RESUME OF LITERATURE. 85 



recently examined at the iron mines) to Twin Mountain and Frog Rock 

 Lake; second, the Ogishkie conglomerate proper of later date, fresher 

 aspect, and more siliceous, evidently derived largely from the disintegration 

 of the other, upon which it lies nnconformably. With this second phase 

 the Animikie quartzite and slates are interstratified (p. 98). 



Partly surrounding Cacaquabic Lake is found a green schist which 

 belongs apparently to a date about the same as the Keewatin portion of 

 the Ogishke conglomerate or is its immediate successor and conformable 

 upon it. Nevertheless they are markedly different. The green schist is 

 apparently formed of basic erupted materials in a fragmental condition and 

 received its stratified arrangement through the agency of water. Volcanic 

 vents in the immediate neighborhood must have given origin to this vast 

 supply of basic materials (p. 108). 



It is concluded that a g-reat basic eruption separated the Animikie and 

 Keewatin, as shown by this volcanic fragmental material, as well as by the 

 existence of mountains of greenstone, which are to be regarded as the 

 probable sources of the fragmental rock (p. 108). 



WiNCHELL, A. Sixteenth Ann. Rept. Geol. and Nat. Hist. Survey Minn., for 

 1887, 1888, pp. 133-391. Unconformability between the Animikie and the Vermilion 

 series: Am. Jour. Sci., 3d ser., Vol. XXXIV, 1887, p. 314. See also: The uncon- 

 formities of the Animikie in Minnesota: Am. Geologist, Vol. 1, 1888, pp. H—ai. Two 

 systems confounded in the Huronian: Am. Geologist, Vol. Ill, 1889, pp. 212-214, 

 339-340. S3'stematic results of a field study of the Archean rocks of the Northwest: 

 Proc. Am. Assoc. Adv. Sci., Thirty-seventh Meeting, 1888, pp. 205-206. The geo- 

 logical position of the Ogishkie conglomerate: Proc. Am. Assoc. Adv. Sci., Thirt}'- 

 eighth Meeting, 1889, pp. 234-23.5. 



' In the above pajDers Alexander Winchell reports that he finds upon 

 Wonder Island, in Lake Saganaga, a conglomerate which contains abundant 

 rounded pebbles in a groundmass of syenite (p. 219). This occurrence 

 gives rise to the following suggestion in the author's mind: 



The inferences from the occurrence are important. A pudding stone like this 

 is universally regarded as of fragmental origin. Not only that, but of origin 

 through aqueous agency. . . . So, if this conglomerate is sedimentary in nature, 

 the syenite groundmass must, at the time of the deposition of the pebbles, have 

 been also in a state of semifluidity under the influence of water. It may have been 

 subjected simultaneously to energetic thermal action; but it was not in that state of 

 fluidity which accompanies and results from recent eruption as molten matter from 



