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Vermilion Lake, Lac la Croix, and Kabetogoma Lake. The origin of 

 the granite is discussed and the same conclusions reached as in a previ- 

 ous article. 1 



The Taconic. — This is unconformable above the Keewatin rocks. 

 It comprises the Animikie and Keweenawan divisions. 



The Animikie rocks enter the state at Pigeon Point, run westward 

 along the international boundary to the eastern part of Sees. 22 and 27 

 T. 65 N., R. 4 W. They reappear again southwestward from Birch 

 Lake on the northwest side of the gabbro mass, and thence continue 

 along the south side of the Giants Range, constituting the Mesabi iron 

 series, to Pokegama Falls. The higher parts of the Animikie are best 

 developed toward the east, while the lower parts are best developed 

 toward the west. 



The Animikie rocks comprise the Pokegama quartzite, Mesabi iron- 

 bearing formation, some limestone and slate, all strictly conformable 

 with one another. The thickness is several hundred feet, sometimes 

 reaching nearly 1000 feet. The dip of the series is uniformly to the 

 south, 8° to 12 . 



The iron-bearing formation and the Pokegama quartzite constitute 

 the base of the formation. The quartzite in places is beneath the iron 

 formation ; in other places it is in the same horizon ; and in still others 

 is above the iron formation. Commonly the base of the Animikie is 

 marked by a conglomerate, containing debris from the underlying 

 Keewatin rocks. This is a narrow horizon which soon graduates 

 upward into a quartzite, known as the Pokegama quartzite, from its 

 typical development near Pokegama Falls on the Mississippi River. 

 The thickness of the quartzite is not known to exceed fifty feet, and is 

 sometimes less than twenty-five feet. 



Above the quartzite, or in alternating beds with it, or below it, 

 appears the iron-bearing or taconyte member of the Animikie, which 

 contains the iron ore deposits of the Mesabi iron range. The ore is 

 usually hematite in the western part of the range and magnetite in 

 the eastern part. It was previously supposed to have been derived 

 from the alteration of a greenish glauconitic sand-rock; but later work 

 has seemed to show that the green-sand is a volcanic sand, and that the 

 so-called taconitic rock itself has resulted from igneous forces. This 



1 The origin of the Archean Igneous Rocks, by N. H. Winchell : Proc. Am. 

 Assoc. Adv. Sci., Vol. XLVII, 1898, pp. 303, 304 (Abstract). Also Am. Geol., Vol. 

 XXII, 1898, pp. 299-310. Summarized Jour. Geol., Vol. VII, 1899, p. 194. 



