754 PRE- CA MBRIA N NOR TH A M ERIC A N LITER A TURE 



certain areas and series the banded pyroclastics have been largely depos- 

 ited in water ; in other areas and series there is no evidence whatever 

 of such deposition. 



The pyroclastics south of Lake Superior, instead of belonging to a 

 single terrane, belong to at least three, distinct, unconformable series. 

 From the base up these are the Archean or Fundamental Complex, the 

 Lower Huronian, and the Upper Huronian. Furthermore, while year 

 after year evidence has been sought upon this point, we have been 

 wholly unable to show that any of the Archean tuffs of the south shore 

 were deposited in water. However, the tuffs of the Lower Huronian 

 and the Upper Huronian have been largely deposited in water, and 

 between ordinary sedimentary rocks showing little or no tufaceous 

 material and ordinary tuffs which give no evidence of water arrange- 

 ment, there are all gradations. 



Winchell ' reviews the stratigraphy of the Lake Superior region. 

 In reference to the Keweenawan series he reaches the following conclu- 

 sions : (i) The eruptive rocks which in Michigan, Wisconsin, and 

 Minnesota have been included in the Keweenawan, consists of two 

 widely differing series of widely separated ages. Included in these 

 pre-Keweenawan eruptives are the great gabbro of Minnesota and the 

 red rocks such as those at the Palisades and at Pigeon Point. This 

 eruptive period is called the Animikie revolution. (2) This period was 

 followed by a long erosion interval, during which were deposited the 

 Sioux quartzites of Dakota, the New Ulm quartzites of Minnesota, the 

 Baraboo and Barron quartzites of Wisconsin, and the quartzites and 

 conglomerates below the Keweenawan diabases in the Penokee dis- 

 trict. In the New Ulm quartzites are found "taconite" jasper pebbles, 

 and these are taken as evidence that this material was derived from the 

 iVnimikie. (3) Following this conglomerate and quartzite is the 

 Keweenawan eruptive age, which separates the Paradoxides horizon 

 from the Dicellocephalus horizon. (4) The Olenellus horizon is sepa- 

 rated from the Paradoxides horizon by the disturbance that closed the 

 Animikie. 



The general succession for the Lake Superior region is 

 given as follows : 



'Crucial Points in the Geology of the Lake Superior Region by N. H. Winchell, 

 Am. GeoL, Vol. XV, 1895, pp. 153-162, 229-234, 295-304,356-363, and Vol. XVI, 

 1895, PP- 12-20, 75-86, 150-162, 269-274, 331-337- 



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