50 THE GEOLOGY OP MINNESOTA. 



[Metamorphisin of the Animikk-. 



river and at Beaver bay, to be confusedly interlarded with and cut by basic trap, and 

 also to appear as if intrusive in the gabbro and in the Beaver Bay diabase. Its 

 physical relations to the gabbro and to the Keweenawan will be given in treating of 

 the igneous rocks of the Taconic. 



At the same time that the northern strike of the Animikie is westward along 

 the south side of the Giant's range, there are points further south where it has been 

 doubtfully identified. There are certain hardened and metamorphic rocks at Duluth 

 which have been referred to the Animikie (Nos. 807, 1966), and the slates which appear 

 at Thomson, and especially at the cuts by the Northern Pacific railroad southeast 

 from Carlton, appear to belong to the Animikie. What may be the direction of 

 strike and dip, and what the irregularities which the Animikie suffers in order to 

 appear at these places, dipping southerly, while along the Giant's range fifty miles 

 further north it also dips southerly, can only be conjectured. In this interval is the 

 St. Louis valley, where not an outcrop occurs, and which is deeply buried under drift 

 and perhaps under the Cretaceous. By reference to the chapter devoted to Carlton 

 county (plate 56) it will be seen that only a portion of the rocks usually known as 

 the Thomson slates are included in the Animikie, the rest being of the Keewatin. 



Metamorphisrn of the Animikie. In St. Louis county, southwe^tward from Birch 

 lake, in the angle between the granite of the Giant's range on the north and the 

 northern line of the gabbro on the south, the Animikie appears in the form of a very 

 fine-grained biotite mica schist with cordierite (Nos. 1708, 370H). The outcrops are 

 not numerous, and it is impossible to define the limits of this metamorphism. The 

 iron ore of the Animikie at the same place is converted to magnetite, accompanied 

 by the generation of more or less actinolite and cummingtonite. 



The mica schist at Little Falls, on the Mississippi, in Morrison county, also has 

 some characters that suggest its Animikie age, viz.: its fine grain, its distinct sedi- 

 mentary structure and its low angle of dip. There is also at Little Falls a massive 

 igneous rock resembling gabbro (No. 1678), which increases the parallelism with the 

 Animikie. At Little Falls the schist is garnetiferous and staurolitic, and at Pike 

 Rapids embraces a bed of limestone (No. 1681). 



The Puckwunge conglomerate. If the Animikie be separated from the Kewee- 

 nawan on the basis of its fragmental rocks, this conglomerate would be the bottom 

 of the Keweenawan; but if the earlier igneous rocks (compare the chapter on the 

 Duluth plate, vol. iv) be included in the Keweenawan, that term will embrace an 

 unknown interval of time and probably some of the latest elastics of the Animikie. 

 This conglomerate expresses a profound and extensive non-conformity and erosion 

 interval. It contains not only pebbles of quartz-porphyry and other forms of the red 

 rock, but much debris from the Animikie slates, including the peculiar rock taconyte 



