682 W. J. MILLER PRE-CAMBRL\N FOLDING IN NORTH AMERICA 



been highly compressed, and he mentions (page 76) a number of writers 

 on the geology of northern New York in support of his contention. He 

 might have added that a dozen years ago the present writer held the 

 same view; but several of the writers mentioned have never professed to 

 have seriously studied this problem, and several others give evidence only 

 for the northwestern (Saint Lawrence Valley) side of the Adirondack 

 region, which the present writer also believes does show evidence of more 

 or less folding. For the ten thousand square miles of the Adirondack 

 region proper, however, only two men, Gushing and Ailing, have really 

 argued for severe, even isoclinal folding, and they have largely ignored 

 the array of evidence to the contrary, as set forth by the present writer 

 in the paper above cited. Unless this array of evidence is seriously taken 

 up and disproved, it is hardly fair to merely state without proof, as 

 Euedemann does, that the conclusion from that evidence is wrong. 

 Ruedemann gives considerable attention to the pre-Cambrian of northern 

 New York because it is a distinct, unusually studied area, in many ways 

 "representative of the whole problem"^ of pre-Cambrian folding. 



Another area of earlier pre-Cambrian rocks which has been carefully 

 studied is the Haliburton-Bancroft district,* covering over four thousand 

 square miles of eastern Ontario, Canada. The region consists mainly of 

 large, crude, oval-shaped granite batholiths protruding through Gren- 

 ville (Archean) strata. These batholiths are arranged with a prevailing 

 trend north 30 degrees east, and the strata usually lap over on them with 

 quaquaversal dips, generally not at very high angles. A structure section 

 across the region would not reveal a very highly folded arrangement of 

 the rocks. It seems not at all unreasonable to interpret this moderate 

 deformation as having resulted mainly from the upwelling of the batho- 

 lithic magma bodies under conditions of not more than slight lateral 

 pressure. 



Structure sections through both the Rainy Lake (Lawson, 1913) and 

 Geneva- Sudbury (Tanton, 1913) districts of Ontario show that the older 

 pre-Cambrian rocks are there considerably folded, but certainly not 

 severely folded. In a number of studied areas of Ontario and Quebec, 

 writers record rather persistently steep dips, while for other areas the 

 degree of deformation is not stated in the publications. 



In a report on the "Selkirks and Interior Plateau of British Colum- 

 bia," Daly^ emphasizes the fact of the remarkable freedom of the 

 Shuswap (pre-Beltian) series from deformation. 



*F. D. Adams and A. E. Barlow: Geol. Sur. Can., Mem. 6, 1910. 

 5R. A. Daly: Geol. Sur. Can., Guide Book No. 8, 1913, p. 153. 



