R^SUMfi OF LITERATURE. 81 



logic similarit}^ to the Animikie rocks are taken to be their folded equivalent. 

 While there is not here the same palpable unconformities as in the other 

 regions discussed, it is believed that there are two groups of rocks, one of 

 crystalline schists, and another of newer detrital rocks, the apparent 

 unconformity between these being due to the intense folding. 



WiNCHELL, A. Report of geological observations made in northeastern Minne- 

 sota during the season of 1886: Fifteenth Ann. Rept. Geol. and Nat. Hist. Survey 

 Minn., for 1886, 1887, pp. 5-207. 



In this report are given the detailed observations made on an extensive 

 trip in northeastern Minnesota. 



The region presents a series of schists flanked on the north and south 

 by massive crystalline rocks. In the western part of the district these 

 rocks are gneissic on both sides, but in the eastern part the schists extend 

 on the north beyond the limits of the map, while on the south the gneissic 

 rocks are replaced by g-abbro and greenstone. The schists and bedded 

 crystallines stand in nearly vertical attitude. 



It is said that the indications of a genetic connection betw*een gray wacke 

 and the mica-schists are ver}^ noteworthy, a gradation from one to the other 

 having been noted in numerous instances (p. 176). Likewise the schists 

 grade into the gneissic rocks, there being nowhere an abrupt passage from 

 one class to the other. In the passage from the schists to the gneisses there 

 is, first, an increase in frequency of ramifying veins, next, lumps of gneiss 

 or granite occur in the schists, and finally there is interstratification of the 

 schists and gneisses (p. 178). The author expresses himself (p. 179) as 

 uncertain whether or not the conglomerate at Ogishkie Muncie Lake, which 

 attains an enormous development and contains varieties of granitic and 

 quartzose bowlders, as well as flint, jasper, porphjay, and greenstone, exists 

 as far west as Vermilion Lake; however, there is apparently no doubt that 

 it lies in the strike of the schists occurring at the west end of the range on 

 Vermilion Lake. It thus seems to be a local development of the schists. 

 The beds of bowlders are interbedded with flinty argillites, which attain 

 their greatest development north of the conglomerates ; the southern border 

 of the conglomerates is concealed by overlying greenstone and gabbro. 

 Some sericitic beds have been discovered within the conglomerate formation. 

 These facts lead the author to conclude that the conglomerate belongs in 

 stratigraphic position within the northern border of the sericitic schists, 



JION XLV — 03 6 



