearing 

 formation. This area is characterized by ridges trending N. 70°-80^ E., with 

 intervening valleys, the larger ones usually occupied by streams or lakes. In this 

 area the topography is very rugged, but the range in altitude is not great. The 

 third area described is the high plateau country lying southeast of the Giants range 

 and underlain by gabbro. The fourth is a small triangular area at the exti'eme east 

 end of the district, lying between the Giants range on the north and the gabbro 

 plateau on the south. In this area a rather peculiar topograph}' is developed. The 

 hills have abrupt north escarpments and gentle south slopes. These ridges lie the 

 one south of the other, and present in profile the appearance of a series of saw 

 teeth; hence they are commonly spoken of as "sawtooth mountains." That the 

 drainage system is immature is shown by the abundance of lakes in the district, by 



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